tcp_output.c 108.0 KB
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/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
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 * Authors:	Ross Biro
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 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

/*
 * Changes:	Pedro Roque	:	Retransmit queue handled by TCP.
 *				:	Fragmentation on mtu decrease
 *				:	Segment collapse on retransmit
 *				:	AF independence
 *
 *		Linus Torvalds	:	send_delayed_ack
 *		David S. Miller	:	Charge memory using the right skb
 *					during syn/ack processing.
 *		David S. Miller :	Output engine completely rewritten.
 *		Andrea Arcangeli:	SYNACK carry ts_recent in tsecr.
 *		Cacophonix Gaul :	draft-minshall-nagle-01
 *		J Hadi Salim	:	ECN support
 *
 */

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#define pr_fmt(fmt) "TCP: " fmt

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#include <net/tcp.h>

#include <linux/compiler.h>
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#include <linux/gfp.h>
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#include <linux/module.h>
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#include <linux/static_key.h>
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#include <trace/events/tcp.h>
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static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp);
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/* Account for new data that has been sent to the network. */
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static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
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{
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	struct inet_connection_sock *icsk = inet_csk(sk);
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	struct tcp_sock *tp = tcp_sk(sk);
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	unsigned int prior_packets = tp->packets_out;
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	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
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	__skb_unlink(skb, &sk->sk_write_queue);
	tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);

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	tp->packets_out += tcp_skb_pcount(skb);
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	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
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		tcp_rearm_rto(sk);
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	NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
		      tcp_skb_pcount(skb));
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}

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/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
 * window scaling factor due to loss of precision.
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 * If window has been shrunk, what should we make? It is not clear at all.
 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
 * invalid. OK, let's make this for now:
 */
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static inline __u32 tcp_acceptable_seq(const struct sock *sk)
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{
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	const struct tcp_sock *tp = tcp_sk(sk);
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	if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
	    (tp->rx_opt.wscale_ok &&
	     ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
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		return tp->snd_nxt;
	else
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		return tcp_wnd_end(tp);
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}

/* Calculate mss to advertise in SYN segment.
 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
 *
 * 1. It is independent of path mtu.
 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
 *    attached devices, because some buggy hosts are confused by
 *    large MSS.
 * 4. We do not make 3, we advertise MSS, calculated from first
 *    hop device mtu, but allow to raise it to ip_rt_min_advmss.
 *    This may be overridden via information stored in routing table.
 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
 *    probably even Jumbo".
 */
static __u16 tcp_advertise_mss(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
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	const struct dst_entry *dst = __sk_dst_get(sk);
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	int mss = tp->advmss;

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	if (dst) {
		unsigned int metric = dst_metric_advmss(dst);

		if (metric < mss) {
			mss = metric;
			tp->advmss = mss;
		}
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	}

	return (__u16)mss;
}

/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
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 * This is the first part of cwnd validation mechanism.
 */
void tcp_cwnd_restart(struct sock *sk, s32 delta)
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{
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	struct tcp_sock *tp = tcp_sk(sk);
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	u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
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	u32 cwnd = tp->snd_cwnd;

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	tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
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	tp->snd_ssthresh = tcp_current_ssthresh(sk);
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	restart_cwnd = min(restart_cwnd, cwnd);

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	while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
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		cwnd >>= 1;
	tp->snd_cwnd = max(cwnd, restart_cwnd);
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	tp->snd_cwnd_stamp = tcp_jiffies32;
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	tp->snd_cwnd_used = 0;
}

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/* Congestion state accounting after a packet has been sent. */
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static void tcp_event_data_sent(struct tcp_sock *tp,
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				struct sock *sk)
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{
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	struct inet_connection_sock *icsk = inet_csk(sk);
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	const u32 now = tcp_jiffies32;
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	if (tcp_packets_in_flight(tp) == 0)
		tcp_ca_event(sk, CA_EVENT_TX_START);

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	tp->lsndtime = now;

	/* If it is a reply for ato after last received
	 * packet, enter pingpong mode.
	 */
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	if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
		icsk->icsk_ack.pingpong = 1;
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}

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/* Account for an ACK we sent. */
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static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
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{
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	tcp_dec_quickack_mode(sk, pkts);
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
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}

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u32 tcp_default_init_rwnd(u32 mss)
{
	/* Initial receive window should be twice of TCP_INIT_CWND to
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	 * enable proper sending of new unsent data during fast recovery
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	 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
	 * limit when mss is larger than 1460.
	 */
	u32 init_rwnd = TCP_INIT_CWND * 2;

	if (mss > 1460)
		init_rwnd = max((1460 * init_rwnd) / mss, 2U);
	return init_rwnd;
}

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/* Determine a window scaling and initial window to offer.
 * Based on the assumption that the given amount of space
 * will be offered. Store the results in the tp structure.
 * NOTE: for smooth operation initial space offering should
 * be a multiple of mss if possible. We assume here that mss >= 1.
 * This MUST be enforced by all callers.
 */
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void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
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			       __u32 *rcv_wnd, __u32 *window_clamp,
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			       int wscale_ok, __u8 *rcv_wscale,
			       __u32 init_rcv_wnd)
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{
	unsigned int space = (__space < 0 ? 0 : __space);

	/* If no clamp set the clamp to the max possible scaled window */
	if (*window_clamp == 0)
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		(*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
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	space = min(*window_clamp, space);

	/* Quantize space offering to a multiple of mss if possible. */
	if (space > mss)
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		space = rounddown(space, mss);
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	/* NOTE: offering an initial window larger than 32767
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	 * will break some buggy TCP stacks. If the admin tells us
	 * it is likely we could be speaking with such a buggy stack
	 * we will truncate our initial window offering to 32K-1
	 * unless the remote has sent us a window scaling option,
	 * which we interpret as a sign the remote TCP is not
	 * misinterpreting the window field as a signed quantity.
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	 */
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	if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
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		(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
	else
		(*rcv_wnd) = space;

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	(*rcv_wscale) = 0;
	if (wscale_ok) {
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		/* Set window scaling on max possible window */
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		space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
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		space = max_t(u32, space, sysctl_rmem_max);
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		space = min_t(u32, space, *window_clamp);
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		while (space > U16_MAX && (*rcv_wscale) < TCP_MAX_WSCALE) {
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			space >>= 1;
			(*rcv_wscale)++;
		}
	}

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	if (mss > (1 << *rcv_wscale)) {
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		if (!init_rcv_wnd) /* Use default unless specified otherwise */
			init_rcv_wnd = tcp_default_init_rwnd(mss);
		*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
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	}

	/* Set the clamp no higher than max representable value */
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	(*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
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}
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EXPORT_SYMBOL(tcp_select_initial_window);
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/* Chose a new window to advertise, update state in tcp_sock for the
 * socket, and return result with RFC1323 scaling applied.  The return
 * value can be stuffed directly into th->window for an outgoing
 * frame.
 */
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static u16 tcp_select_window(struct sock *sk)
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{
	struct tcp_sock *tp = tcp_sk(sk);
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	u32 old_win = tp->rcv_wnd;
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	u32 cur_win = tcp_receive_window(tp);
	u32 new_win = __tcp_select_window(sk);

	/* Never shrink the offered window */
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	if (new_win < cur_win) {
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		/* Danger Will Robinson!
		 * Don't update rcv_wup/rcv_wnd here or else
		 * we will not be able to advertise a zero
		 * window in time.  --DaveM
		 *
		 * Relax Will Robinson.
		 */
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		if (new_win == 0)
			NET_INC_STATS(sock_net(sk),
				      LINUX_MIB_TCPWANTZEROWINDOWADV);
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		new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
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	}
	tp->rcv_wnd = new_win;
	tp->rcv_wup = tp->rcv_nxt;

	/* Make sure we do not exceed the maximum possible
	 * scaled window.
	 */
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	if (!tp->rx_opt.rcv_wscale &&
	    sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
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		new_win = min(new_win, MAX_TCP_WINDOW);
	else
		new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));

	/* RFC1323 scaling applied */
	new_win >>= tp->rx_opt.rcv_wscale;

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	/* If we advertise zero window, disable fast path. */
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	if (new_win == 0) {
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		tp->pred_flags = 0;
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		if (old_win)
			NET_INC_STATS(sock_net(sk),
				      LINUX_MIB_TCPTOZEROWINDOWADV);
	} else if (old_win == 0) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
	}
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	return new_win;
}

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/* Packet ECN state for a SYN-ACK */
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static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
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{
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	const struct tcp_sock *tp = tcp_sk(sk);

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	TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
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	if (!(tp->ecn_flags & TCP_ECN_OK))
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		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
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	else if (tcp_ca_needs_ecn(sk) ||
		 tcp_bpf_ca_needs_ecn(sk))
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		INET_ECN_xmit(sk);
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}

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/* Packet ECN state for a SYN.  */
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static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
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{
	struct tcp_sock *tp = tcp_sk(sk);
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	bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
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	bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
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		tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
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	if (!use_ecn) {
		const struct dst_entry *dst = __sk_dst_get(sk);

		if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
			use_ecn = true;
	}
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	tp->ecn_flags = 0;
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	if (use_ecn) {
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		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
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		tp->ecn_flags = TCP_ECN_OK;
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		if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
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			INET_ECN_xmit(sk);
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	}
}

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static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
{
	if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
		/* tp->ecn_flags are cleared at a later point in time when
		 * SYN ACK is ultimatively being received.
		 */
		TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
}

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static void
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tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
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{
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	if (inet_rsk(req)->ecn_ok)
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		th->ece = 1;
}

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/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
 * be sent.
 */
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static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
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			 struct tcphdr *th, int tcp_header_len)
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{
	struct tcp_sock *tp = tcp_sk(sk);

	if (tp->ecn_flags & TCP_ECN_OK) {
		/* Not-retransmitted data segment: set ECT and inject CWR. */
		if (skb->len != tcp_header_len &&
		    !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
			INET_ECN_xmit(sk);
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			if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
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				tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
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				th->cwr = 1;
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				skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
			}
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		} else if (!tcp_ca_needs_ecn(sk)) {
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			/* ACK or retransmitted segment: clear ECT|CE */
			INET_ECN_dontxmit(sk);
		}
		if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
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			th->ece = 1;
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	}
}

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/* Constructs common control bits of non-data skb. If SYN/FIN is present,
 * auto increment end seqno.
 */
static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
{
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	skb->ip_summed = CHECKSUM_PARTIAL;
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	TCP_SKB_CB(skb)->tcp_flags = flags;
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	TCP_SKB_CB(skb)->sacked = 0;

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	tcp_skb_pcount_set(skb, 1);
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	TCP_SKB_CB(skb)->seq = seq;
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	if (flags & (TCPHDR_SYN | TCPHDR_FIN))
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		seq++;
	TCP_SKB_CB(skb)->end_seq = seq;
}

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static inline bool tcp_urg_mode(const struct tcp_sock *tp)
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{
	return tp->snd_una != tp->snd_up;
}

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#define OPTION_SACK_ADVERTISE	(1 << 0)
#define OPTION_TS		(1 << 1)
#define OPTION_MD5		(1 << 2)
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#define OPTION_WSCALE		(1 << 3)
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#define OPTION_FAST_OPEN_COOKIE	(1 << 8)
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#define OPTION_SMC		(1 << 9)

static void smc_options_write(__be32 *ptr, u16 *options)
{
#if IS_ENABLED(CONFIG_SMC)
	if (static_branch_unlikely(&tcp_have_smc)) {
		if (unlikely(OPTION_SMC & *options)) {
			*ptr++ = htonl((TCPOPT_NOP  << 24) |
				       (TCPOPT_NOP  << 16) |
				       (TCPOPT_EXP <<  8) |
				       (TCPOLEN_EXP_SMC_BASE));
			*ptr++ = htonl(TCPOPT_SMC_MAGIC);
		}
	}
#endif
}
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struct tcp_out_options {
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	u16 options;		/* bit field of OPTION_* */
	u16 mss;		/* 0 to disable */
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	u8 ws;			/* window scale, 0 to disable */
	u8 num_sack_blocks;	/* number of SACK blocks to include */
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	u8 hash_size;		/* bytes in hash_location */
	__u8 *hash_location;	/* temporary pointer, overloaded */
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	__u32 tsval, tsecr;	/* need to include OPTION_TS */
	struct tcp_fastopen_cookie *fastopen_cookie;	/* Fast open cookie */
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};

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/* Write previously computed TCP options to the packet.
 *
 * Beware: Something in the Internet is very sensitive to the ordering of
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 * TCP options, we learned this through the hard way, so be careful here.
 * Luckily we can at least blame others for their non-compliance but from
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 * inter-operability perspective it seems that we're somewhat stuck with
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 * the ordering which we have been using if we want to keep working with
 * those broken things (not that it currently hurts anybody as there isn't
 * particular reason why the ordering would need to be changed).
 *
 * At least SACK_PERM as the first option is known to lead to a disaster
 * (but it may well be that other scenarios fail similarly).
 */
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static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
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			      struct tcp_out_options *opts)
{
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	u16 options = opts->options;	/* mungable copy */
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	if (unlikely(OPTION_MD5 & options)) {
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		*ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
			       (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
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		/* overload cookie hash location */
		opts->hash_location = (__u8 *)ptr;
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		ptr += 4;
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	}
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	if (unlikely(opts->mss)) {
		*ptr++ = htonl((TCPOPT_MSS << 24) |
			       (TCPOLEN_MSS << 16) |
			       opts->mss);
	}

