tcp_output.c 106.4 KB
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/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
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 * Authors:	Ross Biro
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 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

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

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#define pr_fmt(fmt) "TCP: " fmt

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#include <net/tcp.h>

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

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

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

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

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

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

	return (__u16)mss;
}

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

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

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

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

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	tp->lsndtime = now;

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

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

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

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

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

	/* If no clamp set the clamp to the max possible scaled window */
	if (*window_clamp == 0)
		(*window_clamp) = (65535 << 14);
	space = min(*window_clamp, space);

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

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

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	(*rcv_wscale) = 0;
	if (wscale_ok) {
		/* Set window scaling on max possible window
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		 * See RFC1323 for an explanation of the limit to 14
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		 */
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		space = max_t(u32, space, sysctl_tcp_rmem[2]);
		space = max_t(u32, space, sysctl_rmem_max);
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		space = min_t(u32, space, *window_clamp);
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		while (space > 65535 && (*rcv_wscale) < 14) {
			space >>= 1;
			(*rcv_wscale)++;
		}
	}

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

	/* Set the clamp no higher than max representable value */
	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
}
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EXPORT_SYMBOL(tcp_select_initial_window);
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/* Chose a new window to advertise, update state in tcp_sock for the
 * socket, and return result with RFC1323 scaling applied.  The return
 * value can be stuffed directly into th->window for an outgoing
 * frame.
 */
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static u16 tcp_select_window(struct sock *sk)
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{
	struct tcp_sock *tp = tcp_sk(sk);
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	u32 old_win = tp->rcv_wnd;
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	u32 cur_win = tcp_receive_window(tp);
	u32 new_win = __tcp_select_window(sk);

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

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

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

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

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

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

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

	if (!use_ecn) {
		const struct dst_entry *dst = __sk_dst_get(sk);

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

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

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

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

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

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

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	TCP_SKB_CB(skb)->tcp_flags = flags;
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	TCP_SKB_CB(skb)->sacked = 0;

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

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

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#define OPTION_SACK_ADVERTISE	(1 << 0)
#define OPTION_TS		(1 << 1)
#define OPTION_MD5		(1 << 2)
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#define OPTION_WSCALE		(1 << 3)
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#define OPTION_FAST_OPEN_COOKIE	(1 << 8)
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struct tcp_out_options {
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	u16 options;		/* bit field of OPTION_* */
	u16 mss;		/* 0 to disable */
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	u8 ws;			/* window scale, 0 to disable */
	u8 num_sack_blocks;	/* number of SACK blocks to include */
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	u8 hash_size;		/* bytes in hash_location */
	__u8 *hash_location;	/* temporary pointer, overloaded */
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	__u32 tsval, tsecr;	/* need to include OPTION_TS */
	struct tcp_fastopen_cookie *fastopen_cookie;	/* Fast open cookie */
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};

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

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

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

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	if (unlikely(OPTION_WSCALE & options)) {
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		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_WINDOW << 16) |
			       (TCPOLEN_WINDOW << 8) |
			       opts->ws);
	}

	if (unlikely(opts->num_sack_blocks)) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ?
			tp->duplicate_sack : tp->selective_acks;
S
Stephen Hemminger 已提交
498 499 500 501 502
		int this_sack;

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

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

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

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
517 518 519 520 521 522 523 524 525 526 527 528 529
		u8 *p = (u8 *)ptr;
		u32 len; /* Fast Open option length */

		if (foc->exp) {
			len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
			*ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
				     TCPOPT_FASTOPEN_MAGIC);
			p += TCPOLEN_EXP_FASTOPEN_BASE;
		} else {
			len = TCPOLEN_FASTOPEN_BASE + foc->len;
			*p++ = TCPOPT_FASTOPEN;
			*p++ = len;
		}
Y
Yuchung Cheng 已提交
530

531 532 533 534
		memcpy(p, foc->val, foc->len);
		if ((len & 3) == 2) {
			p[foc->len] = TCPOPT_NOP;
			p[foc->len + 1] = TCPOPT_NOP;
Y
Yuchung Cheng 已提交
535
		}
536
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
537
	}
A
Adam Langley 已提交
538 539
}

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

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

	/* We always get an MSS option.  The option bytes which will be seen in
	 * normal data packets should timestamps be used, must be in the MSS
	 * advertised.  But we subtract them from tp->mss_cache so that
	 * calculations in tcp_sendmsg are simpler etc.  So account for this
	 * fact here if necessary.  If we don't do this correctly, as a
	 * receiver we won't recognize data packets as being full sized when we
	 * should, and thus we won't abide by the delayed ACK rules correctly.
	 * SACKs don't matter, we never delay an ACK when we have any of those
	 * going out.  */
	opts->mss = tcp_advertise_mss(sk);
571
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
572

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

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

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
595 596 597 598 599 600
		need = (need + 3) & ~3U;  /* Align to 32 bits */
		if (remaining >= need) {
			opts->options |= OPTION_FAST_OPEN_COOKIE;
			opts->fastopen_cookie = &fastopen->cookie;
			remaining -= need;
			tp->syn_fastopen = 1;
601
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
602 603
		}
	}
604 605

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

608
/* Set up TCP options for SYN-ACKs. */
609 610 611 612 613
static unsigned int tcp_synack_options(struct request_sock *req,
				       unsigned int mss, struct sk_buff *skb,
				       struct tcp_out_options *opts,
				       const struct tcp_md5sig_key *md5,
				       struct tcp_fastopen_cookie *foc)
614
{
A
Adam Langley 已提交
615
	struct inet_request_sock *ireq = inet_rsk(req);
616
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
617

