tcp_output.c 106.9 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;

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

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

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

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

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

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

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

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

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

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

974 975 976 977 978 979
static void tcp_update_skb_after_send(struct tcp_sock *tp, struct sk_buff *skb)
{
	skb->skb_mstamp = tp->tcp_mstamp;
	list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
}

L
Linus Torvalds 已提交
980 981 982 983 984 985 986 987 988 989 990
/* 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.
 */
991 992
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
993
{
994 995 996 997
	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
998
	struct tcp_out_options opts;
999
	unsigned int tcp_options_size, tcp_header_size;
1000
	struct sk_buff *oskb = NULL;
1001
	struct tcp_md5sig_key *md5;
1002 1003 1004 1005
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
1006
	tp = tcp_sk(sk);
1007

1008
	if (clone_it) {
1009 1010
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
1011
		oskb = skb;
1012 1013 1014 1015 1016 1017 1018 1019

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

1020 1021 1022
		if (unlikely(!skb))
			return -ENOBUFS;
	}
1023
	skb->skb_mstamp = tp->tcp_mstamp;
L
Linus Torvalds 已提交
1024

1025 1026
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
1027
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
1028

E
Eric Dumazet 已提交
1029
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
1030 1031 1032 1033 1034
		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);
1035

E
Eric Dumazet 已提交
1036
	/* if no packet is in qdisc/device queue, then allow XPS to select
1037 1038 1039 1040 1041
	 * 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
1042
	 */
1043
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1044

1045 1046 1047 1048 1049 1050 1051
	/* 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;

1052 1053
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
1054 1055 1056

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
1057
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1058
	skb_set_hash_from_sk(skb, sk);
1059
	refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1060

1061 1062
	skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);

1063
	/* Build TCP header and checksum it. */
1064
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
1065 1066
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
1067 1068
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
1069
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
1070
					tcb->tcp_flags);
1071 1072 1073

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
1074

I
Ilpo Järvinen 已提交
1075
	/* The urg_mode check is necessary during a below snd_una win probe */
1076 1077 1078 1079 1080
	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)) {
1081
			th->urg_ptr = htons(0xFFFF);
1082 1083
			th->urg = 1;
		}
1084
	}
L
Linus Torvalds 已提交
1085

1086
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1087
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1088 1089 1090 1091 1092 1093 1094 1095 1096
	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));
	}
1097 1098 1099
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1100
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1101
		tp->af_specific->calc_md5_hash(opts.hash_location,
1102
					       md5, sk, skb);
1103 1104 1105
	}
#endif

1106
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1107

E
Eric Dumazet 已提交
1108
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1109
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1110

1111
	if (skb->len != tcp_header_size) {
1112
		tcp_event_data_sent(tp, sk);
1113
		tp->data_segs_out += tcp_skb_pcount(skb);
1114
		tcp_internal_pacing(sk, skb);
1115
	}
L
Linus Torvalds 已提交
1116

1117
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1118 1119
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1120

1121
	tp->segs_out += tcp_skb_pcount(skb);
1122
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1123
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1124
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1125

E
Eric Dumazet 已提交
1126
	/* Our usage of tstamp should remain private */
T
Thomas Gleixner 已提交
1127
	skb->tstamp = 0;
1128 1129 1130 1131 1132

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

1133
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1134

1135 1136 1137 1138
	if (unlikely(err > 0)) {
		tcp_enter_cwr(sk);
		err = net_xmit_eval(err);
	}
E
Eric Dumazet 已提交
1139
	if (!err && oskb) {
1140
		tcp_update_skb_after_send(tp, oskb);
E
Eric Dumazet 已提交
1141 1142
		tcp_rate_skb_sent(sk, oskb);
	}
1143
	return err;
L
Linus Torvalds 已提交
1144 1145
}

1146
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1147 1148 1149 1150 1151 1152 1153 1154 1155 1156
 *
 * 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;
1157
	__skb_header_release(skb);
1158
	tcp_add_write_queue_tail(sk, skb);
1159 1160
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1161 1162
}

1163
/* Initialize TSO segments for a packet. */
1164
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1165
{
1166
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1167 1168 1169
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1170
		tcp_skb_pcount_set(skb, 1);
1171
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1172
	} else {
1173
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1174
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1175 1176 1177
	}
}

I
Ilpo Järvinen 已提交
1178
/* When a modification to fackets out becomes necessary, we need to check
1179
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1180
 */
1181
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1182 1183
				   int decr)
{
1184 1185
	struct tcp_sock *tp = tcp_sk(sk);

1186
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1187 1188
		return;

1189
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1190 1191 1192
		tp->fackets_out -= decr;
}

1193 1194 1195
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1196
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216
{
	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) &&
1217
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1218 1219 1220 1221 1222
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1223 1224 1225 1226 1227 1228
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);
}

1229 1230 1231 1232
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1233
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1234 1235 1236 1237 1238 1239 1240
	    !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);
1241 1242
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1243 1244 1245
	}
}

1246 1247 1248 1249 1250 1251
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
1252 1253
/* 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
1254
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1255 1256
 * Remember, these are still headerless SKBs at this point.
 */
1257
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1258
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1259 1260 1261
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1262
	int nsize, old_factor;
1263
	int nlen;
1264
	u8 flags;
L
Linus Torvalds 已提交
1265

1266 1267
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1268

L
Linus Torvalds 已提交
1269 1270 1271 1272
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1273
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1274 1275 1276
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1277
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1278
	if (!buff)
L
Linus Torvalds 已提交
1279
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1280

1281 1282
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1283 1284 1285
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1286 1287 1288 1289 1290 1291 1292

