tcp_output.c 106.8 KB
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/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
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 * Authors:	Ross Biro
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 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

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

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#define pr_fmt(fmt) "TCP: " fmt

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#include <net/tcp.h>

#include <linux/compiler.h>
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#include <linux/gfp.h>
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#include <linux/module.h>

/* People can turn this off for buggy TCP's found in printers etc. */
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int sysctl_tcp_retrans_collapse __read_mostly = 1;
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/* People can turn this on to work with those rare, broken TCPs that
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 * interpret the window field as a signed quantity.
 */
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int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
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/* Default TSQ limit of four TSO segments */
int sysctl_tcp_limit_output_bytes __read_mostly = 262144;
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/* This limits the percentage of the congestion window which we
 * will allow a single TSO frame to consume.  Building TSO frames
 * which are too large can cause TCP streams to be bursty.
 */
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int sysctl_tcp_tso_win_divisor __read_mostly = 3;
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/* By default, RFC2861 behavior.  */
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int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
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static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp);
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/* Account for new data that has been sent to the network. */
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static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
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{
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	struct inet_connection_sock *icsk = inet_csk(sk);
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	struct tcp_sock *tp = tcp_sk(sk);
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	unsigned int prior_packets = tp->packets_out;
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	tcp_advance_send_head(sk, skb);
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	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
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	tp->packets_out += tcp_skb_pcount(skb);
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	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
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		tcp_rearm_rto(sk);
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	NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
		      tcp_skb_pcount(skb));
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}

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

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

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

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

	return (__u16)mss;
}

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

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

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

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

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	tp->lsndtime = now;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

487
	if (unlikely(OPTION_WSCALE & options)) {
A
Adam Langley 已提交
488 489 490 491 492 493 494 495 496
		*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
497 498 499 500 501
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
502
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
503
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
504

A
Adam Langley 已提交
505 506
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
507 508 509
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
510

511
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
512
	}
Y
Yuchung Cheng 已提交
513 514 515

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
516 517 518 519 520 521 522 523 524 525 526 527 528
		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
529

530 531 532 533
		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
534
		}
535
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
536
	}
A
Adam Langley 已提交
537 538
}

539 540 541
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
542
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
543
				struct tcp_out_options *opts,
544 545
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
546
	struct tcp_sock *tp = tcp_sk(sk);
547
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
548
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
549

550
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
551 552 553
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
554
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
555
	}
A
Adam Langley 已提交
556 557
#else
	*md5 = NULL;
558
#endif
A
Adam Langley 已提交
559 560 561 562 563 564 565 566 567 568 569

	/* 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);
570
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
571

572
	if (likely(sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
573
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
574
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
575
		opts->tsecr = tp->rx_opt.ts_recent;
576
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
577
	}
578
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
579
		opts->ws = tp->rx_opt.rcv_wscale;
580
		opts->options |= OPTION_WSCALE;
581
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
582
	}
583
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
584
		opts->options |= OPTION_SACK_ADVERTISE;
585
		if (unlikely(!(OPTION_TS & opts->options)))
586
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
587 588
	}

589
	if (fastopen && fastopen->cookie.len >= 0) {
590 591 592 593
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
594 595 596 597 598 599
		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;
600
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
601 602
		}
	}
603 604

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
605 606
}

607
/* Set up TCP options for SYN-ACKs. */
608 609 610 611 612
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)
613
{
A
Adam Langley 已提交
614
	struct inet_request_sock *ireq = inet_rsk(req);
615
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
616

617
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
618
	if (md5) {
A
Adam Langley 已提交
619
		opts->options |= OPTION_MD5;
620 621 622 623 624 625 626
		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
627
		ireq->tstamp_ok &= !ireq->sack_ok;
628 629
	}
#endif
A
Adam Langley 已提交
630

631
	/* We always send an MSS option. */
A
Adam Langley 已提交
632
	opts->mss = mss;
633
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
634 635 636

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
637
		opts->options |= OPTION_WSCALE;
638
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
639
	}
E
Eric Dumazet 已提交
640
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
641
		opts->options |= OPTION_TS;
642
		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
A
Adam Langley 已提交
643
		opts->tsecr = req->ts_recent;
644
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
645 646 647
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
648
		if (unlikely(!ireq->tstamp_ok))
649
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
650
	}
651 652 653 654 655
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
656 657 658 659 660 661 662
		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
663

664
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
665 666
}

667 668 669
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
670
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
671
					struct tcp_out_options *opts,
672 673
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
674
	struct tcp_sock *tp = tcp_sk(sk);
675
	unsigned int size = 0;
676
	unsigned int eff_sacks;
A
Adam Langley 已提交
677

678 679
	opts->options = 0;

A
Adam Langley 已提交
680 681 682 683 684 685 686 687 688 689 690 691
#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
692
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
693 694 695 696
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

697 698
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
699
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
700
		opts->num_sack_blocks =
701
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
702 703 704 705 706 707 708
			      (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
709
}
L
Linus Torvalds 已提交
710

E
Eric Dumazet 已提交
711 712 713 714 715 716 717 718 719

/* 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
720
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
721 722 723 724 725 726 727 728 729 730 731
 *
 * 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);

732 733 734 735
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
736 737 738 739 740 741 742 743
	     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
744
			       0, GFP_ATOMIC);
745
	}
746
}
E
Eric Dumazet 已提交
747
/*
S
stephen hemminger 已提交
748
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
749
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
750
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770
 * 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;
771
		smp_mb__before_atomic();
772 773
		clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);

774
		if (!sk->sk_lock.owned &&
775
		    test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) {
776 777
			bh_lock_sock(sk);
			if (!sock_owned_by_user(sk)) {
778
				clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
779 780 781
				tcp_tsq_handler(sk);
			}
			bh_unlock_sock(sk);
E
Eric Dumazet 已提交
782 783 784 785 786 787
		}

		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
788 789 790 791
#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
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)
{
801
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
802

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

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

885 886 887
		if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
			goto out;

888
		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
889
		nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
890 891 892
		if (nval != oval)
			continue;

E
Eric Dumazet 已提交
893 894
		/* queue this socket to tasklet queue */
		local_irq_save(flags);
895
		tsq = this_cpu_ptr(&tsq_tasklet);
896
		empty = list_empty(&tsq->head);
E
Eric Dumazet 已提交
897
		list_add(&tp->tsq_node, &tsq->head);
898 899
		if (empty)
			tasklet_schedule(&tsq->tasklet);
E
Eric Dumazet 已提交
900
		local_irq_restore(flags);
901
		return;
E
Eric Dumazet 已提交
902
	}
903 904
out:
	sk_free(sk);
E
Eric Dumazet 已提交
905 906
}