618
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
619
	if (md5) {
A
Adam Langley 已提交
620
		opts->options |= OPTION_MD5;
621 622 623 624 625 626 627
		remaining -= TCPOLEN_MD5SIG_ALIGNED;

		/* We can't fit any SACK blocks in a packet with MD5 + TS
		 * options. There was discussion about disabling SACK
		 * rather than TS in order to fit in better with old,
		 * buggy kernels, but that was deemed to be unnecessary.
		 */
E
Eric Dumazet 已提交
628
		ireq->tstamp_ok &= !ireq->sack_ok;
629 630
	}
#endif
A
Adam Langley 已提交
631

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

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

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
657 658 659 660 661 662 663
		need = (need + 3) & ~3U;  /* Align to 32 bits */
		if (remaining >= need) {
			opts->options |= OPTION_FAST_OPEN_COOKIE;
			opts->fastopen_cookie = foc;
			remaining -= need;
		}
	}
C
Christoph Paasch 已提交
664

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

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

679 680
	opts->options = 0;

A
Adam Langley 已提交
681 682 683 684 685 686 687 688 689 690 691 692
#ifdef CONFIG_TCP_MD5SIG
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (unlikely(*md5)) {
		opts->options |= OPTION_MD5;
		size += TCPOLEN_MD5SIG_ALIGNED;
	}
#else
	*md5 = NULL;
#endif

	if (likely(tp->rx_opt.tstamp_ok)) {
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
693
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
694 695 696 697
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

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

	return size;
S
Stephen Hemminger 已提交
710
}
L
Linus Torvalds 已提交
711

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

/* TCP SMALL QUEUES (TSQ)
 *
 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
 * to reduce RTT and bufferbloat.
 * We do this using a special skb destructor (tcp_wfree).
 *
 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
 * needs to be reallocated in a driver.
S
stephen hemminger 已提交
721
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
722 723 724 725 726 727 728 729 730 731 732
 *
 * Since transmit from skb destructor is forbidden, we use a tasklet
 * to process all sockets that eventually need to send more skbs.
 * We use one tasklet per cpu, with its own queue of sockets.
 */
struct tsq_tasklet {
	struct tasklet_struct	tasklet;
	struct list_head	head; /* queue of tcp sockets */
};
static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);

733 734 735 736
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
737 738 739 740 741 742 743 744
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK)) {
		struct tcp_sock *tp = tcp_sk(sk);

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

		tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
J
John Ogness 已提交
745
			       0, GFP_ATOMIC);
746
	}
747
}
E
Eric Dumazet 已提交
748
/*
S
stephen hemminger 已提交
749
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
750
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
751
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769
 * 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);
770
		clear_bit(TSQ_QUEUED, &tp->tsq_flags);
E
Eric Dumazet 已提交
771 772

		sk = (struct sock *)tp;
773 774 775 776 777 778 779 780
		if (!sk->sk_lock.owned &&
		    test_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags)) {
			bh_lock_sock(sk);
			if (!sock_owned_by_user(sk)) {
				clear_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
				tcp_tsq_handler(sk);
			}
			bh_unlock_sock(sk);
E
Eric Dumazet 已提交
781 782 783 784 785 786
		}

		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
787 788 789 790
#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED |		\
			  TCPF_WRITE_TIMER_DEFERRED |	\
			  TCPF_DELACK_TIMER_DEFERRED |	\
			  TCPF_MTU_REDUCED_DEFERRED)
E
Eric Dumazet 已提交
791 792 793 794 795 796 797 798 799 800
/**
 * tcp_release_cb - tcp release_sock() callback
 * @sk: socket
 *
 * called from release_sock() to perform protocol dependent
 * actions before socket release.
 */
void tcp_release_cb(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
801
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
802

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

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

814 815 816 817 818 819 820 821 822 823 824
	/* Here begins the tricky part :
	 * We are called from release_sock() with :
	 * 1) BH disabled
	 * 2) sk_lock.slock spinlock held
	 * 3) socket owned by us (sk->sk_lock.owned == 1)
	 *
	 * But following code is meant to be called from BH handlers,
	 * so we should keep BH disabled, but early release socket ownership
	 */
	sock_release_ownership(sk);

E
Eric Dumazet 已提交
825
	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
826
		tcp_write_timer_handler(sk);
827 828
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
829
	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
830
		tcp_delack_timer_handler(sk);
831 832
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
833
	if (flags & TCPF_MTU_REDUCED_DEFERRED) {
834
		inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
835 836
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855
}
EXPORT_SYMBOL(tcp_release_cb);

void __init tcp_tasklet_init(void)
{
	int i;

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

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

/*
 * Write buffer destructor automatically called from kfree_skb.
S
stephen hemminger 已提交
856
 * We can't xmit new skbs from this context, as we might already
E
Eric Dumazet 已提交
857 858
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
859
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
860 861 862
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);
863
	unsigned long flags, nval, oval;
864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
	int wmem;

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

	/* If this softirq is serviced by ksoftirqd, we are likely under stress.
	 * Wait until our queues (qdisc + devices) are drained.
	 * This gives :
	 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
	 * - chance for incoming ACK (processed by another cpu maybe)
	 *   to migrate this flow (skb->ooo_okay will be eventually set)
	 */
	if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
		goto out;
E
Eric Dumazet 已提交
880