	/* 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
1293 1294 1295
	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;
1296
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1297
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1298

1299
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1300
		/* Copy and checksum data tail into the new buffer. */
1301 1302
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1303 1304 1305 1306 1307 1308
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1309
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1310 1311 1312 1313 1314
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1315
	buff->tstamp = skb->tstamp;
1316
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1317

1318 1319
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1320
	/* Fix up tso_factor for both original and new SKB.  */
1321 1322
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1323

1324 1325 1326
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1327 1328 1329
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1330
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1331 1332
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1333

1334 1335
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1336 1337 1338
	}

	/* Link BUFF into the send queue. */
1339
	__skb_header_release(buff);
1340
	tcp_insert_write_queue_after(skb, buff, sk);
1341
	list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
L
Linus Torvalds 已提交
1342 1343 1344 1345

	return 0;
}

1346 1347
/* 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
1348
 */
1349
static int __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1350
{
1351
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1352 1353
	int i, k, eat;

E
Eric Dumazet 已提交
1354 1355 1356 1357 1358
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
1359
			return 0;
E
Eric Dumazet 已提交
1360
	}
L
Linus Torvalds 已提交
1361 1362
	eat = len;
	k = 0;
1363 1364 1365
	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
1366 1367

		if (size <= eat) {
1368
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1369
			eat -= size;
L
Linus Torvalds 已提交
1370
		} else {
1371
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1372
			if (eat) {
1373 1374
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1375 1376 1377 1378 1379
				eat = 0;
			}
			k++;
		}
	}
1380
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1381 1382 1383

	skb->data_len -= len;
	skb->len = skb->data_len;
1384
	return len;
L
Linus Torvalds 已提交
1385 1386
}

1387
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1388 1389
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1390 1391
	u32 delta_truesize;

1392
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1393 1394
		return -ENOMEM;

1395
	delta_truesize = __pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1396 1397

	TCP_SKB_CB(skb)->seq += len;
1398
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1399

1400 1401 1402 1403 1404 1405
	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
1406

1407
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1408
	if (tcp_skb_pcount(skb) > 1)
1409
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1410 1411 1412 1413

	return 0;
}

1414 1415
/* 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
1416
{
1417 1418
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1419 1420 1421 1422 1423 1424 1425
	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);

1426 1427 1428 1429 1430 1431 1432 1433
	/* 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
1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446
	/* 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;
}

1447 1448 1449 1450 1451 1452 1453 1454
/* 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
1455
/* Inverse of above */
1456
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1457
{
1458 1459
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1460 1461 1462 1463 1464 1465 1466
	int mtu;

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

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

		if (dst && dst_allfrag(dst))
			mtu += icsk->icsk_af_ops->net_frag_header_len;
	}
J
John Heffner 已提交
1474 1475
	return mtu;
}
1476
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1477

1478
/* MTU probing init per socket */
J
John Heffner 已提交
1479 1480 1481 1482
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
1483
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1484

F
Fan Du 已提交
1485
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1486
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1487
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1488
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1489
	icsk->icsk_mtup.probe_size = 0;
1490
	if (icsk->icsk_mtup.enabled)
1491
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
J
John Heffner 已提交
1492
}
E
Eric Dumazet 已提交
1493
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1494

L
Linus Torvalds 已提交
1495 1496 1497 1498 1499 1500
/* 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
1501
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1502 1503
   It also does not include TCP options.

1504
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1505 1506 1507 1508 1509 1510 1511 1512 1513

   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.

1514 1515
   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
1516 1517 1518 1519
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1520
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1521
	int mss_now;
L
Linus Torvalds 已提交
1522

J
John Heffner 已提交
1523 1524
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1525

J
John Heffner 已提交
1526
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1527
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1528 1529

	/* And store cached results */
1530
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1531 1532
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1533
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1534 1535 1536

	return mss_now;
}
E
Eric Dumazet 已提交
1537
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1538 1539 1540 1541

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1542
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1543
{
1544 1545
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1546
	u32 mss_now;
1547
	unsigned int header_len;
A
Adam Langley 已提交
1548 1549
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1550 1551 1552

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1553 1554
	if (dst) {
		u32 mtu = dst_mtu(dst);
1555
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1556 1557 1558
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1559 1560 1561 1562 1563 1564 1565 1566 1567 1568
	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;
	}
1569

L
Linus Torvalds 已提交
1570 1571 1572
	return mss_now;
}

1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591
/* 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;
	}
1592
	tp->snd_cwnd_stamp = tcp_jiffies32;
1593 1594
}

1595
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1596
{
1597
	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1598
	struct tcp_sock *tp = tcp_sk(sk);
1599

1600 1601 1602 1603 1604 1605 1606 1607 1608
	/* 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;
	}
1609

1610
	if (tcp_is_cwnd_limited(sk)) {
1611 1612
		/* Network is feed fully. */
		tp->snd_cwnd_used = 0;
1613
		tp->snd_cwnd_stamp = tcp_jiffies32;
1614 1615 1616 1617 1618
	} else {
		/* Network starves. */
		if (tp->packets_out > tp->snd_cwnd_used)
			tp->snd_cwnd_used = tp->packets_out;

1619
		if (sysctl_tcp_slow_start_after_idle &&
1620
		    (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1621
		    !ca_ops->cong_control)
1622
			tcp_cwnd_application_limited(sk);
1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634

		/* 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);
1635 1636 1637
	}
}

E
Eric Dumazet 已提交
1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651
/* 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
1652
 */
E
Eric Dumazet 已提交
1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667
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,
1668
			    int nonagle)
E
Eric Dumazet 已提交
1669 1670 1671 1672 1673
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1674 1675 1676 1677