907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972
/* Note: Called under hard irq.
 * We can not call TCP stack right away.
 */
enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
{
	struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
	struct sock *sk = (struct sock *)tp;
	unsigned long nval, oval;

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

		if (oval & TSQF_QUEUED)
			break;

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

		if (!atomic_inc_not_zero(&sk->sk_wmem_alloc))
			break;
		/* queue this socket to tasklet queue */
		tsq = this_cpu_ptr(&tsq_tasklet);
		empty = list_empty(&tsq->head);
		list_add(&tp->tsq_node, &tsq->head);
		if (empty)
			tasklet_schedule(&tsq->tasklet);
		break;
	}
	return HRTIMER_NORESTART;
}

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

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

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

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

L
Linus Torvalds 已提交
973 974 975 976 977 978 979 980 981 982 983
/* 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.
 */
984 985
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
986
{
987 988 989 990
	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
991
	struct tcp_out_options opts;
992
	unsigned int tcp_options_size, tcp_header_size;
993
	struct tcp_md5sig_key *md5;
994 995 996 997
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
998
	tp = tcp_sk(sk);
999

1000
	skb->skb_mstamp = tp->tcp_mstamp;
1001
	if (clone_it) {
1002 1003
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
1004
		tcp_rate_skb_sent(sk, skb);
1005

1006 1007 1008 1009 1010 1011 1012
		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
1013

1014 1015
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
1016
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
1017

E
Eric Dumazet 已提交
1018
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
1019 1020 1021 1022 1023
		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);
1024

E
Eric Dumazet 已提交
1025
	/* if no packet is in qdisc/device queue, then allow XPS to select
1026 1027 1028 1029 1030
	 * 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
1031
	 */
1032
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1033

1034 1035 1036 1037 1038 1039 1040
	/* If we had to use memory reserve to allocate this skb,
	 * this might cause drops if packet is looped back :
	 * Other socket might not have SOCK_MEMALLOC.
	 * Packets not looped back do not care about pfmemalloc.
	 */
	skb->pfmemalloc = 0;

1041 1042
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
1043 1044 1045

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
1046
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1047
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
1048
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
1049

1050 1051
	skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);

1052
	/* Build TCP header and checksum it. */
1053
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
1054 1055
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
1056 1057
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
1058
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
1059
					tcb->tcp_flags);
1060 1061 1062

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
1063

I
Ilpo Järvinen 已提交
1064
	/* The urg_mode check is necessary during a below snd_una win probe */
1065 1066 1067 1068 1069
	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)) {
1070
			th->urg_ptr = htons(0xFFFF);
1071 1072
			th->urg = 1;
		}
1073
	}
L
Linus Torvalds 已提交
1074

1075
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1076
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1077 1078 1079 1080 1081 1082 1083 1084 1085
	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));
	}
1086 1087 1088
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1089
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1090
		tp->af_specific->calc_md5_hash(opts.hash_location,
1091
					       md5, sk, skb);
1092 1093 1094
	}
#endif

1095
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1096

E
Eric Dumazet 已提交
1097
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1098
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1099

1100
	if (skb->len != tcp_header_size) {
1101
		tcp_event_data_sent(tp, sk);
1102
		tp->data_segs_out += tcp_skb_pcount(skb);
1103
		tcp_internal_pacing(sk, skb);
1104
	}
L
Linus Torvalds 已提交
1105

1106
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1107 1108
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1109

1110
	tp->segs_out += tcp_skb_pcount(skb);
1111
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1112
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1113
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1114

E
Eric Dumazet 已提交
1115
	/* Our usage of tstamp should remain private */
T
Thomas Gleixner 已提交
1116
	skb->tstamp = 0;
1117 1118 1119 1120 1121

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

1122
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1123

1124
	if (likely(err <= 0))
1125 1126
		return err;

1127
	tcp_enter_cwr(sk);
1128

1129
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1130 1131
}

1132
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1133 1134 1135 1136 1137 1138 1139 1140 1141 1142
 *
 * 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;
1143
	__skb_header_release(skb);
1144
	tcp_add_write_queue_tail(sk, skb);
1145 1146
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1147 1148
}

1149
/* Initialize TSO segments for a packet. */
1150
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1151
{
1152
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1153 1154 1155
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1156
		tcp_skb_pcount_set(skb, 1);
1157
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1158
	} else {
1159
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1160
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1161 1162 1163
	}
}

I
Ilpo Järvinen 已提交
1164
/* When a modification to fackets out becomes necessary, we need to check
1165
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1166
 */
1167
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1168 1169
				   int decr)
{
1170 1171
	struct tcp_sock *tp = tcp_sk(sk);

1172
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1173 1174
		return;

1175
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1176 1177 1178
		tp->fackets_out -= decr;
}

1179 1180 1181
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1182
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202
{
	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) &&
1203
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1204 1205 1206 1207 1208
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1209 1210 1211 1212 1213 1214
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);
}

1215 1216 1217 1218
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1219
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1220 1221 1222 1223 1224 1225 1226
	    !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);
1227 1228
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1229 1230 1231
	}
}

1232 1233 1234 1235 1236 1237
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
1238 1239
/* 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
1240
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1241 1242
 * Remember, these are still headerless SKBs at this point.
 */
1243
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1244
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1245 1246 1247
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1248
	int nsize, old_factor;
1249
	int nlen;
1250
	u8 flags;
L
Linus Torvalds 已提交
1251

1252 1253
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1254

L
Linus Torvalds 已提交
1255 1256 1257 1258
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1259
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1260 1261 1262
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1263
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1264
	if (!buff)
L
Linus Torvalds 已提交
1265
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1266

1267 1268
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1269 1270 1271
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1272 1273 1274 1275 1276 1277 1278

	/* 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
1279 1280 1281
	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;
1282
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1283
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1284

1285
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1286
		/* Copy and checksum data tail into the new buffer. */
1287 1288
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1289 1290 1291 1292 1293 1294
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1295
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1296 1297 1298 1299 1300
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1301
	buff->tstamp = skb->tstamp;
1302
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1303