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	if (likely(OPTION_TS & options)) {
		if (unlikely(OPTION_SACK_ADVERTISE & options)) {
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			*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
				       (TCPOLEN_SACK_PERM << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
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			options &= ~OPTION_SACK_ADVERTISE;
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		} else {
			*ptr++ = htonl((TCPOPT_NOP << 24) |
				       (TCPOPT_NOP << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
		}
		*ptr++ = htonl(opts->tsval);
		*ptr++ = htonl(opts->tsecr);
	}

483
	if (unlikely(OPTION_SACK_ADVERTISE & options)) {
A
Adam Langley 已提交
484 485 486 487 488 489
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_SACK_PERM << 8) |
			       TCPOLEN_SACK_PERM);
	}

490
	if (unlikely(OPTION_WSCALE & options)) {
A
Adam Langley 已提交
491 492 493 494 495 496 497 498 499
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_WINDOW << 16) |
			       (TCPOLEN_WINDOW << 8) |
			       opts->ws);
	}

	if (unlikely(opts->num_sack_blocks)) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ?
			tp->duplicate_sack : tp->selective_acks;
S
Stephen Hemminger 已提交
500 501 502 503 504
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
505
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
506
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
507

A
Adam Langley 已提交
508 509
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
510 511 512
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
513

514
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
515
	}
Y
Yuchung Cheng 已提交
516 517 518

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
519 520 521 522 523 524 525 526 527 528 529 530 531
		u8 *p = (u8 *)ptr;
		u32 len; /* Fast Open option length */

		if (foc->exp) {
			len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
			*ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
				     TCPOPT_FASTOPEN_MAGIC);
			p += TCPOLEN_EXP_FASTOPEN_BASE;
		} else {
			len = TCPOLEN_FASTOPEN_BASE + foc->len;
			*p++ = TCPOPT_FASTOPEN;
			*p++ = len;
		}
Y
Yuchung Cheng 已提交
532

533 534 535 536
		memcpy(p, foc->val, foc->len);
		if ((len & 3) == 2) {
			p[foc->len] = TCPOPT_NOP;
			p[foc->len + 1] = TCPOPT_NOP;
Y
Yuchung Cheng 已提交
537
		}
538
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
539
	}
540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574

	smc_options_write(ptr, &options);
}

static void smc_set_option(const struct tcp_sock *tp,
			   struct tcp_out_options *opts,
			   unsigned int *remaining)
{
#if IS_ENABLED(CONFIG_SMC)
	if (static_branch_unlikely(&tcp_have_smc)) {
		if (tp->syn_smc) {
			if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
				opts->options |= OPTION_SMC;
				*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
			}
		}
	}
#endif
}

static void smc_set_option_cond(const struct tcp_sock *tp,
				const struct inet_request_sock *ireq,
				struct tcp_out_options *opts,
				unsigned int *remaining)
{
#if IS_ENABLED(CONFIG_SMC)
	if (static_branch_unlikely(&tcp_have_smc)) {
		if (tp->syn_smc && ireq->smc_ok) {
			if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
				opts->options |= OPTION_SMC;
				*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
			}
		}
	}
#endif
A
Adam Langley 已提交
575 576
}

577 578 579
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
580
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
581
				struct tcp_out_options *opts,
582 583
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
584
	struct tcp_sock *tp = tcp_sk(sk);
585
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
586
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
587

588
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
589 590 591
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
592
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
593
	}
A
Adam Langley 已提交
594 595
#else
	*md5 = NULL;
596
#endif
A
Adam Langley 已提交
597 598 599 600 601 602 603 604 605 606 607

	/* We always get an MSS option.  The option bytes which will be seen in
	 * normal data packets should timestamps be used, must be in the MSS
	 * advertised.  But we subtract them from tp->mss_cache so that
	 * calculations in tcp_sendmsg are simpler etc.  So account for this
	 * fact here if necessary.  If we don't do this correctly, as a
	 * receiver we won't recognize data packets as being full sized when we
	 * should, and thus we won't abide by the delayed ACK rules correctly.
	 * SACKs don't matter, we never delay an ACK when we have any of those
	 * going out.  */
	opts->mss = tcp_advertise_mss(sk);
608
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
609

610
	if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
611
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
612
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
613
		opts->tsecr = tp->rx_opt.ts_recent;
614
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
615
	}
616
	if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
617
		opts->ws = tp->rx_opt.rcv_wscale;
618
		opts->options |= OPTION_WSCALE;
619
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
620
	}
E
Eric Dumazet 已提交
621
	if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
A
Adam Langley 已提交
622
		opts->options |= OPTION_SACK_ADVERTISE;
623
		if (unlikely(!(OPTION_TS & opts->options)))
624
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
625 626
	}

627
	if (fastopen && fastopen->cookie.len >= 0) {
628 629 630 631
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
632 633 634 635 636 637
		need = (need + 3) & ~3U;  /* Align to 32 bits */
		if (remaining >= need) {
			opts->options |= OPTION_FAST_OPEN_COOKIE;
			opts->fastopen_cookie = &fastopen->cookie;
			remaining -= need;
			tp->syn_fastopen = 1;
638
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
639 640
		}
	}
641

642 643
	smc_set_option(tp, opts, &remaining);

644
	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
645 646
}

647
/* Set up TCP options for SYN-ACKs. */
648 649
static unsigned int tcp_synack_options(const struct sock *sk,
				       struct request_sock *req,
650 651 652 653
				       unsigned int mss, struct sk_buff *skb,
				       struct tcp_out_options *opts,
				       const struct tcp_md5sig_key *md5,
				       struct tcp_fastopen_cookie *foc)
654
{
A
Adam Langley 已提交
655
	struct inet_request_sock *ireq = inet_rsk(req);
656
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
657

658
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
659
	if (md5) {
A
Adam Langley 已提交
660
		opts->options |= OPTION_MD5;
661 662 663 664 665 666 667
		remaining -= TCPOLEN_MD5SIG_ALIGNED;

		/* We can't fit any SACK blocks in a packet with MD5 + TS
		 * options. There was discussion about disabling SACK
		 * rather than TS in order to fit in better with old,
		 * buggy kernels, but that was deemed to be unnecessary.
		 */
E
Eric Dumazet 已提交
668
		ireq->tstamp_ok &= !ireq->sack_ok;
669 670
	}
#endif
A
Adam Langley 已提交
671

672
	/* We always send an MSS option. */
A
Adam Langley 已提交
673
	opts->mss = mss;
674
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
675 676 677

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
678
		opts->options |= OPTION_WSCALE;
679
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
680
	}
E
Eric Dumazet 已提交
681
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
682
		opts->options |= OPTION_TS;
683
		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
A
Adam Langley 已提交
684
		opts->tsecr = req->ts_recent;
685
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
686 687 688
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
689
		if (unlikely(!ireq->tstamp_ok))
690
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
691
	}
692 693 694 695 696
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
697 698 699 700 701 702 703
		need = (need + 3) & ~3U;  /* Align to 32 bits */
		if (remaining >= need) {
			opts->options |= OPTION_FAST_OPEN_COOKIE;
			opts->fastopen_cookie = foc;
			remaining -= need;
		}
	}
C
Christoph Paasch 已提交
704

705 706
	smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);

707
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
708 709
}

710 711 712
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
713
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
714
					struct tcp_out_options *opts,
715 716
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
717
	struct tcp_sock *tp = tcp_sk(sk);
718
	unsigned int size = 0;
719
	unsigned int eff_sacks;
A
Adam Langley 已提交
720

721 722
	opts->options = 0;

A
Adam Langley 已提交
723 724 725 726 727 728 729 730 731 732 733 734
#ifdef CONFIG_TCP_MD5SIG
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (unlikely(*md5)) {
		opts->options |= OPTION_MD5;
		size += TCPOLEN_MD5SIG_ALIGNED;
	}
#else
	*md5 = NULL;
#endif

	if (likely(tp->rx_opt.tstamp_ok)) {
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
735
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
736 737 738 739
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

740 741
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
742
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
743
		opts->num_sack_blocks =
744
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
745 746 747 748 749 750 751
			      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
			      TCPOLEN_SACK_PERBLOCK);
		size += TCPOLEN_SACK_BASE_ALIGNED +
			opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
	}

	return size;
S
Stephen Hemminger 已提交
752
}
L
Linus Torvalds 已提交
753

E
Eric Dumazet 已提交
754 755 756 757 758 759 760 761 762

/* TCP SMALL QUEUES (TSQ)
 *
 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
 * to reduce RTT and bufferbloat.
 * We do this using a special skb destructor (tcp_wfree).
 *
 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
 * needs to be reallocated in a driver.
S
stephen hemminger 已提交
763
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
764 765 766 767 768 769 770 771 772 773 774
 *
 * Since transmit from skb destructor is forbidden, we use a tasklet
 * to process all sockets that eventually need to send more skbs.
 * We use one tasklet per cpu, with its own queue of sockets.
 */
struct tsq_tasklet {
	struct tasklet_struct	tasklet;
	struct list_head	head; /* queue of tcp sockets */
};
static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);

775 776 777 778
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
779 780 781 782
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK)) {
		struct tcp_sock *tp = tcp_sk(sk);

		if (tp->lost_out > tp->retrans_out &&
783 784
		    tp->snd_cwnd > tcp_packets_in_flight(tp)) {
			tcp_mstamp_refresh(tp);
785
			tcp_xmit_retransmit_queue(sk);
786
		}
787 788

		tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
J
John Ogness 已提交
789
			       0, GFP_ATOMIC);
790
	}
791
}
E
Eric Dumazet 已提交
792
/*
S
stephen hemminger 已提交
793
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
794
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
795
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815
 * interrupt us (non NAPI drivers)
 */
static void tcp_tasklet_func(unsigned long data)
{
	struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
	LIST_HEAD(list);
	unsigned long flags;
	struct list_head *q, *n;
	struct tcp_sock *tp;
	struct sock *sk;

	local_irq_save(flags);
	list_splice_init(&tsq->head, &list);
	local_irq_restore(flags);

	list_for_each_safe(q, n, &list) {
		tp = list_entry(q, struct tcp_sock, tsq_node);
		list_del(&tp->tsq_node);

		sk = (struct sock *)tp;
816
		smp_mb__before_atomic();
817 818
		clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);

819
		if (!sk->sk_lock.owned &&
820
		    test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) {
821 822
			bh_lock_sock(sk);
			if (!sock_owned_by_user(sk)) {
823
				clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
824 825 826
				tcp_tsq_handler(sk);
			}
			bh_unlock_sock(sk);
E
Eric Dumazet 已提交
827 828 829 830 831 832
		}

		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
833 834 835 836
#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED |		\
			  TCPF_WRITE_TIMER_DEFERRED |	\
			  TCPF_DELACK_TIMER_DEFERRED |	\
			  TCPF_MTU_REDUCED_DEFERRED)
E
Eric Dumazet 已提交
837 838 839 840 841 842 843 844 845
/**
 * tcp_release_cb - tcp release_sock() callback
 * @sk: socket
 *
 * called from release_sock() to perform protocol dependent
 * actions before socket release.
 */
void tcp_release_cb(struct sock *sk)
{
846
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
847

848 849
	/* perform an atomic operation only if at least one flag is set */
	do {
850
		flags = sk->sk_tsq_flags;
851 852 853
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
854
	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
855

E
Eric Dumazet 已提交
856
	if (flags & TCPF_TSQ_DEFERRED)
857 858
		tcp_tsq_handler(sk);

859 860 861 862 863 864 865 866 867 868 869
	/* Here begins the tricky part :
	 * We are called from release_sock() with :
	 * 1) BH disabled
	 * 2) sk_lock.slock spinlock held
	 * 3) socket owned by us (sk->sk_lock.owned == 1)
	 *
	 * But following code is meant to be called from BH handlers,
	 * so we should keep BH disabled, but early release socket ownership
	 */
	sock_release_ownership(sk);

E
Eric Dumazet 已提交
870
	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
871
		tcp_write_timer_handler(sk);
872 873
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
874
	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
875
		tcp_delack_timer_handler(sk);
876 877
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
878
	if (flags & TCPF_MTU_REDUCED_DEFERRED) {
879
		inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
880 881
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900
}
EXPORT_SYMBOL(tcp_release_cb);

void __init tcp_tasklet_init(void)
{
	int i;

	for_each_possible_cpu(i) {
		struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);

		INIT_LIST_HEAD(&tsq->head);
		tasklet_init(&tsq->tasklet,
			     tcp_tasklet_func,
			     (unsigned long)tsq);
	}
}

/*
 * Write buffer destructor automatically called from kfree_skb.
S
stephen hemminger 已提交
901
 * We can't xmit new skbs from this context, as we might already
E
Eric Dumazet 已提交
902 903
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
904
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
905 906 907
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);
908
	unsigned long flags, nval, oval;
909 910 911 912

	/* Keep one reference on sk_wmem_alloc.
	 * Will be released by sk_free() from here or tcp_tasklet_func()
	 */
913
	WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
914 915 916 917 918 919 920 921

	/* If this softirq is serviced by ksoftirqd, we are likely under stress.
	 * Wait until our queues (qdisc + devices) are drained.
	 * This gives :
	 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
	 * - chance for incoming ACK (processed by another cpu maybe)
	 *   to migrate this flow (skb->ooo_okay will be eventually set)
	 */
922
	if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
923
		goto out;
E
Eric Dumazet 已提交
924

925
	for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
E
Eric Dumazet 已提交
926
		struct tsq_tasklet *tsq;
927
		bool empty;
E
Eric Dumazet 已提交
928

929 930 931
		if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
			goto out;