881
	for (oval = READ_ONCE(tp->tsq_flags);; oval = nval) {
E
Eric Dumazet 已提交
882
		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;
889 890 891 892
		nval = cmpxchg(&tp->tsq_flags, oval, nval);
		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
}

L
Linus Torvalds 已提交
907 908 909 910 911 912 913 914 915 916 917
/* 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.
 */
918 919
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
920
{
921 922 923 924
	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
925
	struct tcp_out_options opts;
926
	unsigned int tcp_options_size, tcp_header_size;
927
	struct tcp_md5sig_key *md5;
928 929 930 931
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
932
	tp = tcp_sk(sk);
933

934
	if (clone_it) {
935
		skb_mstamp_get(&skb->skb_mstamp);
936 937
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
938
		tcp_rate_skb_sent(sk, skb);
939

940 941 942 943 944 945 946
		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
947

948 949
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
950
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
951

E
Eric Dumazet 已提交
952
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
953 954 955 956 957
		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);
958

E
Eric Dumazet 已提交
959
	/* if no packet is in qdisc/device queue, then allow XPS to select
960 961 962 963 964
	 * 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
965
	 */
966
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
967

968 969
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
970 971 972

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
973
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
974
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
975
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
976 977

	/* Build TCP header and checksum it. */
978
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
979 980
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
981 982
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
983
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
984
					tcb->tcp_flags);
985 986 987

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
988

I
Ilpo Järvinen 已提交
989
	/* The urg_mode check is necessary during a below snd_una win probe */
990 991 992 993 994
	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)) {
995
			th->urg_ptr = htons(0xFFFF);
996 997
			th->urg = 1;
		}
998
	}
L
Linus Torvalds 已提交
999

1000
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1001
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1002 1003 1004 1005 1006 1007 1008 1009 1010
	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));
	}
1011 1012 1013
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1014
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1015
		tp->af_specific->calc_md5_hash(opts.hash_location,
1016
					       md5, sk, skb);
1017 1018 1019
	}
#endif

1020
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1021

E
Eric Dumazet 已提交
1022
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1023
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1024

1025
	if (skb->len != tcp_header_size) {
1026
		tcp_event_data_sent(tp, sk);
1027 1028
		tp->data_segs_out += tcp_skb_pcount(skb);
	}
L
Linus Torvalds 已提交
1029

1030
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1031 1032
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1033

1034
	tp->segs_out += tcp_skb_pcount(skb);
1035
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1036
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1037
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1038

E
Eric Dumazet 已提交
1039 1040
	/* Our usage of tstamp should remain private */
	skb->tstamp.tv64 = 0;
1041 1042 1043 1044 1045

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

1046
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1047

1048
	if (likely(err <= 0))
1049 1050
		return err;

1051
	tcp_enter_cwr(sk);
1052

1053
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1054 1055
}

1056
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1057 1058 1059 1060 1061 1062 1063 1064 1065 1066
 *
 * 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;
1067
	__skb_header_release(skb);
1068
	tcp_add_write_queue_tail(sk, skb);
1069 1070
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1071 1072
}

1073
/* Initialize TSO segments for a packet. */
1074
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1075
{
1076
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1077 1078 1079
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1080
		tcp_skb_pcount_set(skb, 1);
1081
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1082
	} else {
1083
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1084
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1085 1086 1087
	}
}

I
Ilpo Järvinen 已提交
1088
/* When a modification to fackets out becomes necessary, we need to check
1089
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1090
 */
1091
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1092 1093
				   int decr)
{
1094 1095
	struct tcp_sock *tp = tcp_sk(sk);

1096
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1097 1098
		return;

1099
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1100 1101 1102
		tp->fackets_out -= decr;
}

1103 1104 1105
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1106
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126
{
	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) &&
1127
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1128 1129 1130 1131 1132
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1133 1134 1135 1136 1137 1138
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);
}

1139 1140 1141 1142
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1143
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1144 1145 1146 1147 1148 1149 1150
	    !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);
1151 1152
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1153 1154 1155
	}
}

1156 1157 1158 1159 1160 1161
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
1162 1163
/* 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
1164
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1165 1166
 * Remember, these are still headerless SKBs at this point.
 */
1167
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1168
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1169 1170 1171
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1172
	int nsize, old_factor;
1173
	int nlen;
1174
	u8 flags;
L
Linus Torvalds 已提交
1175

1176 1177
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1178

L
Linus Torvalds 已提交
1179 1180 1181 1182
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1183
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1184 1185 1186
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1187
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1188
	if (!buff)
L
Linus Torvalds 已提交
1189
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1190

1191 1192
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1193 1194 1195
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1196 1197 1198 1199 1200 1201 1202

	/* 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
1203 1204 1205
	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;
1206
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1207
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1208

1209
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1210
		/* Copy and checksum data tail into the new buffer. */
1211 1212
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1213 1214 1215 1216 1217 1218
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1219
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1220 1221 1222 1223 1224
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1225
	buff->tstamp = skb->tstamp;
1226
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1227

1228 1229
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1230
	/* Fix up tso_factor for both original and new SKB.  */
1231 1232
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1233

1234 1235 1236
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1237 1238 1239
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1240
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1241 1242
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1243

1244 1245
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1246 1247 1248
	}

	/* Link BUFF into the send queue. */
1249
	__skb_header_release(buff);
1250
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1251 1252 1253 1254 1255 1256 1257 1258

	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.
 */
1259
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1260
{
1261
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1262 1263
	int i, k, eat;

