tcp_output.c 106.8 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>

/* People can turn this off for buggy TCP's found in printers etc. */
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int sysctl_tcp_retrans_collapse __read_mostly = 1;
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/* People can turn this on to work with those rare, broken TCPs that
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 * interpret the window field as a signed quantity.
 */
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int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
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/* Default TSQ limit of four TSO segments */
int sysctl_tcp_limit_output_bytes __read_mostly = 262144;
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/* This limits the percentage of the congestion window which we
 * will allow a single TSO frame to consume.  Building TSO frames
 * which are too large can cause TCP streams to be bursty.
 */
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int sysctl_tcp_tso_win_divisor __read_mostly = 3;
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/* By default, RFC2861 behavior.  */
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int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
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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, const 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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	tcp_advance_send_head(sk, skb);
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	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
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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.
 */
void tcp_select_initial_window(int __space, __u32 mss,
			       __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 (sysctl_tcp_workaround_signed_windows)
		(*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, sysctl_tcp_rmem[2]);
		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 && 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;

	/* 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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	skb->csum = 0;

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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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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);
	}

482
	if (unlikely(OPTION_SACK_ADVERTISE & options)) {
A
Adam Langley 已提交
483 484 485 486 487 488
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_SACK_PERM << 8) |
			       TCPOLEN_SACK_PERM);
	}

489
	if (unlikely(OPTION_WSCALE & options)) {
A
Adam Langley 已提交
490 491 492 493 494 495 496 497 498
		*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
499 500 501 502 503
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
504
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
505
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
506

A
Adam Langley 已提交
507 508
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
509 510 511
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
512

513
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
514
	}
Y
Yuchung Cheng 已提交
515 516 517

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
518 519 520 521 522 523 524 525 526 527 528 529 530
		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
531

532 533 534 535
		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
536
		}
537
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
538
	}
A
Adam Langley 已提交
539 540
}

541 542 543
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
544
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
545
				struct tcp_out_options *opts,
546 547
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
548
	struct tcp_sock *tp = tcp_sk(sk);
549
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
550
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
551

552
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
553 554 555
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
556
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
557
	}
A
Adam Langley 已提交
558 559
#else
	*md5 = NULL;
560
#endif
A
Adam Langley 已提交
561 562 563 564 565 566 567 568 569 570 571

	/* 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);
572
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
573

574
	if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
575
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
576
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
577
		opts->tsecr = tp->rx_opt.ts_recent;
578
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
579
	}
580
	if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
581
		opts->ws = tp->rx_opt.rcv_wscale;
582
		opts->options |= OPTION_WSCALE;
583
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
584
	}
E
Eric Dumazet 已提交
585
	if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
A
Adam Langley 已提交
586
		opts->options |= OPTION_SACK_ADVERTISE;
587
		if (unlikely(!(OPTION_TS & opts->options)))
588
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
589 590
	}

591
	if (fastopen && fastopen->cookie.len >= 0) {
592 593 594 595
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
596 597 598 599 600 601
		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;
602
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
603 604
		}
	}
605 606

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
607 608
}

609
/* Set up TCP options for SYN-ACKs. */
610 611 612 613 614
static unsigned int tcp_synack_options(struct request_sock *req,
				       unsigned int mss, struct sk_buff *skb,
				       struct tcp_out_options *opts,
				       const struct tcp_md5sig_key *md5,
				       struct tcp_fastopen_cookie *foc)
615
{
A
Adam Langley 已提交
616
	struct inet_request_sock *ireq = inet_rsk(req);
617
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
618

619
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
620
	if (md5) {
A
Adam Langley 已提交
621
		opts->options |= OPTION_MD5;
622 623 624 625 626 627 628
		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
629
		ireq->tstamp_ok &= !ireq->sack_ok;
630 631
	}
#endif
A
Adam Langley 已提交
632

633
	/* We always send an MSS option. */
A
Adam Langley 已提交
634
	opts->mss = mss;
635
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
636 637 638

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
639
		opts->options |= OPTION_WSCALE;
640
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
641
	}
E
Eric Dumazet 已提交
642
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
643
		opts->options |= OPTION_TS;
644
		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
A
Adam Langley 已提交
645
		opts->tsecr = req->ts_recent;
646
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
647 648 649
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
650
		if (unlikely(!ireq->tstamp_ok))
651
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
652
	}
653 654 655 656 657
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
658 659 660 661 662 663 664
		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
665

666
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
667 668
}

669 670 671
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
672
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
673
					struct tcp_out_options *opts,
674 675
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
676
	struct tcp_sock *tp = tcp_sk(sk);
677
	unsigned int size = 0;
678
	unsigned int eff_sacks;
A
Adam Langley 已提交
679

680 681
	opts->options = 0;

A
Adam Langley 已提交
682 683 684 685 686 687 688 689 690 691 692 693
#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
694
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
695 696 697 698
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

699 700
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
701
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
702
		opts->num_sack_blocks =
703
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
704 705 706 707 708 709 710
			      (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
711
}
L
Linus Torvalds 已提交
712

E
Eric Dumazet 已提交
713 714 715 716 717 718 719 720 721

/* 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
722
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
723 724 725 726 727 728 729 730 731 732 733
 *
 * 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);

734 735 736 737
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
738 739 740 741 742 743 744 745
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK)) {
		struct tcp_sock *tp = tcp_sk(sk);

		if (tp->lost_out > tp->retrans_out &&
		    tp->snd_cwnd > tcp_packets_in_flight(tp))
			tcp_xmit_retransmit_queue(sk);

		tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
J
John Ogness 已提交
746
			       0, GFP_ATOMIC);
747
	}
748
}
E
Eric Dumazet 已提交
749
/*
S
stephen hemminger 已提交
750
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
751
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
752
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772
 * 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;
773
		smp_mb__before_atomic();
774 775
		clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);

776
		if (!sk->sk_lock.owned &&
777
		    test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) {
778 779
			bh_lock_sock(sk);
			if (!sock_owned_by_user(sk)) {
780
				clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
781 782 783
				tcp_tsq_handler(sk);
			}
			bh_unlock_sock(sk);
E
Eric Dumazet 已提交
784 785 786 787 788 789
		}

		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
790 791 792 793
#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
794 795 796 797 798 799 800 801 802
/**
 * 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)
{
803
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
804

805 806
	/* perform an atomic operation only if at least one flag is set */
	do {
807
		flags = sk->sk_tsq_flags;
808 809 810
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
811
	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
812

E
Eric Dumazet 已提交
813
	if (flags & TCPF_TSQ_DEFERRED)
814 815
		tcp_tsq_handler(sk);

816 817 818 819 820 821 822 823 824 825 826
	/* 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
827
	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
828
		tcp_write_timer_handler(sk);
829 830
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
831
	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
832
		tcp_delack_timer_handler(sk);
833 834
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
835
	if (flags & TCPF_MTU_REDUCED_DEFERRED) {
836
		inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
837 838
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857
}
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
858
 * We can't xmit new skbs from this context, as we might already
E
Eric Dumazet 已提交
859 860
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
861
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
862 863 864
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);
865
	unsigned long flags, nval, oval;
866 867 868 869