1304 1305
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1306
	/* Fix up tso_factor for both original and new SKB.  */
1307 1308
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1309

1310 1311 1312
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1313 1314 1315
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1316
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1317 1318
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1319

1320 1321
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1322 1323 1324
	}

	/* Link BUFF into the send queue. */
1325
	__skb_header_release(buff);
1326
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1327 1328 1329 1330 1331 1332 1333 1334

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

E
Eric Dumazet 已提交
1340 1341 1342 1343 1344
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
1345
			return 0;
E
Eric Dumazet 已提交
1346
	}
L
Linus Torvalds 已提交
1347 1348
	eat = len;
	k = 0;
1349 1350 1351
	shinfo = skb_shinfo(skb);
	for (i = 0; i < shinfo->nr_frags; i++) {
		int size = skb_frag_size(&shinfo->frags[i]);
E
Eric Dumazet 已提交
1352 1353

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

1368
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1369 1370
	skb->data_len -= len;
	skb->len = skb->data_len;
1371
	return len;
L
Linus Torvalds 已提交
1372 1373
}

1374
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1375 1376
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1377 1378
	u32 delta_truesize;

1379
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1380 1381
		return -ENOMEM;

1382
	delta_truesize = __pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1383 1384

	TCP_SKB_CB(skb)->seq += len;
1385
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1386

1387 1388 1389 1390 1391 1392
	if (delta_truesize) {
		skb->truesize	   -= delta_truesize;
		sk->sk_wmem_queued -= delta_truesize;
		sk_mem_uncharge(sk, delta_truesize);
		sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
	}
L
Linus Torvalds 已提交
1393

1394
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1395
	if (tcp_skb_pcount(skb) > 1)
1396
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1397 1398 1399 1400

	return 0;
}

1401 1402
/* 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
1403
{
1404 1405
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1406 1407 1408 1409 1410 1411 1412
	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);

1413 1414 1415 1416 1417 1418 1419 1420
	/* 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
1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433
	/* 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;
}

1434 1435 1436 1437 1438 1439 1440 1441
/* 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
1442
/* Inverse of above */
1443
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1444
{
1445 1446
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1447 1448 1449 1450 1451 1452 1453
	int mtu;

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

1454 1455 1456 1457 1458 1459 1460
	/* 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
1461 1462
	return mtu;
}
1463
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1464

1465
/* MTU probing init per socket */
J
John Heffner 已提交
1466 1467 1468 1469
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
1470
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1471

F
Fan Du 已提交
1472
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1473
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1474
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1475
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1476
	icsk->icsk_mtup.probe_size = 0;
1477
	if (icsk->icsk_mtup.enabled)
1478
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
J
John Heffner 已提交
1479
}
E
Eric Dumazet 已提交
1480
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1481

L
Linus Torvalds 已提交
1482 1483 1484 1485 1486 1487
/* 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
1488
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1489 1490
   It also does not include TCP options.

1491
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1492 1493 1494 1495 1496 1497 1498 1499 1500

   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.

1501 1502
   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
1503 1504 1505 1506
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1507
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1508
	int mss_now;
L
Linus Torvalds 已提交
1509

J
John Heffner 已提交
1510 1511
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1512

J
John Heffner 已提交
1513
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1514
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1515 1516

	/* And store cached results */
1517
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1518 1519
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1520
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1521 1522 1523

	return mss_now;
}
E
Eric Dumazet 已提交
1524
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1525 1526 1527 1528

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1529
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1530
{
1531 1532
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1533
	u32 mss_now;
1534
	unsigned int header_len;
A
Adam Langley 已提交
1535 1536
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1537 1538 1539

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1540 1541
	if (dst) {
		u32 mtu = dst_mtu(dst);
1542
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1543 1544 1545
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1546 1547 1548 1549 1550 1551 1552 1553 1554 1555
	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;
	}
1556

L
Linus Torvalds 已提交
1557 1558 1559
	return mss_now;
}

1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578
/* 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;
	}
1579
	tp->snd_cwnd_stamp = tcp_jiffies32;
1580 1581
}

1582
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1583
{
1584
	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1585
	struct tcp_sock *tp = tcp_sk(sk);
1586

1587 1588 1589 1590 1591 1592 1593 1594 1595
	/* 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;
	}
1596

1597
	if (tcp_is_cwnd_limited(sk)) {
1598 1599
		/* Network is feed fully. */
		tp->snd_cwnd_used = 0;
1600
		tp->snd_cwnd_stamp = tcp_jiffies32;
1601 1602 1603 1604 1605
	} else {
		/* Network starves. */
		if (tp->packets_out > tp->snd_cwnd_used)
			tp->snd_cwnd_used = tp->packets_out;

1606
		if (sysctl_tcp_slow_start_after_idle &&
1607
		    (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1608
		    !ca_ops->cong_control)
1609
			tcp_cwnd_application_limited(sk);
1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621

		/* 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);
1622 1623 1624
	}
}

E
Eric Dumazet 已提交
1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638
/* 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
1639
 */
E
Eric Dumazet 已提交
1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654
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,
1655
			    int nonagle)
E
Eric Dumazet 已提交
1656 1657 1658 1659 1660
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1661 1662 1663 1664

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1665 1666
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677
{
	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.
	 */
1678
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1679 1680 1681

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1682
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1683

1684 1685 1686 1687 1688 1689 1690 1691
/* 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;

1692 1693
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1694 1695
}

E
Eric Dumazet 已提交
1696 1697 1698 1699 1700 1701
/* 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)
1702
{
1703
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1704
	u32 partial, needed, window, max_len;
1705

1706
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1707
	max_len = mss_now * max_segs;
1708

1709 1710
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1711

1712 1713
	needed = min(skb->len, window);

1714 1715
	if (max_len <= needed)
		return max_len;
1716

E
Eric Dumazet 已提交
1717 1718 1719 1720 1721
	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
	 */
1722
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1723 1724 1725
		return needed - partial;

	return needed;
1726 1727 1728 1729 1730
}

/* 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.
 */
1731 1732
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1733
{
E
Eric Dumazet 已提交
1734
	u32 in_flight, cwnd, halfcwnd;
1735 1736

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1737 1738
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1739 1740 1741 1742
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1743 1744
	if (in_flight >= cwnd)
		return 0;
1745

E
Eric Dumazet 已提交
1746 1747 1748 1749 1750
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1751 1752
}