E
Eric Dumazet 已提交
1264 1265 1266 1267 1268 1269 1270
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
			return;
	}
L
Linus Torvalds 已提交
1271 1272
	eat = len;
	k = 0;
1273 1274 1275
	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
1276 1277

		if (size <= eat) {
1278
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1279
			eat -= size;
L
Linus Torvalds 已提交
1280
		} else {
1281
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1282
			if (eat) {
1283 1284
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1285 1286 1287 1288 1289
				eat = 0;
			}
			k++;
		}
	}
1290
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1291

1292
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1293 1294 1295 1296
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1297
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1298 1299
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1300
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1301 1302
		return -ENOMEM;

E
Eric Dumazet 已提交
1303
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1304 1305

	TCP_SKB_CB(skb)->seq += len;
1306
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1307 1308 1309

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1310
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1311 1312
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1313
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1314
	if (tcp_skb_pcount(skb) > 1)
1315
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1316 1317 1318 1319

	return 0;
}

1320 1321
/* 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
1322
{
1323 1324
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1325 1326 1327 1328 1329 1330 1331
	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);

1332 1333 1334 1335 1336 1337 1338 1339
	/* 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
1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352
	/* 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;
}

1353 1354 1355 1356 1357 1358 1359 1360
/* 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
1361
/* Inverse of above */
1362
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1363
{
1364 1365
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1366 1367 1368 1369 1370 1371 1372
	int mtu;

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

1373 1374 1375 1376 1377 1378 1379
	/* 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
1380 1381
	return mtu;
}
1382
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1383

1384
/* MTU probing init per socket */
J
John Heffner 已提交
1385 1386 1387 1388
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
1389
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1390

F
Fan Du 已提交
1391
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1392
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1393
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1394
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1395
	icsk->icsk_mtup.probe_size = 0;
1396 1397
	if (icsk->icsk_mtup.enabled)
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
J
John Heffner 已提交
1398
}
E
Eric Dumazet 已提交
1399
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1400

L
Linus Torvalds 已提交
1401 1402 1403 1404 1405 1406
/* 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
1407
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1408 1409
   It also does not include TCP options.

1410
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1411 1412 1413 1414 1415 1416 1417 1418 1419

   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.

1420 1421
   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
1422 1423 1424 1425
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1426
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1427
	int mss_now;
L
Linus Torvalds 已提交
1428

J
John Heffner 已提交
1429 1430
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1431

J
John Heffner 已提交
1432
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1433
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1434 1435

	/* And store cached results */
1436
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1437 1438
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1439
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1440 1441 1442

	return mss_now;
}
E
Eric Dumazet 已提交
1443
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1444 1445 1446 1447

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1448
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1449
{
1450 1451
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1452
	u32 mss_now;
1453
	unsigned int header_len;
A
Adam Langley 已提交
1454 1455
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1456 1457 1458

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1459 1460
	if (dst) {
		u32 mtu = dst_mtu(dst);
1461
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1462 1463 1464
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1465 1466 1467 1468 1469 1470 1471 1472 1473 1474
	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;
	}
1475

L
Linus Torvalds 已提交
1476 1477 1478
	return mss_now;
}

1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500
/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
 * As additional protections, we do not touch cwnd in retransmission phases,
 * and if application hit its sndbuf limit recently.
 */
static void tcp_cwnd_application_limited(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);

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

1501
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1502
{
1503
	struct tcp_sock *tp = tcp_sk(sk);
1504

1505 1506 1507 1508 1509 1510 1511 1512 1513
	/* 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;
	}
1514

1515
	if (tcp_is_cwnd_limited(sk)) {
1516 1517 1518 1519 1520 1521 1522 1523
		/* Network is feed fully. */
		tp->snd_cwnd_used = 0;
		tp->snd_cwnd_stamp = tcp_time_stamp;
	} else {
		/* Network starves. */
		if (tp->packets_out > tp->snd_cwnd_used)
			tp->snd_cwnd_used = tp->packets_out;

1524 1525
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1526
			tcp_cwnd_application_limited(sk);
1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538

		/* 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);
1539 1540 1541
	}
}

E
Eric Dumazet 已提交
1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555
/* 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
1556
 */
E
Eric Dumazet 已提交
1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571
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,
1572
			    int nonagle)
E
Eric Dumazet 已提交
1573 1574 1575 1576 1577
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1578 1579 1580 1581

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1582 1583
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594
{
	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.
	 */
1595
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1596 1597 1598

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1599
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1600

1601 1602 1603 1604 1605 1606 1607 1608
/* 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;

1609 1610
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1611 1612
}

E
Eric Dumazet 已提交
1613 1614 1615 1616 1617 1618
/* 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)
1619
{
1620
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1621
	u32 partial, needed, window, max_len;
1622

1623
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1624
	max_len = mss_now * max_segs;
1625

1626 1627
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1628

1629 1630
	needed = min(skb->len, window);

1631 1632
	if (max_len <= needed)
		return max_len;
1633

E
Eric Dumazet 已提交
1634 1635 1636 1637 1638
	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
	 */
1639
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1640 1641 1642
		return needed - partial;

	return needed;
1643 1644 1645 1646 1647
}

/* 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.
 */
1648 1649
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1650
{
E
Eric Dumazet 已提交
1651
	u32 in_flight, cwnd, halfcwnd;
1652 1653

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1654 1655
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1656 1657 1658 1659
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1660 1661
	if (in_flight >= cwnd)
		return 0;
1662

