tcp_output.c 105.9 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_EARLY_RETRANS ||
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	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
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		tcp_rearm_rto(sk);
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	}
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	NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
		      tcp_skb_pcount(skb));
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}

/* SND.NXT, if window was not shrunk.
 * 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))
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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);
	tp->snd_cwnd_stamp = tcp_time_stamp;
	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);
	const u32 now = tcp_time_stamp;
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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)
		(*window_clamp) = (65535 << 14);
	space = min(*window_clamp, space);

	/* Quantize space offering to a multiple of mss if possible. */
	if (space > mss)
		space = (space / mss) * mss;

	/* 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) {
		/* Set window scaling on max possible window
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		 * See RFC1323 for an explanation of the limit to 14
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		 */
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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 > 65535 && (*rcv_wscale) < 14) {
			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 */
	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
}
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EXPORT_SYMBOL(tcp_select_initial_window);
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/* Chose a new window to advertise, update state in tcp_sock for the
 * socket, and return result with RFC1323 scaling applied.  The return
 * value can be stuffed directly into th->window for an outgoing
 * frame.
 */
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static u16 tcp_select_window(struct sock *sk)
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{
	struct tcp_sock *tp = tcp_sk(sk);
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	u32 old_win = tp->rcv_wnd;
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	u32 cur_win = tcp_receive_window(tp);
	u32 new_win = __tcp_select_window(sk);

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

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

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

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

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

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	TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
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	if (!(tp->ecn_flags & TCP_ECN_OK))
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		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
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	else if (tcp_ca_needs_ecn(sk))
		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 use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
		       tcp_ca_needs_ecn(sk);

	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))
			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);
	}

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	if (unlikely(OPTION_SACK_ADVERTISE & options)) {
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		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_SACK_PERM << 8) |
			       TCPOLEN_SACK_PERM);
	}

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	if (unlikely(OPTION_WSCALE & options)) {
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		*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
498 499 500 501 502
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
503
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
504
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
505

A
Adam Langley 已提交
506 507
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
508 509 510
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
511

512
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
513
	}
Y
Yuchung Cheng 已提交
514 515 516

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
517 518 519 520 521 522 523 524 525 526 527 528 529
		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
530

531 532 533 534
		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
535
		}
536
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
537
	}
A
Adam Langley 已提交
538 539
}

540 541 542
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
543
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
544
				struct tcp_out_options *opts,
545 546
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
547
	struct tcp_sock *tp = tcp_sk(sk);
548
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
549
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
550

551
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
552 553 554
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
555
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
556
	}
A
Adam Langley 已提交
557 558
#else
	*md5 = NULL;
559
#endif
A
Adam Langley 已提交
560 561 562 563 564 565 566 567 568 569 570

	/* 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);
571
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
572

573
	if (likely(sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
574
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
575
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
576
		opts->tsecr = tp->rx_opt.ts_recent;
577
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
578
	}
579
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
580
		opts->ws = tp->rx_opt.rcv_wscale;
581
		opts->options |= OPTION_WSCALE;
582
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
583
	}
584
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
585
		opts->options |= OPTION_SACK_ADVERTISE;
586
		if (unlikely(!(OPTION_TS & opts->options)))
587
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
588 589
	}

590
	if (fastopen && fastopen->cookie.len >= 0) {
591 592 593 594
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
595 596 597 598 599 600
		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;
601
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
602 603
		}
	}
604 605

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
606 607
}

608
/* Set up TCP options for SYN-ACKs. */
609 610 611 612 613
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)
614
{
A
Adam Langley 已提交
615
	struct inet_request_sock *ireq = inet_rsk(req);
616
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
617

618
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
619
	if (md5) {
A
Adam Langley 已提交
620
		opts->options |= OPTION_MD5;
621 622 623 624 625 626 627
		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
628
		ireq->tstamp_ok &= !ireq->sack_ok;
629 630
	}
#endif
A
Adam Langley 已提交
631

632
	/* We always send an MSS option. */
A
Adam Langley 已提交
633
	opts->mss = mss;
634
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
635 636 637

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
638
		opts->options |= OPTION_WSCALE;
639
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
640
	}
E
Eric Dumazet 已提交
641
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
642
		opts->options |= OPTION_TS;
643
		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
A
Adam Langley 已提交
644
		opts->tsecr = req->ts_recent;
645
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
646 647 648
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
649
		if (unlikely(!ireq->tstamp_ok))
650
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
651
	}
652 653 654 655 656
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
657 658 659 660 661 662 663
		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
664

665
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
666 667
}

668 669 670
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
671
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
672
					struct tcp_out_options *opts,
673 674
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
675
	struct tcp_sock *tp = tcp_sk(sk);
676
	unsigned int size = 0;
677
	unsigned int eff_sacks;
A
Adam Langley 已提交
678

679 680
	opts->options = 0;

A
Adam Langley 已提交
681 682 683 684 685 686 687 688 689 690 691 692
#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
693
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
694 695 696 697
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

698 699
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
700
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
701
		opts->num_sack_blocks =
702
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
703 704 705 706 707 708 709
			      (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
710
}
L
Linus Torvalds 已提交
711

E
Eric Dumazet 已提交
712 713 714 715 716 717 718 719 720

/* 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
721
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
722 723 724 725 726 727 728 729 730 731 732
 *
 * 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);

733 734 735 736
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
737 738 739 740 741 742 743 744
	     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
745
			       0, GFP_ATOMIC);
746
	}
747
}
E
Eric Dumazet 已提交
748
/*
S
stephen hemminger 已提交
749
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
750
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
751
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774
 * 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;
		bh_lock_sock(sk);

		if (!sock_owned_by_user(sk)) {
775
			tcp_tsq_handler(sk);
E
Eric Dumazet 已提交
776 777
		} else {
			/* defer the work to tcp_release_cb() */
778
			set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
E
Eric Dumazet 已提交
779 780 781 782 783 784 785 786
		}
		bh_unlock_sock(sk);

		clear_bit(TSQ_QUEUED, &tp->tsq_flags);
		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
787 788 789 790
#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
791 792 793 794 795 796 797 798 799 800
/**
 * 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)
{
	struct tcp_sock *tp = tcp_sk(sk);
801
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
802

803 804 805 806 807 808 809 810
	/* perform an atomic operation only if at least one flag is set */
	do {
		flags = tp->tsq_flags;
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
	} while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);

E
Eric Dumazet 已提交
811
	if (flags & TCPF_TSQ_DEFERRED)
812 813
		tcp_tsq_handler(sk);