932
		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
933
		nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
934 935 936
		if (nval != oval)
			continue;

E
Eric Dumazet 已提交
937 938
		/* queue this socket to tasklet queue */
		local_irq_save(flags);
939
		tsq = this_cpu_ptr(&tsq_tasklet);
940
		empty = list_empty(&tsq->head);
E
Eric Dumazet 已提交
941
		list_add(&tp->tsq_node, &tsq->head);
942 943
		if (empty)
			tasklet_schedule(&tsq->tasklet);
E
Eric Dumazet 已提交
944
		local_irq_restore(flags);
945
		return;
E
Eric Dumazet 已提交
946
	}
947 948
out:
	sk_free(sk);
E
Eric Dumazet 已提交
949 950
}

951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971
/* Note: Called under hard irq.
 * We can not call TCP stack right away.
 */
enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
{
	struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
	struct sock *sk = (struct sock *)tp;
	unsigned long nval, oval;

	for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
		struct tsq_tasklet *tsq;
		bool empty;

		if (oval & TSQF_QUEUED)
			break;

		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
		nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
		if (nval != oval)
			continue;

972
		if (!refcount_inc_not_zero(&sk->sk_wmem_alloc))
973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016
			break;
		/* queue this socket to tasklet queue */
		tsq = this_cpu_ptr(&tsq_tasklet);
		empty = list_empty(&tsq->head);
		list_add(&tp->tsq_node, &tsq->head);
		if (empty)
			tasklet_schedule(&tsq->tasklet);
		break;
	}
	return HRTIMER_NORESTART;
}

/* BBR congestion control needs pacing.
 * Same remark for SO_MAX_PACING_RATE.
 * sch_fq packet scheduler is efficiently handling pacing,
 * but is not always installed/used.
 * Return true if TCP stack should pace packets itself.
 */
static bool tcp_needs_internal_pacing(const struct sock *sk)
{
	return smp_load_acquire(&sk->sk_pacing_status) == SK_PACING_NEEDED;
}

static void tcp_internal_pacing(struct sock *sk, const struct sk_buff *skb)
{
	u64 len_ns;
	u32 rate;

	if (!tcp_needs_internal_pacing(sk))
		return;
	rate = sk->sk_pacing_rate;
	if (!rate || rate == ~0U)
		return;

	/* Should account for header sizes as sch_fq does,
	 * but lets make things simple.
	 */
	len_ns = (u64)skb->len * NSEC_PER_SEC;
	do_div(len_ns, rate);
	hrtimer_start(&tcp_sk(sk)->pacing_timer,
		      ktime_add_ns(ktime_get(), len_ns),
		      HRTIMER_MODE_ABS_PINNED);
}

1017 1018 1019 1020 1021 1022
static void tcp_update_skb_after_send(struct tcp_sock *tp, struct sk_buff *skb)
{
	skb->skb_mstamp = tp->tcp_mstamp;
	list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
}

L
Linus Torvalds 已提交
1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033
/* This routine actually transmits TCP packets queued in by
 * tcp_do_sendmsg().  This is used by both the initial
 * transmission and possible later retransmissions.
 * All SKB's seen here are completely headerless.  It is our
 * job to build the TCP header, and pass the packet down to
 * IP so it can do the same plus pass the packet off to the
 * device.
 *
 * We are working here with either a clone of the original
 * SKB, or a fresh unique copy made by the retransmit engine.
 */
1034 1035
static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
			    gfp_t gfp_mask)
L
Linus Torvalds 已提交
1036
{
1037 1038 1039 1040
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct inet_sock *inet;
	struct tcp_sock *tp;
	struct tcp_skb_cb *tcb;
A
Adam Langley 已提交
1041
	struct tcp_out_options opts;
1042
	unsigned int tcp_options_size, tcp_header_size;
1043
	struct sk_buff *oskb = NULL;
1044
	struct tcp_md5sig_key *md5;
1045 1046 1047 1048
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
1049
	tp = tcp_sk(sk);
1050

1051
	if (clone_it) {
1052 1053
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
1054
		oskb = skb;
1055 1056 1057 1058 1059 1060 1061 1062

		tcp_skb_tsorted_save(oskb) {
			if (unlikely(skb_cloned(oskb)))
				skb = pskb_copy(oskb, gfp_mask);
			else
				skb = skb_clone(oskb, gfp_mask);
		} tcp_skb_tsorted_restore(oskb);

1063 1064 1065
		if (unlikely(!skb))
			return -ENOBUFS;
	}
1066
	skb->skb_mstamp = tp->tcp_mstamp;
L
Linus Torvalds 已提交
1067

1068 1069
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
1070
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
1071

E
Eric Dumazet 已提交
1072
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
1073 1074 1075 1076 1077
		tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
	else
		tcp_options_size = tcp_established_options(sk, skb, &opts,
							   &md5);
	tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1078

E
Eric Dumazet 已提交
1079
	/* if no packet is in qdisc/device queue, then allow XPS to select
1080 1081 1082 1083 1084
	 * another queue. We can be called from tcp_tsq_handler()
	 * which holds one reference to sk_wmem_alloc.
	 *
	 * TODO: Ideally, in-flight pure ACK packets should not matter here.
	 * One way to get this would be to set skb->truesize = 2 on them.
E
Eric Dumazet 已提交
1085
	 */
1086
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1087

1088 1089 1090 1091 1092 1093 1094
	/* If we had to use memory reserve to allocate this skb,
	 * this might cause drops if packet is looped back :
	 * Other socket might not have SOCK_MEMALLOC.
	 * Packets not looped back do not care about pfmemalloc.
	 */
	skb->pfmemalloc = 0;

1095 1096
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
1097 1098 1099

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
1100
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1101
	skb_set_hash_from_sk(skb, sk);
1102
	refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1103

1104 1105
	skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);

1106
	/* Build TCP header and checksum it. */
1107
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
1108 1109
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
1110 1111
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
1112
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
1113
					tcb->tcp_flags);
1114 1115 1116

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
1117

I
Ilpo Järvinen 已提交
1118
	/* The urg_mode check is necessary during a below snd_una win probe */
1119 1120 1121 1122 1123
	if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
		if (before(tp->snd_up, tcb->seq + 0x10000)) {
			th->urg_ptr = htons(tp->snd_up - tcb->seq);
			th->urg = 1;
		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1124
			th->urg_ptr = htons(0xFFFF);
1125 1126
			th->urg = 1;
		}
1127
	}
L
Linus Torvalds 已提交
1128

1129
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1130
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1131 1132 1133 1134 1135 1136 1137 1138 1139
	if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
		th->window      = htons(tcp_select_window(sk));
		tcp_ecn_send(sk, skb, th, tcp_header_size);
	} else {
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
		th->window	= htons(min(tp->rcv_wnd, 65535U));
	}
1140 1141 1142
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1143
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1144
		tp->af_specific->calc_md5_hash(opts.hash_location,
1145
					       md5, sk, skb);
1146 1147 1148
	}
#endif

1149
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1150

E
Eric Dumazet 已提交
1151
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1152
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1153

1154
	if (skb->len != tcp_header_size) {
1155
		tcp_event_data_sent(tp, sk);
1156
		tp->data_segs_out += tcp_skb_pcount(skb);
1157
		tcp_internal_pacing(sk, skb);
1158
	}
L
Linus Torvalds 已提交
1159

1160
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1161 1162
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1163

1164
	tp->segs_out += tcp_skb_pcount(skb);
1165
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1166
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1167
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1168

E
Eric Dumazet 已提交
1169
	/* Our usage of tstamp should remain private */
T
Thomas Gleixner 已提交
1170
	skb->tstamp = 0;
1171 1172 1173 1174 1175

	/* Cleanup our debris for IP stacks */
	memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
			       sizeof(struct inet6_skb_parm)));

1176
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1177

1178 1179 1180 1181
	if (unlikely(err > 0)) {
		tcp_enter_cwr(sk);
		err = net_xmit_eval(err);
	}
E
Eric Dumazet 已提交
1182
	if (!err && oskb) {
1183
		tcp_update_skb_after_send(tp, oskb);
E
Eric Dumazet 已提交
1184 1185
		tcp_rate_skb_sent(sk, oskb);
	}
1186
	return err;
L
Linus Torvalds 已提交
1187 1188
}

1189
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1190 1191 1192 1193 1194 1195 1196 1197 1198 1199
 *
 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
 * otherwise socket can stall.
 */
static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);

	/* Advance write_seq and place onto the write_queue. */
	tp->write_seq = TCP_SKB_CB(skb)->end_seq;
1200
	__skb_header_release(skb);
1201
	tcp_add_write_queue_tail(sk, skb);
1202 1203
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1204 1205
}

1206
/* Initialize TSO segments for a packet. */
1207
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1208
{
1209
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1210 1211 1212
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1213
		tcp_skb_pcount_set(skb, 1);
1214
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1215
	} else {
1216
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1217
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1218 1219 1220
	}
}

1221 1222 1223
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1224
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242
{
	struct tcp_sock *tp = tcp_sk(sk);

	tp->packets_out -= decr;

	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
		tp->sacked_out -= decr;
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
		tp->retrans_out -= decr;
	if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
		tp->lost_out -= decr;

	/* Reno case is special. Sigh... */
	if (tcp_is_reno(tp) && decr > 0)
		tp->sacked_out -= min_t(u32, tp->sacked_out, decr);

	if (tp->lost_skb_hint &&
	    before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
Y
Yuchung Cheng 已提交
1243
	    (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1244 1245 1246 1247 1248
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1249 1250 1251 1252 1253 1254
static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
{
	return TCP_SKB_CB(skb)->txstamp_ack ||
		(skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
}

1255 1256 1257 1258
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1259
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1260 1261 1262 1263 1264 1265 1266
	    !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
		struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
		u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;

		shinfo->tx_flags &= ~tsflags;
		shinfo2->tx_flags |= tsflags;
		swap(shinfo->tskey, shinfo2->tskey);
1267 1268
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1269 1270 1271
	}
}

1272 1273 1274 1275 1276 1277
static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
{
	TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
	TCP_SKB_CB(skb)->eor = 0;
}

1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289
/* Insert buff after skb on the write or rtx queue of sk.  */
static void tcp_insert_write_queue_after(struct sk_buff *skb,
					 struct sk_buff *buff,
					 struct sock *sk,
					 enum tcp_queue tcp_queue)
{
	if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
		__skb_queue_after(&sk->sk_write_queue, skb, buff);
	else
		tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
}

L
Linus Torvalds 已提交
1290 1291
/* Function to create two new TCP segments.  Shrinks the given segment
 * to the specified size and appends a new segment with the rest of the
1292
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1293 1294
 * Remember, these are still headerless SKBs at this point.
 */
1295 1296
int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
		 struct sk_buff *skb, u32 len,
1297
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1298 1299 1300
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1301
	int nsize, old_factor;
1302
	int nlen;
1303
	u8 flags;
L
Linus Torvalds 已提交
1304

1305 1306
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1307

L
Linus Torvalds 已提交
1308 1309 1310 1311
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1312
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1313 1314 1315
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1316
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1317
	if (!buff)
L
Linus Torvalds 已提交
1318
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1319

1320 1321
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1322 1323 1324
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1325 1326 1327 1328 1329 1330 1331

	/* Correct the sequence numbers. */
	TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
	TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;

	/* PSH and FIN should only be set in the second packet. */
E
Eric Dumazet 已提交
1332 1333 1334
	flags = TCP_SKB_CB(skb)->tcp_flags;
	TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
	TCP_SKB_CB(buff)->tcp_flags = flags;
1335
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1336
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1337

1338
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1339
		/* Copy and checksum data tail into the new buffer. */
1340 1341
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1342 1343 1344 1345 1346 1347
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1348
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1349 1350 1351 1352 1353
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1354
	buff->tstamp = skb->tstamp;
1355
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1356

1357 1358
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1359
	/* Fix up tso_factor for both original and new SKB.  */
1360 1361
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1362

1363 1364 1365
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1366 1367 1368
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1369
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1370 1371
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1372

1373 1374
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1375 1376 1377
	}

	/* Link BUFF into the send queue. */
1378
	__skb_header_release(buff);
1379
	tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1380 1381
	if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
		list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
L
Linus Torvalds 已提交
1382 1383 1384 1385

	return 0;
}

1386 1387
/* This is similar to __pskb_pull_tail(). The difference is that pulled
 * data is not copied, but immediately discarded.
L
Linus Torvalds 已提交
1388
 */
1389
static int __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1390
{
1391
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1392 1393
	int i, k, eat;

E
Eric Dumazet 已提交
1394 1395 1396 1397 1398
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
1399
			return 0;
E
Eric Dumazet 已提交
1400
	}
L
Linus Torvalds 已提交
1401 1402
	eat = len;
	k = 0;
1403 1404 1405
	shinfo = skb_shinfo(skb);
	for (i = 0; i < shinfo->nr_frags; i++) {
		int size = skb_frag_size(&shinfo->frags[i]);
E
Eric Dumazet 已提交
1406 1407

		if (size <= eat) {
1408
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1409
			eat -= size;
L
Linus Torvalds 已提交
1410
		} else {
1411
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1412
			if (eat) {
1413 1414
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1415 1416 1417 1418 1419
				eat = 0;
			}
			k++;
		}
	}
1420
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1421 1422 1423

	skb->data_len -= len;
	skb->len = skb->data_len;
1424
	return len;
L
Linus Torvalds 已提交
1425 1426
}

1427
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1428 1429
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1430 1431
	u32 delta_truesize;