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1678 1679
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690
{
	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.
	 */
1691
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1692 1693 1694

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1695
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1696

1697 1698 1699 1700 1701 1702 1703 1704
/* 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;

1705 1706
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1707 1708
}

E
Eric Dumazet 已提交
1709 1710 1711 1712 1713 1714
/* 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)
1715
{
1716
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1717
	u32 partial, needed, window, max_len;
1718

1719
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1720
	max_len = mss_now * max_segs;
1721

1722 1723
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1724

1725 1726
	needed = min(skb->len, window);

1727 1728
	if (max_len <= needed)
		return max_len;
1729

E
Eric Dumazet 已提交
1730 1731 1732 1733 1734
	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
	 */
1735
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1736 1737 1738
		return needed - partial;

	return needed;
1739 1740 1741 1742 1743
}

/* 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.
 */
1744 1745
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1746
{
E
Eric Dumazet 已提交
1747
	u32 in_flight, cwnd, halfcwnd;
1748 1749

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1750 1751
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1752 1753 1754 1755
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1756 1757
	if (in_flight >= cwnd)
		return 0;
1758

E
Eric Dumazet 已提交
1759 1760 1761 1762 1763
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1764 1765
}

1766
/* Initialize TSO state of a skb.
1767
 * This must be invoked the first time we consider transmitting
1768 1769
 * SKB onto the wire.
 */
1770
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1771 1772 1773
{
	int tso_segs = tcp_skb_pcount(skb);

1774
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1775
		tcp_set_skb_tso_segs(skb, mss_now);
1776 1777 1778 1779 1780 1781
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1782
/* Return true if the Nagle test allows this packet to be
1783 1784
 * sent now.
 */
E
Eric Dumazet 已提交
1785 1786
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1787 1788 1789 1790 1791 1792 1793 1794
{
	/* 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
1795
		return true;
1796

Y
Yuchung Cheng 已提交
1797 1798
	/* 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
1799
		return true;
1800

1801
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1802
		return true;
1803

E
Eric Dumazet 已提交
1804
	return false;
1805 1806 1807
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1808 1809 1810
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1811 1812 1813 1814 1815 1816
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1817
	return !after(end_seq, tcp_wnd_end(tp));
1818 1819 1820 1821 1822 1823 1824 1825 1826
}

/* 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).
 */
1827
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1828
			unsigned int mss_now, gfp_t gfp)
1829 1830 1831
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1832
	u8 flags;
1833 1834

	/* All of a TSO frame must be composed of paged data.  */
1835
	if (skb->len != skb->data_len)
1836
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1837

1838
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1839
	if (unlikely(!buff))
1840 1841
		return -ENOMEM;

1842 1843
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1844
	buff->truesize += nlen;
1845 1846 1847 1848 1849 1850 1851 1852
	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
1853 1854 1855
	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;
1856 1857 1858 1859

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

1860 1861
	tcp_skb_fragment_eor(skb, buff);

1862
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1863
	skb_split(skb, buff, len);
1864
	tcp_fragment_tstamp(skb, buff);
1865 1866

	/* Fix up tso_factor for both original and new SKB.  */
1867 1868
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1869 1870

	/* Link BUFF into the send queue. */
1871
	__skb_header_release(buff);
1872
	tcp_insert_write_queue_after(skb, buff, sk);
1873 1874 1875 1876 1877 1878 1879 1880 1881

	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.
 */
1882
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1883
				 bool *is_cwnd_limited, u32 max_segs)
1884
{
1885
	const struct inet_connection_sock *icsk = inet_csk(sk);
1886 1887 1888
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *head;
1889
	int win_divisor;
1890

E
Eric Dumazet 已提交
1891
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1892
		goto send_now;
1893

1894
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1895 1896
		goto send_now;

E
Eric Dumazet 已提交
1897 1898 1899
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
1900
	if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
J
John Heffner 已提交
1901
		goto send_now;
1902

1903 1904
	in_flight = tcp_packets_in_flight(tp);

1905
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1906

1907
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1908 1909 1910 1911 1912 1913

	/* 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);

1914
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1915
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1916
		goto send_now;
1917

1918 1919 1920 1921
	/* 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;

1922 1923
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1924 1925 1926 1927 1928
		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.
		 */
1929
		chunk /= win_divisor;
1930
		if (limit >= chunk)
J
John Heffner 已提交
1931
			goto send_now;
1932 1933 1934 1935 1936 1937
	} 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.
		 */
1938
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1939
			goto send_now;
1940 1941
	}

1942
	head = tcp_write_queue_head(sk);
1943

1944
	age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
1945 1946 1947 1948
	/* 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
1949
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1950

1951
	if (cong_win < send_win && cong_win <= skb->len)
1952 1953
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1954
	return true;
J
John Heffner 已提交
1955 1956

send_now:
E
Eric Dumazet 已提交
1957
	return false;
1958 1959
}

1960 1961 1962 1963 1964 1965 1966 1967 1968
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;
1969
	delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980
	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 */
1981
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1982 1983 1984
	}
}

J
John Heffner 已提交
1985
/* Create a new MTU probe if we are ready.
1986 1987 1988 1989
 * 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
1990 1991
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1992 1993
 *         -1 otherwise
 */
J
John Heffner 已提交
1994 1995 1996
static int tcp_mtu_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
1997
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
1998
	struct sk_buff *skb, *nskb, *next;
1999
	struct net *net = sock_net(sk);
J
John Heffner 已提交
2000
	int probe_size;
2001
	int size_needed;
2002
	int copy, len;
J
John Heffner 已提交
2003
	int mss_now;
2004
	int interval;
J
John Heffner 已提交
2005 2006 2007 2008