	/* Keep one reference on sk_wmem_alloc.
	 * Will be released by sk_free() from here or tcp_tasklet_func()
	 */
870
	WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
871 872 873 874 875 876 877 878

	/* 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)
	 */
879
	if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
880
		goto out;
E
Eric Dumazet 已提交
881

882
	for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
E
Eric Dumazet 已提交
883
		struct tsq_tasklet *tsq;
884
		bool empty;
E
Eric Dumazet 已提交
885

886 887 888
		if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
			goto out;

889
		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
890
		nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
891 892 893
		if (nval != oval)
			continue;

E
Eric Dumazet 已提交
894 895
		/* queue this socket to tasklet queue */
		local_irq_save(flags);
896
		tsq = this_cpu_ptr(&tsq_tasklet);
897
		empty = list_empty(&tsq->head);
E
Eric Dumazet 已提交
898
		list_add(&tp->tsq_node, &tsq->head);
899 900
		if (empty)
			tasklet_schedule(&tsq->tasklet);
E
Eric Dumazet 已提交
901
		local_irq_restore(flags);
902
		return;
E
Eric Dumazet 已提交
903
	}
904 905
out:
	sk_free(sk);
E
Eric Dumazet 已提交
906 907
}

908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928
/* 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;

929
		if (!refcount_inc_not_zero(&sk->sk_wmem_alloc))
930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973
			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);
}

L
Linus Torvalds 已提交
974 975 976 977 978 979 980 981 982 983 984
/* 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.
 */
985 986
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
987
{
988 989 990 991
	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
992
	struct tcp_out_options opts;
993
	unsigned int tcp_options_size, tcp_header_size;
994
	struct tcp_md5sig_key *md5;
995 996 997 998
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
999
	tp = tcp_sk(sk);
1000

1001
	skb->skb_mstamp = tp->tcp_mstamp;
1002
	if (clone_it) {
1003 1004
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
1005
		tcp_rate_skb_sent(sk, skb);
1006

1007 1008 1009 1010 1011 1012 1013
		if (unlikely(skb_cloned(skb)))
			skb = pskb_copy(skb, gfp_mask);
		else
			skb = skb_clone(skb, gfp_mask);
		if (unlikely(!skb))
			return -ENOBUFS;
	}
L
Linus Torvalds 已提交
1014

1015 1016
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
1017
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
1018

E
Eric Dumazet 已提交
1019
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
1020 1021 1022 1023 1024
		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);
1025

E
Eric Dumazet 已提交
1026
	/* if no packet is in qdisc/device queue, then allow XPS to select
1027 1028 1029 1030 1031
	 * 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
1032
	 */
1033
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1034

1035 1036 1037 1038 1039 1040 1041
	/* 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;

1042 1043
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
1044 1045 1046

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
1047
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1048
	skb_set_hash_from_sk(skb, sk);
1049
	refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1050

1051 1052
	skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);

1053
	/* Build TCP header and checksum it. */
1054
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
1055 1056
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
1057 1058
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
1059
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
1060
					tcb->tcp_flags);
1061 1062 1063

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
1064

I
Ilpo Järvinen 已提交
1065
	/* The urg_mode check is necessary during a below snd_una win probe */
1066 1067 1068 1069 1070
	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)) {
1071
			th->urg_ptr = htons(0xFFFF);
1072 1073
			th->urg = 1;
		}
1074
	}
L
Linus Torvalds 已提交
1075

1076
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1077
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1078 1079 1080 1081 1082 1083 1084 1085 1086
	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));
	}
1087 1088 1089
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1090
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1091
		tp->af_specific->calc_md5_hash(opts.hash_location,
1092
					       md5, sk, skb);
1093 1094 1095
	}
#endif

1096
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1097

E
Eric Dumazet 已提交
1098
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1099
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1100

1101
	if (skb->len != tcp_header_size) {
1102
		tcp_event_data_sent(tp, sk);
1103
		tp->data_segs_out += tcp_skb_pcount(skb);
1104
		tcp_internal_pacing(sk, skb);
1105
	}
L
Linus Torvalds 已提交
1106

1107
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1108 1109
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1110

1111
	tp->segs_out += tcp_skb_pcount(skb);
1112
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1113
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1114
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1115

E
Eric Dumazet 已提交
1116
	/* Our usage of tstamp should remain private */
T
Thomas Gleixner 已提交
1117
	skb->tstamp = 0;
1118 1119 1120 1121 1122

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

1123
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1124

1125
	if (likely(err <= 0))
1126 1127
		return err;

1128
	tcp_enter_cwr(sk);
1129

1130
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1131 1132
}

1133
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
 *
 * 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;
1144
	__skb_header_release(skb);
1145
	tcp_add_write_queue_tail(sk, skb);
1146 1147
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1148 1149
}

1150
/* Initialize TSO segments for a packet. */
1151
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1152
{
1153
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1154 1155 1156
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1157
		tcp_skb_pcount_set(skb, 1);
1158
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1159
	} else {
1160
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1161
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1162 1163 1164
	}
}

I
Ilpo Järvinen 已提交
1165
/* When a modification to fackets out becomes necessary, we need to check
1166
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1167
 */
1168
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1169 1170
				   int decr)
{
1171 1172
	struct tcp_sock *tp = tcp_sk(sk);

1173
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1174 1175
		return;

1176
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1177 1178 1179
		tp->fackets_out -= decr;
}

1180 1181 1182
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1183
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203
{
	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);

	tcp_adjust_fackets_out(sk, skb, decr);

	if (tp->lost_skb_hint &&
	    before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1204
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1205 1206 1207 1208 1209
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1210 1211 1212 1213 1214 1215
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);
}

1216 1217 1218 1219
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1220
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1221 1222 1223 1224 1225 1226 1227
	    !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);
1228 1229
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1230 1231 1232
	}
}

1233 1234 1235 1236 1237 1238
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;
}

L
Linus Torvalds 已提交
1239 1240
/* 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
1241
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1242 1243
 * Remember, these are still headerless SKBs at this point.
 */
1244
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1245
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1246 1247 1248
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1249
	int nsize, old_factor;
1250
	int nlen;
1251
	u8 flags;
L
Linus Torvalds 已提交
1252

1253 1254
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1255

L
Linus Torvalds 已提交
1256 1257 1258 1259
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1260
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1261 1262 1263
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1264
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1265
	if (!buff)
L
Linus Torvalds 已提交
1266
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1267

1268 1269
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1270 1271 1272
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1273 1274 1275 1276 1277 1278 1279

	/* 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
1280 1281 1282
	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;
1283
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1284
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1285