1432
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1433 1434
		return -ENOMEM;

1435
	delta_truesize = __pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1436 1437

	TCP_SKB_CB(skb)->seq += len;
1438
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1439

1440 1441 1442 1443 1444 1445
	if (delta_truesize) {
		skb->truesize	   -= delta_truesize;
		sk->sk_wmem_queued -= delta_truesize;
		sk_mem_uncharge(sk, delta_truesize);
		sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
	}
L
Linus Torvalds 已提交
1446

1447
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1448
	if (tcp_skb_pcount(skb) > 1)
1449
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1450 1451 1452 1453

	return 0;
}

1454 1455
/* Calculate MSS not accounting any TCP options.  */
static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
J
John Heffner 已提交
1456
{
1457 1458
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1459 1460 1461 1462 1463 1464 1465
	int mss_now;

	/* Calculate base mss without TCP options:
	   It is MMS_S - sizeof(tcphdr) of rfc1122
	 */
	mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);

1466 1467 1468 1469 1470 1471 1472 1473
	/* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
	if (icsk->icsk_af_ops->net_frag_header_len) {
		const struct dst_entry *dst = __sk_dst_get(sk);

		if (dst && dst_allfrag(dst))
			mss_now -= icsk->icsk_af_ops->net_frag_header_len;
	}

J
John Heffner 已提交
1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486
	/* Clamp it (mss_clamp does not include tcp options) */
	if (mss_now > tp->rx_opt.mss_clamp)
		mss_now = tp->rx_opt.mss_clamp;

	/* Now subtract optional transport overhead */
	mss_now -= icsk->icsk_ext_hdr_len;

	/* Then reserve room for full set of TCP options and 8 bytes of data */
	if (mss_now < 48)
		mss_now = 48;
	return mss_now;
}

1487 1488 1489 1490 1491 1492 1493 1494
/* Calculate MSS. Not accounting for SACKs here.  */
int tcp_mtu_to_mss(struct sock *sk, int pmtu)
{
	/* Subtract TCP options size, not including SACKs */
	return __tcp_mtu_to_mss(sk, pmtu) -
	       (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
}

J
John Heffner 已提交
1495
/* Inverse of above */
1496
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1497
{
1498 1499
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1500 1501 1502 1503 1504 1505 1506
	int mtu;

	mtu = mss +
	      tp->tcp_header_len +
	      icsk->icsk_ext_hdr_len +
	      icsk->icsk_af_ops->net_header_len;

1507 1508 1509 1510 1511 1512 1513
	/* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
	if (icsk->icsk_af_ops->net_frag_header_len) {
		const struct dst_entry *dst = __sk_dst_get(sk);

		if (dst && dst_allfrag(dst))
			mtu += icsk->icsk_af_ops->net_frag_header_len;
	}
J
John Heffner 已提交
1514 1515
	return mtu;
}
1516
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1517

1518
/* MTU probing init per socket */
J
John Heffner 已提交
1519 1520 1521 1522
void tcp_mtup_init(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
F
Fan Du 已提交
1523
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1524

F
Fan Du 已提交
1525
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1526
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1527
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1528
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1529
	icsk->icsk_mtup.probe_size = 0;
1530
	if (icsk->icsk_mtup.enabled)
1531
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
J
John Heffner 已提交
1532
}
E
Eric Dumazet 已提交
1533
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1534

L
Linus Torvalds 已提交
1535 1536 1537 1538 1539 1540
/* This function synchronize snd mss to current pmtu/exthdr set.

   tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
   for TCP options, but includes only bare TCP header.

   tp->rx_opt.mss_clamp is mss negotiated at connection setup.
S
Stephen Hemminger 已提交
1541
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1542 1543
   It also does not include TCP options.

1544
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1545 1546 1547 1548 1549 1550 1551 1552 1553

   tp->mss_cache is current effective sending mss, including
   all tcp options except for SACKs. It is evaluated,
   taking into account current pmtu, but never exceeds
   tp->rx_opt.mss_clamp.

   NOTE1. rfc1122 clearly states that advertised MSS
   DOES NOT include either tcp or ip options.

1554 1555
   NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
   are READ ONLY outside this function.		--ANK (980731)
L
Linus Torvalds 已提交
1556 1557 1558 1559
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1560
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1561
	int mss_now;
L
Linus Torvalds 已提交
1562

J
John Heffner 已提交
1563 1564
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1565

J
John Heffner 已提交
1566
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1567
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1568 1569

	/* And store cached results */
1570
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1571 1572
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1573
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1574 1575 1576

	return mss_now;
}
E
Eric Dumazet 已提交
1577
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1578 1579 1580 1581

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1582
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1583
{
1584 1585
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1586
	u32 mss_now;
1587
	unsigned int header_len;
A
Adam Langley 已提交
1588 1589
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1590 1591 1592

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1593 1594
	if (dst) {
		u32 mtu = dst_mtu(dst);
1595
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1596 1597 1598
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1599 1600 1601 1602 1603 1604 1605 1606 1607 1608
	header_len = tcp_established_options(sk, NULL, &opts, &md5) +
		     sizeof(struct tcphdr);
	/* The mss_cache is sized based on tp->tcp_header_len, which assumes
	 * some common options. If this is an odd packet (because we have SACK
	 * blocks etc) then our calculated header_len will be different, and
	 * we have to adjust mss_now correspondingly */
	if (header_len != tp->tcp_header_len) {
		int delta = (int) header_len - tp->tcp_header_len;
		mss_now -= delta;
	}
1609

L
Linus Torvalds 已提交
1610 1611 1612
	return mss_now;
}

1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631
/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
 * As additional protections, we do not touch cwnd in retransmission phases,
 * and if application hit its sndbuf limit recently.
 */
static void tcp_cwnd_application_limited(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
	    sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
		/* Limited by application or receiver window. */
		u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
		u32 win_used = max(tp->snd_cwnd_used, init_win);
		if (win_used < tp->snd_cwnd) {
			tp->snd_ssthresh = tcp_current_ssthresh(sk);
			tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
		}
		tp->snd_cwnd_used = 0;
	}
1632
	tp->snd_cwnd_stamp = tcp_jiffies32;
1633 1634
}

1635
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1636
{
1637
	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1638
	struct tcp_sock *tp = tcp_sk(sk);
1639

1640 1641 1642 1643 1644 1645 1646 1647 1648
	/* Track the maximum number of outstanding packets in each
	 * window, and remember whether we were cwnd-limited then.
	 */
	if (!before(tp->snd_una, tp->max_packets_seq) ||
	    tp->packets_out > tp->max_packets_out) {
		tp->max_packets_out = tp->packets_out;
		tp->max_packets_seq = tp->snd_nxt;
		tp->is_cwnd_limited = is_cwnd_limited;
	}
1649

1650
	if (tcp_is_cwnd_limited(sk)) {
1651 1652
		/* Network is feed fully. */
		tp->snd_cwnd_used = 0;
1653
		tp->snd_cwnd_stamp = tcp_jiffies32;
1654 1655 1656 1657 1658
	} else {
		/* Network starves. */
		if (tp->packets_out > tp->snd_cwnd_used)
			tp->snd_cwnd_used = tp->packets_out;

1659
		if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
1660
		    (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1661
		    !ca_ops->cong_control)
1662
			tcp_cwnd_application_limited(sk);
1663 1664 1665 1666 1667

		/* The following conditions together indicate the starvation
		 * is caused by insufficient sender buffer:
		 * 1) just sent some data (see tcp_write_xmit)
		 * 2) not cwnd limited (this else condition)
1668
		 * 3) no more data to send (tcp_write_queue_empty())
1669 1670
		 * 4) application is hitting buffer limit (SOCK_NOSPACE)
		 */
1671
		if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1672 1673 1674
		    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
		    (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
			tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1675 1676 1677
	}
}

E
Eric Dumazet 已提交
1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691
/* Minshall's variant of the Nagle send check. */
static bool tcp_minshall_check(const struct tcp_sock *tp)
{
	return after(tp->snd_sml, tp->snd_una) &&
		!after(tp->snd_sml, tp->snd_nxt);
}

/* Update snd_sml if this skb is under mss
 * Note that a TSO packet might end with a sub-mss segment
 * The test is really :
 * if ((skb->len % mss) != 0)
 *        tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
 * But we can avoid doing the divide again given we already have
 *  skb_pcount = skb->len / mss_now
1692
 */
E
Eric Dumazet 已提交
1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707
static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
				const struct sk_buff *skb)
{
	if (skb->len < tcp_skb_pcount(skb) * mss_now)
		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
}

/* Return false, if packet can be sent now without violation Nagle's rules:
 * 1. It is full sized. (provided by caller in %partial bool)
 * 2. Or it contains FIN. (already checked by caller)
 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
 *    With Minshall's modification: all sent small packets are ACKed.
 */
static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1708
			    int nonagle)
E
Eric Dumazet 已提交
1709 1710 1711 1712 1713
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1714 1715 1716 1717

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1718 1719
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1720 1721 1722
{
	u32 bytes, segs;

1723
	bytes = min(sk->sk_pacing_rate >> sk->sk_pacing_shift,
E
Eric Dumazet 已提交
1724 1725 1726 1727 1728 1729 1730
		    sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);

	/* Goal is to send at least one packet per ms,
	 * not one big TSO packet every 100 ms.
	 * This preserves ACK clocking and is consistent
	 * with tcp_tso_should_defer() heuristic.
	 */
1731
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1732 1733 1734

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1735
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1736

1737 1738 1739 1740 1741 1742 1743 1744
/* Return the number of segments we want in the skb we are transmitting.
 * See if congestion control module wants to decide; otherwise, autosize.
 */
static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
{
	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
	u32 tso_segs = ca_ops->tso_segs_goal ? ca_ops->tso_segs_goal(sk) : 0;

1745
	return tso_segs ? :
1746 1747
		tcp_tso_autosize(sk, mss_now,
				 sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
1748 1749
}

E
Eric Dumazet 已提交
1750 1751 1752 1753 1754 1755
/* Returns the portion of skb which can be sent right away */
static unsigned int tcp_mss_split_point(const struct sock *sk,
					const struct sk_buff *skb,
					unsigned int mss_now,
					unsigned int max_segs,
					int nonagle)
1756
{
1757
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1758
	u32 partial, needed, window, max_len;
1759

1760
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1761
	max_len = mss_now * max_segs;
1762

1763 1764
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1765

1766 1767
	needed = min(skb->len, window);

1768 1769
	if (max_len <= needed)
		return max_len;
1770

E
Eric Dumazet 已提交
1771 1772 1773 1774 1775
	partial = needed % mss_now;
	/* If last segment is not a full MSS, check if Nagle rules allow us
	 * to include this last segment in this skb.
	 * Otherwise, we'll split the skb at last MSS boundary
	 */
1776
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1777 1778 1779
		return needed - partial;

	return needed;
1780 1781 1782 1783 1784
}

/* Can at least one segment of SKB be sent right now, according to the
 * congestion window rules?  If so, return how many segments are allowed.
 */
1785 1786
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1787
{
E
Eric Dumazet 已提交
1788
	u32 in_flight, cwnd, halfcwnd;
1789 1790

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1791 1792
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1793 1794 1795 1796
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1797 1798
	if (in_flight >= cwnd)
		return 0;
1799

E
Eric Dumazet 已提交
1800 1801 1802 1803 1804
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1805 1806
}

1807
/* Initialize TSO state of a skb.
1808
 * This must be invoked the first time we consider transmitting
1809 1810
 * SKB onto the wire.
 */
1811
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1812 1813 1814
{
	int tso_segs = tcp_skb_pcount(skb);

1815
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1816
		tcp_set_skb_tso_segs(skb, mss_now);
1817 1818 1819 1820 1821 1822
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1823
/* Return true if the Nagle test allows this packet to be
1824 1825
 * sent now.
 */
E
Eric Dumazet 已提交
1826 1827
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1828 1829 1830 1831 1832 1833 1834 1835
{
	/* Nagle rule does not apply to frames, which sit in the middle of the
	 * write_queue (they have no chances to get new data).
	 *
	 * This is implemented in the callers, where they modify the 'nonagle'
	 * argument based upon the location of SKB in the send queue.
	 */
	if (nonagle & TCP_NAGLE_PUSH)
E
Eric Dumazet 已提交
1836
		return true;
1837

Y
Yuchung Cheng 已提交
1838 1839
	/* Don't use the nagle rule for urgent data (or for the final FIN). */
	if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
E
Eric Dumazet 已提交
1840
		return true;
1841

1842
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1843
		return true;
1844

E
Eric Dumazet 已提交
1845
	return false;
1846 1847 1848
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1849 1850 1851
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1852 1853 1854 1855 1856 1857
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

	if (skb->len > cur_mss)
		end_seq = TCP_SKB_CB(skb)->seq + cur_mss;

1858
	return !after(end_seq, tcp_wnd_end(tp));
1859 1860 1861 1862 1863 1864 1865 1866 1867
}

/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
 * which is put after SKB on the list.  It is very much like
 * tcp_fragment() except that it may make several kinds of assumptions
 * in order to speed up the splitting operation.  In particular, we
 * know that all the data is in scatter-gather pages, and that the
 * packet has never been sent out before (and thus is not cloned).
 */
1868 1869
static int tso_fragment(struct sock *sk, enum tcp_queue tcp_queue,
			struct sk_buff *skb, unsigned int len,
1870
			unsigned int mss_now, gfp_t gfp)
1871 1872 1873
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1874
	u8 flags;
1875 1876