E
Eric Dumazet 已提交
1663 1664 1665 1666 1667
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1668 1669
}

1670
/* Initialize TSO state of a skb.
1671
 * This must be invoked the first time we consider transmitting
1672 1673
 * SKB onto the wire.
 */
1674
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1675 1676 1677
{
	int tso_segs = tcp_skb_pcount(skb);

1678
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1679
		tcp_set_skb_tso_segs(skb, mss_now);
1680 1681 1682 1683 1684 1685
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1686
/* Return true if the Nagle test allows this packet to be
1687 1688
 * sent now.
 */
E
Eric Dumazet 已提交
1689 1690
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1691 1692 1693 1694 1695 1696 1697 1698
{
	/* 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
1699
		return true;
1700

Y
Yuchung Cheng 已提交
1701 1702
	/* 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
1703
		return true;
1704

1705
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1706
		return true;
1707

E
Eric Dumazet 已提交
1708
	return false;
1709 1710 1711
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1712 1713 1714
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1715 1716 1717 1718 1719 1720
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1721
	return !after(end_seq, tcp_wnd_end(tp));
1722 1723
}

1724
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1725 1726 1727
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1728
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1729 1730
				 unsigned int cur_mss, int nonagle)
{
1731
	const struct tcp_sock *tp = tcp_sk(sk);
1732 1733
	unsigned int cwnd_quota;

1734
	tcp_init_tso_segs(skb, cur_mss);
1735 1736 1737 1738 1739

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1740
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1741 1742 1743 1744 1745
		cwnd_quota = 0;

	return cwnd_quota;
}

1746
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1747
bool tcp_may_send_now(struct sock *sk)
1748
{
1749
	const struct tcp_sock *tp = tcp_sk(sk);
1750
	struct sk_buff *skb = tcp_send_head(sk);
1751

E
Eric Dumazet 已提交
1752
	return skb &&
I
Ilpo Järvinen 已提交
1753
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1754
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1755
			      tp->nonagle : TCP_NAGLE_PUSH));
1756 1757 1758 1759 1760 1761 1762 1763 1764
}

/* 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).
 */
1765
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1766
			unsigned int mss_now, gfp_t gfp)
1767 1768 1769
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1770
	u8 flags;
1771 1772

	/* All of a TSO frame must be composed of paged data.  */
1773
	if (skb->len != skb->data_len)
1774
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1775

1776
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1777
	if (unlikely(!buff))
1778 1779
		return -ENOMEM;

1780 1781
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1782
	buff->truesize += nlen;
1783 1784 1785 1786 1787 1788 1789 1790
	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
1791 1792 1793
	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;
1794 1795 1796 1797

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

1798 1799
	tcp_skb_fragment_eor(skb, buff);

1800
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1801
	skb_split(skb, buff, len);
1802
	tcp_fragment_tstamp(skb, buff);
1803 1804

	/* Fix up tso_factor for both original and new SKB.  */
1805 1806
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1807 1808

	/* Link BUFF into the send queue. */
1809
	__skb_header_release(buff);
1810
	tcp_insert_write_queue_after(skb, buff, sk);
1811 1812 1813 1814 1815 1816 1817 1818 1819

	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.
 */
1820
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1821
				 bool *is_cwnd_limited, u32 max_segs)
1822
{
1823
	const struct inet_connection_sock *icsk = inet_csk(sk);
1824 1825 1826 1827
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct skb_mstamp now;
	struct sk_buff *head;
1828
	int win_divisor;
1829

E
Eric Dumazet 已提交
1830
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1831
		goto send_now;
1832

1833
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1834 1835
		goto send_now;

E
Eric Dumazet 已提交
1836 1837 1838 1839
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
	if ((s32)(tcp_time_stamp - tp->lsndtime) > 0)
J
John Heffner 已提交
1840
		goto send_now;
1841

1842 1843
	in_flight = tcp_packets_in_flight(tp);

1844
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1845

1846
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1847 1848 1849 1850 1851 1852

	/* 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);

1853
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1854
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1855
		goto send_now;
1856

1857 1858 1859 1860
	/* 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;

1861 1862
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1863 1864 1865 1866 1867
		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.
		 */
1868
		chunk /= win_divisor;
1869
		if (limit >= chunk)
J
John Heffner 已提交
1870
			goto send_now;
1871 1872 1873 1874 1875 1876
	} 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.
		 */
1877
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1878
			goto send_now;
1879 1880
	}

1881 1882 1883 1884 1885 1886 1887
	head = tcp_write_queue_head(sk);
	skb_mstamp_get(&now);
	age = skb_mstamp_us_delta(&now, &head->skb_mstamp);
	/* If next ACK is likely to come too late (half srtt), do not defer */
	if (age < (tp->srtt_us >> 4))
		goto send_now;

E
Eric Dumazet 已提交
1888
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1889

1890
	if (cong_win < send_win && cong_win <= skb->len)
1891 1892
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1893
	return true;
J
John Heffner 已提交
1894 1895

send_now:
E
Eric Dumazet 已提交
1896
	return false;
1897 1898
}

1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923
static inline void tcp_mtu_check_reprobe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	struct net *net = sock_net(sk);
	u32 interval;
	s32 delta;

	interval = net->ipv4.sysctl_tcp_probe_interval;
	delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp;
	if (unlikely(delta >= interval * HZ)) {
		int mss = tcp_current_mss(sk);

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

		/* Update probe time stamp */
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
	}
}