814 815 816 817 818 819 820 821 822 823 824
	/* 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
825
	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
826
		tcp_write_timer_handler(sk);
827 828
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
829
	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
830
		tcp_delack_timer_handler(sk);
831 832
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
833
	if (flags & TCPF_MTU_REDUCED_DEFERRED) {
834
		inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
835 836
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855
}
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
856
 * We can't xmit new skbs from this context, as we might already
E
Eric Dumazet 已提交
857 858
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
859
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
860 861 862
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);
863
	unsigned long flags, nval, oval;
864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
	int wmem;

	/* Keep one reference on sk_wmem_alloc.
	 * Will be released by sk_free() from here or tcp_tasklet_func()
	 */
	wmem = atomic_sub_return(skb->truesize - 1, &sk->sk_wmem_alloc);

	/* 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)
	 */
	if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
		goto out;
E
Eric Dumazet 已提交
880

881
	for (oval = READ_ONCE(tp->tsq_flags);; oval = nval) {
E
Eric Dumazet 已提交
882 883
		struct tsq_tasklet *tsq;

884 885 886 887 888 889 890 891
		if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
			goto out;

		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
		nval = cmpxchg(&tp->tsq_flags, oval, nval);
		if (nval != oval)
			continue;

E
Eric Dumazet 已提交
892 893
		/* queue this socket to tasklet queue */
		local_irq_save(flags);
894
		tsq = this_cpu_ptr(&tsq_tasklet);
E
Eric Dumazet 已提交
895 896 897
		list_add(&tp->tsq_node, &tsq->head);
		tasklet_schedule(&tsq->tasklet);
		local_irq_restore(flags);
898
		return;
E
Eric Dumazet 已提交
899
	}
900 901
out:
	sk_free(sk);
E
Eric Dumazet 已提交
902 903
}

L
Linus Torvalds 已提交
904 905 906 907 908 909 910 911 912 913 914
/* 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.
 */
915 916
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
917
{
918 919 920 921
	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
922
	struct tcp_out_options opts;
923
	unsigned int tcp_options_size, tcp_header_size;
924
	struct tcp_md5sig_key *md5;
925 926 927 928
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
929
	tp = tcp_sk(sk);
930

931
	if (clone_it) {
932
		skb_mstamp_get(&skb->skb_mstamp);
933 934
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
935
		tcp_rate_skb_sent(sk, skb);
936

937 938 939 940 941 942 943
		if (unlikely(skb_cloned(skb)))
			skb = pskb_copy(skb, gfp_mask);
		else
			skb = skb_clone(skb, gfp_mask);
		if (unlikely(!skb))
			return -ENOBUFS;
	}
L
Linus Torvalds 已提交
944

945 946
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
947
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
948

E
Eric Dumazet 已提交
949
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
950 951 952 953 954
		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);
955

E
Eric Dumazet 已提交
956
	/* if no packet is in qdisc/device queue, then allow XPS to select
957 958 959 960 961
	 * 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
962
	 */
963
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
964

965 966
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
967 968 969

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
970
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
971
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
972
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
973 974

	/* Build TCP header and checksum it. */
975
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
976 977
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
978 979
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
980
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
981
					tcb->tcp_flags);
982 983 984

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
985

I
Ilpo Järvinen 已提交
986
	/* The urg_mode check is necessary during a below snd_una win probe */
987 988 989 990 991
	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)) {
992
			th->urg_ptr = htons(0xFFFF);
993 994
			th->urg = 1;
		}
995
	}
L
Linus Torvalds 已提交
996

997
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
998
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
999 1000 1001 1002 1003 1004 1005 1006 1007
	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));
	}
1008 1009 1010
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1011
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1012
		tp->af_specific->calc_md5_hash(opts.hash_location,
1013
					       md5, sk, skb);
1014 1015 1016
	}
#endif

1017
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1018

E
Eric Dumazet 已提交
1019
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1020
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1021

1022
	if (skb->len != tcp_header_size) {
1023
		tcp_event_data_sent(tp, sk);
1024 1025
		tp->data_segs_out += tcp_skb_pcount(skb);
	}
L
Linus Torvalds 已提交
1026

1027
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1028 1029
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1030

1031
	tp->segs_out += tcp_skb_pcount(skb);
1032
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1033
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1034
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1035

E
Eric Dumazet 已提交
1036 1037
	/* Our usage of tstamp should remain private */
	skb->tstamp.tv64 = 0;
1038 1039 1040 1041 1042

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

1043
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1044

1045
	if (likely(err <= 0))
1046 1047
		return err;

1048
	tcp_enter_cwr(sk);
1049

1050
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1051 1052
}

1053
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
 *
 * 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;
1064
	__skb_header_release(skb);
1065
	tcp_add_write_queue_tail(sk, skb);
1066 1067
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1068 1069
}

1070
/* Initialize TSO segments for a packet. */
1071
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1072
{
1073
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1074 1075 1076
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1077
		tcp_skb_pcount_set(skb, 1);
1078
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1079
	} else {
1080
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1081
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1082 1083 1084
	}
}

I
Ilpo Järvinen 已提交
1085
/* When a modification to fackets out becomes necessary, we need to check
1086
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1087
 */
1088
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1089 1090
				   int decr)
{
1091 1092
	struct tcp_sock *tp = tcp_sk(sk);

1093
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1094 1095
		return;

1096
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1097 1098 1099
		tp->fackets_out -= decr;
}

1100 1101 1102
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1103
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123
{
	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) &&
1124
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1125 1126 1127 1128 1129
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1130 1131 1132 1133 1134 1135
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);
}

1136 1137 1138 1139
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1140
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1141 1142 1143 1144 1145 1146 1147
	    !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);
1148 1149
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1150 1151 1152
	}
}

1153 1154 1155 1156 1157 1158
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
1159 1160
/* 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
1161
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1162 1163
 * Remember, these are still headerless SKBs at this point.
 */
1164
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1165
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1166 1167 1168
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1169
	int nsize, old_factor;
1170
	int nlen;
1171
	u8 flags;
L
Linus Torvalds 已提交
1172

1173 1174
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1175

L
Linus Torvalds 已提交
1176 1177 1178 1179
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1180
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1181 1182 1183
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1184
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1185
	if (!buff)
L
Linus Torvalds 已提交
1186
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1187

1188 1189
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1190 1191 1192
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1193 1194 1195 1196 1197 1198 1199

	/* 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
1200 1201 1202
	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;
1203
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1204
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1205

1206
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1207
		/* Copy and checksum data tail into the new buffer. */
1208 1209
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1210 1211 1212 1213 1214 1215
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1216
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1217 1218 1219 1220 1221
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1222
	buff->tstamp = skb->tstamp;
1223
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1224

1225 1226
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1227
	/* Fix up tso_factor for both original and new SKB.  */
1228 1229
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1230

1231 1232 1233
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1234 1235 1236
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1237
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1238 1239
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1240