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
2009 2010 2011 2012 2013 2014 2015
	 * 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
2016 2017
		return -1;

2018 2019 2020 2021
	/* 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
2022
	mss_now = tcp_current_mss(sk);
2023 2024
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
2025
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2026
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2027 2028 2029 2030
	/* 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.
	 */
2031
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2032 2033 2034 2035 2036
		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
2037 2038 2039 2040
		return -1;
	}

	/* Have enough data in the send queue to probe? */
2041
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
2042 2043
		return -1;

2044 2045
	if (tp->snd_wnd < size_needed)
		return -1;
2046
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2047
		return 0;
J
John Heffner 已提交
2048

2049 2050 2051
	/* 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
2052 2053 2054 2055 2056 2057
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
2058
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2059
	if (!nskb)
J
John Heffner 已提交
2060
		return -1;
2061 2062
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2063

2064
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2065 2066 2067

	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
2068
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2069 2070
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2071
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2072

2073 2074
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2075
	len = 0;
2076
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2077
		copy = min_t(int, skb->len, probe_size - len);
2078
		if (nskb->ip_summed) {
J
John Heffner 已提交
2079
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2080 2081 2082 2083 2084 2085
		} 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
2086 2087 2088 2089

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2090
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2091
			tcp_unlink_write_queue(skb, sk);
2092
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2093
		} else {
E
Eric Dumazet 已提交
2094
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2095
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2096 2097
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2098
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2099 2100
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2101 2102
			} else {
				__pskb_trim_head(skb, copy);
2103
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2104 2105 2106 2107 2108
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2109 2110 2111

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2112
	}
2113
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2114 2115

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2116 2117
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2118 2119
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2120
		 * effectively two packets. */
J
John Heffner 已提交
2121
		tp->snd_cwnd--;
2122
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2123 2124

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2125 2126
		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
2127 2128 2129 2130 2131 2132 2133

		return 1;
	}

	return -1;
}

2134 2135 2136 2137 2138 2139
static bool tcp_pacing_check(const struct sock *sk)
{
	return tcp_needs_internal_pacing(sk) &&
	       hrtimer_active(&tcp_sk(sk)->pacing_timer);
}

2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159
/* 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;

2160
	if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2161 2162 2163 2164 2165 2166 2167 2168 2169
		/* 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;

2170
		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2171 2172 2173 2174 2175
		/* It is possible TX completion already happened
		 * before we set TSQ_THROTTLED, so we must
		 * test again the condition.
		 */
		smp_mb__after_atomic();
2176
		if (refcount_read(&sk->sk_wmem_alloc) > limit)
2177 2178 2179 2180 2181
			return true;
	}
	return false;
}

2182 2183
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
2184
	const u32 now = tcp_jiffies32;
2185
	enum tcp_chrono old = tp->chrono_type;
2186

2187 2188
	if (old > TCP_CHRONO_UNSPEC)
		tp->chrono_stat[old - 1] += now - tp->chrono_start;
2189 2190 2191 2192 2193 2194 2195 2196 2197
	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
2198 2199
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2200 2201 2202 2203 2204 2205 2206 2207 2208 2209
	 * 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);

2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221

	/* 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);
2222 2223
}

L
Linus Torvalds 已提交
2224 2225 2226 2227
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2228 2229 2230 2231
 * 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
2232 2233 2234
 * 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
2235 2236
 * 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
2237
 */
E
Eric Dumazet 已提交
2238 2239
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
2240 2241
{
	struct tcp_sock *tp = tcp_sk(sk);
2242
	struct sk_buff *skb;
2243 2244
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2245
	int result;
2246
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2247
	u32 max_segs;
L
Linus Torvalds 已提交
2248

2249
	sent_pkts = 0;
J
John Heffner 已提交
2250

2251 2252 2253 2254
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2255
			return false;
2256 2257 2258
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2259 2260
	}

2261
	max_segs = tcp_tso_segs(sk, mss_now);
2262
	tcp_mstamp_refresh(tp);
2263
	while ((skb = tcp_send_head(sk))) {
2264 2265
		unsigned int limit;

2266 2267 2268
		if (tcp_pacing_check(sk))
			break;

2269
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2270
		BUG_ON(!tso_segs);
2271

2272
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2273
			/* "skb_mstamp" is used as a start point for the retransmit timer */
2274
			tcp_update_skb_after_send(tp, skb);
2275
			goto repair; /* Skip network transmission */
2276
		}
2277

2278
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2279 2280 2281 2282 2283 2284 2285
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2286

2287 2288
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2289
			break;
2290
		}
2291

2292
		if (tso_segs == 1) {
2293 2294 2295 2296 2297
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2298
			if (!push_one &&
E
Eric Dumazet 已提交
2299 2300
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2301 2302
				break;
		}
2303

E
Eric Dumazet 已提交
2304
		limit = mss_now;
2305
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2306 2307 2308 2309 2310 2311 2312 2313 2314 2315
			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;

2316 2317
		if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
			clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
2318 2319
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2320

2321
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2322
			break;
L
Linus Torvalds 已提交
2323

2324
repair:
2325 2326 2327
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2328
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2329

2330
		tcp_minshall_update(tp, mss_now, skb);
2331
		sent_pkts += tcp_skb_pcount(skb);
2332 2333 2334

		if (push_one)
			break;
2335
	}
L
Linus Torvalds 已提交
2336

2337 2338 2339 2340 2341
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2342
	if (likely(sent_pkts)) {
2343 2344
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2345 2346 2347 2348