	/* All of a TSO frame must be composed of paged data.  */
1877
	if (skb->len != skb->data_len)
1878
		return tcp_fragment(sk, tcp_queue, skb, len, mss_now, gfp);
1879

1880
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1881
	if (unlikely(!buff))
1882 1883
		return -ENOMEM;

1884 1885
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1886
	buff->truesize += nlen;
1887 1888 1889 1890 1891 1892 1893 1894
	skb->truesize -= nlen;

	/* Correct the sequence numbers. */
	TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
	TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;

	/* PSH and FIN should only be set in the second packet. */
E
Eric Dumazet 已提交
1895 1896 1897
	flags = TCP_SKB_CB(skb)->tcp_flags;
	TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
	TCP_SKB_CB(buff)->tcp_flags = flags;
1898 1899 1900 1901

	/* This packet was never sent out yet, so no SACK bits. */
	TCP_SKB_CB(buff)->sacked = 0;

1902 1903
	tcp_skb_fragment_eor(skb, buff);

1904
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1905
	skb_split(skb, buff, len);
1906
	tcp_fragment_tstamp(skb, buff);
1907 1908

	/* Fix up tso_factor for both original and new SKB.  */
1909 1910
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1911 1912

	/* Link BUFF into the send queue. */
1913
	__skb_header_release(buff);
1914
	tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1915 1916 1917 1918 1919 1920 1921 1922 1923

	return 0;
}

/* Try to defer sending, if possible, in order to minimize the amount
 * of TSO splitting we do.  View it as a kind of TSO Nagle test.
 *
 * This algorithm is from John Heffner.
 */
1924
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1925
				 bool *is_cwnd_limited, u32 max_segs)
1926
{
1927
	const struct inet_connection_sock *icsk = inet_csk(sk);
1928 1929 1930
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *head;
1931
	int win_divisor;
1932

E
Eric Dumazet 已提交
1933
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1934
		goto send_now;
1935

1936
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1937 1938
		goto send_now;

E
Eric Dumazet 已提交
1939 1940 1941
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
1942
	if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
J
John Heffner 已提交
1943
		goto send_now;
1944

1945 1946
	in_flight = tcp_packets_in_flight(tp);

1947
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1948

1949
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1950 1951 1952 1953 1954 1955

	/* From in_flight test above, we know that cwnd > in_flight.  */
	cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;

	limit = min(send_win, cong_win);

1956
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1957
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1958
		goto send_now;
1959

1960 1961 1962 1963
	/* Middle in queue won't get any more data, full sendable already? */
	if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
		goto send_now;

1964
	win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
1965
	if (win_divisor) {
1966 1967 1968 1969 1970
		u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);

		/* If at least some fraction of a window is available,
		 * just use it.
		 */
1971
		chunk /= win_divisor;
1972
		if (limit >= chunk)
J
John Heffner 已提交
1973
			goto send_now;
1974 1975 1976 1977 1978 1979
	} else {
		/* Different approach, try not to defer past a single
		 * ACK.  Receiver should ACK every other full sized
		 * frame, so if we have space for more than 3 frames
		 * then send now.
		 */
1980
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1981
			goto send_now;
1982 1983
	}

1984 1985 1986 1987
	/* TODO : use tsorted_sent_queue ? */
	head = tcp_rtx_queue_head(sk);
	if (!head)
		goto send_now;
1988
	age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
1989 1990 1991 1992
	/* If next ACK is likely to come too late (half srtt), do not defer */
	if (age < (tp->srtt_us >> 4))
		goto send_now;

E
Eric Dumazet 已提交
1993
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1994

1995
	if (cong_win < send_win && cong_win <= skb->len)
1996 1997
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1998
	return true;
J
John Heffner 已提交
1999 2000

send_now:
E
Eric Dumazet 已提交
2001
	return false;
2002 2003
}

2004 2005 2006 2007 2008 2009 2010 2011 2012
static inline void tcp_mtu_check_reprobe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	struct net *net = sock_net(sk);
	u32 interval;
	s32 delta;

	interval = net->ipv4.sysctl_tcp_probe_interval;
2013
	delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024
	if (unlikely(delta >= interval * HZ)) {
		int mss = tcp_current_mss(sk);

		/* Update current search range */
		icsk->icsk_mtup.probe_size = 0;
		icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
			sizeof(struct tcphdr) +
			icsk->icsk_af_ops->net_header_len;
		icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);

		/* Update probe time stamp */
2025
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2026 2027 2028
	}
}

J
John Heffner 已提交
2029
/* Create a new MTU probe if we are ready.
2030 2031 2032 2033
 * MTU probe is regularly attempting to increase the path MTU by
 * deliberately sending larger packets.  This discovers routing
 * changes resulting in larger path MTUs.
 *
J
John Heffner 已提交
2034 2035
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
2036 2037
 *         -1 otherwise
 */
J
John Heffner 已提交
2038 2039 2040
static int tcp_mtu_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
2041
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2042
	struct sk_buff *skb, *nskb, *next;
2043
	struct net *net = sock_net(sk);
J
John Heffner 已提交
2044
	int probe_size;
2045
	int size_needed;
2046
	int copy, len;
J
John Heffner 已提交
2047
	int mss_now;
2048
	int interval;
J
John Heffner 已提交
2049 2050 2051 2052

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
2053 2054 2055 2056 2057 2058 2059
	 * not SACKing (the variable headers throw things off)
	 */
	if (likely(!icsk->icsk_mtup.enabled ||
		   icsk->icsk_mtup.probe_size ||
		   inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
		   tp->snd_cwnd < 11 ||
		   tp->rx_opt.num_sacks || tp->rx_opt.dsack))
J
John Heffner 已提交
2060 2061
		return -1;

2062 2063 2064 2065
	/* Use binary search for probe_size between tcp_mss_base,
	 * and current mss_clamp. if (search_high - search_low)
	 * smaller than a threshold, backoff from probing.
	 */
I
Ilpo Järvinen 已提交
2066
	mss_now = tcp_current_mss(sk);
2067 2068
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
2069
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2070
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2071 2072 2073 2074
	/* When misfortune happens, we are reprobing actively,
	 * and then reprobe timer has expired. We stick with current
	 * probing process by not resetting search range to its orignal.
	 */
2075
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2076 2077 2078 2079 2080
		interval < net->ipv4.sysctl_tcp_probe_threshold) {
		/* Check whether enough time has elaplased for
		 * another round of probing.
		 */
		tcp_mtu_check_reprobe(sk);
J
John Heffner 已提交
2081 2082 2083 2084
		return -1;
	}

	/* Have enough data in the send queue to probe? */
2085
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
2086 2087
		return -1;

2088 2089
	if (tp->snd_wnd < size_needed)
		return -1;
2090
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2091
		return 0;
J
John Heffner 已提交
2092

2093 2094 2095
	/* Do we need to wait to drain cwnd? With none in flight, don't stall */
	if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
		if (!tcp_packets_in_flight(tp))
J
John Heffner 已提交
2096 2097 2098 2099 2100 2101
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
2102
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2103
	if (!nskb)
J
John Heffner 已提交
2104
		return -1;
2105 2106
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2107

2108
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2109 2110 2111

	TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
	TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
E
Eric Dumazet 已提交
2112
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2113 2114
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2115
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2116

2117
	tcp_insert_write_queue_before(nskb, skb, sk);
2118
	tcp_highest_sack_replace(sk, skb, nskb);
2119

J
John Heffner 已提交
2120
	len = 0;
2121
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2122
		copy = min_t(int, skb->len, probe_size - len);
2123
		if (nskb->ip_summed) {
J
John Heffner 已提交
2124
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2125 2126 2127 2128 2129 2130
		} else {
			__wsum csum = skb_copy_and_csum_bits(skb, 0,
							     skb_put(nskb, copy),
							     copy, 0);
			nskb->csum = csum_block_add(nskb->csum, csum, len);
		}
J
John Heffner 已提交
2131 2132 2133 2134

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2135
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2136
			tcp_unlink_write_queue(skb, sk);
2137
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2138
		} else {
E
Eric Dumazet 已提交
2139
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2140
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2141 2142
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2143
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2144 2145
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2146 2147
			} else {
				__pskb_trim_head(skb, copy);
2148
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2149 2150 2151 2152 2153
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2154 2155 2156

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2157
	}
2158
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2159 2160

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2161 2162
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2163 2164
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2165
		 * effectively two packets. */
J
John Heffner 已提交
2166
		tp->snd_cwnd--;
2167
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2168 2169

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2170 2171
		tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
		tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
J
John Heffner 已提交
2172 2173 2174 2175 2176 2177 2178

		return 1;
	}

	return -1;
}

2179 2180 2181 2182 2183 2184
static bool tcp_pacing_check(const struct sock *sk)
{
	return tcp_needs_internal_pacing(sk) &&
	       hrtimer_active(&tcp_sk(sk)->pacing_timer);
}

2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200
/* TCP Small Queues :
 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
 * (These limits are doubled for retransmits)
 * This allows for :
 *  - better RTT estimation and ACK scheduling
 *  - faster recovery
 *  - high rates
 * Alas, some drivers / subsystems require a fair amount
 * of queued bytes to ensure line rate.
 * One example is wifi aggregation (802.11 AMPDU)
 */
static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
				  unsigned int factor)
{
	unsigned int limit;

2201
	limit = max(2 * skb->truesize, sk->sk_pacing_rate >> sk->sk_pacing_shift);
2202 2203
	limit = min_t(u32, limit,
		      sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
2204 2205
	limit <<= factor;

2206
	if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2207
		/* Always send skb if rtx queue is empty.
2208 2209 2210 2211
		 * No need to wait for TX completion to call us back,
		 * after softirq/tasklet schedule.
		 * This helps when TX completions are delayed too much.
		 */
2212
		if (tcp_rtx_queue_empty(sk))
2213 2214
			return false;

2215
		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2216 2217 2218 2219 2220
		/* It is possible TX completion already happened
		 * before we set TSQ_THROTTLED, so we must
		 * test again the condition.
		 */
		smp_mb__after_atomic();
2221
		if (refcount_read(&sk->sk_wmem_alloc) > limit)
2222 2223 2224 2225 2226
			return true;
	}
	return false;
}

2227 2228
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
2229
	const u32 now = tcp_jiffies32;
2230
	enum tcp_chrono old = tp->chrono_type;
2231

2232 2233
	if (old > TCP_CHRONO_UNSPEC)
		tp->chrono_stat[old - 1] += now - tp->chrono_start;
2234 2235 2236 2237 2238 2239 2240 2241 2242
	tp->chrono_start = now;
	tp->chrono_type = new;
}

void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
{
	struct tcp_sock *tp = tcp_sk(sk);

	/* If there are multiple conditions worthy of tracking in a
2243 2244
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2245 2246 2247 2248 2249 2250 2251 2252 2253 2254
	 * starts happening, stop the previous chrono and start a new one.
	 */
	if (type > tp->chrono_type)
		tcp_chrono_set(tp, type);
}

void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
{
	struct tcp_sock *tp = tcp_sk(sk);

2255 2256 2257 2258 2259 2260 2261 2262

	/* There are multiple conditions worthy of tracking in a
	 * chronograph, so that the highest priority enum takes
	 * precedence over the other conditions (see tcp_chrono_start).
	 * If a condition stops, we only stop chrono tracking if
	 * it's the "most interesting" or current chrono we are
	 * tracking and starts busy chrono if we have pending data.
	 */
2263
	if (tcp_rtx_and_write_queues_empty(sk))
2264 2265 2266
		tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
	else if (type == tp->chrono_type)
		tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2267 2268
}

L
Linus Torvalds 已提交
2269 2270 2271 2272
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2273 2274 2275 2276
 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
 * account rare use of URG, this is not a big flaw.
 *
N
Nandita Dukkipati 已提交
2277 2278 2279
 * Send at most one packet when push_one > 0. Temporarily ignore
 * cwnd limit to force at most one packet out when push_one == 2.