1241 1242
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1243 1244 1245
	}

	/* Link BUFF into the send queue. */
1246
	__skb_header_release(buff);
1247
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1248 1249 1250 1251 1252 1253 1254 1255

	return 0;
}

/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
 * eventually). The difference is that pulled data not copied, but
 * immediately discarded.
 */
1256
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1257
{
1258
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1259 1260
	int i, k, eat;

E
Eric Dumazet 已提交
1261 1262 1263 1264 1265 1266 1267
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
			return;
	}
L
Linus Torvalds 已提交
1268 1269
	eat = len;
	k = 0;
1270 1271 1272
	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
1273 1274

		if (size <= eat) {
1275
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1276
			eat -= size;
L
Linus Torvalds 已提交
1277
		} else {
1278
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1279
			if (eat) {
1280 1281
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1282 1283 1284 1285 1286
				eat = 0;
			}
			k++;
		}
	}
1287
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1288

1289
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1290 1291 1292 1293
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1294
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1295 1296
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1297
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1298 1299
		return -ENOMEM;

E
Eric Dumazet 已提交
1300
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1301 1302

	TCP_SKB_CB(skb)->seq += len;
1303
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1304 1305 1306

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1307
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1308 1309
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1310
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1311
	if (tcp_skb_pcount(skb) > 1)
1312
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1313 1314 1315 1316

	return 0;
}

1317 1318
/* 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
1319
{
1320 1321
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1322 1323 1324 1325 1326 1327 1328
	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);

1329 1330 1331 1332 1333 1334 1335 1336
	/* 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
1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349
	/* 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;
}

1350 1351 1352 1353 1354 1355 1356 1357
/* 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
1358
/* Inverse of above */
1359
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1360
{
1361 1362
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1363 1364 1365 1366 1367 1368 1369
	int mtu;

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

1370 1371 1372 1373 1374 1375 1376
	/* 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
1377 1378
	return mtu;
}
1379
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1380

1381
/* MTU probing init per socket */
J
John Heffner 已提交
1382 1383 1384 1385
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
1386
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1387

F
Fan Du 已提交
1388
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1389
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1390
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1391
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1392
	icsk->icsk_mtup.probe_size = 0;
1393 1394
	if (icsk->icsk_mtup.enabled)
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
J
John Heffner 已提交
1395
}
E
Eric Dumazet 已提交
1396
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1397

L
Linus Torvalds 已提交
1398 1399 1400 1401 1402 1403
/* 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
1404
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1405 1406
   It also does not include TCP options.

1407
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1408 1409 1410 1411 1412 1413 1414 1415 1416

   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.

1417 1418
   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
1419 1420 1421 1422
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1423
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1424
	int mss_now;
L
Linus Torvalds 已提交
1425

J
John Heffner 已提交
1426 1427
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1428

J
John Heffner 已提交
1429
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1430
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1431 1432

	/* And store cached results */
1433
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1434 1435
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1436
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1437 1438 1439

	return mss_now;
}
E
Eric Dumazet 已提交
1440
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1441 1442 1443 1444

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1445
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1446
{
1447 1448
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1449
	u32 mss_now;
1450
	unsigned int header_len;
A
Adam Langley 已提交
1451 1452
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1453 1454 1455

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1456 1457
	if (dst) {
		u32 mtu = dst_mtu(dst);
1458
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1459 1460 1461
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1462 1463 1464 1465 1466 1467 1468 1469 1470 1471
	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;
	}
1472

L
Linus Torvalds 已提交
1473 1474 1475
	return mss_now;
}

1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497
/* 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;
	}
	tp->snd_cwnd_stamp = tcp_time_stamp;
}

1498
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1499
{
1500
	struct tcp_sock *tp = tcp_sk(sk);
1501

1502 1503 1504 1505 1506 1507 1508 1509 1510
	/* 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;
	}
1511

1512
	if (tcp_is_cwnd_limited(sk)) {
1513 1514 1515 1516 1517 1518 1519 1520
		/* Network is feed fully. */
		tp->snd_cwnd_used = 0;
		tp->snd_cwnd_stamp = tcp_time_stamp;
	} else {
		/* Network starves. */
		if (tp->packets_out > tp->snd_cwnd_used)
			tp->snd_cwnd_used = tp->packets_out;

1521 1522
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1523
			tcp_cwnd_application_limited(sk);
1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535

		/* 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);
1536 1537 1538
	}
}

E
Eric Dumazet 已提交
1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552
/* 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
1553
 */
E
Eric Dumazet 已提交
1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568
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,
1569
			    int nonagle)
E
Eric Dumazet 已提交
1570 1571 1572 1573 1574
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1575 1576 1577 1578

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1579 1580
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591
{
	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.
	 */
1592
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1593 1594 1595

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1596
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1597

1598 1599 1600 1601 1602 1603 1604 1605
/* 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;

1606 1607
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1608 1609
}

E
Eric Dumazet 已提交
1610 1611 1612 1613 1614 1615
/* 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)
1616
{
1617
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1618
	u32 partial, needed, window, max_len;
1619

1620
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1621
	max_len = mss_now * max_segs;
1622

1623 1624
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1625

1626 1627
	needed = min(skb->len, window);

1628 1629
	if (max_len <= needed)
		return max_len;
1630

E
Eric Dumazet 已提交
1631 1632 1633 1634 1635
	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
	 */
1636
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1637 1638 1639
		return needed - partial;

	return needed;
1640 1641 1642 1643 1644
}

/* 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.
 */
1645 1646
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1647
{
E
Eric Dumazet 已提交
1648
	u32 in_flight, cwnd, halfcwnd;
1649 1650

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1651 1652
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1653 1654 1655 1656
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1657 1658
	if (in_flight >= cwnd)
		return 0;
1659

E
Eric Dumazet 已提交
1660 1661 1662 1663 1664
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1665 1666
}

1667
/* Initialize TSO state of a skb.
1668
 * This must be invoked the first time we consider transmitting
1669 1670
 * SKB onto the wire.
 */
1671
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1672 1673 1674
{
	int tso_segs = tcp_skb_pcount(skb);

1675
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1676
		tcp_set_skb_tso_segs(skb, mss_now);
1677 1678 1679 1680 1681 1682
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1683
/* Return true if the Nagle test allows this packet to be
1684 1685
 * sent now.
 */
E
Eric Dumazet 已提交
1686 1687
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1688 1689 1690 1691 1692 1693 1694 1695
{
	/* 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
1696
		return true;
1697

Y
Yuchung Cheng 已提交
1698 1699
	/* 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
1700
		return true;
1701

1702
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1703
		return true;
1704

E
Eric Dumazet 已提交
1705
	return false;
1706 1707 1708
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1709 1710 1711
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1712 1713 1714 1715 1716 1717
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1718
	return !after(end_seq, tcp_wnd_end(tp));
1719 1720
}