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2349
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2350
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2351
		return false;
L
Linus Torvalds 已提交
2352
	}
2353
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2354 2355 2356 2357 2358 2359
}

bool tcp_schedule_loss_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
2360
	u32 timeout, rto_delta_us;
N
Nandita Dukkipati 已提交
2361 2362 2363 2364

	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
2365
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2366 2367 2368 2369 2370
		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
2371 2372 2373
	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
2374 2375 2376 2377 2378 2379
		return false;

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

2380
	/* Probe timeout is 2*rtt. Add minimum RTO to account
2381 2382
	 * 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
2383
	 */
2384 2385 2386 2387 2388 2389 2390 2391 2392
	if (tp->srtt_us) {
		timeout = usecs_to_jiffies(tp->srtt_us >> 2);
		if (tp->packets_out == 1)
			timeout += TCP_RTO_MIN;
		else
			timeout += TCP_TIMEOUT_MIN;
	} else {
		timeout = TCP_TIMEOUT_INIT;
	}
N
Nandita Dukkipati 已提交
2393

2394 2395 2396 2397
	/* 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
2398 2399 2400 2401 2402 2403

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

2404 2405 2406 2407 2408 2409 2410
/* 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)
{
2411
	if (unlikely(skb_fclone_busy(sk, skb))) {
2412 2413
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2414 2415 2416 2417 2418
		return true;
	}
	return false;
}

2419
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2420 2421 2422 2423
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2424
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2425 2426 2427 2428
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440
	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
2441 2442
	}

N
Nandita Dukkipati 已提交
2443 2444 2445 2446
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2447 2448 2449 2450
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2451 2452 2453
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2454 2455 2456 2457 2458
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2459 2460
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2461
			goto rearm_timer;
2462
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2463 2464 2465 2466 2467
	}

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

2468
	if (__tcp_retransmit_skb(sk, skb, 1))
2469
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2470

N
Nandita Dukkipati 已提交
2471
	/* Record snd_nxt for loss detection. */
2472
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2473

2474
probe_sent:
2475
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2476 2477
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2478
rearm_timer:
2479
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2480 2481
}

2482 2483 2484 2485
/* 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.
 */
2486 2487
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2488
{
2489 2490 2491 2492 2493 2494 2495
	/* 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;

2496
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2497
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2498
		tcp_check_probe_timer(sk);
2499 2500
}

2501 2502 2503 2504 2505
/* 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)
{
2506
	struct sk_buff *skb = tcp_send_head(sk);
2507 2508 2509

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

2510
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2511 2512
}

L
Linus Torvalds 已提交
2513 2514
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2515
 *
L
Linus Torvalds 已提交
2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533
 * 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.
2534
 *
L
Linus Torvalds 已提交
2535 2536
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2537
 *
L
Linus Torvalds 已提交
2538
 * BSD seems to make the following compromise:
2539
 *
L
Linus Torvalds 已提交
2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566
 *	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)
{
2567
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2568
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2569
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2570 2571 2572 2573 2574
	 * 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
	 */
2575
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2576
	int free_space = tcp_space(sk);
2577 2578
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2579 2580
	int window;

2581
	if (unlikely(mss > full_space)) {
2582
		mss = full_space;
2583 2584 2585
		if (mss <= 0)
			return 0;
	}
2586
	if (free_space < (full_space >> 1)) {
2587
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2588

2589
		if (tcp_under_memory_pressure(sk))
2590 2591
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2592

2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605
		/* 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
2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621
			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.
		 */
2622
		window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
L
Linus Torvalds 已提交
2623
	} else {
2624
		window = tp->rcv_wnd;
L
Linus Torvalds 已提交
2625 2626 2627 2628 2629 2630 2631 2632 2633
		/* 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)
2634
			window = rounddown(free_space, mss);
2635
		else if (mss == full_space &&
2636
			 free_space > window + (full_space >> 1))
2637
			window = free_space;
L
Linus Torvalds 已提交
2638 2639 2640 2641 2642
	}

	return window;
}

2643 2644
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2645
{
2646 2647 2648
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2649 2650
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2651
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2652
		shinfo->tskey = next_shinfo->tskey;
2653 2654
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2655 2656 2657
	}
}

2658
/* Collapses two adjacent SKB's during retransmission. */
2659
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2660 2661
{
	struct tcp_sock *tp = tcp_sk(sk);
2662
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2663
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2664

2665 2666
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2667

2668
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2669

2670 2671 2672 2673 2674 2675 2676
	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;
	}
2677
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2678

2679
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2680

2681 2682
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2683

2684 2685
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2686

2687 2688
	/* 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
2689

2690
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2691
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2692 2693 2694 2695 2696

	/* 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;
2697
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2698 2699

	/* changed transmit queue under us so clear hints */
2700 2701 2702
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2703

2704 2705
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2706 2707
	tcp_skb_collapse_tstamp(skb, next_skb);

2708
	sk_wmem_free_skb(sk, next_skb);
2709
	return true;
L
Linus Torvalds 已提交
2710 2711
}

2712
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2713
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2714 2715
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2716
		return false;
2717
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2718
		return false;
2719
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2720
		return false;
E
Eric Dumazet 已提交
2721
	/* Some heuristics for collapsing over SACK'd could be invented */
2722
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2723
		return false;
2724

E
Eric Dumazet 已提交
2725
	return true;
2726 2727
}

2728 2729 2730
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2731 2732 2733 2734 2735
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
2736
	bool first = true;
2737 2738 2739

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2740
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2741 2742 2743 2744 2745 2746
		return;

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

2747 2748 2749
		if (!tcp_skb_can_collapse_to(to))
			break;