J
John Heffner 已提交
1924
/* Create a new MTU probe if we are ready.
1925 1926 1927 1928
 * 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
1929 1930
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1931 1932
 *         -1 otherwise
 */
J
John Heffner 已提交
1933 1934 1935 1936 1937
static int tcp_mtu_probe(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct sk_buff *skb, *nskb, *next;
1938
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1939 1940
	int len;
	int probe_size;
1941
	int size_needed;
J
John Heffner 已提交
1942 1943
	int copy;
	int mss_now;
1944
	int interval;
J
John Heffner 已提交
1945 1946 1947 1948 1949 1950 1951 1952 1953

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
	 * not SACKing (the variable headers throw things off) */
	if (!icsk->icsk_mtup.enabled ||
	    icsk->icsk_mtup.probe_size ||
	    inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
	    tp->snd_cwnd < 11 ||
1954
	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
J
John Heffner 已提交
1955 1956
		return -1;

1957 1958 1959 1960
	/* 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
1961
	mss_now = tcp_current_mss(sk);
1962 1963
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
1964
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1965
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1966 1967 1968 1969
	/* 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.
	 */
1970
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1971 1972 1973 1974 1975
		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
1976 1977 1978 1979
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1980
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1981 1982
		return -1;

1983 1984
	if (tp->snd_wnd < size_needed)
		return -1;
1985
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1986
		return 0;
J
John Heffner 已提交
1987

1988 1989 1990
	/* 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
1991 1992 1993 1994 1995 1996
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
1997
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1998
	if (!nskb)
J
John Heffner 已提交
1999
		return -1;
2000 2001
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2002

2003
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2004 2005 2006

	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
2007
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2008 2009
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2010
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2011

2012 2013
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2014
	len = 0;
2015
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2016
		copy = min_t(int, skb->len, probe_size - len);
2017
		if (nskb->ip_summed) {
J
John Heffner 已提交
2018
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2019 2020 2021 2022 2023 2024
		} 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
2025 2026 2027 2028

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2029
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2030
			tcp_unlink_write_queue(skb, sk);
2031
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2032
		} else {
E
Eric Dumazet 已提交
2033
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2034
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2035 2036
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2037
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2038 2039
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2040 2041
			} else {
				__pskb_trim_head(skb, copy);
2042
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2043 2044 2045 2046 2047
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2048 2049 2050

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2051
	}
2052
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2053 2054

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2055 2056
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2057 2058
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2059
		 * effectively two packets. */
J
John Heffner 已提交
2060
		tp->snd_cwnd--;
2061
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2062 2063

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2064 2065
		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
2066 2067 2068 2069 2070 2071 2072

		return 1;
	}

	return -1;
}

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

2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114
		set_bit(TSQ_THROTTLED, &tcp_sk(sk)->tsq_flags);
		/* It is possible TX completion already happened
		 * before we set TSQ_THROTTLED, so we must
		 * test again the condition.
		 */
		smp_mb__after_atomic();
		if (atomic_read(&sk->sk_wmem_alloc) > limit)
			return true;
	}
	return false;
}

2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
	const u32 now = tcp_time_stamp;

	if (tp->chrono_type > TCP_CHRONO_UNSPEC)
		tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start;
	tp->chrono_start = now;
	tp->chrono_type = new;
}

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

	/* If there are multiple conditions worthy of tracking in a
2130 2131
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2132 2133 2134 2135 2136 2137 2138 2139 2140 2141
	 * 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);

2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153

	/* 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);
2154 2155
}

L
Linus Torvalds 已提交
2156 2157 2158 2159
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2160 2161 2162 2163
 * 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
2164 2165 2166
 * 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
2167 2168
 * 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
2169
 */
E
Eric Dumazet 已提交
2170 2171
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
2172 2173
{
	struct tcp_sock *tp = tcp_sk(sk);
2174
	struct sk_buff *skb;
2175 2176
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2177
	int result;
2178
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2179
	u32 max_segs;
L
Linus Torvalds 已提交
2180

2181
	sent_pkts = 0;
J
John Heffner 已提交
2182

2183 2184 2185 2186
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2187
			return false;
2188 2189 2190
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2191 2192
	}

2193
	max_segs = tcp_tso_segs(sk, mss_now);
2194
	while ((skb = tcp_send_head(sk))) {
2195 2196
		unsigned int limit;

2197
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2198
		BUG_ON(!tso_segs);
2199

2200
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2201 2202
			/* "skb_mstamp" is used as a start point for the retransmit timer */
			skb_mstamp_get(&skb->skb_mstamp);
2203
			goto repair; /* Skip network transmission */
2204
		}
2205

2206
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2207 2208 2209 2210 2211 2212 2213
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2214

2215 2216
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2217
			break;
2218
		}
2219

2220
		if (tso_segs == 1) {
2221 2222 2223 2224 2225
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2226
			if (!push_one &&
E
Eric Dumazet 已提交
2227 2228
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2229 2230
				break;
		}
2231

E
Eric Dumazet 已提交
2232
		limit = mss_now;
2233
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2234 2235 2236 2237 2238 2239 2240 2241 2242 2243
			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;

2244 2245
		if (test_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags))
			clear_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
2246 2247
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2248

2249
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2250
			break;
L
Linus Torvalds 已提交
2251

2252
repair:
2253 2254 2255
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2256
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2257