1286
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1287
		/* Copy and checksum data tail into the new buffer. */
1288 1289
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1290 1291 1292 1293 1294 1295
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1296
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1297 1298 1299 1300 1301
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1302
	buff->tstamp = skb->tstamp;
1303
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1304

1305 1306
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1307
	/* Fix up tso_factor for both original and new SKB.  */
1308 1309
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1310

1311 1312 1313
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1314 1315 1316
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1317
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1318 1319
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1320

1321 1322
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1323 1324 1325
	}

	/* Link BUFF into the send queue. */
1326
	__skb_header_release(buff);
1327
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1328 1329 1330 1331

	return 0;
}

1332 1333
/* 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
1334
 */
1335
static int __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1336
{
1337
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1338 1339
	int i, k, eat;

E
Eric Dumazet 已提交
1340 1341 1342 1343 1344
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
1345
			return 0;
E
Eric Dumazet 已提交
1346
	}
L
Linus Torvalds 已提交
1347 1348
	eat = len;
	k = 0;
1349 1350 1351
	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
1352 1353

		if (size <= eat) {
1354
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1355
			eat -= size;
L
Linus Torvalds 已提交
1356
		} else {
1357
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1358
			if (eat) {
1359 1360
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1361 1362 1363 1364 1365
				eat = 0;
			}
			k++;
		}
	}
1366
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1367 1368 1369

	skb->data_len -= len;
	skb->len = skb->data_len;
1370
	return len;
L
Linus Torvalds 已提交
1371 1372
}

1373
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1374 1375
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1376 1377
	u32 delta_truesize;

1378
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1379 1380
		return -ENOMEM;

1381
	delta_truesize = __pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1382 1383

	TCP_SKB_CB(skb)->seq += len;
1384
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1385

1386 1387 1388 1389 1390 1391
	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
1392

1393
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1394
	if (tcp_skb_pcount(skb) > 1)
1395
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1396 1397 1398 1399

	return 0;
}

1400 1401
/* 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
1402
{
1403 1404
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1405 1406 1407 1408 1409 1410 1411
	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);

1412 1413 1414 1415 1416 1417 1418 1419
	/* 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
1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432
	/* 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;
}

1433 1434 1435 1436 1437 1438 1439 1440
/* 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
1441
/* Inverse of above */
1442
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1443
{
1444 1445
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1446 1447 1448 1449 1450 1451 1452
	int mtu;

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

1453 1454 1455 1456 1457 1458 1459
	/* 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
1460 1461
	return mtu;
}
1462
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1463

1464
/* MTU probing init per socket */
J
John Heffner 已提交
1465 1466 1467 1468
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
1469
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1470

F
Fan Du 已提交
1471
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1472
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1473
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1474
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1475
	icsk->icsk_mtup.probe_size = 0;
1476
	if (icsk->icsk_mtup.enabled)
1477
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
J
John Heffner 已提交
1478
}
E
Eric Dumazet 已提交
1479
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1480

L
Linus Torvalds 已提交
1481 1482 1483 1484 1485 1486
/* 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
1487
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1488 1489
   It also does not include TCP options.

1490
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1491 1492 1493 1494 1495 1496 1497 1498 1499

   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.

1500 1501
   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
1502 1503 1504 1505
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1506
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1507
	int mss_now;
L
Linus Torvalds 已提交
1508

J
John Heffner 已提交
1509 1510
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1511

J
John Heffner 已提交
1512
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1513
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1514 1515

	/* And store cached results */
1516
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1517 1518
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1519
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1520 1521 1522

	return mss_now;
}
E
Eric Dumazet 已提交
1523
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1524 1525 1526 1527

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1528
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1529
{
1530 1531
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1532
	u32 mss_now;
1533
	unsigned int header_len;
A
Adam Langley 已提交
1534 1535
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1536 1537 1538

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1539 1540
	if (dst) {
		u32 mtu = dst_mtu(dst);
1541
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1542 1543 1544
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1545 1546 1547 1548 1549 1550 1551 1552 1553 1554
	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;
	}
1555

L
Linus Torvalds 已提交
1556 1557 1558
	return mss_now;
}

1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
/* 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;
	}
1578
	tp->snd_cwnd_stamp = tcp_jiffies32;
1579 1580
}

1581
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1582
{
1583
	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1584
	struct tcp_sock *tp = tcp_sk(sk);
1585

1586 1587 1588 1589 1590 1591 1592 1593 1594
	/* 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;
	}
1595

1596
	if (tcp_is_cwnd_limited(sk)) {
1597 1598
		/* Network is feed fully. */
		tp->snd_cwnd_used = 0;
1599
		tp->snd_cwnd_stamp = tcp_jiffies32;
1600 1601 1602 1603 1604
	} else {
		/* Network starves. */
		if (tp->packets_out > tp->snd_cwnd_used)
			tp->snd_cwnd_used = tp->packets_out;

1605
		if (sysctl_tcp_slow_start_after_idle &&
1606
		    (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1607
		    !ca_ops->cong_control)
1608
			tcp_cwnd_application_limited(sk);
1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620

		/* 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)
		 * 3) no more data to send (null tcp_send_head )
		 * 4) application is hitting buffer limit (SOCK_NOSPACE)
		 */
		if (!tcp_send_head(sk) && sk->sk_socket &&
		    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);
1621 1622 1623
	}
}

E
Eric Dumazet 已提交
1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637
/* 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
1638
 */
E
Eric Dumazet 已提交
1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653
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,
1654
			    int nonagle)
E
Eric Dumazet 已提交
1655 1656 1657 1658 1659
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1660 1661 1662 1663

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1664 1665
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676
{
	u32 bytes, segs;

	bytes = min(sk->sk_pacing_rate >> 10,
		    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.
	 */
1677
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1678 1679 1680

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1681
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1682

1683 1684 1685 1686 1687 1688 1689 1690
/* 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;

1691 1692
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1693 1694
}

E
Eric Dumazet 已提交
1695 1696 1697 1698 1699 1700
/* 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)
1701
{
1702
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1703
	u32 partial, needed, window, max_len;
1704

1705
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1706
	max_len = mss_now * max_segs;
1707

1708 1709
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1710

1711 1712
	needed = min(skb->len, window);

1713 1714
	if (max_len <= needed)
		return max_len;
1715

E
Eric Dumazet 已提交
1716 1717 1718 1719 1720
	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
	 */
1721
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1722 1723 1724
		return needed - partial;

	return needed;
1725 1726 1727 1728 1729
}

/* 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.
 */
1730 1731
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1732
{
E
Eric Dumazet 已提交
1733
	u32 in_flight, cwnd, halfcwnd;
1734 1735

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1736 1737
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1738 1739 1740 1741
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1742 1743
	if (in_flight >= cwnd)
		return 0;
1744

E
Eric Dumazet 已提交
1745 1746 1747 1748 1749
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1750 1751
}

1752
/* Initialize TSO state of a skb.
1753
 * This must be invoked the first time we consider transmitting
1754 1755
 * SKB onto the wire.
 */
1756
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1757 1758 1759
{
	int tso_segs = tcp_skb_pcount(skb);