2750 2751 2752
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2753
			first = false;
2754 2755 2756 2757 2758 2759 2760 2761 2762
			continue;
		}

		if (space < 0)
			break;

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

2763 2764
		if (!tcp_collapse_retrans(sk, to))
			break;
2765 2766 2767
	}
}

L
Linus Torvalds 已提交
2768 2769 2770 2771
/* 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.
 */
2772
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2773
{
J
John Heffner 已提交
2774
	struct inet_connection_sock *icsk = inet_csk(sk);
2775
	struct tcp_sock *tp = tcp_sk(sk);
2776
	unsigned int cur_mss;
2777 2778
	int diff, len, err;

L
Linus Torvalds 已提交
2779

2780 2781
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2782 2783
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2784
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2785
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2786
	 */
2787
	if (refcount_read(&sk->sk_wmem_alloc) >
2788 2789
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2790 2791
		return -EAGAIN;

2792 2793 2794
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2795 2796 2797 2798 2799 2800 2801
	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;
	}

2802 2803 2804
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2805
	cur_mss = tcp_current_mss(sk);
2806

L
Linus Torvalds 已提交
2807 2808 2809 2810 2811
	/* 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.
	 */
2812 2813
	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
2814 2815
		return -EAGAIN;

2816 2817 2818
	len = cur_mss * segs;
	if (skb->len > len) {
		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2819
			return -ENOMEM; /* We'll try again later. */
2820
	} else {
2821 2822
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2823

2824 2825 2826 2827 2828 2829 2830
		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
2831 2832
	}

2833 2834 2835 2836
	/* 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);

2837 2838 2839 2840 2841 2842 2843
	/* 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;

2844 2845 2846 2847 2848 2849
	/* 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)) {
2850 2851
		struct sk_buff *nskb;

2852 2853 2854 2855 2856 2857
		tcp_skb_tsorted_save(skb) {
			nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
			err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
				     -ENOBUFS;
		} tcp_skb_tsorted_restore(skb);

2858
		if (!err)
2859
			tcp_update_skb_after_send(tp, skb);
E
Eric Dumazet 已提交
2860
	} else {
2861
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2862
	}
2863

2864
	if (likely(!err)) {
2865
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2866 2867
	} else if (err != -EBUSY) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2868
	}
2869
	return err;
2870 2871
}

2872
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2873 2874
{
	struct tcp_sock *tp = tcp_sk(sk);
2875
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2876 2877 2878

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2879
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2880
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2881 2882 2883 2884 2885 2886 2887
		}
#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
2888
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2889 2890

	}
Y
Yuchung Cheng 已提交
2891 2892 2893 2894

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907
	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)
{
2908
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2909 2910
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2911
	struct sk_buff *hole = NULL;
2912
	u32 max_segs;
2913
	int mib_idx;
2914

2915 2916 2917
	if (!tp->packets_out)
		return;

2918
	if (tp->retransmit_skb_hint) {
2919
		skb = tp->retransmit_skb_hint;
2920
	} else {
2921
		skb = tcp_write_queue_head(sk);
2922
	}
L
Linus Torvalds 已提交
2923

2924
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2925
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2926
		__u8 sacked;
2927
		int segs;
L
Linus Torvalds 已提交
2928

2929 2930
		if (skb == tcp_send_head(sk))
			break;
2931 2932 2933 2934

		if (tcp_pacing_check(sk))
			break;

2935
		/* we could do better than to assign each time */
2936
		if (!hole)
2937
			tp->retransmit_skb_hint = skb;
2938

2939 2940
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2941
			return;
E
Eric Dumazet 已提交
2942
		sacked = TCP_SKB_CB(skb)->sacked;
2943 2944 2945 2946
		/* 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
2947

2948 2949
		if (tp->retrans_out >= tp->lost_out) {
			break;
2950
		} else if (!(sacked & TCPCB_LOST)) {
2951
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2952 2953
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2954

2955 2956 2957 2958 2959 2960
		} 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
2961

2962
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2963 2964
			continue;

2965 2966 2967
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2968
		if (tcp_retransmit_skb(sk, skb, segs))
2969
			return;
2970

2971
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2972

2973
		if (tcp_in_cwnd_reduction(sk))
2974 2975
			tp->prr_out += tcp_skb_pcount(skb);

2976 2977
		if (skb == tcp_write_queue_head(sk) &&
		    icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
2978 2979 2980
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2981 2982 2983
	}
}

2984 2985
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2986 2987
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2988 2989
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2990
 */
2991
void sk_forced_mem_schedule(struct sock *sk, int size)
2992
{
2993
	int amt;
2994 2995 2996 2997 2998

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2999 3000
	sk_memory_allocated_add(sk, amt);

3001 3002
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3003 3004
}

3005 3006
/* 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
3007 3008 3009
 */
void tcp_send_fin(struct sock *sk)
{
3010
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
3011 3012
	struct tcp_sock *tp = tcp_sk(sk);

3013 3014 3015 3016
	/* 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
3017
	 */
3018
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
3019 3020 3021
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
3022
		tp->write_seq++;
3023 3024 3025 3026 3027 3028 3029 3030 3031 3032
		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
3033
	} else {
3034 3035 3036 3037 3038
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3039
		}
3040
		INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3041
		skb_reserve(skb, MAX_TCP_HEADER);
3042
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3043
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3044
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3045
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3046 3047
		tcp_queue_skb(sk, skb);
	}
3048
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3049 3050 3051 3052 3053
}

/* 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
3054
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3055
 */
A
Al Viro 已提交
3056
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3057 3058 3059
{
	struct sk_buff *skb;

3060 3061
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);