1721
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1722 1723 1724
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1725
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1726 1727
				 unsigned int cur_mss, int nonagle)
{
1728
	const struct tcp_sock *tp = tcp_sk(sk);
1729 1730
	unsigned int cwnd_quota;

1731
	tcp_init_tso_segs(skb, cur_mss);
1732 1733 1734 1735 1736

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1737
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1738 1739 1740 1741 1742
		cwnd_quota = 0;

	return cwnd_quota;
}

1743
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1744
bool tcp_may_send_now(struct sock *sk)
1745
{
1746
	const struct tcp_sock *tp = tcp_sk(sk);
1747
	struct sk_buff *skb = tcp_send_head(sk);
1748

E
Eric Dumazet 已提交
1749
	return skb &&
I
Ilpo Järvinen 已提交
1750
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1751
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1752
			      tp->nonagle : TCP_NAGLE_PUSH));
1753 1754 1755 1756 1757 1758 1759 1760 1761
}

/* 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).
 */
1762
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1763
			unsigned int mss_now, gfp_t gfp)
1764 1765 1766
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1767
	u8 flags;
1768 1769

	/* All of a TSO frame must be composed of paged data.  */
1770
	if (skb->len != skb->data_len)
1771
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1772

1773
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1774
	if (unlikely(!buff))
1775 1776
		return -ENOMEM;

1777 1778
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1779
	buff->truesize += nlen;
1780 1781 1782 1783 1784 1785 1786 1787
	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
1788 1789 1790
	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;
1791 1792 1793 1794

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

1795 1796
	tcp_skb_fragment_eor(skb, buff);

1797
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1798
	skb_split(skb, buff, len);
1799
	tcp_fragment_tstamp(skb, buff);
1800 1801

	/* Fix up tso_factor for both original and new SKB.  */
1802 1803
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1804 1805

	/* Link BUFF into the send queue. */
1806
	__skb_header_release(buff);
1807
	tcp_insert_write_queue_after(skb, buff, sk);
1808 1809 1810 1811 1812 1813 1814 1815 1816

	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.
 */
1817
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1818
				 bool *is_cwnd_limited, u32 max_segs)
1819
{
1820
	const struct inet_connection_sock *icsk = inet_csk(sk);
1821 1822 1823 1824
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct skb_mstamp now;
	struct sk_buff *head;
1825
	int win_divisor;
1826

E
Eric Dumazet 已提交
1827
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1828
		goto send_now;
1829

1830
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1831 1832
		goto send_now;

E
Eric Dumazet 已提交
1833 1834 1835 1836
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
	if ((s32)(tcp_time_stamp - tp->lsndtime) > 0)
J
John Heffner 已提交
1837
		goto send_now;
1838

1839 1840
	in_flight = tcp_packets_in_flight(tp);

1841
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1842

1843
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1844 1845 1846 1847 1848 1849

	/* 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);

1850
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1851
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1852
		goto send_now;
1853

1854 1855 1856 1857
	/* 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;

1858 1859
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1860 1861 1862 1863 1864
		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.
		 */
1865
		chunk /= win_divisor;
1866
		if (limit >= chunk)
J
John Heffner 已提交
1867
			goto send_now;
1868 1869 1870 1871 1872 1873
	} 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.
		 */
1874
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1875
			goto send_now;
1876 1877
	}

1878 1879 1880 1881 1882 1883 1884
	head = tcp_write_queue_head(sk);
	skb_mstamp_get(&now);
	age = skb_mstamp_us_delta(&now, &head->skb_mstamp);
	/* 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
1885
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1886

1887
	if (cong_win < send_win && cong_win <= skb->len)
1888 1889
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1890
	return true;
J
John Heffner 已提交
1891 1892

send_now:
E
Eric Dumazet 已提交
1893
	return false;
1894 1895
}

1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920
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;
	delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp;
	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 */
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
	}
}

J
John Heffner 已提交
1921
/* Create a new MTU probe if we are ready.
1922 1923 1924 1925
 * 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
1926 1927
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1928 1929
 *         -1 otherwise
 */
J
John Heffner 已提交
1930 1931 1932 1933 1934
static int tcp_mtu_probe(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct sk_buff *skb, *nskb, *next;
1935
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1936 1937
	int len;
	int probe_size;
1938
	int size_needed;
J
John Heffner 已提交
1939 1940
	int copy;
	int mss_now;
1941
	int interval;
J
John Heffner 已提交
1942 1943 1944 1945 1946 1947 1948 1949 1950

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
	 * not SACKing (the variable headers throw things off) */
	if (!icsk->icsk_mtup.enabled ||
	    icsk->icsk_mtup.probe_size ||
	    inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
	    tp->snd_cwnd < 11 ||
1951
	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
J
John Heffner 已提交
1952 1953
		return -1;

1954 1955 1956 1957
	/* 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
1958
	mss_now = tcp_current_mss(sk);
1959 1960
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
1961
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1962
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1963 1964 1965 1966
	/* 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.
	 */
1967
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1968 1969 1970 1971 1972
		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
1973 1974 1975 1976
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1977
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1978 1979
		return -1;

1980 1981
	if (tp->snd_wnd < size_needed)
		return -1;
1982
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1983
		return 0;
J
John Heffner 已提交
1984

1985 1986 1987
	/* 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
1988 1989 1990 1991 1992 1993
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
1994
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1995
	if (!nskb)
J
John Heffner 已提交
1996
		return -1;
1997 1998
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
1999

2000
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2001 2002 2003

	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
2004
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2005 2006
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2007
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2008

2009 2010
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2011
	len = 0;
2012
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2013
		copy = min_t(int, skb->len, probe_size - len);
2014
		if (nskb->ip_summed) {
J
John Heffner 已提交
2015
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2016 2017 2018 2019 2020 2021
		} 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
2022 2023 2024 2025

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2026
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2027
			tcp_unlink_write_queue(skb, sk);
2028
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2029
		} else {
E
Eric Dumazet 已提交
2030
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2031
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2032 2033
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2034
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2035 2036
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2037 2038
			} else {
				__pskb_trim_head(skb, copy);
2039
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2040 2041 2042 2043 2044
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2045 2046 2047

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2048
	}
2049
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2050 2051

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2052 2053
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2054 2055
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2056
		 * effectively two packets. */
J
John Heffner 已提交
2057
		tp->snd_cwnd--;
2058
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2059 2060