1760
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1761
		tcp_set_skb_tso_segs(skb, mss_now);
1762 1763 1764 1765 1766 1767
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1768
/* Return true if the Nagle test allows this packet to be
1769 1770
 * sent now.
 */
E
Eric Dumazet 已提交
1771 1772
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1773 1774 1775 1776 1777 1778 1779 1780
{
	/* 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
1781
		return true;
1782

Y
Yuchung Cheng 已提交
1783 1784
	/* 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
1785
		return true;
1786

1787
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1788
		return true;
1789

E
Eric Dumazet 已提交
1790
	return false;
1791 1792 1793
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1794 1795 1796
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1797 1798 1799 1800 1801 1802
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1803
	return !after(end_seq, tcp_wnd_end(tp));
1804 1805
}

1806
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1807 1808 1809
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1810
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1811 1812
				 unsigned int cur_mss, int nonagle)
{
1813
	const struct tcp_sock *tp = tcp_sk(sk);
1814 1815
	unsigned int cwnd_quota;

1816
	tcp_init_tso_segs(skb, cur_mss);
1817 1818 1819 1820 1821

	if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
		return 0;

	cwnd_quota = tcp_cwnd_test(tp, skb);
1822
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1823 1824 1825 1826 1827
		cwnd_quota = 0;

	return cwnd_quota;
}

1828
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1829
bool tcp_may_send_now(struct sock *sk)
1830
{
1831
	const struct tcp_sock *tp = tcp_sk(sk);
1832
	struct sk_buff *skb = tcp_send_head(sk);
1833

E
Eric Dumazet 已提交
1834
	return skb &&
I
Ilpo Järvinen 已提交
1835
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1836
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1837
			      tp->nonagle : TCP_NAGLE_PUSH));
1838 1839 1840 1841 1842 1843 1844 1845 1846
}

/* 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).
 */
1847
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1848
			unsigned int mss_now, gfp_t gfp)
1849 1850 1851
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1852
	u8 flags;
1853 1854

	/* All of a TSO frame must be composed of paged data.  */
1855
	if (skb->len != skb->data_len)
1856
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1857

1858
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1859
	if (unlikely(!buff))
1860 1861
		return -ENOMEM;

1862 1863
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1864
	buff->truesize += nlen;
1865 1866 1867 1868 1869 1870 1871 1872
	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
1873 1874 1875
	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;
1876 1877 1878 1879

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

1880 1881
	tcp_skb_fragment_eor(skb, buff);

1882
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1883
	skb_split(skb, buff, len);
1884
	tcp_fragment_tstamp(skb, buff);
1885 1886

	/* Fix up tso_factor for both original and new SKB.  */
1887 1888
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1889 1890

	/* Link BUFF into the send queue. */
1891
	__skb_header_release(buff);
1892
	tcp_insert_write_queue_after(skb, buff, sk);
1893 1894 1895 1896 1897 1898 1899 1900 1901

	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.
 */
1902
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1903
				 bool *is_cwnd_limited, u32 max_segs)
1904
{
1905
	const struct inet_connection_sock *icsk = inet_csk(sk);
1906 1907 1908
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *head;
1909
	int win_divisor;
1910

E
Eric Dumazet 已提交
1911
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1912
		goto send_now;
1913

1914
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1915 1916
		goto send_now;

E
Eric Dumazet 已提交
1917 1918 1919
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
1920
	if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
J
John Heffner 已提交
1921
		goto send_now;
1922

1923 1924
	in_flight = tcp_packets_in_flight(tp);

1925
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1926

1927
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1928 1929 1930 1931 1932 1933

	/* 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);

1934
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1935
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1936
		goto send_now;
1937

1938 1939 1940 1941
	/* 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;

1942 1943
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1944 1945 1946 1947 1948
		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.
		 */
1949
		chunk /= win_divisor;
1950
		if (limit >= chunk)
J
John Heffner 已提交
1951
			goto send_now;
1952 1953 1954 1955 1956 1957
	} 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.
		 */
1958
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1959
			goto send_now;
1960 1961
	}

1962
	head = tcp_write_queue_head(sk);
1963

1964
	age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
1965 1966 1967 1968
	/* 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
1969
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1970

1971
	if (cong_win < send_win && cong_win <= skb->len)
1972 1973
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1974
	return true;
J
John Heffner 已提交
1975 1976

send_now:
E
Eric Dumazet 已提交
1977
	return false;
1978 1979
}

1980 1981 1982 1983 1984 1985 1986 1987 1988
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;
1989
	delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
	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 */
2001
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2002 2003 2004
	}
}

J
John Heffner 已提交
2005
/* Create a new MTU probe if we are ready.
2006 2007 2008 2009
 * 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
2010 2011
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
2012 2013
 *         -1 otherwise
 */
J
John Heffner 已提交
2014 2015 2016
static int tcp_mtu_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
2017
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2018
	struct sk_buff *skb, *nskb, *next;
2019
	struct net *net = sock_net(sk);
J
John Heffner 已提交
2020
	int probe_size;
2021
	int size_needed;
2022
	int copy, len;
J
John Heffner 已提交
2023
	int mss_now;
2024
	int interval;
J
John Heffner 已提交
2025 2026 2027 2028

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
2029 2030 2031 2032 2033 2034 2035
	 * 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
2036 2037
		return -1;

2038 2039 2040 2041
	/* 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
2042
	mss_now = tcp_current_mss(sk);
2043 2044
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
2045
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2046
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2047 2048 2049 2050
	/* 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.
	 */
2051
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2052 2053 2054 2055 2056
		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
2057 2058 2059 2060
		return -1;
	}

	/* Have enough data in the send queue to probe? */
2061
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
2062 2063
		return -1;

2064 2065
	if (tp->snd_wnd < size_needed)
		return -1;
2066
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2067
		return 0;
J
John Heffner 已提交
2068

2069 2070 2071
	/* 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
2072 2073 2074 2075 2076 2077
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
2078
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2079
	if (!nskb)
J
John Heffner 已提交
2080
		return -1;
2081 2082
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2083

2084
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2085 2086 2087

	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
2088
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2089 2090
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2091
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2092

2093 2094
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2095
	len = 0;
2096
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2097
		copy = min_t(int, skb->len, probe_size - len);
2098
		if (nskb->ip_summed) {
J
John Heffner 已提交
2099
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2100 2101 2102 2103 2104 2105
		} 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
2106 2107 2108 2109

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2110
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2111
			tcp_unlink_write_queue(skb, sk);
2112
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2113
		} else {
E
Eric Dumazet 已提交
2114
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2115
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2116 2117
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2118
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2119 2120
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2121 2122
			} else {
				__pskb_trim_head(skb, copy);
2123
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2124 2125 2126 2127 2128
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2129 2130 2131

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2132
	}
2133
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2134 2135