E
Eric Dumazet 已提交
2280 2281
 * Returns true, if no segments are in flight and we have queued segments,
 * but cannot send anything now because of SWS or another problem.
L
Linus Torvalds 已提交
2282
 */
E
Eric Dumazet 已提交
2283 2284
static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp)
L
Linus Torvalds 已提交
2285 2286
{
	struct tcp_sock *tp = tcp_sk(sk);
2287
	struct sk_buff *skb;
2288 2289
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2290
	int result;
2291
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2292
	u32 max_segs;
L
Linus Torvalds 已提交
2293

2294
	sent_pkts = 0;
J
John Heffner 已提交
2295

2296
	tcp_mstamp_refresh(tp);
2297 2298 2299 2300
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2301
			return false;
2302 2303 2304
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2305 2306
	}

2307
	max_segs = tcp_tso_segs(sk, mss_now);
2308
	while ((skb = tcp_send_head(sk))) {
2309 2310
		unsigned int limit;

2311 2312 2313
		if (tcp_pacing_check(sk))
			break;

2314
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2315
		BUG_ON(!tso_segs);
2316

2317
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2318
			/* "skb_mstamp" is used as a start point for the retransmit timer */
2319
			tcp_update_skb_after_send(tp, skb);
2320
			goto repair; /* Skip network transmission */
2321
		}
2322

2323
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2324 2325 2326 2327 2328 2329 2330
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2331

2332 2333
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2334
			break;
2335
		}
2336

2337
		if (tso_segs == 1) {
2338 2339 2340 2341 2342
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2343
			if (!push_one &&
E
Eric Dumazet 已提交
2344 2345
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2346 2347
				break;
		}
2348

E
Eric Dumazet 已提交
2349
		limit = mss_now;
2350
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2351 2352 2353 2354 2355 2356 2357
			limit = tcp_mss_split_point(sk, skb, mss_now,
						    min_t(unsigned int,
							  cwnd_quota,
							  max_segs),
						    nonagle);

		if (skb->len > limit &&
2358 2359
		    unlikely(tso_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
					  skb, limit, mss_now, gfp)))
E
Eric Dumazet 已提交
2360 2361
			break;

2362 2363
		if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
			clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
2364 2365
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2366

2367
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2368
			break;
L
Linus Torvalds 已提交
2369

2370
repair:
2371 2372 2373
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2374
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2375

2376
		tcp_minshall_update(tp, mss_now, skb);
2377
		sent_pkts += tcp_skb_pcount(skb);
2378 2379 2380

		if (push_one)
			break;
2381
	}
L
Linus Torvalds 已提交
2382

2383 2384 2385 2386 2387
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2388
	if (likely(sent_pkts)) {
2389 2390
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2391 2392 2393

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
2394
			tcp_schedule_loss_probe(sk, false);
2395
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2396
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2397
		return false;
L
Linus Torvalds 已提交
2398
	}
2399
	return !tp->packets_out && !tcp_write_queue_empty(sk);
N
Nandita Dukkipati 已提交
2400 2401
}

2402
bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
N
Nandita Dukkipati 已提交
2403 2404 2405
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
2406
	u32 timeout, rto_delta_us;
2407
	int early_retrans;
N
Nandita Dukkipati 已提交
2408 2409 2410 2411

	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
2412
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2413 2414
		return false;

2415
	early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
N
Nandita Dukkipati 已提交
2416
	/* Schedule a loss probe in 2*RTT for SACK capable connections
N
Neal Cardwell 已提交
2417
	 * not in loss recovery, that are either limited by cwnd or application.
N
Nandita Dukkipati 已提交
2418
	 */
2419
	if ((early_retrans != 3 && early_retrans != 4) ||
Y
Yuchung Cheng 已提交
2420
	    !tp->packets_out || !tcp_is_sack(tp) ||
N
Neal Cardwell 已提交
2421 2422
	    (icsk->icsk_ca_state != TCP_CA_Open &&
	     icsk->icsk_ca_state != TCP_CA_CWR))
N
Nandita Dukkipati 已提交
2423 2424
		return false;

2425
	/* Probe timeout is 2*rtt. Add minimum RTO to account
2426 2427
	 * for delayed ack when there's one outstanding packet. If no RTT
	 * sample is available then probe after TCP_TIMEOUT_INIT.
N
Nandita Dukkipati 已提交
2428
	 */
2429 2430 2431 2432 2433 2434 2435 2436 2437
	if (tp->srtt_us) {
		timeout = usecs_to_jiffies(tp->srtt_us >> 2);
		if (tp->packets_out == 1)
			timeout += TCP_RTO_MIN;
		else
			timeout += TCP_TIMEOUT_MIN;
	} else {
		timeout = TCP_TIMEOUT_INIT;
	}
N
Nandita Dukkipati 已提交
2438

2439
	/* If the RTO formula yields an earlier time, then use that time. */
2440 2441 2442
	rto_delta_us = advancing_rto ?
			jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
			tcp_rto_delta_us(sk);  /* How far in future is RTO? */
2443 2444
	if (rto_delta_us > 0)
		timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
N
Nandita Dukkipati 已提交
2445 2446 2447 2448 2449 2450

	inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
				  TCP_RTO_MAX);
	return true;
}

2451 2452 2453 2454 2455 2456 2457
/* Thanks to skb fast clones, we can detect if a prior transmit of
 * a packet is still in a qdisc or driver queue.
 * In this case, there is very little point doing a retransmit !
 */
static bool skb_still_in_host_queue(const struct sock *sk,
				    const struct sk_buff *skb)
{
2458
	if (unlikely(skb_fclone_busy(sk, skb))) {
2459 2460
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2461 2462 2463 2464 2465
		return true;
	}
	return false;
}

2466
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2467 2468 2469 2470
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2471
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2472 2473 2474 2475
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2476
	skb = tcp_send_head(sk);
2477 2478 2479 2480 2481 2482
	if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
		pcount = tp->packets_out;
		tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
		if (tp->packets_out > pcount)
			goto probe_sent;
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2483
	}
2484
	skb = skb_rb_last(&sk->tcp_rtx_queue);
N
Nandita Dukkipati 已提交
2485

N
Nandita Dukkipati 已提交
2486 2487 2488 2489
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2490 2491 2492 2493
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2494 2495 2496
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2497 2498 2499 2500 2501
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2502 2503
		if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
					  (pcount - 1) * mss, mss,
2504
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2505
			goto rearm_timer;
2506
		skb = skb_rb_next(skb);
N
Nandita Dukkipati 已提交
2507 2508 2509 2510 2511
	}

	if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
		goto rearm_timer;

2512
	if (__tcp_retransmit_skb(sk, skb, 1))
2513
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2514

N
Nandita Dukkipati 已提交
2515
	/* Record snd_nxt for loss detection. */
2516
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2517

2518
probe_sent:
2519
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2520 2521
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2522
rearm_timer:
2523
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2524 2525
}

2526 2527 2528 2529
/* Push out any pending frames which were held back due to
 * TCP_CORK or attempt at coalescing tiny packets.
 * The socket must be locked by the caller.
 */
2530 2531
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2532
{
2533 2534 2535 2536 2537 2538 2539
	/* If we are closed, the bytes will have to remain here.
	 * In time closedown will finish, we empty the write queue and
	 * all will be happy.
	 */
	if (unlikely(sk->sk_state == TCP_CLOSE))
		return;

2540
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2541
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2542
		tcp_check_probe_timer(sk);
2543 2544
}

2545 2546 2547 2548 2549
/* Send _single_ skb sitting at the send head. This function requires
 * true push pending frames to setup probe timer etc.
 */
void tcp_push_one(struct sock *sk, unsigned int mss_now)
{
2550
	struct sk_buff *skb = tcp_send_head(sk);
2551 2552 2553

	BUG_ON(!skb || skb->len < mss_now);

2554
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2555 2556
}

L
Linus Torvalds 已提交
2557 2558
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2559
 *
L
Linus Torvalds 已提交
2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577
 * 1. The window can never be shrunk once it is offered (RFC 793)
 * 2. We limit memory per socket
 *
 * RFC 1122:
 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
 *  RECV.NEXT + RCV.WIN fixed until:
 *  RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
 *
 * i.e. don't raise the right edge of the window until you can raise
 * it at least MSS bytes.
 *
 * Unfortunately, the recommended algorithm breaks header prediction,
 * since header prediction assumes th->window stays fixed.
 *
 * Strictly speaking, keeping th->window fixed violates the receiver
 * side SWS prevention criteria. The problem is that under this rule
 * a stream of single byte packets will cause the right side of the
 * window to always advance by a single byte.
2578
 *
L
Linus Torvalds 已提交
2579 2580
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2581
 *
L
Linus Torvalds 已提交
2582
 * BSD seems to make the following compromise:
2583
 *
L
Linus Torvalds 已提交
2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610
 *	If the free space is less than the 1/4 of the maximum
 *	space available and the free space is less than 1/2 mss,
 *	then set the window to 0.
 *	[ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
 *	Otherwise, just prevent the window from shrinking
 *	and from being larger than the largest representable value.
 *
 * This prevents incremental opening of the window in the regime
 * where TCP is limited by the speed of the reader side taking
 * data out of the TCP receive queue. It does nothing about
 * those cases where the window is constrained on the sender side
 * because the pipeline is full.
 *
 * BSD also seems to "accidentally" limit itself to windows that are a
 * multiple of MSS, at least until the free space gets quite small.
 * This would appear to be a side effect of the mbuf implementation.
 * Combining these two algorithms results in the observed behavior
 * of having a fixed window size at almost all times.
 *
 * Below we obtain similar behavior by forcing the offered window to
 * a multiple of the mss when it is feasible to do so.
 *
 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
 * Regular options like TIMESTAMP are taken into account.
 */
u32 __tcp_select_window(struct sock *sk)
{
2611
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2612
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2613
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2614 2615 2616 2617 2618
	 * here.  I don't know if the value based on our guesses
	 * of peer's MSS is better for the performance.  It's more correct
	 * but may be worse for the performance because of rcv_mss
	 * fluctuations.  --SAW  1998/11/1
	 */
2619
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2620
	int free_space = tcp_space(sk);
2621 2622
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2623 2624
	int window;

2625
	if (unlikely(mss > full_space)) {
2626
		mss = full_space;
2627 2628 2629
		if (mss <= 0)
			return 0;
	}
2630
	if (free_space < (full_space >> 1)) {
2631
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2632

2633
		if (tcp_under_memory_pressure(sk))
2634 2635
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2636

2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649
		/* free_space might become our new window, make sure we don't
		 * increase it due to wscale.
		 */
		free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);

		/* if free space is less than mss estimate, or is below 1/16th
		 * of the maximum allowed, try to move to zero-window, else
		 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
		 * new incoming data is dropped due to memory limits.
		 * With large window, mss test triggers way too late in order
		 * to announce zero window in time before rmem limit kicks in.
		 */
		if (free_space < (allowed_space >> 4) || free_space < mss)
L
Linus Torvalds 已提交
2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665
			return 0;
	}

	if (free_space > tp->rcv_ssthresh)
		free_space = tp->rcv_ssthresh;

	/* Don't do rounding if we are using window scaling, since the
	 * scaled window will not line up with the MSS boundary anyway.
	 */
	if (tp->rx_opt.rcv_wscale) {
		window = free_space;

		/* Advertise enough space so that it won't get scaled away.
		 * Import case: prevent zero window announcement if
		 * 1<<rcv_wscale > mss.
		 */
2666
		window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
L
Linus Torvalds 已提交
2667
	} else {
2668
		window = tp->rcv_wnd;
L
Linus Torvalds 已提交
2669 2670 2671 2672 2673 2674 2675 2676 2677
		/* Get the largest window that is a nice multiple of mss.
		 * Window clamp already applied above.
		 * If our current window offering is within 1 mss of the
		 * free space we just keep it. This prevents the divide
		 * and multiply from happening most of the time.
		 * We also don't do any window rounding when the free space
		 * is too small.
		 */
		if (window <= free_space - mss || window > free_space)
2678
			window = rounddown(free_space, mss);
2679
		else if (mss == full_space &&
2680
			 free_space > window + (full_space >> 1))
2681
			window = free_space;
L
Linus Torvalds 已提交
2682 2683 2684 2685 2686
	}

	return window;
}

2687 2688
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2689
{
2690 2691 2692
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2693 2694
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2695
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2696
		shinfo->tskey = next_shinfo->tskey;
2697 2698
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2699 2700 2701
	}
}

2702
/* Collapses two adjacent SKB's during retransmission. */
2703
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2704 2705
{
	struct tcp_sock *tp = tcp_sk(sk);
2706
	struct sk_buff *next_skb = skb_rb_next(skb);
2707
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2708

2709 2710
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2711

2712
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2713

2714 2715 2716 2717 2718 2719 2720
	if (next_skb_size) {
		if (next_skb_size <= skb_availroom(skb))
			skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
				      next_skb_size);
		else if (!skb_shift(skb, next_skb, next_skb_size))
			return false;
	}
2721
	tcp_highest_sack_replace(sk, next_skb, skb);
L
Linus Torvalds 已提交
2722

2723 2724
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2725

2726 2727
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2728

2729 2730
	/* Update sequence range on original skb. */
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
L
Linus Torvalds 已提交
2731

2732
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2733
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2734 2735 2736 2737 2738

	/* All done, get rid of second SKB and account for it so
	 * packet counting does not break.
	 */
	TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2739
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2740 2741

	/* changed transmit queue under us so clear hints */
2742 2743 2744
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2745

2746 2747
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2748 2749
	tcp_skb_collapse_tstamp(skb, next_skb);

2750
	tcp_rtx_queue_unlink_and_free(next_skb, sk);
2751
	return true;
L
Linus Torvalds 已提交
2752 2753
}

2754
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2755
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2756 2757
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2758
		return false;
2759
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2760
		return false;
E
Eric Dumazet 已提交
2761
	/* Some heuristics for collapsing over SACK'd could be invented */
2762
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2763
		return false;
2764

E
Eric Dumazet 已提交
2765
	return true;
2766 2767
}

2768 2769 2770
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2771 2772 2773 2774 2775
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
				     int space)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb = to, *tmp;
E
Eric Dumazet 已提交
2776
	bool first = true;
2777

2778
	if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
2779
		return;
E
Eric Dumazet 已提交
2780
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2781 2782
		return;

2783
	skb_rbtree_walk_from_safe(skb, tmp) {
2784 2785 2786
		if (!tcp_can_collapse(sk, skb))
			break;

2787 2788 2789
		if (!tcp_skb_can_collapse_to(to))
			break;

2790 2791 2792
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2793
			first = false;
2794 2795 2796 2797 2798 2799 2800 2801 2802
			continue;
		}

		if (space < 0)
			break;

		if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
			break;

2803 2804
		if (!tcp_collapse_retrans(sk, to))
			break;
2805 2806 2807
	}
}

L
Linus Torvalds 已提交
2808 2809 2810 2811
/* This retransmits one SKB.  Policy decisions and retransmit queue
 * state updates are done by the caller.  Returns non-zero if an
 * error occurred which prevented the send.
 */
2812
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2813
{
J
John Heffner 已提交
2814
	struct inet_connection_sock *icsk = inet_csk(sk);
2815
	struct tcp_sock *tp = tcp_sk(sk);
2816
	unsigned int cur_mss;
2817 2818
	int diff, len, err;