1753
/* Initialize TSO state of a skb.
1754
 * This must be invoked the first time we consider transmitting
1755 1756
 * SKB onto the wire.
 */
1757
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1758 1759 1760
{
	int tso_segs = tcp_skb_pcount(skb);

1761
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1762
		tcp_set_skb_tso_segs(skb, mss_now);
1763 1764 1765 1766 1767 1768
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1769
/* Return true if the Nagle test allows this packet to be
1770 1771
 * sent now.
 */
E
Eric Dumazet 已提交
1772 1773
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1774 1775 1776 1777 1778 1779 1780 1781
{
	/* 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
1782
		return true;
1783

Y
Yuchung Cheng 已提交
1784 1785
	/* 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
1786
		return true;
1787

1788
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1789
		return true;
1790

E
Eric Dumazet 已提交
1791
	return false;
1792 1793 1794
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1795 1796 1797
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1798 1799 1800 1801 1802 1803
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1804
	return !after(end_seq, tcp_wnd_end(tp));
1805 1806
}

1807
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1808 1809 1810
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1811
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1812 1813
				 unsigned int cur_mss, int nonagle)
{
1814
	const struct tcp_sock *tp = tcp_sk(sk);
1815 1816
	unsigned int cwnd_quota;

1817
	tcp_init_tso_segs(skb, cur_mss);
1818 1819 1820 1821 1822

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1823
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1824 1825 1826 1827 1828
		cwnd_quota = 0;

	return cwnd_quota;
}

1829
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1830
bool tcp_may_send_now(struct sock *sk)
1831
{
1832
	const struct tcp_sock *tp = tcp_sk(sk);
1833
	struct sk_buff *skb = tcp_send_head(sk);
1834

E
Eric Dumazet 已提交
1835
	return skb &&
I
Ilpo Järvinen 已提交
1836
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1837
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1838
			      tp->nonagle : TCP_NAGLE_PUSH));
1839 1840 1841 1842 1843 1844 1845 1846 1847
}

/* 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).
 */
1848
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1849
			unsigned int mss_now, gfp_t gfp)
1850 1851 1852
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1853
	u8 flags;
1854 1855

	/* All of a TSO frame must be composed of paged data.  */
1856
	if (skb->len != skb->data_len)
1857
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1858

1859
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1860
	if (unlikely(!buff))
1861 1862
		return -ENOMEM;

1863 1864
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1865
	buff->truesize += nlen;
1866 1867 1868 1869 1870 1871 1872 1873
	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
1874 1875 1876
	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;
1877 1878 1879 1880

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

1881 1882
	tcp_skb_fragment_eor(skb, buff);

1883
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1884
	skb_split(skb, buff, len);
1885
	tcp_fragment_tstamp(skb, buff);
1886 1887

	/* Fix up tso_factor for both original and new SKB.  */
1888 1889
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1890 1891

	/* Link BUFF into the send queue. */
1892
	__skb_header_release(buff);
1893
	tcp_insert_write_queue_after(skb, buff, sk);
1894 1895 1896 1897 1898 1899 1900 1901 1902

	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.
 */
1903
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1904
				 bool *is_cwnd_limited, u32 max_segs)
1905
{
1906
	const struct inet_connection_sock *icsk = inet_csk(sk);
1907 1908 1909
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *head;
1910
	int win_divisor;
1911

E
Eric Dumazet 已提交
1912
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1913
		goto send_now;
1914

1915
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1916 1917
		goto send_now;

E
Eric Dumazet 已提交
1918 1919 1920
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
1921
	if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
J
John Heffner 已提交
1922
		goto send_now;
1923

1924 1925
	in_flight = tcp_packets_in_flight(tp);

1926
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1927

1928
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1929 1930 1931 1932 1933 1934

	/* 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);

1935
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1936
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1937
		goto send_now;
1938

1939 1940 1941 1942
	/* 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;

1943 1944
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1945 1946 1947 1948 1949
		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.
		 */
1950
		chunk /= win_divisor;
1951
		if (limit >= chunk)
J
John Heffner 已提交
1952
			goto send_now;
1953 1954 1955 1956 1957 1958
	} 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.
		 */
1959
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1960
			goto send_now;
1961 1962
	}

1963
	head = tcp_write_queue_head(sk);
1964 1965

	age = skb_mstamp_us_delta(&tp->tcp_mstamp, &head->skb_mstamp);
1966 1967 1968 1969
	/* 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
1970
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1971

1972
	if (cong_win < send_win && cong_win <= skb->len)
1973 1974
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1975
	return true;
J
John Heffner 已提交
1976 1977

send_now:
E
Eric Dumazet 已提交
1978
	return false;
1979 1980
}

1981 1982 1983 1984 1985 1986 1987 1988 1989
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;
1990
	delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
	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 */
2002
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2003 2004 2005
	}
}

J
John Heffner 已提交
2006
/* Create a new MTU probe if we are ready.
2007 2008 2009 2010
 * 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
2011 2012
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
2013 2014
 *         -1 otherwise
 */
J
John Heffner 已提交
2015 2016 2017
static int tcp_mtu_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
2018
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2019
	struct sk_buff *skb, *nskb, *next;
2020
	struct net *net = sock_net(sk);
J
John Heffner 已提交
2021
	int probe_size;
2022
	int size_needed;
2023
	int copy, len;
J
John Heffner 已提交
2024
	int mss_now;
2025
	int interval;
J
John Heffner 已提交
2026 2027 2028 2029

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
2030 2031 2032 2033 2034 2035 2036
	 * not SACKing (the variable headers throw things off)
	 */
	if (likely(!icsk->icsk_mtup.enabled ||
		   icsk->icsk_mtup.probe_size ||
		   inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
		   tp->snd_cwnd < 11 ||
		   tp->rx_opt.num_sacks || tp->rx_opt.dsack))
J
John Heffner 已提交
2037 2038
		return -1;

2039 2040 2041 2042
	/* 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
2043
	mss_now = tcp_current_mss(sk);
2044 2045
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
2046
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2047
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2048 2049 2050 2051
	/* 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.
	 */
2052
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2053 2054 2055 2056 2057
		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
2058 2059 2060 2061
		return -1;
	}

	/* Have enough data in the send queue to probe? */
2062
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
2063 2064
		return -1;

2065 2066
	if (tp->snd_wnd < size_needed)
		return -1;
2067
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2068
		return 0;
J
John Heffner 已提交
2069