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2061 2062
		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
2063 2064 2065 2066 2067 2068 2069

		return 1;
	}

	return -1;
}

2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102
/* 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;

	if (atomic_read(&sk->sk_wmem_alloc) > limit) {
		set_bit(TSQ_THROTTLED, &tcp_sk(sk)->tsq_flags);
		/* It is possible TX completion already happened
		 * before we set TSQ_THROTTLED, so we must
		 * test again the condition.
		 */
		smp_mb__after_atomic();
		if (atomic_read(&sk->sk_wmem_alloc) > limit)
			return true;
	}
	return false;
}

2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
	const u32 now = tcp_time_stamp;

	if (tp->chrono_type > TCP_CHRONO_UNSPEC)
		tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start;
	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
2118 2119
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2120 2121 2122 2123 2124 2125 2126 2127 2128 2129
	 * 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);

2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141

	/* 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);
2142 2143
}

L
Linus Torvalds 已提交
2144 2145 2146 2147
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2148 2149 2150 2151
 * 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
2152 2153 2154
 * 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
2155 2156
 * 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
2157
 */
E
Eric Dumazet 已提交
2158 2159
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
2160 2161
{
	struct tcp_sock *tp = tcp_sk(sk);
2162
	struct sk_buff *skb;
2163 2164
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2165
	int result;
2166
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2167
	u32 max_segs;
L
Linus Torvalds 已提交
2168

2169
	sent_pkts = 0;
J
John Heffner 已提交
2170

2171 2172 2173 2174
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2175
			return false;
2176 2177 2178
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2179 2180
	}

2181
	max_segs = tcp_tso_segs(sk, mss_now);
2182
	while ((skb = tcp_send_head(sk))) {
2183 2184
		unsigned int limit;

2185
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2186
		BUG_ON(!tso_segs);
2187

2188
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2189 2190
			/* "skb_mstamp" is used as a start point for the retransmit timer */
			skb_mstamp_get(&skb->skb_mstamp);
2191
			goto repair; /* Skip network transmission */
2192
		}
2193

2194
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2195 2196 2197 2198 2199 2200 2201
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2202

2203 2204
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2205
			break;
2206
		}
2207

2208
		if (tso_segs == 1) {
2209 2210 2211 2212 2213
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2214
			if (!push_one &&
E
Eric Dumazet 已提交
2215 2216
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2217 2218
				break;
		}
2219

E
Eric Dumazet 已提交
2220
		limit = mss_now;
2221
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2222 2223 2224 2225 2226 2227 2228 2229 2230 2231
			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;

2232 2233
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2234

2235
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2236
			break;
L
Linus Torvalds 已提交
2237

2238
repair:
2239 2240 2241
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2242
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2243

2244
		tcp_minshall_update(tp, mss_now, skb);
2245
		sent_pkts += tcp_skb_pcount(skb);
2246 2247 2248

		if (push_one)
			break;
2249
	}
L
Linus Torvalds 已提交
2250

2251 2252 2253 2254 2255
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2256
	if (likely(sent_pkts)) {
2257 2258
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2259 2260 2261 2262

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2263
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2264
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2265
		return false;
L
Linus Torvalds 已提交
2266
	}
2267
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2268 2269 2270 2271 2272 2273 2274
}

bool tcp_schedule_loss_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	u32 timeout, tlp_time_stamp, rto_time_stamp;
2275
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286

	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
		return false;
	/* No consecutive loss probes. */
	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
		tcp_rearm_rto(sk);
		return false;
	}
	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
2287
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2288 2289 2290 2291 2292 2293 2294 2295 2296
		return false;

	/* TLP is only scheduled when next timer event is RTO. */
	if (icsk->icsk_pending != ICSK_TIME_RETRANS)
		return false;

	/* Schedule a loss probe in 2*RTT for SACK capable connections
	 * in Open state, that are either limited by cwnd or application.
	 */
2297
	if (sysctl_tcp_early_retrans < 3 || !tp->packets_out ||
N
Nandita Dukkipati 已提交
2298 2299 2300 2301 2302 2303 2304 2305
	    !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
		return false;

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

	/* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2306 2307
	 * 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
2308
	 */
2309
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328
	if (tp->packets_out == 1)
		timeout = max_t(u32, timeout,
				(rtt + (rtt >> 1) + TCP_DELACK_MAX));
	timeout = max_t(u32, timeout, msecs_to_jiffies(10));

	/* If RTO is shorter, just schedule TLP in its place. */
	tlp_time_stamp = tcp_time_stamp + timeout;
	rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
	if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
		s32 delta = rto_time_stamp - tcp_time_stamp;
		if (delta > 0)
			timeout = delta;
	}

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

2329 2330 2331 2332 2333 2334 2335
/* 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)
{
2336
	if (unlikely(skb_fclone_busy(sk, skb))) {
2337 2338
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2339 2340 2341 2342 2343
		return true;
	}
	return false;
}

2344
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2345 2346 2347 2348
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2349
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2350 2351 2352 2353
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365
	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
2366 2367
	}

N
Nandita Dukkipati 已提交
2368 2369 2370 2371
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2372 2373 2374 2375
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2376 2377 2378
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2379 2380 2381 2382 2383
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2384 2385
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2386
			goto rearm_timer;
2387
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2388 2389 2390 2391 2392
	}

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

2393
	if (__tcp_retransmit_skb(sk, skb, 1))
2394
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2395

N
Nandita Dukkipati 已提交
2396
	/* Record snd_nxt for loss detection. */
2397
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2398

2399
probe_sent:
2400
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2401 2402
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2403
rearm_timer:
2404
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2405 2406
}

2407 2408 2409 2410
/* 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.
 */
2411 2412
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2413
{
2414 2415 2416 2417 2418 2419 2420
	/* 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;

2421
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2422
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2423
		tcp_check_probe_timer(sk);
2424 2425
}

2426 2427 2428 2429 2430
/* 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)
{
2431
	struct sk_buff *skb = tcp_send_head(sk);
2432 2433 2434

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

2435
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2436 2437
}

L
Linus Torvalds 已提交
2438 2439
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2440
 *
L
Linus Torvalds 已提交
2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458
 * 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.
2459
 *
L
Linus Torvalds 已提交
2460 2461
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2462
 *
L
Linus Torvalds 已提交
2463
 * BSD seems to make the following compromise:
2464
 *
L
Linus Torvalds 已提交
2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491
 *	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)
{
2492
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2493
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2494
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2495 2496 2497 2498 2499
	 * 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
	 */
2500
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2501
	int free_space = tcp_space(sk);
2502 2503
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2504 2505 2506
	int window;

	if (mss > full_space)
2507
		mss = full_space;
L
Linus Torvalds 已提交
2508

2509
	if (free_space < (full_space >> 1)) {
2510
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2511

2512
		if (tcp_under_memory_pressure(sk))
2513 2514
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2515