L
Linus Torvalds 已提交
2819

2820 2821
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2822 2823
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2824
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2825
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2826
	 */
2827
	if (refcount_read(&sk->sk_wmem_alloc) >
2828 2829
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2830 2831
		return -EAGAIN;

2832 2833 2834
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2835 2836 2837 2838 2839 2840 2841
	if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
		if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
			BUG();
		if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
			return -ENOMEM;
	}

2842 2843 2844
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2845
	cur_mss = tcp_current_mss(sk);
2846

L
Linus Torvalds 已提交
2847 2848 2849 2850 2851
	/* If receiver has shrunk his window, and skb is out of
	 * new window, do not retransmit it. The exception is the
	 * case, when window is shrunk to zero. In this case
	 * our retransmit serves as a zero window probe.
	 */
2852 2853
	if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
	    TCP_SKB_CB(skb)->seq != tp->snd_una)
L
Linus Torvalds 已提交
2854 2855
		return -EAGAIN;

2856 2857
	len = cur_mss * segs;
	if (skb->len > len) {
2858 2859
		if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
				 cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2860
			return -ENOMEM; /* We'll try again later. */
2861
	} else {
2862 2863
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2864

2865 2866 2867 2868 2869 2870 2871
		diff = tcp_skb_pcount(skb);
		tcp_set_skb_tso_segs(skb, cur_mss);
		diff -= tcp_skb_pcount(skb);
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
		if (skb->len < cur_mss)
			tcp_retrans_try_collapse(sk, skb, cur_mss);
L
Linus Torvalds 已提交
2872 2873
	}

2874 2875 2876 2877
	/* RFC3168, section 6.1.1.1. ECN fallback */
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
		tcp_ecn_clear_syn(sk, skb);

2878 2879 2880 2881 2882 2883 2884
	/* Update global and local TCP statistics. */
	segs = tcp_skb_pcount(skb);
	TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
	tp->total_retrans += segs;

2885 2886 2887 2888 2889 2890
	/* make sure skb->data is aligned on arches that require it
	 * and check if ack-trimming & collapsing extended the headroom
	 * beyond what csum_start can cover.
	 */
	if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
		     skb_headroom(skb) >= 0xFFFF)) {
2891 2892
		struct sk_buff *nskb;

2893 2894 2895 2896 2897 2898
		tcp_skb_tsorted_save(skb) {
			nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
			err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
				     -ENOBUFS;
		} tcp_skb_tsorted_restore(skb);

2899
		if (!err) {
2900
			tcp_update_skb_after_send(tp, skb);
2901 2902
			tcp_rate_skb_sent(sk, skb);
		}
E
Eric Dumazet 已提交
2903
	} else {
2904
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2905
	}
2906

2907
	if (likely(!err)) {
2908
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2909
		trace_tcp_retransmit_skb(sk, skb);
2910 2911
	} else if (err != -EBUSY) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2912
	}
2913
	return err;
2914 2915
}

2916
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2917 2918
{
	struct tcp_sock *tp = tcp_sk(sk);
2919
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2920 2921 2922

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2923
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2924
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2925 2926 2927 2928 2929 2930 2931
		}
#endif
		TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
		tp->retrans_out += tcp_skb_pcount(skb);

		/* Save stamp of the first retransmit. */
		if (!tp->retrans_stamp)
E
Eric Dumazet 已提交
2932
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2933 2934

	}
Y
Yuchung Cheng 已提交
2935 2936 2937 2938

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2939 2940 2941 2942 2943 2944 2945 2946 2947 2948
	return err;
}

/* This gets called after a retransmit timeout, and the initially
 * retransmitted data is acknowledged.  It tries to continue
 * resending the rest of the retransmit queue, until either
 * we've sent it all or the congestion window limit is reached.
 */
void tcp_xmit_retransmit_queue(struct sock *sk)
{
2949
	const struct inet_connection_sock *icsk = inet_csk(sk);
2950
	struct sk_buff *skb, *rtx_head, *hole = NULL;
L
Linus Torvalds 已提交
2951
	struct tcp_sock *tp = tcp_sk(sk);
2952
	u32 max_segs;
2953
	int mib_idx;
2954

2955 2956 2957
	if (!tp->packets_out)
		return;

2958 2959
	rtx_head = tcp_rtx_queue_head(sk);
	skb = tp->retransmit_skb_hint ?: rtx_head;
2960
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2961
	skb_rbtree_walk_from(skb) {
E
Eric Dumazet 已提交
2962
		__u8 sacked;
2963
		int segs;
L
Linus Torvalds 已提交
2964

2965 2966 2967
		if (tcp_pacing_check(sk))
			break;

2968
		/* we could do better than to assign each time */
2969
		if (!hole)
2970
			tp->retransmit_skb_hint = skb;
2971

2972 2973
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2974
			return;
E
Eric Dumazet 已提交
2975
		sacked = TCP_SKB_CB(skb)->sacked;
2976 2977 2978 2979
		/* In case tcp_shift_skb_data() have aggregated large skbs,
		 * we need to make sure not sending too bigs TSO packets
		 */
		segs = min_t(int, segs, max_segs);
L
Linus Torvalds 已提交
2980

2981 2982
		if (tp->retrans_out >= tp->lost_out) {
			break;
2983
		} else if (!(sacked & TCPCB_LOST)) {
2984
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2985 2986
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2987

2988 2989 2990 2991 2992 2993
		} else {
			if (icsk->icsk_ca_state != TCP_CA_Loss)
				mib_idx = LINUX_MIB_TCPFASTRETRANS;
			else
				mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
		}
L
Linus Torvalds 已提交
2994

2995
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2996 2997
			continue;

2998 2999 3000
		if (tcp_small_queue_check(sk, skb, 1))
			return;

3001
		if (tcp_retransmit_skb(sk, skb, segs))
3002
			return;
3003

3004
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
3005

3006
		if (tcp_in_cwnd_reduction(sk))
3007 3008
			tp->prr_out += tcp_skb_pcount(skb);

3009
		if (skb == rtx_head &&
3010
		    icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3011 3012 3013
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3014 3015 3016
	}
}

3017 3018
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
3019 3020
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
3021 3022
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
3023
 */
3024
void sk_forced_mem_schedule(struct sock *sk, int size)
3025
{
3026
	int amt;
3027 3028 3029 3030 3031

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3032 3033
	sk_memory_allocated_add(sk, amt);

3034 3035
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3036 3037
}

3038 3039
/* Send a FIN. The caller locks the socket for us.
 * We should try to send a FIN packet really hard, but eventually give up.
L
Linus Torvalds 已提交
3040 3041 3042
 */
void tcp_send_fin(struct sock *sk)
{
3043
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
3044 3045
	struct tcp_sock *tp = tcp_sk(sk);

3046 3047 3048 3049
	/* Optimization, tack on the FIN if we have one skb in write queue and
	 * this skb was not yet sent, or we are under memory pressure.
	 * Note: in the latter case, FIN packet will be sent after a timeout,
	 * as TCP stack thinks it has already been transmitted.
L
Linus Torvalds 已提交
3050
	 */
3051 3052 3053 3054
	if (!tskb && tcp_under_memory_pressure(sk))
		tskb = skb_rb_last(&sk->tcp_rtx_queue);

	if (tskb) {
3055 3056 3057
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
3058
		tp->write_seq++;
3059
		if (tcp_write_queue_empty(sk)) {
3060 3061 3062 3063 3064 3065 3066 3067 3068
			/* This means tskb was already sent.
			 * Pretend we included the FIN on previous transmit.
			 * We need to set tp->snd_nxt to the value it would have
			 * if FIN had been sent. This is because retransmit path
			 * does not change tp->snd_nxt.
			 */
			tp->snd_nxt++;
			return;
		}
L
Linus Torvalds 已提交
3069
	} else {
3070 3071 3072 3073 3074
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3075
		}
3076
		INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3077
		skb_reserve(skb, MAX_TCP_HEADER);
3078
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3079
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3080
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3081
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3082 3083
		tcp_queue_skb(sk, skb);
	}
3084
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3085 3086 3087 3088 3089
}

/* We get here when a process closes a file descriptor (either due to
 * an explicit close() or as a byproduct of exit()'ing) and there
 * was unread data in the receive queue.  This behavior is recommended
3090
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3091
 */
A
Al Viro 已提交
3092
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3093 3094 3095
{
	struct sk_buff *skb;

3096 3097
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);

L
Linus Torvalds 已提交
3098 3099 3100
	/* NOTE: No TCP options attached and we never retransmit this. */
	skb = alloc_skb(MAX_TCP_HEADER, priority);
	if (!skb) {
P
Pavel Emelyanov 已提交
3101
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3102 3103 3104 3105 3106
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3107
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3108
			     TCPHDR_ACK | TCPHDR_RST);
3109
	tcp_mstamp_refresh(tcp_sk(sk));
L
Linus Torvalds 已提交
3110
	/* Send it off. */
3111
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3112
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3113 3114 3115 3116 3117

	/* skb of trace_tcp_send_reset() keeps the skb that caused RST,
	 * skb here is different to the troublesome skb, so use NULL
	 */
	trace_tcp_send_reset(sk, NULL);
L
Linus Torvalds 已提交
3118 3119
}

3120 3121
/* Send a crossed SYN-ACK during socket establishment.
 * WARNING: This routine must only be called when we have already sent
L
Linus Torvalds 已提交
3122 3123 3124 3125 3126 3127
 * a SYN packet that crossed the incoming SYN that caused this routine
 * to get called. If this assumption fails then the initial rcv_wnd
 * and rcv_wscale values will not be correct.
 */
int tcp_send_synack(struct sock *sk)
{
3128
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3129

3130
	skb = tcp_rtx_queue_head(sk);
3131
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3132
		pr_err("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3133 3134
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3135
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3136
		if (skb_cloned(skb)) {
3137 3138 3139 3140 3141
			struct sk_buff *nskb;

			tcp_skb_tsorted_save(skb) {
				nskb = skb_copy(skb, GFP_ATOMIC);
			} tcp_skb_tsorted_restore(skb);
3142
			if (!nskb)
L
Linus Torvalds 已提交
3143
				return -ENOMEM;
3144
			INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3145
			tcp_rtx_queue_unlink_and_free(skb, sk);
3146
			__skb_header_release(nskb);
3147
			tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3148 3149
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3150 3151 3152
			skb = nskb;
		}

E
Eric Dumazet 已提交
3153
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3154
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3155
	}
3156
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3157 3158
}

3159 3160 3161 3162 3163 3164 3165 3166 3167
/**
 * tcp_make_synack - Prepare a SYN-ACK.
 * sk: listener socket
 * dst: dst entry attached to the SYNACK
 * req: request_sock pointer
 *
 * Allocate one skb and build a SYNACK packet.
 * @dst is consumed : Caller should not use it again.
 */
3168
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3169
				struct request_sock *req,
3170
				struct tcp_fastopen_cookie *foc,
3171
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3172
{
3173
	struct inet_request_sock *ireq = inet_rsk(req);
3174
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3175
	struct tcp_md5sig_key *md5 = NULL;
3176 3177
	struct tcp_out_options opts;
	struct sk_buff *skb;
3178
	int tcp_header_size;
3179
	struct tcphdr *th;
3180
	int mss;
L
Linus Torvalds 已提交
3181

3182
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3183 3184
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3185
		return NULL;
3186
	}
L
Linus Torvalds 已提交
3187 3188 3189
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3190 3191
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3192
		skb_set_owner_w(skb, req_to_sk(req));
3193 3194 3195 3196 3197 3198 3199
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3200 3201 3202 3203 3204
		/* sk is a const pointer, because we want to express multiple
		 * cpu might call us concurrently.
		 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
		 */
		skb_set_owner_w(skb, (struct sock *)sk);
3205
		break;
3206
	}
3207
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3208

E
Eric Dumazet 已提交
3209
	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3210

A
Adam Langley 已提交
3211
	memset(&opts, 0, sizeof(opts));
3212 3213
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
3214
		skb->skb_mstamp = cookie_init_timestamp(req);
3215 3216
	else
#endif
3217
		skb->skb_mstamp = tcp_clock_us();
E
Eric Dumazet 已提交
3218 3219 3220

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3221
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3222
#endif
3223
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3224 3225
	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
					     foc) + sizeof(*th);
3226

3227 3228
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3229

3230
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3231 3232 3233
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3234
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3235
	th->source = htons(ireq->ir_num);
3236
	th->dest = ireq->ir_rmt_port;
3237
	skb->mark = ireq->ir_mark;
3238 3239
	skb->ip_summed = CHECKSUM_PARTIAL;
	th->seq = htonl(tcp_rsk(req)->snt_isn);
3240 3241
	/* XXX data is queued and acked as is. No buffer/window check */
	th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
L
Linus Torvalds 已提交
3242 3243

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3244
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3245
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3246
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3247
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3248 3249 3250

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3251
	if (md5)
3252
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3253
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3254
	rcu_read_unlock();
3255 3256
#endif

3257
	/* Do not fool tcpdump (if any), clean our debris */
T
Thomas Gleixner 已提交
3258
	skb->tstamp = 0;
L
Linus Torvalds 已提交
3259 3260
	return skb;
}
E
Eric Dumazet 已提交
3261
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3262