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2136 2137
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2138 2139
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2140
		 * effectively two packets. */
J
John Heffner 已提交
2141
		tp->snd_cwnd--;
2142
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2143 2144

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2145 2146
		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
2147 2148 2149 2150 2151 2152 2153

		return 1;
	}

	return -1;
}

2154 2155 2156 2157 2158 2159
static bool tcp_pacing_check(const struct sock *sk)
{
	return tcp_needs_internal_pacing(sk) &&
	       hrtimer_active(&tcp_sk(sk)->pacing_timer);
}

2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179
/* 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;

	limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
	limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
	limit <<= factor;

2180
	if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2181 2182 2183 2184 2185 2186 2187 2188 2189
		/* Always send the 1st or 2nd skb in write queue.
		 * No need to wait for TX completion to call us back,
		 * after softirq/tasklet schedule.
		 * This helps when TX completions are delayed too much.
		 */
		if (skb == sk->sk_write_queue.next ||
		    skb->prev == sk->sk_write_queue.next)
			return false;

2190
		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2191 2192 2193 2194 2195
		/* It is possible TX completion already happened
		 * before we set TSQ_THROTTLED, so we must
		 * test again the condition.
		 */
		smp_mb__after_atomic();
2196
		if (refcount_read(&sk->sk_wmem_alloc) > limit)
2197 2198 2199 2200 2201
			return true;
	}
	return false;
}

2202 2203
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
2204
	const u32 now = tcp_jiffies32;
2205
	enum tcp_chrono old = tp->chrono_type;
2206

2207 2208
	if (old > TCP_CHRONO_UNSPEC)
		tp->chrono_stat[old - 1] += now - tp->chrono_start;
2209 2210 2211 2212 2213 2214 2215 2216 2217
	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
2218 2219
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2220 2221 2222 2223 2224 2225 2226 2227 2228 2229
	 * 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);

2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241

	/* 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.
	 */
	if (tcp_write_queue_empty(sk))
		tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
	else if (type == tp->chrono_type)
		tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2242 2243
}

L
Linus Torvalds 已提交
2244 2245 2246 2247
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2248 2249 2250 2251
 * 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
2252 2253 2254
 * 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
2255 2256
 * 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
2257
 */
E
Eric Dumazet 已提交
2258 2259
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
2260 2261
{
	struct tcp_sock *tp = tcp_sk(sk);
2262
	struct sk_buff *skb;
2263 2264
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2265
	int result;
2266
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2267
	u32 max_segs;
L
Linus Torvalds 已提交
2268

2269
	sent_pkts = 0;
J
John Heffner 已提交
2270

2271 2272 2273 2274
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2275
			return false;
2276 2277 2278
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2279 2280
	}

2281
	max_segs = tcp_tso_segs(sk, mss_now);
2282
	tcp_mstamp_refresh(tp);
2283
	while ((skb = tcp_send_head(sk))) {
2284 2285
		unsigned int limit;

2286 2287 2288
		if (tcp_pacing_check(sk))
			break;

2289
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2290
		BUG_ON(!tso_segs);
2291

2292
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2293
			/* "skb_mstamp" is used as a start point for the retransmit timer */
2294
			skb->skb_mstamp = tp->tcp_mstamp;
2295
			goto repair; /* Skip network transmission */
2296
		}
2297

2298
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2299 2300 2301 2302 2303 2304 2305
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2306

2307 2308
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2309
			break;
2310
		}
2311

2312
		if (tso_segs == 1) {
2313 2314 2315 2316 2317
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2318
			if (!push_one &&
E
Eric Dumazet 已提交
2319 2320
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2321 2322
				break;
		}
2323

E
Eric Dumazet 已提交
2324
		limit = mss_now;
2325
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2326 2327 2328 2329 2330 2331 2332 2333 2334 2335
			limit = tcp_mss_split_point(sk, skb, mss_now,
						    min_t(unsigned int,
							  cwnd_quota,
							  max_segs),
						    nonagle);

		if (skb->len > limit &&
		    unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
			break;

2336 2337
		if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
			clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
2338 2339
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2340

2341
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2342
			break;
L
Linus Torvalds 已提交
2343

2344
repair:
2345 2346 2347
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2348
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2349

2350
		tcp_minshall_update(tp, mss_now, skb);
2351
		sent_pkts += tcp_skb_pcount(skb);
2352 2353 2354

		if (push_one)
			break;
2355
	}
L
Linus Torvalds 已提交
2356

2357 2358 2359 2360 2361
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2362
	if (likely(sent_pkts)) {
2363 2364
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2365 2366 2367 2368

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2369
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2370
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2371
		return false;
L
Linus Torvalds 已提交
2372
	}
2373
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2374 2375 2376 2377 2378 2379
}

bool tcp_schedule_loss_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
2380
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
2381
	u32 timeout, rto_delta_us;
N
Nandita Dukkipati 已提交
2382 2383 2384 2385

	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
2386
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2387 2388 2389 2390 2391
		return false;

	/* Schedule a loss probe in 2*RTT for SACK capable connections
	 * in Open state, that are either limited by cwnd or application.
	 */
Y
Yuchung Cheng 已提交
2392 2393 2394
	if ((sysctl_tcp_early_retrans != 3 && sysctl_tcp_early_retrans != 4) ||
	    !tp->packets_out || !tcp_is_sack(tp) ||
	    icsk->icsk_ca_state != TCP_CA_Open)
N
Nandita Dukkipati 已提交
2395 2396 2397 2398 2399 2400 2401
		return false;

	if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
	     tcp_send_head(sk))
		return false;

	/* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2402 2403
	 * 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
2404
	 */
2405
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2406 2407 2408 2409 2410
	if (tp->packets_out == 1)
		timeout = max_t(u32, timeout,
				(rtt + (rtt >> 1) + TCP_DELACK_MAX));
	timeout = max_t(u32, timeout, msecs_to_jiffies(10));

2411 2412 2413 2414
	/* If the RTO formula yields an earlier time, then use that time. */
	rto_delta_us = tcp_rto_delta_us(sk);  /* How far in future is RTO? */
	if (rto_delta_us > 0)
		timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
N
Nandita Dukkipati 已提交
2415 2416 2417 2418 2419 2420

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

2421 2422 2423 2424 2425 2426 2427
/* 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)
{
2428
	if (unlikely(skb_fclone_busy(sk, skb))) {
2429 2430
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2431 2432 2433 2434 2435
		return true;
	}
	return false;
}

2436
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2437 2438 2439 2440
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2441
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2442 2443 2444 2445
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457
	skb = tcp_send_head(sk);
	if (skb) {
		if (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;
		}
		skb = tcp_write_queue_prev(sk, skb);
	} else {
		skb = tcp_write_queue_tail(sk);
N
Nandita Dukkipati 已提交
2458 2459
	}

N
Nandita Dukkipati 已提交
2460 2461 2462 2463
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2464 2465 2466 2467
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2468 2469 2470
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2471 2472 2473 2474 2475
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2476 2477
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2478
			goto rearm_timer;
2479
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2480 2481 2482 2483 2484
	}