2258
		tcp_minshall_update(tp, mss_now, skb);
2259
		sent_pkts += tcp_skb_pcount(skb);
2260 2261 2262

		if (push_one)
			break;
2263
	}
L
Linus Torvalds 已提交
2264

2265 2266 2267 2268 2269
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2270
	if (likely(sent_pkts)) {
2271 2272
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2273 2274 2275 2276

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2277
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2278
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2279
		return false;
L
Linus Torvalds 已提交
2280
	}
2281
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2282 2283 2284 2285 2286 2287 2288
}

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;
2289
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300

	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
		return false;
	/* No consecutive loss probes. */
	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
		tcp_rearm_rto(sk);
		return false;
	}
	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
2301
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2302 2303 2304 2305 2306 2307 2308 2309 2310
		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.
	 */
2311
	if (sysctl_tcp_early_retrans < 3 || !tp->packets_out ||
N
Nandita Dukkipati 已提交
2312 2313 2314 2315 2316 2317 2318 2319
	    !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
		return false;

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

	/* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2320 2321
	 * 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
2322
	 */
2323
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342
	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;
}

2343 2344 2345 2346 2347 2348 2349
/* 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)
{
2350
	if (unlikely(skb_fclone_busy(sk, skb))) {
2351 2352
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2353 2354 2355 2356 2357
		return true;
	}
	return false;
}

2358
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2359 2360 2361 2362
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2363
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2364 2365 2366 2367
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379
	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
2380 2381
	}

N
Nandita Dukkipati 已提交
2382 2383 2384 2385
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2386 2387 2388 2389
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2390 2391 2392
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2393 2394 2395 2396 2397
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2398 2399
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2400
			goto rearm_timer;
2401
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2402 2403 2404 2405 2406
	}

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

2407
	if (__tcp_retransmit_skb(sk, skb, 1))
2408
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2409

N
Nandita Dukkipati 已提交
2410
	/* Record snd_nxt for loss detection. */
2411
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2412

2413
probe_sent:
2414
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2415 2416
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2417
rearm_timer:
2418
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2419 2420
}

2421 2422 2423 2424
/* 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.
 */
2425 2426
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2427
{
2428 2429 2430 2431 2432 2433 2434
	/* 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;

2435
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2436
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2437
		tcp_check_probe_timer(sk);
2438 2439
}

2440 2441 2442 2443 2444
/* 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)
{
2445
	struct sk_buff *skb = tcp_send_head(sk);
2446 2447 2448

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

2449
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2450 2451
}

L
Linus Torvalds 已提交
2452 2453
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2454
 *
L
Linus Torvalds 已提交
2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472
 * 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.
2473
 *
L
Linus Torvalds 已提交
2474 2475
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2476
 *
L
Linus Torvalds 已提交
2477
 * BSD seems to make the following compromise:
2478
 *
L
Linus Torvalds 已提交
2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505
 *	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)
{
2506
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2507
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2508
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2509 2510 2511 2512 2513
	 * 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
	 */
2514
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2515
	int free_space = tcp_space(sk);
2516 2517
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2518 2519 2520
	int window;

	if (mss > full_space)
2521
		mss = full_space;
L
Linus Torvalds 已提交
2522

2523
	if (free_space < (full_space >> 1)) {
2524
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2525

2526
		if (tcp_under_memory_pressure(sk))
2527 2528
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2529

2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542
		/* 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
2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572
			return 0;
	}

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

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

		/* Advertise enough space so that it won't get scaled away.
		 * Import case: prevent zero window announcement if
		 * 1<<rcv_wscale > mss.
		 */
		if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
			window = (((window >> tp->rx_opt.rcv_wscale) + 1)
				  << tp->rx_opt.rcv_wscale);
	} else {
		/* Get the largest window that is a nice multiple of mss.
		 * Window clamp already applied above.
		 * If our current window offering is within 1 mss of the
		 * free space we just keep it. This prevents the divide
		 * and multiply from happening most of the time.
		 * We also don't do any window rounding when the free space
		 * is too small.
		 */
		if (window <= free_space - mss || window > free_space)
2573
			window = (free_space / mss) * mss;
2574
		else if (mss == full_space &&
2575
			 free_space > window + (full_space >> 1))
2576
			window = free_space;
L
Linus Torvalds 已提交
2577 2578 2579 2580 2581
	}

	return window;
}

2582 2583
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2584
{
2585 2586 2587
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2588 2589
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2590
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2591
		shinfo->tskey = next_shinfo->tskey;
2592 2593
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2594 2595 2596
	}
}

2597
/* Collapses two adjacent SKB's during retransmission. */
2598
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2599 2600
{
	struct tcp_sock *tp = tcp_sk(sk);
2601
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2602
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2603

2604 2605
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2606

2607
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2608

2609 2610 2611 2612 2613 2614 2615
	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;
	}
2616
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2617

2618
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2619

2620 2621
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2622

2623 2624
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2625

2626 2627
	/* 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
2628

2629
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2630
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2631 2632 2633 2634 2635

	/* 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;
2636
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2637 2638

	/* changed transmit queue under us so clear hints */
2639 2640 2641
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2642

2643 2644
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2645 2646
	tcp_skb_collapse_tstamp(skb, next_skb);

2647
	sk_wmem_free_skb(sk, next_skb);
2648
	return true;
L
Linus Torvalds 已提交
2649 2650
}

2651
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2652
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2653 2654
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2655
		return false;
2656
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2657
		return false;
2658
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2659
		return false;
E
Eric Dumazet 已提交
2660
	/* Some heuristics for collapsing over SACK'd could be invented */
2661
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2662
		return false;
2663