2070 2071 2072
	/* 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
2073 2074 2075 2076 2077 2078
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
2079
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2080
	if (!nskb)
J
John Heffner 已提交
2081
		return -1;
2082 2083
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2084

2085
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2086 2087 2088

	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
2089
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2090 2091
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2092
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2093

2094 2095
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2096
	len = 0;
2097
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2098
		copy = min_t(int, skb->len, probe_size - len);
2099
		if (nskb->ip_summed) {
J
John Heffner 已提交
2100
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2101 2102 2103 2104 2105 2106
		} 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
2107 2108 2109 2110

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2111
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2112
			tcp_unlink_write_queue(skb, sk);
2113
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2114
		} else {
E
Eric Dumazet 已提交
2115
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2116
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2117 2118
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2119
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2120 2121
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2122 2123
			} else {
				__pskb_trim_head(skb, copy);
2124
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2125 2126 2127 2128 2129
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2130 2131 2132

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2133
	}
2134
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2135 2136

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2137 2138
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2139 2140
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2141
		 * effectively two packets. */
J
John Heffner 已提交
2142
		tp->snd_cwnd--;
2143
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2144 2145

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2146 2147
		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
2148 2149 2150 2151 2152 2153 2154

		return 1;
	}

	return -1;
}

2155 2156 2157 2158 2159 2160
static bool tcp_pacing_check(const struct sock *sk)
{
	return tcp_needs_internal_pacing(sk) &&
	       hrtimer_active(&tcp_sk(sk)->pacing_timer);
}

2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181
/* 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) {
2182 2183 2184 2185 2186 2187 2188 2189 2190
		/* Always send the 1st or 2nd skb in write queue.
		 * No need to wait for TX completion to call us back,
		 * after softirq/tasklet schedule.
		 * This helps when TX completions are delayed too much.
		 */
		if (skb == sk->sk_write_queue.next ||
		    skb->prev == sk->sk_write_queue.next)
			return false;

2191
		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202
		/* 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;
}

2203 2204
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
2205
	const u32 now = tcp_jiffies32;
2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217

	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
2218 2219
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2220 2221 2222 2223 2224 2225 2226 2227 2228 2229
	 * starts happening, stop the previous chrono and start a new one.
	 */
	if (type > tp->chrono_type)
		tcp_chrono_set(tp, type);
}

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

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

	/* There are multiple conditions worthy of tracking in a
	 * chronograph, so that the highest priority enum takes
	 * precedence over the other conditions (see tcp_chrono_start).
	 * If a condition stops, we only stop chrono tracking if
	 * it's the "most interesting" or current chrono we are
	 * tracking and starts busy chrono if we have pending data.
	 */
	if (tcp_write_queue_empty(sk))
		tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
	else if (type == tp->chrono_type)
		tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2242 2243
}

L
Linus Torvalds 已提交
2244 2245 2246 2247
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2248 2249 2250 2251
 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
 * account rare use of URG, this is not a big flaw.
 *
N
Nandita Dukkipati 已提交
2252 2253 2254
 * Send at most one packet when push_one > 0. Temporarily ignore
 * cwnd limit to force at most one packet out when push_one == 2.

E
Eric Dumazet 已提交
2255 2256
 * Returns true, if no segments are in flight and we have queued segments,
 * but cannot send anything now because of SWS or another problem.
L
Linus Torvalds 已提交
2257
 */
E
Eric Dumazet 已提交
2258 2259
static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp)
L
Linus Torvalds 已提交
2260 2261
{
	struct tcp_sock *tp = tcp_sk(sk);
2262
	struct sk_buff *skb;
2263 2264
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2265
	int result;
2266
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2267
	u32 max_segs;
L
Linus Torvalds 已提交
2268

2269
	sent_pkts = 0;
J
John Heffner 已提交
2270

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

2281
	max_segs = tcp_tso_segs(sk, mss_now);
2282
	skb_mstamp_get(&tp->tcp_mstamp);
2283
	while ((skb = tcp_send_head(sk))) {
2284 2285
		unsigned int limit;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2369
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2370
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2371
		return false;
L
Linus Torvalds 已提交
2372
	}
2373
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2374 2375 2376 2377 2378 2379 2380
}

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;
2381
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2382 2383 2384 2385 2386 2387 2388 2389 2390

	/* 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.
	 */
2391
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2392 2393 2394 2395 2396 2397 2398 2399 2400
		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.
	 */
Y
Yuchung Cheng 已提交
2401 2402 2403
	if ((sysctl_tcp_early_retrans != 3 && sysctl_tcp_early_retrans != 4) ||
	    !tp->packets_out || !tcp_is_sack(tp) ||
	    icsk->icsk_ca_state != TCP_CA_Open)
N
Nandita Dukkipati 已提交
2404 2405 2406 2407 2408 2409 2410
		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
2411 2412
	 * 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
2413
	 */
2414
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433
	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;
}

2434 2435 2436 2437 2438 2439 2440
/* 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)
{
2441
	if (unlikely(skb_fclone_busy(sk, skb))) {
2442 2443
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2444 2445 2446 2447 2448
		return true;
	}
	return false;
}

2449
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2450 2451 2452 2453
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2454
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2455 2456 2457 2458
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470
	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
2471 2472
	}

N
Nandita Dukkipati 已提交
2473 2474 2475 2476
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2477 2478 2479 2480
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2481 2482 2483
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2484 2485 2486 2487 2488
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2489 2490
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2491
			goto rearm_timer;
2492
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2493 2494 2495 2496 2497
	}

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

2498
	if (__tcp_retransmit_skb(sk, skb, 1))
2499
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2500

N
Nandita Dukkipati 已提交
2501
	/* Record snd_nxt for loss detection. */
2502
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2503

2504
probe_sent:
2505
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2506 2507
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2508
rearm_timer:
2509
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2510 2511
}

2512 2513 2514 2515
/* 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.
 */
2516 2517
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2518
{
2519 2520 2521 2522 2523 2524 2525
	/* 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;

2526
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2527
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2528
		tcp_check_probe_timer(sk);
2529 2530
}

2531 2532 2533 2534 2535
/* 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)
{
2536
	struct sk_buff *skb = tcp_send_head(sk);
2537 2538 2539