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

2485
	if (__tcp_retransmit_skb(sk, skb, 1))
2486
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2487

N
Nandita Dukkipati 已提交
2488
	/* Record snd_nxt for loss detection. */
2489
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2490

2491
probe_sent:
2492
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2493 2494
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2495
rearm_timer:
2496
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2497 2498
}

2499 2500 2501 2502
/* 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.
 */
2503 2504
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2505
{
2506 2507 2508 2509 2510 2511 2512
	/* 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;

2513
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2514
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2515
		tcp_check_probe_timer(sk);
2516 2517
}

2518 2519 2520 2521 2522
/* 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)
{
2523
	struct sk_buff *skb = tcp_send_head(sk);
2524 2525 2526

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

2527
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2528 2529
}

L
Linus Torvalds 已提交
2530 2531
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2532
 *
L
Linus Torvalds 已提交
2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550
 * 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.
2551
 *
L
Linus Torvalds 已提交
2552 2553
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2554
 *
L
Linus Torvalds 已提交
2555
 * BSD seems to make the following compromise:
2556
 *
L
Linus Torvalds 已提交
2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583
 *	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)
{
2584
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2585
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2586
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2587 2588 2589 2590 2591
	 * 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
	 */
2592
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2593
	int free_space = tcp_space(sk);
2594 2595
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2596 2597
	int window;

2598
	if (unlikely(mss > full_space)) {
2599
		mss = full_space;
2600 2601 2602
		if (mss <= 0)
			return 0;
	}
2603
	if (free_space < (full_space >> 1)) {
2604
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2605

2606
		if (tcp_under_memory_pressure(sk))
2607 2608
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2609

2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622
		/* 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
2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638
			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.
		 */
2639
		window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
L
Linus Torvalds 已提交
2640
	} else {
2641
		window = tp->rcv_wnd;
L
Linus Torvalds 已提交
2642 2643 2644 2645 2646 2647 2648 2649 2650
		/* 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)
2651
			window = rounddown(free_space, mss);
2652
		else if (mss == full_space &&
2653
			 free_space > window + (full_space >> 1))
2654
			window = free_space;
L
Linus Torvalds 已提交
2655 2656 2657 2658 2659
	}

	return window;
}

2660 2661
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2662
{
2663 2664 2665
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2666 2667
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2668
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2669
		shinfo->tskey = next_shinfo->tskey;
2670 2671
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2672 2673 2674
	}
}

2675
/* Collapses two adjacent SKB's during retransmission. */
2676
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2677 2678
{
	struct tcp_sock *tp = tcp_sk(sk);
2679
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2680
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2681

2682 2683
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2684

2685
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2686

2687 2688 2689 2690 2691 2692 2693
	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;
	}
2694
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2695

2696
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2697

2698 2699
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2700

2701 2702
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2703

2704 2705
	/* 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
2706

2707
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2708
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2709 2710 2711 2712 2713

	/* 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;
2714
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2715 2716

	/* changed transmit queue under us so clear hints */
2717 2718 2719
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2720

2721 2722
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2723 2724
	tcp_skb_collapse_tstamp(skb, next_skb);

2725
	sk_wmem_free_skb(sk, next_skb);
2726
	return true;
L
Linus Torvalds 已提交
2727 2728
}

2729
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2730
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2731 2732
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2733
		return false;
2734
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2735
		return false;
2736
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2737
		return false;
E
Eric Dumazet 已提交
2738
	/* Some heuristics for collapsing over SACK'd could be invented */
2739
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2740
		return false;
2741

E
Eric Dumazet 已提交
2742
	return true;
2743 2744
}

2745 2746 2747
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2748 2749 2750 2751 2752
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
2753
	bool first = true;
2754 2755 2756

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2757
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2758 2759 2760 2761 2762 2763
		return;

	tcp_for_write_queue_from_safe(skb, tmp, sk) {
		if (!tcp_can_collapse(sk, skb))
			break;

2764 2765 2766
		if (!tcp_skb_can_collapse_to(to))
			break;

2767 2768 2769
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2770
			first = false;
2771 2772 2773 2774 2775 2776 2777 2778 2779
			continue;
		}

		if (space < 0)
			break;

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

2780 2781
		if (!tcp_collapse_retrans(sk, to))
			break;
2782 2783 2784
	}
}

L
Linus Torvalds 已提交
2785 2786 2787 2788
/* 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.
 */
2789
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2790
{
J
John Heffner 已提交
2791
	struct inet_connection_sock *icsk = inet_csk(sk);
2792
	struct tcp_sock *tp = tcp_sk(sk);
2793
	unsigned int cur_mss;
2794 2795
	int diff, len, err;

L
Linus Torvalds 已提交
2796

2797 2798
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2799 2800
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2801
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2802
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2803
	 */
2804
	if (refcount_read(&sk->sk_wmem_alloc) >
2805 2806
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2807 2808
		return -EAGAIN;

2809 2810 2811
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2812 2813 2814 2815 2816 2817 2818
	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;
	}

2819 2820 2821
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2822
	cur_mss = tcp_current_mss(sk);
2823

L
Linus Torvalds 已提交
2824 2825 2826 2827 2828
	/* 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.
	 */
2829 2830
	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
2831 2832
		return -EAGAIN;

2833 2834 2835
	len = cur_mss * segs;
	if (skb->len > len) {
		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2836
			return -ENOMEM; /* We'll try again later. */
2837
	} else {
2838 2839
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2840

2841 2842 2843 2844 2845 2846 2847
		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
2848 2849
	}

2850 2851 2852 2853
	/* 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);

2854 2855 2856 2857 2858 2859 2860
	/* 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;

2861 2862 2863 2864 2865 2866
	/* 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)) {
2867 2868
		struct sk_buff *nskb;

2869
		skb->skb_mstamp = tp->tcp_mstamp;
2870
		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2871 2872
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2873
	} else {
2874
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2875
	}
2876

2877
	if (likely(!err)) {
2878
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2879 2880
	} else if (err != -EBUSY) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2881
	}
2882
	return err;
2883 2884
}

2885
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2886 2887
{
	struct tcp_sock *tp = tcp_sk(sk);
2888
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2889 2890 2891

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2892
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2893
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2894 2895 2896 2897 2898 2899 2900
		}
#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
2901
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2902 2903

	}
Y
Yuchung Cheng 已提交
2904 2905 2906 2907

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920
	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.
 * If doing SACK, the first ACK which comes back for a timeout
 * based retransmit packet might feed us FACK information again.
 * If so, we use it to avoid unnecessarily retransmissions.
 */
void tcp_xmit_retransmit_queue(struct sock *sk)
{
2921
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2922 2923
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2924
	struct sk_buff *hole = NULL;
2925
	u32 max_segs;
2926
	int mib_idx;
2927

2928 2929 2930
	if (!tp->packets_out)
		return;