2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528
		/* 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
2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558
			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.
	 */
	window = tp->rcv_wnd;
	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.
		 */
		if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
			window = (((window >> tp->rx_opt.rcv_wscale) + 1)
				  << tp->rx_opt.rcv_wscale);
	} else {
		/* 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)
2559
			window = (free_space / mss) * mss;
2560
		else if (mss == full_space &&
2561
			 free_space > window + (full_space >> 1))
2562
			window = free_space;
L
Linus Torvalds 已提交
2563 2564 2565 2566 2567
	}

	return window;
}

2568 2569
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2570
{
2571 2572 2573
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2574 2575
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2576
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2577
		shinfo->tskey = next_shinfo->tskey;
2578 2579
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2580 2581 2582
	}
}

2583
/* Collapses two adjacent SKB's during retransmission. */
2584
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2585 2586
{
	struct tcp_sock *tp = tcp_sk(sk);
2587
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2588
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2589

2590 2591
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2592

2593
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2594

2595 2596 2597 2598 2599 2600 2601
	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;
	}
2602
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2603

2604
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2605

2606 2607
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2608

2609 2610
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2611

2612 2613
	/* 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
2614

2615
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2616
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2617 2618 2619 2620 2621

	/* 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;
2622
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2623 2624

	/* changed transmit queue under us so clear hints */
2625 2626 2627
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2628

2629 2630
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2631 2632
	tcp_skb_collapse_tstamp(skb, next_skb);

2633
	sk_wmem_free_skb(sk, next_skb);
2634
	return true;
L
Linus Torvalds 已提交
2635 2636
}

2637
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2638
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2639 2640
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2641
		return false;
2642
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2643
		return false;
2644
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2645
		return false;
E
Eric Dumazet 已提交
2646
	/* Some heuristics for collapsing over SACK'd could be invented */
2647
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2648
		return false;
2649

E
Eric Dumazet 已提交
2650
	return true;
2651 2652
}

2653 2654 2655
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2656 2657 2658 2659 2660
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
2661
	bool first = true;
2662 2663 2664

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2665
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2666 2667 2668 2669 2670 2671
		return;

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

2672 2673 2674
		if (!tcp_skb_can_collapse_to(to))
			break;

2675 2676 2677
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2678
			first = false;
2679 2680 2681 2682 2683 2684 2685 2686 2687
			continue;
		}

		if (space < 0)
			break;

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

2688 2689
		if (!tcp_collapse_retrans(sk, to))
			break;
2690 2691 2692
	}
}

L
Linus Torvalds 已提交
2693 2694 2695 2696
/* 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.
 */
2697
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2698
{
J
John Heffner 已提交
2699
	struct inet_connection_sock *icsk = inet_csk(sk);
2700
	struct tcp_sock *tp = tcp_sk(sk);
2701
	unsigned int cur_mss;
2702 2703
	int diff, len, err;

L
Linus Torvalds 已提交
2704

2705 2706
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2707 2708
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2709
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2710
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2711 2712
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
2713 2714
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2715 2716
		return -EAGAIN;

2717 2718 2719
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2720 2721 2722 2723 2724 2725 2726
	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;
	}

2727 2728 2729
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2730
	cur_mss = tcp_current_mss(sk);
2731

L
Linus Torvalds 已提交
2732 2733 2734 2735 2736
	/* 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.
	 */
2737 2738
	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
2739 2740
		return -EAGAIN;

2741 2742 2743
	len = cur_mss * segs;
	if (skb->len > len) {
		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2744
			return -ENOMEM; /* We'll try again later. */
2745
	} else {
2746 2747
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2748

2749 2750 2751 2752 2753 2754 2755
		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
2756 2757
	}

2758 2759 2760 2761
	/* 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);

2762 2763 2764 2765 2766 2767
	/* 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)) {
2768 2769 2770 2771
		struct sk_buff *nskb;

		skb_mstamp_get(&skb->skb_mstamp);
		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2772 2773
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2774
	} else {
2775
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2776
	}
2777

2778
	if (likely(!err)) {
2779 2780
		segs = tcp_skb_pcount(skb);

2781
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2782
		/* Update global TCP statistics. */
2783
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
2784
		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2785
			__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2786
		tp->total_retrans += segs;
2787
	}
2788
	return err;
2789 2790
}

2791
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2792 2793
{
	struct tcp_sock *tp = tcp_sk(sk);
2794
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2795 2796 2797

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2798
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2799
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2800 2801 2802 2803 2804 2805 2806
		}
#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
2807
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2808

2809
	} else if (err != -EBUSY) {
2810
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
L
Linus Torvalds 已提交
2811
	}
Y
Yuchung Cheng 已提交
2812 2813 2814 2815

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2816 2817 2818
	return err;
}

2819 2820 2821
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
E
Eric Dumazet 已提交
2822
static bool tcp_can_forward_retransmit(struct sock *sk)
2823 2824
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2825
	const struct tcp_sock *tp = tcp_sk(sk);
2826 2827 2828

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
E
Eric Dumazet 已提交
2829
		return false;
2830 2831 2832

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
E
Eric Dumazet 已提交
2833
		return false;
2834 2835 2836 2837 2838 2839 2840 2841 2842 2843

	/* Yeah, we have to make difficult choice between forward transmission
	 * and retransmission... Both ways have their merits...
	 *
	 * For now we do not retransmit anything, while we have some new
	 * segments to send. In the other cases, follow rule 3 for
	 * NextSeg() specified in RFC3517.
	 */

	if (tcp_may_send_now(sk))
E
Eric Dumazet 已提交
2844
		return false;
2845

E
Eric Dumazet 已提交
2846
	return true;
2847 2848
}

L
Linus Torvalds 已提交
2849 2850 2851 2852 2853 2854 2855 2856 2857 2858
/* 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)
{
2859
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2860 2861
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2862
	struct sk_buff *hole = NULL;
2863
	u32 max_segs, last_lost;
2864
	int mib_idx;
2865
	int fwd_rexmitting = 0;
2866

2867 2868 2869
	if (!tp->packets_out)
		return;

2870 2871 2872
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2873
	if (tp->retransmit_skb_hint) {
2874
		skb = tp->retransmit_skb_hint;
2875 2876 2877 2878
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2879
		skb = tcp_write_queue_head(sk);
2880 2881
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2882

2883
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2884
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2885
		__u8 sacked;
2886
		int segs;
L
Linus Torvalds 已提交
2887

2888 2889 2890
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2891
		if (!hole)
2892
			tp->retransmit_skb_hint = skb;
2893

2894 2895
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2896
			return;
E
Eric Dumazet 已提交
2897
		sacked = TCP_SKB_CB(skb)->sacked;
2898 2899 2900 2901
		/* 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
2902

2903 2904 2905 2906 2907
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2908