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

2540
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2541 2542
}

L
Linus Torvalds 已提交
2543 2544
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2545
 *
L
Linus Torvalds 已提交
2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563
 * 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.
2564
 *
L
Linus Torvalds 已提交
2565 2566
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2567
 *
L
Linus Torvalds 已提交
2568
 * BSD seems to make the following compromise:
2569
 *
L
Linus Torvalds 已提交
2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596
 *	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)
{
2597
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2598
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2599
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2600 2601 2602 2603 2604
	 * 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
	 */
2605
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2606
	int free_space = tcp_space(sk);
2607 2608
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2609 2610
	int window;

2611
	if (unlikely(mss > full_space)) {
2612
		mss = full_space;
2613 2614 2615
		if (mss <= 0)
			return 0;
	}
2616
	if (free_space < (full_space >> 1)) {
2617
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2618

2619
		if (tcp_under_memory_pressure(sk))
2620 2621
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2622

2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635
		/* 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
2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651
			return 0;
	}

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

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

		/* Advertise enough space so that it won't get scaled away.
		 * Import case: prevent zero window announcement if
		 * 1<<rcv_wscale > mss.
		 */
2652
		window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
L
Linus Torvalds 已提交
2653
	} else {
2654
		window = tp->rcv_wnd;
L
Linus Torvalds 已提交
2655 2656 2657 2658 2659 2660 2661 2662 2663
		/* 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)
2664
			window = rounddown(free_space, mss);
2665
		else if (mss == full_space &&
2666
			 free_space > window + (full_space >> 1))
2667
			window = free_space;
L
Linus Torvalds 已提交
2668 2669 2670 2671 2672
	}

	return window;
}

2673 2674
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2675
{
2676 2677 2678
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2679 2680
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2681
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2682
		shinfo->tskey = next_shinfo->tskey;
2683 2684
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2685 2686 2687
	}
}

2688
/* Collapses two adjacent SKB's during retransmission. */
2689
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2690 2691
{
	struct tcp_sock *tp = tcp_sk(sk);
2692
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2693
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2694

2695 2696
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2697

2698
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2699

2700 2701 2702 2703 2704 2705 2706
	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;
	}
2707
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2708

2709
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2710

2711 2712
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2713

2714 2715
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2716

2717 2718
	/* 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
2719

2720
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2721
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2722 2723 2724 2725 2726

	/* 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;
2727
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2728 2729

	/* changed transmit queue under us so clear hints */
2730 2731 2732
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2733

2734 2735
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2736 2737
	tcp_skb_collapse_tstamp(skb, next_skb);

2738
	sk_wmem_free_skb(sk, next_skb);
2739
	return true;
L
Linus Torvalds 已提交
2740 2741
}

2742
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2743
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2744 2745
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2746
		return false;
2747
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2748
		return false;
2749
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2750
		return false;
E
Eric Dumazet 已提交
2751
	/* Some heuristics for collapsing over SACK'd could be invented */
2752
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2753
		return false;
2754

E
Eric Dumazet 已提交
2755
	return true;
2756 2757
}

2758 2759 2760
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2761 2762 2763 2764 2765
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
2766
	bool first = true;
2767 2768 2769

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2770
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2771 2772 2773 2774 2775 2776
		return;

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

2777 2778 2779
		if (!tcp_skb_can_collapse_to(to))
			break;

2780 2781 2782
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2783
			first = false;
2784 2785 2786 2787 2788 2789 2790 2791 2792
			continue;
		}

		if (space < 0)
			break;

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

2793 2794
		if (!tcp_collapse_retrans(sk, to))
			break;
2795 2796 2797
	}
}

L
Linus Torvalds 已提交
2798 2799 2800 2801
/* 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.
 */
2802
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2803
{
J
John Heffner 已提交
2804
	struct inet_connection_sock *icsk = inet_csk(sk);
2805
	struct tcp_sock *tp = tcp_sk(sk);
2806
	unsigned int cur_mss;
2807 2808
	int diff, len, err;

L
Linus Torvalds 已提交
2809

2810 2811
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2812 2813
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2814
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2815
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2816 2817
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
2818 2819
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2820 2821
		return -EAGAIN;

2822 2823 2824
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2825 2826 2827 2828 2829 2830 2831
	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;
	}

2832 2833 2834
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2835
	cur_mss = tcp_current_mss(sk);
2836

L
Linus Torvalds 已提交
2837 2838 2839 2840 2841
	/* 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.
	 */
2842 2843
	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
2844 2845
		return -EAGAIN;

2846 2847 2848
	len = cur_mss * segs;
	if (skb->len > len) {
		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2849
			return -ENOMEM; /* We'll try again later. */
2850
	} else {
2851 2852
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2853

2854 2855 2856 2857 2858 2859 2860
		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
2861 2862
	}

2863 2864 2865 2866
	/* 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);

2867 2868 2869 2870 2871 2872 2873
	/* Update global and local TCP statistics. */
	segs = tcp_skb_pcount(skb);
	TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
	tp->total_retrans += segs;

2874 2875 2876 2877 2878 2879
	/* 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)) {
2880 2881
		struct sk_buff *nskb;

2882
		skb->skb_mstamp = tp->tcp_mstamp;
2883
		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2884 2885
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2886
	} else {
2887
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2888
	}
2889

2890
	if (likely(!err)) {
2891
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2892 2893
	} else if (err != -EBUSY) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2894
	}
2895
	return err;
2896 2897
}

2898
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2899 2900
{
	struct tcp_sock *tp = tcp_sk(sk);
2901
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2902 2903 2904

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2905
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2906
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2907 2908 2909 2910 2911 2912 2913
		}
#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
2914
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2915 2916

	}
Y
Yuchung Cheng 已提交
2917 2918 2919 2920

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933
	return err;
}

/* This gets called after a retransmit timeout, and the initially
 * retransmitted data is acknowledged.  It tries to continue
 * resending the rest of the retransmit queue, until either
 * we've sent it all or the congestion window limit is reached.
 * If doing SACK, the first ACK which comes back for a timeout
 * based retransmit packet might feed us FACK information again.
 * If so, we use it to avoid unnecessarily retransmissions.
 */
void tcp_xmit_retransmit_queue(struct sock *sk)
{
2934
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2935 2936
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2937
	struct sk_buff *hole = NULL;
2938
	u32 max_segs;
2939
	int mib_idx;
2940

2941 2942 2943
	if (!tp->packets_out)
		return;