3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281
static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	const struct tcp_congestion_ops *ca;
	u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);

	if (ca_key == TCP_CA_UNSPEC)
		return;

	rcu_read_lock();
	ca = tcp_ca_find_key(ca_key);
	if (likely(ca && try_module_get(ca->owner))) {
		module_put(icsk->icsk_ca_ops->owner);
		icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
		icsk->icsk_ca_ops = ca;
	}
	rcu_read_unlock();
}

3282
/* Do all connect socket setups that can be done AF independent. */
3283
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3284
{
3285
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3286 3287
	struct tcp_sock *tp = tcp_sk(sk);
	__u8 rcv_wscale;
3288
	u32 rcv_wnd;
L
Linus Torvalds 已提交
3289 3290 3291 3292

	/* We'll fix this up when we get a response from the other end.
	 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
	 */
3293 3294 3295
	tp->tcp_header_len = sizeof(struct tcphdr);
	if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
		tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
L
Linus Torvalds 已提交
3296

3297
#ifdef CONFIG_TCP_MD5SIG
3298
	if (tp->af_specific->md5_lookup(sk, sk))
3299 3300 3301
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3302 3303 3304 3305
	/* If user gave his TCP_MAXSEG, record it to clamp */
	if (tp->rx_opt.user_mss)
		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
	tp->max_window = 0;
J
John Heffner 已提交
3306
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3307 3308
	tcp_sync_mss(sk, dst_mtu(dst));

3309 3310
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3311 3312
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
E
Eric Dumazet 已提交
3313
	tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3314

L
Linus Torvalds 已提交
3315 3316
	tcp_initialize_rcv_mss(sk);

3317 3318 3319 3320 3321
	/* limit the window selection if the user enforce a smaller rx buffer */
	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
	    (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
		tp->window_clamp = tcp_full_space(sk);

3322 3323 3324 3325
	rcv_wnd = tcp_rwnd_init_bpf(sk);
	if (rcv_wnd == 0)
		rcv_wnd = dst_metric(dst, RTAX_INITRWND);

3326
	tcp_select_initial_window(sk, tcp_full_space(sk),
L
Linus Torvalds 已提交
3327 3328 3329
				  tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
				  &tp->rcv_wnd,
				  &tp->window_clamp,
3330
				  sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3331
				  &rcv_wscale,
3332
				  rcv_wnd);
L
Linus Torvalds 已提交
3333 3334 3335 3336 3337 3338 3339

	tp->rx_opt.rcv_wscale = rcv_wscale;
	tp->rcv_ssthresh = tp->rcv_wnd;

	sk->sk_err = 0;
	sock_reset_flag(sk, SOCK_DONE);
	tp->snd_wnd = 0;
3340
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3341 3342
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3343
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3344
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3345 3346 3347

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3348
	else
3349
		tp->rcv_tstamp = tcp_jiffies32;
P
Pavel Emelyanov 已提交
3350 3351
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3352

3353
	inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3354
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3355 3356 3357
	tcp_clear_retrans(tp);
}

3358 3359 3360 3361 3362 3363
static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);

	tcb->end_seq += skb->len;
3364
	__skb_header_release(skb);
3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
	tp->write_seq = tcb->end_seq;
	tp->packets_out += tcp_skb_pcount(skb);
}

/* Build and send a SYN with data and (cached) Fast Open cookie. However,
 * queue a data-only packet after the regular SYN, such that regular SYNs
 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
 * only the SYN sequence, the data are retransmitted in the first ACK.
 * If cookie is not cached or other error occurs, falls back to send a
 * regular SYN with Fast Open cookie request option.
 */
static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcp_fastopen_request *fo = tp->fastopen_req;
3382
	int space, err = 0;
3383
	struct sk_buff *syn_data;
3384

3385
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3386
	if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3387 3388 3389 3390 3391 3392
		goto fallback;

	/* MSS for SYN-data is based on cached MSS and bounded by PMTU and
	 * user-MSS. Reserve maximum option space for middleboxes that add
	 * private TCP options. The cost is reduced data space in SYN :(
	 */
E
Eric Dumazet 已提交
3393 3394
	tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);

3395
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3396 3397
		MAX_TCP_OPTION_SPACE;

3398 3399 3400 3401 3402
	space = min_t(size_t, space, fo->size);

	/* limit to order-0 allocations */
	space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));

3403
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3404
	if (!syn_data)
3405
		goto fallback;
3406 3407
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3408 3409 3410 3411
	if (space) {
		int copied = copy_from_iter(skb_put(syn_data, space), space,
					    &fo->data->msg_iter);
		if (unlikely(!copied)) {
E
Eric Dumazet 已提交
3412
			tcp_skb_tsorted_anchor_cleanup(syn_data);
3413 3414 3415 3416 3417 3418 3419
			kfree_skb(syn_data);
			goto fallback;
		}
		if (copied != space) {
			skb_trim(syn_data, copied);
			space = copied;
		}
3420
	}
3421 3422 3423 3424
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3425

3426
	tcp_connect_queue_skb(sk, syn_data);
3427 3428
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3429

3430
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3431

3432
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3433

3434 3435 3436 3437 3438 3439 3440 3441
	/* Now full SYN+DATA was cloned and sent (or not),
	 * remove the SYN from the original skb (syn_data)
	 * we keep in write queue in case of a retransmit, as we
	 * also have the SYN packet (with no data) in the same queue.
	 */
	TCP_SKB_CB(syn_data)->seq++;
	TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
	if (!err) {
3442
		tp->syn_data = (fo->copied > 0);
3443
		tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
3444
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3445 3446 3447
		goto done;
	}

3448 3449
	/* data was not sent, put it in write_queue */
	__skb_queue_tail(&sk->sk_write_queue, syn_data);
3450 3451
	tp->packets_out -= tcp_skb_pcount(syn_data);

3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463
fallback:
	/* Send a regular SYN with Fast Open cookie request option */
	if (fo->cookie.len > 0)
		fo->cookie.len = 0;
	err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
	if (err)
		tp->syn_fastopen = 0;
done:
	fo->cookie.len = -1;  /* Exclude Fast Open option for SYN retries */
	return err;
}

3464
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3465 3466 3467 3468
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3469
	int err;
L
Linus Torvalds 已提交
3470

3471
	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB);
3472 3473 3474 3475

	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

L
Linus Torvalds 已提交
3476 3477
	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3478 3479 3480 3481 3482
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3483
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3484
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3485 3486
		return -ENOBUFS;

C
Changli Gao 已提交
3487
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3488 3489
	tcp_mstamp_refresh(tp);
	tp->retrans_stamp = tcp_time_stamp(tp);
3490
	tcp_connect_queue_skb(sk, buff);
3491
	tcp_ecn_send_syn(sk, buff);
3492
	tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
L
Linus Torvalds 已提交
3493

3494 3495 3496
	/* Send off SYN; include data in Fast Open. */
	err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
	      tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3497 3498
	if (err == -ECONNREFUSED)
		return err;
3499 3500 3501 3502 3503 3504

	/* We change tp->snd_nxt after the tcp_transmit_skb() call
	 * in order to make this packet get counted in tcpOutSegs.
	 */
	tp->snd_nxt = tp->write_seq;
	tp->pushed_seq = tp->write_seq;
3505 3506 3507 3508 3509
	buff = tcp_send_head(sk);
	if (unlikely(buff)) {
		tp->snd_nxt	= TCP_SKB_CB(buff)->seq;
		tp->pushed_seq	= TCP_SKB_CB(buff)->seq;
	}
P
Pavel Emelyanov 已提交
3510
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3511 3512

	/* Timer for repeating the SYN until an answer. */
3513 3514
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3515 3516
	return 0;
}
E
Eric Dumazet 已提交
3517
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3518 3519 3520 3521 3522 3523 3524

/* Send out a delayed ack, the caller does the policy checking
 * to see if we should even be here.  See tcp_input.c:tcp_ack_snd_check()
 * for details.
 */
void tcp_send_delayed_ack(struct sock *sk)
{
3525 3526
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3527 3528
	unsigned long timeout;

3529 3530
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3531
	if (ato > TCP_DELACK_MIN) {
3532
		const struct tcp_sock *tp = tcp_sk(sk);
3533
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3534

3535 3536
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3537 3538 3539 3540 3541
			max_ato = TCP_DELACK_MAX;

		/* Slow path, intersegment interval is "high". */

		/* If some rtt estimate is known, use it to bound delayed ack.
3542
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3543 3544
		 * directly.
		 */
3545 3546 3547
		if (tp->srtt_us) {
			int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
					TCP_DELACK_MIN);
L
Linus Torvalds 已提交
3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559

			if (rtt < max_ato)
				max_ato = rtt;
		}

		ato = min(ato, max_ato);
	}

	/* Stay within the limit we were given */
	timeout = jiffies + ato;

	/* Use new timeout only if there wasn't a older one earlier. */
3560
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3561 3562 3563
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3564 3565
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3566 3567 3568 3569
			tcp_send_ack(sk);
			return;
		}

3570 3571
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3572
	}
3573 3574 3575
	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
	icsk->icsk_ack.timeout = timeout;
	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
L
Linus Torvalds 已提交
3576 3577 3578 3579 3580
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3581
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3582

3583 3584 3585
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3586

3587 3588
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3589 3590 3591 3592
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3593 3594 3595
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3596 3597 3598 3599 3600
		inet_csk_schedule_ack(sk);
		inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
					  TCP_DELACK_MAX, TCP_RTO_MAX);
		return;
L
Linus Torvalds 已提交
3601
	}
3602 3603 3604

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3605
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3606

E
Eric Dumazet 已提交
3607 3608 3609 3610 3611 3612
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 */
	skb_set_tcp_pure_ack(buff);

3613
	/* Send it off, this clears delayed acks for us. */
3614
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3615
}
3616
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628

/* This routine sends a packet with an out of date sequence
 * number. It assumes the other end will try to ack it.
 *
 * Question: what should we make while urgent mode?
 * 4.4BSD forces sending single byte of data. We cannot send
 * out of window data, because we have SND.NXT==SND.MAX...
 *
 * Current solution: to send TWO zero-length segments in urgent mode:
 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
 * out-of-date with SND.UNA-1 to probe window.
 */
3629
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3630 3631 3632 3633 3634
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3635 3636
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3637
	if (!skb)
L
Linus Torvalds 已提交
3638 3639 3640 3641 3642 3643 3644 3645
		return -1;

	/* Reserve space for headers and set control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
	/* Use a previous sequence.  This should cause the other
	 * end to send an ack.  Don't queue or clone SKB, just
	 * send it.
	 */
C
Changli Gao 已提交
3646
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3647
	NET_INC_STATS(sock_net(sk), mib);
3648
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3649 3650
}

3651
/* Called from setsockopt( ... TCP_REPAIR ) */
P
Pavel Emelyanov 已提交
3652 3653 3654 3655
void tcp_send_window_probe(struct sock *sk)
{
	if (sk->sk_state == TCP_ESTABLISHED) {
		tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3656
		tcp_mstamp_refresh(tcp_sk(sk));
3657
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3658 3659 3660
	}
}

3661
/* Initiate keepalive or window probe from timer. */
3662
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3663
{
3664 3665
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3666

3667 3668 3669
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3670 3671
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3672
		int err;
I
Ilpo Järvinen 已提交
3673
		unsigned int mss = tcp_current_mss(sk);
3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685
		unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;

		if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
			tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;

		/* We are probing the opening of a window
		 * but the window size is != 0
		 * must have been a result SWS avoidance ( sender )
		 */
		if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
		    skb->len > mss) {
			seg_size = min(seg_size, mss);
E
Eric Dumazet 已提交
3686
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3687 3688
			if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
					 skb, seg_size, mss, GFP_ATOMIC))
3689 3690
				return -1;
		} else if (!tcp_skb_pcount(skb))
3691
			tcp_set_skb_tso_segs(skb, mss);
3692

E
Eric Dumazet 已提交
3693
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3694 3695 3696 3697 3698
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
		if (!err)
			tcp_event_new_data_sent(sk, skb);
		return err;
	} else {
I
Ilpo Järvinen 已提交
3699
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3700 3701
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3702 3703 3704 3705 3706 3707 3708 3709
	}
}

/* A window probe timeout has occurred.  If window is not closed send
 * a partial packet else a zero probe.
 */
void tcp_send_probe0(struct sock *sk)
{
3710
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3711
	struct tcp_sock *tp = tcp_sk(sk);
3712
	struct net *net = sock_net(sk);
3713
	unsigned long probe_max;
L
Linus Torvalds 已提交
3714 3715
	int err;

3716
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3717

3718
	if (tp->packets_out || tcp_write_queue_empty(sk)) {
L
Linus Torvalds 已提交
3719
		/* Cancel probe timer, if it is not required. */
3720
		icsk->icsk_probes_out = 0;
3721
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3722 3723 3724 3725
		return;
	}

	if (err <= 0) {
3726
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3727
			icsk->icsk_backoff++;
3728
		icsk->icsk_probes_out++;
3729
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3730 3731
	} else {
		/* If packet was not sent due to local congestion,
3732
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3733 3734 3735 3736
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3737 3738
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3739
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3740
	}
3741
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3742
				  tcp_probe0_when(sk, probe_max),
3743
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3744
}
3745

3746
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3747 3748 3749 3750 3751
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3752
	tcp_rsk(req)->txhash = net_tx_rndhash();
3753
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3754
	if (!res) {
E
Eric Dumazet 已提交
3755
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3756
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3757 3758
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3759
		trace_tcp_retransmit_synack(sk, req);
3760 3761 3762 3763
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);