2931
	if (tp->retransmit_skb_hint) {
2932
		skb = tp->retransmit_skb_hint;
2933
	} else {
2934
		skb = tcp_write_queue_head(sk);
2935
	}
L
Linus Torvalds 已提交
2936

2937
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2938
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2939
		__u8 sacked;
2940
		int segs;
L
Linus Torvalds 已提交
2941

2942 2943
		if (skb == tcp_send_head(sk))
			break;
2944 2945 2946 2947

		if (tcp_pacing_check(sk))
			break;

2948
		/* we could do better than to assign each time */
2949
		if (!hole)
2950
			tp->retransmit_skb_hint = skb;
2951

2952 2953
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2954
			return;
E
Eric Dumazet 已提交
2955
		sacked = TCP_SKB_CB(skb)->sacked;
2956 2957 2958 2959
		/* 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
2960

2961 2962
		if (tp->retrans_out >= tp->lost_out) {
			break;
2963
		} else if (!(sacked & TCPCB_LOST)) {
2964
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2965 2966
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2967

2968 2969 2970 2971 2972 2973
		} 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
2974

2975
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2976 2977
			continue;

2978 2979 2980
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2981
		if (tcp_retransmit_skb(sk, skb, segs))
2982
			return;
2983

2984
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2985

2986
		if (tcp_in_cwnd_reduction(sk))
2987 2988
			tp->prr_out += tcp_skb_pcount(skb);

2989 2990
		if (skb == tcp_write_queue_head(sk) &&
		    icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
2991 2992 2993
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2994 2995 2996
	}
}

2997 2998
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2999 3000
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
3001 3002
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
3003
 */
3004
void sk_forced_mem_schedule(struct sock *sk, int size)
3005
{
3006
	int amt;
3007 3008 3009 3010 3011

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3012 3013
	sk_memory_allocated_add(sk, amt);

3014 3015
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3016 3017
}

3018 3019
/* 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
3020 3021 3022
 */
void tcp_send_fin(struct sock *sk)
{
3023
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
3024 3025
	struct tcp_sock *tp = tcp_sk(sk);

3026 3027 3028 3029
	/* 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
3030
	 */
3031
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
3032 3033 3034
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
3035
		tp->write_seq++;
3036 3037 3038 3039 3040 3041 3042 3043 3044 3045
		if (!tcp_send_head(sk)) {
			/* 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
3046
	} else {
3047 3048 3049 3050 3051
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3052
		}
3053
		skb_reserve(skb, MAX_TCP_HEADER);
3054
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3055
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3056
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3057
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3058 3059
		tcp_queue_skb(sk, skb);
	}
3060
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3061 3062 3063 3064 3065
}

/* 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
3066
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3067
 */
A
Al Viro 已提交
3068
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3069 3070 3071
{
	struct sk_buff *skb;

3072 3073
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);

L
Linus Torvalds 已提交
3074 3075 3076
	/* 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
3077
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3078 3079 3080 3081 3082
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3083
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3084
			     TCPHDR_ACK | TCPHDR_RST);
3085
	tcp_mstamp_refresh(tcp_sk(sk));
L
Linus Torvalds 已提交
3086
	/* Send it off. */
3087
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3088
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3089 3090
}

3091 3092
/* 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
3093 3094 3095 3096 3097 3098
 * 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)
{
3099
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3100

3101
	skb = tcp_write_queue_head(sk);
3102
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3103
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3104 3105
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3106
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3107 3108
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
3109
			if (!nskb)
L
Linus Torvalds 已提交
3110
				return -ENOMEM;
3111
			tcp_unlink_write_queue(skb, sk);
3112
			__skb_header_release(nskb);
3113
			__tcp_add_write_queue_head(sk, nskb);
3114 3115 3116
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3117 3118 3119
			skb = nskb;
		}

E
Eric Dumazet 已提交
3120
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3121
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3122
	}
3123
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3124 3125
}

3126 3127 3128 3129 3130 3131 3132 3133 3134
/**
 * 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.
 */
3135
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3136
				struct request_sock *req,
3137
				struct tcp_fastopen_cookie *foc,
3138
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3139
{
3140
	struct inet_request_sock *ireq = inet_rsk(req);
3141
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3142
	struct tcp_md5sig_key *md5 = NULL;
3143 3144
	struct tcp_out_options opts;
	struct sk_buff *skb;
3145
	int tcp_header_size;
3146
	struct tcphdr *th;
3147
	int mss;
L
Linus Torvalds 已提交
3148

3149
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3150 3151
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3152
		return NULL;
3153
	}
L
Linus Torvalds 已提交
3154 3155 3156
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3157 3158
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3159
		skb_set_owner_w(skb, req_to_sk(req));
3160 3161 3162 3163 3164 3165 3166
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3167 3168 3169 3170 3171
		/* 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);
3172
		break;
3173
	}
3174
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3175

E
Eric Dumazet 已提交
3176
	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3177

A
Adam Langley 已提交
3178
	memset(&opts, 0, sizeof(opts));
3179 3180
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
3181
		skb->skb_mstamp = cookie_init_timestamp(req);
3182 3183
	else
#endif
3184
		skb->skb_mstamp = tcp_clock_us();
E
Eric Dumazet 已提交
3185 3186 3187

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3188
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3189
#endif
3190
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3191 3192
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3193

3194 3195
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3196

3197
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3198 3199 3200
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3201
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3202
	th->source = htons(ireq->ir_num);
3203
	th->dest = ireq->ir_rmt_port;
3204
	skb->mark = ireq->ir_mark;
3205 3206 3207 3208
	/* Setting of flags are superfluous here for callers (and ECE is
	 * not even correctly set)
	 */
	tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
C
Changli Gao 已提交
3209
			     TCPHDR_SYN | TCPHDR_ACK);
3210

L
Linus Torvalds 已提交
3211
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3212 3213
	/* 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
3214 3215

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3216
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3217
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3218
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3219
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3220 3221 3222

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3223
	if (md5)
3224
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3225
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3226
	rcu_read_unlock();
3227 3228
#endif

3229
	/* Do not fool tcpdump (if any), clean our debris */
T
Thomas Gleixner 已提交
3230
	skb->tstamp = 0;
L
Linus Torvalds 已提交
3231 3232
	return skb;
}
E
Eric Dumazet 已提交
3233
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3234

3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253
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();
}

3254
/* Do all connect socket setups that can be done AF independent. */
3255
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3256
{
3257
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3258 3259
	struct tcp_sock *tp = tcp_sk(sk);
	__u8 rcv_wscale;
3260
	u32 rcv_wnd;
L
Linus Torvalds 已提交
3261 3262 3263 3264

	/* 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.
	 */
3265 3266 3267
	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
3268

3269
#ifdef CONFIG_TCP_MD5SIG
3270
	if (tp->af_specific->md5_lookup(sk, sk))
3271 3272 3273
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3274 3275 3276 3277
	/* 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
3278
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3279 3280
	tcp_sync_mss(sk, dst_mtu(dst));