2909
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2910
			tp->retransmit_high = last_lost;
2911 2912 2913
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
2914
			if (hole) {
2915 2916 2917 2918 2919
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2920

2921
		} else if (!(sacked & TCPCB_LOST)) {
2922
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2923 2924
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2925

2926
		} else {
2927
			last_lost = TCP_SKB_CB(skb)->end_seq;
2928 2929 2930 2931 2932
			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
2933

2934
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2935 2936
			continue;

2937 2938 2939
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2940
		if (tcp_retransmit_skb(sk, skb, segs))
2941
			return;
2942

2943
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2944

2945
		if (tcp_in_cwnd_reduction(sk))
2946 2947
			tp->prr_out += tcp_skb_pcount(skb);

2948
		if (skb == tcp_write_queue_head(sk))
2949 2950 2951
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2952 2953 2954
	}
}

2955 2956
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2957 2958
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2959 2960
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2961
 */
2962
void sk_forced_mem_schedule(struct sock *sk, int size)
2963
{
2964
	int amt;
2965 2966 2967 2968 2969

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2970 2971
	sk_memory_allocated_add(sk, amt);

2972 2973
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
2974 2975
}

2976 2977
/* 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
2978 2979 2980
 */
void tcp_send_fin(struct sock *sk)
{
2981
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2982 2983
	struct tcp_sock *tp = tcp_sk(sk);

2984 2985 2986 2987
	/* 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
2988
	 */
2989
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
2990 2991 2992
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
2993
		tp->write_seq++;
2994 2995 2996 2997 2998 2999 3000 3001 3002 3003
		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
3004
	} else {
3005 3006 3007 3008 3009
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3010
		}
3011
		skb_reserve(skb, MAX_TCP_HEADER);
3012
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3013
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3014
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3015
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3016 3017
		tcp_queue_skb(sk, skb);
	}
3018
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3019 3020 3021 3022 3023
}

/* 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
3024
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3025
 */
A
Al Viro 已提交
3026
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3027 3028 3029 3030 3031 3032
{
	struct sk_buff *skb;

	/* 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
3033
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3034 3035 3036 3037 3038
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3039
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3040
			     TCPHDR_ACK | TCPHDR_RST);
3041
	skb_mstamp_get(&skb->skb_mstamp);
L
Linus Torvalds 已提交
3042
	/* Send it off. */
3043
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3044
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3045

P
Pavel Emelyanov 已提交
3046
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
3047 3048
}

3049 3050
/* 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
3051 3052 3053 3054 3055 3056
 * 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)
{
3057
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3058

3059
	skb = tcp_write_queue_head(sk);
3060
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3061
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3062 3063
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3064
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3065 3066
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
3067
			if (!nskb)
L
Linus Torvalds 已提交
3068
				return -ENOMEM;
3069
			tcp_unlink_write_queue(skb, sk);
3070
			__skb_header_release(nskb);
3071
			__tcp_add_write_queue_head(sk, nskb);
3072 3073 3074
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3075 3076 3077
			skb = nskb;
		}

E
Eric Dumazet 已提交
3078
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3079
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3080
	}
3081
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3082 3083
}

3084 3085 3086 3087 3088 3089 3090 3091 3092
/**
 * 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.
 */
3093
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3094
				struct request_sock *req,
3095
				struct tcp_fastopen_cookie *foc,
3096
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3097
{
3098
	struct inet_request_sock *ireq = inet_rsk(req);
3099
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3100
	struct tcp_md5sig_key *md5 = NULL;
3101 3102
	struct tcp_out_options opts;
	struct sk_buff *skb;
3103
	int tcp_header_size;
3104 3105
	struct tcphdr *th;
	u16 user_mss;
3106
	int mss;
L
Linus Torvalds 已提交
3107

3108
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3109 3110
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3111
		return NULL;
3112
	}
L
Linus Torvalds 已提交
3113 3114 3115
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3116 3117
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3118
		skb_set_owner_w(skb, req_to_sk(req));
3119 3120 3121 3122 3123 3124 3125
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3126 3127 3128 3129 3130
		/* 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);
3131
		break;
3132
	}
3133
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3134

3135
	mss = dst_metric_advmss(dst);
3136 3137 3138
	user_mss = READ_ONCE(tp->rx_opt.user_mss);
	if (user_mss && user_mss < mss)
		mss = user_mss;
3139

A
Adam Langley 已提交
3140
	memset(&opts, 0, sizeof(opts));
3141 3142
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
3143
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3144 3145
	else
#endif
E
Eric Dumazet 已提交
3146
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
3147 3148 3149

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3150
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3151
#endif
3152
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3153 3154
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3155

3156 3157
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3158

3159
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3160 3161 3162
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3163
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3164
	th->source = htons(ireq->ir_num);
3165
	th->dest = ireq->ir_rmt_port;
3166 3167 3168 3169
	/* 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
3170
			     TCPHDR_SYN | TCPHDR_ACK);
3171

L
Linus Torvalds 已提交
3172
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3173 3174
	/* 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
3175 3176

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3177
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3178
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3179
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3180
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3181 3182 3183

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3184
	if (md5)
3185
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3186
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3187
	rcu_read_unlock();
3188 3189
#endif

3190 3191
	/* Do not fool tcpdump (if any), clean our debris */
	skb->tstamp.tv64 = 0;
L
Linus Torvalds 已提交
3192 3193
	return skb;
}
E
Eric Dumazet 已提交
3194
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3195

3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214
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();
}

3215
/* Do all connect socket setups that can be done AF independent. */
3216
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3217
{
3218
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3219 3220 3221 3222 3223 3224 3225
	struct tcp_sock *tp = tcp_sk(sk);
	__u8 rcv_wscale;

	/* 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.
	 */
	tp->tcp_header_len = sizeof(struct tcphdr) +
3226
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3227

3228
#ifdef CONFIG_TCP_MD5SIG
3229
	if (tp->af_specific->md5_lookup(sk, sk))
3230 3231 3232
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3233 3234 3235 3236
	/* 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
3237
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3238 3239
	tcp_sync_mss(sk, dst_mtu(dst));

3240 3241
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3242 3243
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3244
	tp->advmss = dst_metric_advmss(dst);
3245 3246 3247
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
		tp->advmss = tp->rx_opt.user_mss;

L
Linus Torvalds 已提交
3248 3249
	tcp_initialize_rcv_mss(sk);

3250 3251 3252 3253 3254
	/* 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);

L
Linus Torvalds 已提交
3255 3256 3257 3258
	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,
3259
				  sysctl_tcp_window_scaling,
3260 3261
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3262 3263 3264 3265 3266 3267 3268

	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;
3269
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3270 3271
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3272
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3273
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3274 3275 3276