2944
	if (tp->retransmit_skb_hint) {
2945
		skb = tp->retransmit_skb_hint;
2946
	} else {
2947
		skb = tcp_write_queue_head(sk);
2948
	}
L
Linus Torvalds 已提交
2949

2950
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2951
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2952
		__u8 sacked;
2953
		int segs;
L
Linus Torvalds 已提交
2954

2955 2956
		if (skb == tcp_send_head(sk))
			break;
2957 2958 2959 2960

		if (tcp_pacing_check(sk))
			break;

2961
		/* we could do better than to assign each time */
2962
		if (!hole)
2963
			tp->retransmit_skb_hint = skb;
2964

2965 2966
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2967
			return;
E
Eric Dumazet 已提交
2968
		sacked = TCP_SKB_CB(skb)->sacked;
2969 2970 2971 2972
		/* 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
2973

2974 2975
		if (tp->retrans_out >= tp->lost_out) {
			break;
2976
		} else if (!(sacked & TCPCB_LOST)) {
2977
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2978 2979
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2980

2981 2982 2983 2984 2985 2986
		} else {
			if (icsk->icsk_ca_state != TCP_CA_Loss)
				mib_idx = LINUX_MIB_TCPFASTRETRANS;
			else
				mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
		}
L
Linus Torvalds 已提交
2987

2988
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2989 2990
			continue;

2991 2992 2993
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2994
		if (tcp_retransmit_skb(sk, skb, segs))
2995
			return;
2996

2997
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2998

2999
		if (tcp_in_cwnd_reduction(sk))
3000 3001
			tp->prr_out += tcp_skb_pcount(skb);

3002 3003
		if (skb == tcp_write_queue_head(sk) &&
		    icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3004 3005 3006
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3007 3008 3009
	}
}

3010 3011
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
3012 3013
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
3014 3015
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
3016
 */
3017
void sk_forced_mem_schedule(struct sock *sk, int size)
3018
{
3019
	int amt;
3020 3021 3022 3023 3024

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3025 3026
	sk_memory_allocated_add(sk, amt);

3027 3028
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3029 3030
}

3031 3032
/* 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
3033 3034 3035
 */
void tcp_send_fin(struct sock *sk)
{
3036
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
3037 3038
	struct tcp_sock *tp = tcp_sk(sk);

3039 3040 3041 3042
	/* 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
3043
	 */
3044
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
3045 3046 3047
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
3048
		tp->write_seq++;
3049 3050 3051 3052 3053 3054 3055 3056 3057 3058
		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
3059
	} else {
3060 3061 3062 3063 3064
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3065
		}
3066
		skb_reserve(skb, MAX_TCP_HEADER);
3067
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3068
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3069
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3070
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3071 3072
		tcp_queue_skb(sk, skb);
	}
3073
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3074 3075 3076 3077 3078
}

/* 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
3079
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3080
 */
A
Al Viro 已提交
3081
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3082 3083 3084
{
	struct sk_buff *skb;

3085 3086
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);

L
Linus Torvalds 已提交
3087 3088 3089
	/* 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
3090
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3091 3092 3093 3094 3095
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3096
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3097
			     TCPHDR_ACK | TCPHDR_RST);
3098
	skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
L
Linus Torvalds 已提交
3099
	/* Send it off. */
3100
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3101
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3102 3103
}

3104 3105
/* 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
3106 3107 3108 3109 3110 3111
 * 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)
{
3112
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3113

3114
	skb = tcp_write_queue_head(sk);
3115
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3116
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3117 3118
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3119
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3120 3121
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
3122
			if (!nskb)
L
Linus Torvalds 已提交
3123
				return -ENOMEM;
3124
			tcp_unlink_write_queue(skb, sk);
3125
			__skb_header_release(nskb);
3126
			__tcp_add_write_queue_head(sk, nskb);
3127 3128 3129
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3130 3131 3132
			skb = nskb;
		}

E
Eric Dumazet 已提交
3133
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3134
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3135
	}
3136
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3137 3138
}

3139 3140 3141 3142 3143 3144 3145 3146 3147
/**
 * 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.
 */
3148
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3149
				struct request_sock *req,
3150
				struct tcp_fastopen_cookie *foc,
3151
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3152
{
3153
	struct inet_request_sock *ireq = inet_rsk(req);
3154
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3155
	struct tcp_md5sig_key *md5 = NULL;
3156 3157
	struct tcp_out_options opts;
	struct sk_buff *skb;
3158
	int tcp_header_size;
3159
	struct tcphdr *th;
3160
	int mss;
L
Linus Torvalds 已提交
3161

3162
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3163 3164
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3165
		return NULL;
3166
	}
L
Linus Torvalds 已提交
3167 3168 3169
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3170 3171
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3172
		skb_set_owner_w(skb, req_to_sk(req));
3173 3174 3175 3176 3177 3178 3179
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3180 3181 3182 3183 3184
		/* 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);
3185
		break;
3186
	}
3187
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3188

E
Eric Dumazet 已提交
3189
	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3190

A
Adam Langley 已提交
3191
	memset(&opts, 0, sizeof(opts));
3192 3193
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
3194
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3195 3196
	else
#endif
E
Eric Dumazet 已提交
3197
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
3198 3199 3200

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3201
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3202
#endif
3203
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3204 3205
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3206

3207 3208
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3209

3210
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3211 3212 3213
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3214
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3215
	th->source = htons(ireq->ir_num);
3216
	th->dest = ireq->ir_rmt_port;
3217 3218 3219 3220
	/* 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
3221
			     TCPHDR_SYN | TCPHDR_ACK);
3222

L
Linus Torvalds 已提交
3223
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3224 3225
	/* 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
3226 3227

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3228
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3229
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3230
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3231
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3232 3233 3234

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3235
	if (md5)
3236
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3237
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3238
	rcu_read_unlock();
3239 3240
#endif

3241
	/* Do not fool tcpdump (if any), clean our debris */
T
Thomas Gleixner 已提交
3242
	skb->tstamp = 0;
L
Linus Torvalds 已提交
3243 3244
	return skb;
}
E
Eric Dumazet 已提交
3245
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3246

3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265
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();
}

3266
/* Do all connect socket setups that can be done AF independent. */
3267
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3268
{
3269
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3270 3271 3272 3273 3274 3275 3276
	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) +
3277
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3278