3281 3282
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3283 3284
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
E
Eric Dumazet 已提交
3285
	tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3286

L
Linus Torvalds 已提交
3287 3288
	tcp_initialize_rcv_mss(sk);

3289 3290 3291 3292 3293
	/* 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);

3294 3295 3296 3297
	rcv_wnd = tcp_rwnd_init_bpf(sk);
	if (rcv_wnd == 0)
		rcv_wnd = dst_metric(dst, RTAX_INITRWND);

L
Linus Torvalds 已提交
3298 3299 3300 3301
	tcp_select_initial_window(tcp_full_space(sk),
				  tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
				  &tp->rcv_wnd,
				  &tp->window_clamp,
3302
				  sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3303
				  &rcv_wscale,
3304
				  rcv_wnd);
L
Linus Torvalds 已提交
3305 3306 3307 3308 3309 3310 3311

	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;
3312
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3313 3314
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3315
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3316
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3317 3318 3319

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3320
	else
3321
		tp->rcv_tstamp = tcp_jiffies32;
P
Pavel Emelyanov 已提交
3322 3323
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3324

3325
	inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3326
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3327 3328 3329
	tcp_clear_retrans(tp);
}

3330 3331 3332 3333 3334 3335
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;
3336
	__skb_header_release(skb);
3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354
	__tcp_add_write_queue_tail(sk, skb);
	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;
3355
	int space, err = 0;
3356
	struct sk_buff *syn_data;
3357

3358
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3359
	if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3360 3361 3362 3363 3364 3365
		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
3366 3367
	tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);

3368
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3369 3370
		MAX_TCP_OPTION_SPACE;

3371 3372 3373 3374 3375
	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));

3376
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3377
	if (!syn_data)
3378
		goto fallback;
3379 3380
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391
	if (space) {
		int copied = copy_from_iter(skb_put(syn_data, space), space,
					    &fo->data->msg_iter);
		if (unlikely(!copied)) {
			kfree_skb(syn_data);
			goto fallback;
		}
		if (copied != space) {
			skb_trim(syn_data, copied);
			space = copied;
		}
3392
	}
3393 3394 3395 3396
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3397

3398
	tcp_connect_queue_skb(sk, syn_data);
3399 3400
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3401

3402
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3403

3404
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3405

3406 3407 3408 3409 3410 3411 3412 3413
	/* 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) {
3414
		tp->syn_data = (fo->copied > 0);
3415
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430
		goto done;
	}

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;
}

3431
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3432 3433 3434 3435
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3436
	int err;
L
Linus Torvalds 已提交
3437

3438
	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB);
L
Linus Torvalds 已提交
3439 3440
	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3441 3442 3443 3444 3445
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3446
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3447
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3448 3449
		return -ENOBUFS;

C
Changli Gao 已提交
3450
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3451 3452
	tcp_mstamp_refresh(tp);
	tp->retrans_stamp = tcp_time_stamp(tp);
3453
	tcp_connect_queue_skb(sk, buff);
3454
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3455

3456 3457 3458
	/* 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);
3459 3460
	if (err == -ECONNREFUSED)
		return err;
3461 3462 3463 3464 3465 3466

	/* 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;
P
Pavel Emelyanov 已提交
3467
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3468 3469

	/* Timer for repeating the SYN until an answer. */
3470 3471
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3472 3473
	return 0;
}
E
Eric Dumazet 已提交
3474
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3475 3476 3477 3478 3479 3480 3481

/* 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)
{
3482 3483
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3484 3485
	unsigned long timeout;

3486 3487
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3488
	if (ato > TCP_DELACK_MIN) {
3489
		const struct tcp_sock *tp = tcp_sk(sk);
3490
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3491

3492 3493
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3494 3495 3496 3497 3498
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3499
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3500 3501
		 * directly.
		 */
3502 3503 3504
		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
3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516

			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. */
3517
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3518 3519 3520
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3521 3522
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3523 3524 3525 3526
			tcp_send_ack(sk);
			return;
		}

3527 3528
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3529
	}
3530 3531 3532
	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
3533 3534 3535 3536 3537
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3538
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3539

3540 3541 3542
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3543

3544 3545
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3546 3547 3548 3549
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3550 3551 3552
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3553 3554 3555 3556 3557
		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
3558
	}
3559 3560 3561

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3562
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3563

E
Eric Dumazet 已提交
3564 3565 3566 3567 3568 3569
	/* 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);

3570
	/* Send it off, this clears delayed acks for us. */
3571
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3572
}
3573
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585

/* 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.
 */
3586
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3587 3588 3589 3590 3591
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3592 3593
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3594
	if (!skb)
L
Linus Torvalds 已提交
3595 3596 3597 3598 3599 3600 3601 3602
		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
3603
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3604
	NET_INC_STATS(sock_net(sk), mib);
3605
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3606 3607
}

3608
/* Called from setsockopt( ... TCP_REPAIR ) */
P
Pavel Emelyanov 已提交
3609 3610 3611 3612
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;
3613
		tcp_mstamp_refresh(tcp_sk(sk));
3614
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3615 3616 3617
	}
}

3618
/* Initiate keepalive or window probe from timer. */
3619
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3620
{
3621 3622
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3623

3624 3625 3626
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3627 3628
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3629
		int err;
I
Ilpo Järvinen 已提交
3630
		unsigned int mss = tcp_current_mss(sk);
3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642
		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
3643
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3644
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3645 3646
				return -1;
		} else if (!tcp_skb_pcount(skb))
3647
			tcp_set_skb_tso_segs(skb, mss);
3648

E
Eric Dumazet 已提交
3649
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3650 3651 3652 3653 3654
		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
3655
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3656 3657
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3658 3659 3660 3661 3662 3663 3664 3665
	}
}

/* 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)
{
3666
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3667
	struct tcp_sock *tp = tcp_sk(sk);
3668
	struct net *net = sock_net(sk);
3669
	unsigned long probe_max;
L
Linus Torvalds 已提交
3670 3671
	int err;

3672
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3673

3674
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3675
		/* Cancel probe timer, if it is not required. */
3676
		icsk->icsk_probes_out = 0;
3677
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3678 3679 3680 3681
		return;
	}

	if (err <= 0) {
3682
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3683
			icsk->icsk_backoff++;
3684
		icsk->icsk_probes_out++;
3685
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3686 3687
	} else {
		/* If packet was not sent due to local congestion,
3688
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3689 3690 3691 3692
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3693 3694
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3695
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3696
	}
3697
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3698
				  tcp_probe0_when(sk, probe_max),
3699
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3700
}
3701

3702
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3703 3704 3705 3706 3707
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3708
	tcp_rsk(req)->txhash = net_tx_rndhash();
3709
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3710
	if (!res) {
E
Eric Dumazet 已提交
3711
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3712
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3713 3714
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3715 3716 3717 3718
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);