L
Linus Torvalds 已提交
3062 3063 3064
	/* 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
3065
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3066 3067 3068 3069 3070
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3071
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3072
			     TCPHDR_ACK | TCPHDR_RST);
3073
	tcp_mstamp_refresh(tcp_sk(sk));
L
Linus Torvalds 已提交
3074
	/* Send it off. */
3075
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3076
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3077 3078
}

3079 3080
/* 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
3081 3082 3083 3084 3085 3086
 * 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)
{
3087
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3088

3089
	skb = tcp_write_queue_head(sk);
3090
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3091
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3092 3093
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3094
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3095
		if (skb_cloned(skb)) {
3096 3097 3098 3099 3100
			struct sk_buff *nskb;

			tcp_skb_tsorted_save(skb) {
				nskb = skb_copy(skb, GFP_ATOMIC);
			} tcp_skb_tsorted_restore(skb);
3101
			if (!nskb)
L
Linus Torvalds 已提交
3102
				return -ENOMEM;
3103
			INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3104
			tcp_unlink_write_queue(skb, sk);
3105
			__skb_header_release(nskb);
3106
			__tcp_add_write_queue_head(sk, nskb);
3107 3108 3109
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3110 3111 3112
			skb = nskb;
		}

E
Eric Dumazet 已提交
3113
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3114
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3115
	}
3116
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3117 3118
}

3119 3120 3121 3122 3123 3124 3125 3126 3127
/**
 * 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.
 */
3128
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3129
				struct request_sock *req,
3130
				struct tcp_fastopen_cookie *foc,
3131
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3132
{
3133
	struct inet_request_sock *ireq = inet_rsk(req);
3134
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3135
	struct tcp_md5sig_key *md5 = NULL;
3136 3137
	struct tcp_out_options opts;
	struct sk_buff *skb;
3138
	int tcp_header_size;
3139
	struct tcphdr *th;
3140
	int mss;
L
Linus Torvalds 已提交
3141

3142
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3143 3144
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3145
		return NULL;
3146
	}
L
Linus Torvalds 已提交
3147 3148 3149
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3150 3151
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3152
		skb_set_owner_w(skb, req_to_sk(req));
3153 3154 3155 3156 3157 3158 3159
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3160 3161 3162 3163 3164
		/* 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);
3165
		break;
3166
	}
3167
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3168

E
Eric Dumazet 已提交
3169
	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3170

A
Adam Langley 已提交
3171
	memset(&opts, 0, sizeof(opts));
3172 3173
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
3174
		skb->skb_mstamp = cookie_init_timestamp(req);
3175 3176
	else
#endif
3177
		skb->skb_mstamp = tcp_clock_us();
E
Eric Dumazet 已提交
3178 3179 3180

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3181
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3182
#endif
3183
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3184 3185
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3186

3187 3188
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3189

3190
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3191 3192 3193
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3194
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3195
	th->source = htons(ireq->ir_num);
3196
	th->dest = ireq->ir_rmt_port;
3197
	skb->mark = ireq->ir_mark;
3198 3199 3200 3201
	/* 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
3202
			     TCPHDR_SYN | TCPHDR_ACK);
3203

L
Linus Torvalds 已提交
3204
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3205 3206
	/* 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
3207 3208

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3209
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3210
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3211
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3212
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3213 3214 3215

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3216
	if (md5)
3217
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3218
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3219
	rcu_read_unlock();
3220 3221
#endif

3222
	/* Do not fool tcpdump (if any), clean our debris */
T
Thomas Gleixner 已提交
3223
	skb->tstamp = 0;
L
Linus Torvalds 已提交
3224 3225
	return skb;
}
E
Eric Dumazet 已提交
3226
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3227

3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246
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();
}

3247
/* Do all connect socket setups that can be done AF independent. */
3248
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3249
{
3250
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3251 3252
	struct tcp_sock *tp = tcp_sk(sk);
	__u8 rcv_wscale;
3253
	u32 rcv_wnd;
L
Linus Torvalds 已提交
3254 3255 3256 3257

	/* 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.
	 */
3258 3259 3260
	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
3261

3262
#ifdef CONFIG_TCP_MD5SIG
3263
	if (tp->af_specific->md5_lookup(sk, sk))
3264 3265 3266
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3267 3268 3269 3270
	/* 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
3271
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3272 3273
	tcp_sync_mss(sk, dst_mtu(dst));

3274 3275
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3276 3277
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
E
Eric Dumazet 已提交
3278
	tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3279

L
Linus Torvalds 已提交
3280 3281
	tcp_initialize_rcv_mss(sk);

3282 3283 3284 3285 3286
	/* 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);

3287 3288 3289 3290
	rcv_wnd = tcp_rwnd_init_bpf(sk);
	if (rcv_wnd == 0)
		rcv_wnd = dst_metric(dst, RTAX_INITRWND);

L
Linus Torvalds 已提交
3291 3292 3293 3294
	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,
3295
				  sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3296
				  &rcv_wscale,
3297
				  rcv_wnd);
L
Linus Torvalds 已提交
3298 3299 3300 3301 3302 3303 3304

	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;
3305
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3306 3307
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3308
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3309
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3310 3311 3312

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3313
	else
3314
		tp->rcv_tstamp = tcp_jiffies32;
P
Pavel Emelyanov 已提交
3315 3316
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3317

3318
	inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3319
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3320 3321 3322
	tcp_clear_retrans(tp);
}

3323 3324 3325 3326 3327 3328
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;
3329
	__skb_header_release(skb);
3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347
	__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;
3348
	int space, err = 0;
3349
	struct sk_buff *syn_data;
3350