3279
#ifdef CONFIG_TCP_MD5SIG
3280
	if (tp->af_specific->md5_lookup(sk, sk))
3281 3282 3283
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3284 3285 3286 3287
	/* 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
3288
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3289 3290
	tcp_sync_mss(sk, dst_mtu(dst));

3291 3292
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3293 3294
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
E
Eric Dumazet 已提交
3295
	tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3296

L
Linus Torvalds 已提交
3297 3298
	tcp_initialize_rcv_mss(sk);

3299 3300 3301 3302 3303
	/* 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
3304 3305 3306 3307
	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,
3308
				  sysctl_tcp_window_scaling,
3309 3310
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3311 3312 3313 3314 3315 3316 3317

	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;
3318
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3319 3320
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3321
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3322
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3323 3324 3325

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3326
	else
3327
		tp->rcv_tstamp = tcp_jiffies32;
P
Pavel Emelyanov 已提交
3328 3329
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3330

3331 3332
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3333 3334 3335
	tcp_clear_retrans(tp);
}

3336 3337 3338 3339 3340 3341
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;
3342
	__skb_header_release(skb);
3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360
	__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;
3361
	int space, err = 0;
3362
	struct sk_buff *syn_data;
3363

3364
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3365
	if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3366 3367 3368 3369 3370 3371
		goto fallback;

	/* MSS for SYN-data is based on cached MSS and bounded by PMTU and
	 * user-MSS. Reserve maximum option space for middleboxes that add
	 * private TCP options. The cost is reduced data space in SYN :(
	 */
E
Eric Dumazet 已提交
3372 3373
	tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);

3374
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3375 3376
		MAX_TCP_OPTION_SPACE;

3377 3378 3379 3380 3381
	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));

3382
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3383
	if (!syn_data)
3384
		goto fallback;
3385 3386
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397
	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;
		}
3398
	}
3399 3400 3401 3402
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3403

3404
	tcp_connect_queue_skb(sk, syn_data);
3405 3406
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3407

3408
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3409

3410
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3411

3412 3413 3414 3415 3416 3417 3418 3419
	/* 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) {
3420
		tp->syn_data = (fo->copied > 0);
3421
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436
		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;
}

3437
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3438 3439 3440 3441
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3442
	int err;
L
Linus Torvalds 已提交
3443 3444 3445

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3446 3447 3448 3449 3450
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3451
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3452
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3453 3454
		return -ENOBUFS;

C
Changli Gao 已提交
3455
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3456 3457
	skb_mstamp_get(&tp->tcp_mstamp);
	tp->retrans_stamp = tp->tcp_mstamp.stamp_jiffies;
3458
	tcp_connect_queue_skb(sk, buff);
3459
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3460

3461 3462 3463
	/* 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);
3464 3465
	if (err == -ECONNREFUSED)
		return err;
3466 3467 3468 3469 3470 3471

	/* 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
3472
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3473 3474

	/* Timer for repeating the SYN until an answer. */
3475 3476
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3477 3478
	return 0;
}
E
Eric Dumazet 已提交
3479
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3480 3481 3482 3483 3484 3485 3486

/* 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)
{
3487 3488
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3489 3490
	unsigned long timeout;

3491 3492
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3493
	if (ato > TCP_DELACK_MIN) {
3494
		const struct tcp_sock *tp = tcp_sk(sk);
3495
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3496

3497 3498
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3499 3500 3501 3502 3503
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3504
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3505 3506
		 * directly.
		 */
3507 3508 3509
		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
3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521

			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. */
3522
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3523 3524 3525
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3526 3527
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3528 3529 3530 3531
			tcp_send_ack(sk);
			return;
		}

3532 3533
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3534
	}
3535 3536 3537
	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
3538 3539 3540 3541 3542
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3543
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3544

3545 3546 3547
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3548

3549 3550
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3551 3552 3553 3554
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3555 3556 3557
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3558 3559 3560 3561 3562
		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
3563
	}
3564 3565 3566

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3567
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3568

E
Eric Dumazet 已提交
3569 3570 3571 3572 3573 3574
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 */
	skb_set_tcp_pure_ack(buff);

3575
	/* Send it off, this clears delayed acks for us. */
3576
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3577
}
3578
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590

/* 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.
 */
3591
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3592 3593 3594 3595 3596
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3597 3598
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3599
	if (!skb)
L
Linus Torvalds 已提交
3600 3601 3602 3603 3604 3605 3606 3607
		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
3608
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3609
	NET_INC_STATS(sock_net(sk), mib);
3610
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3611 3612
}

3613
/* Called from setsockopt( ... TCP_REPAIR ) */
P
Pavel Emelyanov 已提交
3614 3615 3616 3617
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;
3618
		skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
3619
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3620 3621 3622
	}
}

3623
/* Initiate keepalive or window probe from timer. */
3624
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3625
{
3626 3627
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3628

3629 3630 3631
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3632 3633
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3634
		int err;
I
Ilpo Järvinen 已提交
3635
		unsigned int mss = tcp_current_mss(sk);
3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647
		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
3648
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3649
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3650 3651
				return -1;
		} else if (!tcp_skb_pcount(skb))
3652
			tcp_set_skb_tso_segs(skb, mss);
3653

E
Eric Dumazet 已提交
3654
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3655 3656 3657 3658 3659
		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
3660
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3661 3662
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3663 3664 3665 3666 3667 3668 3669 3670
	}
}

/* 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)
{
3671
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3672
	struct tcp_sock *tp = tcp_sk(sk);
3673
	struct net *net = sock_net(sk);
3674
	unsigned long probe_max;
L
Linus Torvalds 已提交
3675 3676
	int err;

3677
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3678

3679
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3680
		/* Cancel probe timer, if it is not required. */
3681
		icsk->icsk_probes_out = 0;
3682
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3683 3684 3685 3686
		return;
	}

	if (err <= 0) {
3687
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3688
			icsk->icsk_backoff++;
3689
		icsk->icsk_probes_out++;
3690
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3691 3692
	} else {
		/* If packet was not sent due to local congestion,
3693
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3694 3695 3696 3697
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3698 3699
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3700
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3701
	}
3702
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3703
				  tcp_probe0_when(sk, probe_max),
3704
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3705
}
3706

3707
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3708 3709 3710 3711 3712
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3713
	tcp_rsk(req)->txhash = net_tx_rndhash();
3714
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3715
	if (!res) {
E
Eric Dumazet 已提交
3716
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3717
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3718 3719
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3720 3721 3722 3723
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);