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3277 3278
	else
		tp->rcv_tstamp = tcp_time_stamp;
P
Pavel Emelyanov 已提交
3279 3280
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3281

3282 3283
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3284 3285 3286
	tcp_clear_retrans(tp);
}

3287 3288 3289 3290 3291 3292
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;
3293
	__skb_header_release(skb);
3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311
	__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;
3312
	int syn_loss = 0, space, err = 0;
3313
	unsigned long last_syn_loss = 0;
3314
	struct sk_buff *syn_data;
3315

3316
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3317 3318 3319 3320 3321 3322 3323 3324
	tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
			       &syn_loss, &last_syn_loss);
	/* Recurring FO SYN losses: revert to regular handshake temporarily */
	if (syn_loss > 1 &&
	    time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
		fo->cookie.len = -1;
		goto fallback;
	}
3325

3326 3327 3328
	if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
		fo->cookie.len = -1;
	else if (fo->cookie.len <= 0)
3329 3330 3331 3332 3333 3334 3335 3336
		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 :(
	 */
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3337
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3338 3339
		MAX_TCP_OPTION_SPACE;

3340 3341 3342 3343 3344
	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));

3345
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3346
	if (!syn_data)
3347
		goto fallback;
3348 3349
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360
	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;
		}
3361
	}
3362 3363 3364 3365
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3366

3367
	tcp_connect_queue_skb(sk, syn_data);
3368 3369
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3370

3371
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3372

3373
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3374

3375 3376 3377 3378 3379 3380 3381 3382
	/* 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) {
3383
		tp->syn_data = (fo->copied > 0);
3384
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399
		goto done;
	}

fallback:
	/* Send a regular SYN with Fast Open cookie request option */
	if (fo->cookie.len > 0)
		fo->cookie.len = 0;
	err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
	if (err)
		tp->syn_fastopen = 0;
done:
	fo->cookie.len = -1;  /* Exclude Fast Open option for SYN retries */
	return err;
}

3400
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3401 3402 3403 3404
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3405
	int err;
L
Linus Torvalds 已提交
3406 3407 3408

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3409 3410 3411 3412 3413
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3414
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3415
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3416 3417
		return -ENOBUFS;

C
Changli Gao 已提交
3418
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
E
Eric Dumazet 已提交
3419
	tp->retrans_stamp = tcp_time_stamp;
3420
	tcp_connect_queue_skb(sk, buff);
3421
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3422

3423 3424 3425
	/* 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);
3426 3427
	if (err == -ECONNREFUSED)
		return err;
3428 3429 3430 3431 3432 3433

	/* We change tp->snd_nxt after the tcp_transmit_skb() call
	 * in order to make this packet get counted in tcpOutSegs.
	 */
	tp->snd_nxt = tp->write_seq;
	tp->pushed_seq = tp->write_seq;
P
Pavel Emelyanov 已提交
3434
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3435 3436

	/* Timer for repeating the SYN until an answer. */
3437 3438
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3439 3440
	return 0;
}
E
Eric Dumazet 已提交
3441
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3442 3443 3444 3445 3446 3447 3448

/* 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)
{
3449 3450
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3451 3452
	unsigned long timeout;

3453 3454
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3455
	if (ato > TCP_DELACK_MIN) {
3456
		const struct tcp_sock *tp = tcp_sk(sk);
3457
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3458

3459 3460
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3461 3462 3463 3464 3465
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3466
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3467 3468
		 * directly.
		 */
3469 3470 3471
		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
3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483

			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. */
3484
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3485 3486 3487
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3488 3489
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3490 3491 3492 3493
			tcp_send_ack(sk);
			return;
		}

3494 3495
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3496
	}
3497 3498 3499
	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
3500 3501 3502 3503 3504
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3505
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3506

3507 3508 3509
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3510

3511 3512
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3513 3514 3515 3516
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3517 3518 3519
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3520 3521 3522 3523 3524
		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
3525
	}
3526 3527 3528

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3529
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3530

E
Eric Dumazet 已提交
3531 3532 3533 3534 3535 3536 3537 3538
	/* 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
	 * We also avoid tcp_wfree() overhead (cache line miss accessing
	 * tp->tsq_flags) by using regular sock_wfree()
	 */
	skb_set_tcp_pure_ack(buff);

3539
	/* Send it off, this clears delayed acks for us. */
E
Eric Dumazet 已提交
3540
	skb_mstamp_get(&buff->skb_mstamp);
3541
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3542
}
3543
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555

/* 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.
 */
3556
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3557 3558 3559 3560 3561
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3562 3563
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3564
	if (!skb)
L
Linus Torvalds 已提交
3565 3566 3567 3568 3569 3570 3571 3572
		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
3573
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
E
Eric Dumazet 已提交
3574
	skb_mstamp_get(&skb->skb_mstamp);
3575
	NET_INC_STATS(sock_net(sk), mib);
3576
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3577 3578
}

P
Pavel Emelyanov 已提交
3579 3580 3581 3582
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;
3583
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3584 3585 3586
	}
}

3587
/* Initiate keepalive or window probe from timer. */
3588
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3589
{
3590 3591
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3592

3593 3594 3595
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3596 3597
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3598
		int err;
I
Ilpo Järvinen 已提交
3599
		unsigned int mss = tcp_current_mss(sk);
3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611
		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
3612
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3613
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3614 3615
				return -1;
		} else if (!tcp_skb_pcount(skb))
3616
			tcp_set_skb_tso_segs(skb, mss);
3617

E
Eric Dumazet 已提交
3618
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3619 3620 3621 3622 3623
		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
3624
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3625 3626
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3627 3628 3629 3630 3631 3632 3633 3634
	}
}

/* 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)
{
3635
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3636
	struct tcp_sock *tp = tcp_sk(sk);
3637
	struct net *net = sock_net(sk);
3638
	unsigned long probe_max;
L
Linus Torvalds 已提交
3639 3640
	int err;

3641
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3642

3643
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3644
		/* Cancel probe timer, if it is not required. */
3645
		icsk->icsk_probes_out = 0;
3646
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3647 3648 3649 3650
		return;
	}

	if (err <= 0) {
3651
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3652
			icsk->icsk_backoff++;
3653
		icsk->icsk_probes_out++;
3654
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3655 3656
	} else {
		/* If packet was not sent due to local congestion,
3657
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3658 3659 3660 3661
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3662 3663
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3664
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3665
	}
3666
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3667
				  tcp_probe0_when(sk, probe_max),
3668
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3669
}
3670

3671
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3672 3673 3674 3675 3676
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3677
	tcp_rsk(req)->txhash = net_tx_rndhash();
3678
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3679
	if (!res) {
E
Eric Dumazet 已提交
3680
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3681
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3682 3683
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3684 3685 3686 3687
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);