3351
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3352
	if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3353 3354 3355 3356 3357 3358
		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
3359 3360
	tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);

3361
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3362 3363
		MAX_TCP_OPTION_SPACE;

3364 3365 3366 3367 3368
	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));

3369
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3370
	if (!syn_data)
3371
		goto fallback;
3372 3373
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384
	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;
		}
3385
	}
3386 3387 3388 3389
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3390

3391
	tcp_connect_queue_skb(sk, syn_data);
3392 3393
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3394

3395
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3396

3397
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3398

3399 3400 3401 3402 3403 3404 3405 3406
	/* 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) {
3407
		tp->syn_data = (fo->copied > 0);
3408
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3409 3410 3411
		goto done;
	}

3412 3413 3414 3415
	/* data was not sent, this is our new send_head */
	sk->sk_send_head = syn_data;
	tp->packets_out -= tcp_skb_pcount(syn_data);

3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427
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;
}

3428
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3429 3430 3431 3432
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3433
	int err;
L
Linus Torvalds 已提交
3434

3435
	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB);
3436 3437 3438 3439

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

L
Linus Torvalds 已提交
3440 3441
	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3442 3443 3444 3445 3446
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3447
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3448
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3449 3450
		return -ENOBUFS;

C
Changli Gao 已提交
3451
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3452 3453
	tcp_mstamp_refresh(tp);
	tp->retrans_stamp = tcp_time_stamp(tp);
3454
	tcp_connect_queue_skb(sk, buff);
3455
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3456

3457 3458 3459
	/* 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);
3460 3461
	if (err == -ECONNREFUSED)
		return err;
3462 3463 3464 3465 3466 3467

	/* 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;
3468 3469 3470 3471 3472
	buff = tcp_send_head(sk);
	if (unlikely(buff)) {
		tp->snd_nxt	= TCP_SKB_CB(buff)->seq;
		tp->pushed_seq	= TCP_SKB_CB(buff)->seq;
	}
P
Pavel Emelyanov 已提交
3473
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3474 3475

	/* Timer for repeating the SYN until an answer. */
3476 3477
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3478 3479
	return 0;
}
E
Eric Dumazet 已提交
3480
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3481 3482 3483 3484 3485 3486 3487

/* 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)
{
3488 3489
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3490 3491
	unsigned long timeout;

3492 3493
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3494
	if (ato > TCP_DELACK_MIN) {
3495
		const struct tcp_sock *tp = tcp_sk(sk);
3496
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3497

3498 3499
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3500 3501 3502 3503 3504
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3505
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3506 3507
		 * directly.
		 */
3508 3509 3510
		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
3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522

			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. */
3523
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3524 3525 3526
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3527 3528
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3529 3530 3531 3532
			tcp_send_ack(sk);
			return;
		}

3533 3534
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3535
	}
3536 3537 3538
	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
3539 3540 3541 3542 3543
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3544
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3545

3546 3547 3548
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3549

3550 3551
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3552 3553 3554 3555
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3556 3557 3558
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3559 3560 3561 3562 3563
		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
3564
	}
3565 3566 3567

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3568
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3569

E
Eric Dumazet 已提交
3570 3571 3572 3573 3574 3575
	/* 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);

3576
	/* Send it off, this clears delayed acks for us. */
3577
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3578
}
3579
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591

/* 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.
 */
3592
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3593 3594 3595 3596 3597
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3598 3599
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3600
	if (!skb)
L
Linus Torvalds 已提交
3601 3602 3603 3604 3605 3606 3607 3608
		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
3609
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3610
	NET_INC_STATS(sock_net(sk), mib);
3611
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3612 3613
}

3614
/* Called from setsockopt( ... TCP_REPAIR ) */
P
Pavel Emelyanov 已提交
3615 3616 3617 3618
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;
3619
		tcp_mstamp_refresh(tcp_sk(sk));
3620
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3621 3622 3623
	}
}

3624
/* Initiate keepalive or window probe from timer. */
3625
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3626
{
3627 3628
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3629

3630 3631 3632
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3633 3634
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3635
		int err;
I
Ilpo Järvinen 已提交
3636
		unsigned int mss = tcp_current_mss(sk);
3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648
		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
3649
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3650
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3651 3652
				return -1;
		} else if (!tcp_skb_pcount(skb))
3653
			tcp_set_skb_tso_segs(skb, mss);
3654

E
Eric Dumazet 已提交
3655
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3656 3657 3658 3659 3660
		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
3661
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3662 3663
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3664 3665 3666 3667 3668 3669 3670 3671
	}
}

/* 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)
{
3672
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3673
	struct tcp_sock *tp = tcp_sk(sk);
3674
	struct net *net = sock_net(sk);
3675
	unsigned long probe_max;
L
Linus Torvalds 已提交
3676 3677
	int err;

3678
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3679

3680
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3681
		/* Cancel probe timer, if it is not required. */
3682
		icsk->icsk_probes_out = 0;
3683
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3684 3685 3686 3687
		return;
	}

	if (err <= 0) {
3688
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3689
			icsk->icsk_backoff++;
3690
		icsk->icsk_probes_out++;
3691
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3692 3693
	} else {
		/* If packet was not sent due to local congestion,
3694
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3695 3696 3697 3698
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3699 3700
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3701
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3702
	}
3703
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3704
				  tcp_probe0_when(sk, probe_max),
3705
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3706
}
3707

3708
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3709 3710 3711 3712 3713
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3714
	tcp_rsk(req)->txhash = net_tx_rndhash();
3715
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3716
	if (!res) {
E
Eric Dumazet 已提交
3717
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3718
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3719 3720
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3721 3722 3723 3724
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);