E
Eric Dumazet 已提交
2664
	return true;
2665 2666
}

2667 2668 2669
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2670 2671 2672 2673 2674
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
2675
	bool first = true;
2676 2677 2678

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2679
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2680 2681 2682 2683 2684 2685
		return;

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

2686 2687 2688
		if (!tcp_skb_can_collapse_to(to))
			break;

2689 2690 2691
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2692
			first = false;
2693 2694 2695 2696 2697 2698 2699 2700 2701
			continue;
		}

		if (space < 0)
			break;

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

2702 2703
		if (!tcp_collapse_retrans(sk, to))
			break;
2704 2705 2706
	}
}

L
Linus Torvalds 已提交
2707 2708 2709 2710
/* 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.
 */
2711
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2712
{
J
John Heffner 已提交
2713
	struct inet_connection_sock *icsk = inet_csk(sk);
2714
	struct tcp_sock *tp = tcp_sk(sk);
2715
	unsigned int cur_mss;
2716 2717
	int diff, len, err;

L
Linus Torvalds 已提交
2718

2719 2720
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2721 2722
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2723
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2724
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2725 2726
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
2727 2728
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2729 2730
		return -EAGAIN;

2731 2732 2733
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2734 2735 2736 2737 2738 2739 2740
	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;
	}

2741 2742 2743
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2744
	cur_mss = tcp_current_mss(sk);
2745

L
Linus Torvalds 已提交
2746 2747 2748 2749 2750
	/* 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.
	 */
2751 2752
	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
2753 2754
		return -EAGAIN;

2755 2756 2757
	len = cur_mss * segs;
	if (skb->len > len) {
		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2758
			return -ENOMEM; /* We'll try again later. */
2759
	} else {
2760 2761
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2762

2763 2764 2765 2766 2767 2768 2769
		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
2770 2771
	}

2772 2773 2774 2775
	/* 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);

2776 2777 2778 2779 2780 2781
	/* 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)) {
2782 2783 2784 2785
		struct sk_buff *nskb;

		skb_mstamp_get(&skb->skb_mstamp);
		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2786 2787
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2788
	} else {
2789
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2790
	}
2791

2792
	if (likely(!err)) {
2793 2794
		segs = tcp_skb_pcount(skb);

2795
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2796
		/* Update global TCP statistics. */
2797
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
2798
		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2799
			__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2800
		tp->total_retrans += segs;
2801
	}
2802
	return err;
2803 2804
}

2805
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2806 2807
{
	struct tcp_sock *tp = tcp_sk(sk);
2808
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2809 2810 2811

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2812
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2813
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2814 2815 2816 2817 2818 2819 2820
		}
#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
2821
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2822

2823
	} else if (err != -EBUSY) {
2824
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
L
Linus Torvalds 已提交
2825
	}
Y
Yuchung Cheng 已提交
2826 2827 2828 2829

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2830 2831 2832
	return err;
}

2833 2834 2835
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
E
Eric Dumazet 已提交
2836
static bool tcp_can_forward_retransmit(struct sock *sk)
2837 2838
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2839
	const struct tcp_sock *tp = tcp_sk(sk);
2840 2841 2842

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
E
Eric Dumazet 已提交
2843
		return false;
2844 2845 2846

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
E
Eric Dumazet 已提交
2847
		return false;
2848 2849 2850 2851 2852 2853 2854 2855 2856 2857

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

	if (tcp_may_send_now(sk))
E
Eric Dumazet 已提交
2858
		return false;
2859

E
Eric Dumazet 已提交
2860
	return true;
2861 2862
}

L
Linus Torvalds 已提交
2863 2864 2865 2866 2867 2868 2869 2870 2871 2872
/* 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)
{
2873
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2874 2875
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2876
	struct sk_buff *hole = NULL;
2877
	u32 max_segs, last_lost;
2878
	int mib_idx;
2879
	int fwd_rexmitting = 0;
2880

2881 2882 2883
	if (!tp->packets_out)
		return;

2884 2885 2886
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2887
	if (tp->retransmit_skb_hint) {
2888
		skb = tp->retransmit_skb_hint;
2889 2890 2891 2892
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2893
		skb = tcp_write_queue_head(sk);
2894 2895
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2896

2897
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2898
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2899
		__u8 sacked;
2900
		int segs;
L
Linus Torvalds 已提交
2901

2902 2903 2904
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2905
		if (!hole)
2906
			tp->retransmit_skb_hint = skb;
2907

2908 2909
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2910
			return;
E
Eric Dumazet 已提交
2911
		sacked = TCP_SKB_CB(skb)->sacked;
2912 2913 2914 2915
		/* 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
2916

2917 2918 2919 2920 2921
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2922

2923
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2924
			tp->retransmit_high = last_lost;
2925 2926 2927
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
2928
			if (hole) {
2929 2930 2931 2932 2933
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2934

2935
		} else if (!(sacked & TCPCB_LOST)) {
2936
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2937 2938
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2939

2940
		} else {
2941
			last_lost = TCP_SKB_CB(skb)->end_seq;
2942 2943 2944 2945 2946
			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
2947

2948
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2949 2950
			continue;

2951 2952 2953
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2954
		if (tcp_retransmit_skb(sk, skb, segs))
2955
			return;
2956

2957
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2958

2959
		if (tcp_in_cwnd_reduction(sk))
2960 2961
			tp->prr_out += tcp_skb_pcount(skb);

2962
		if (skb == tcp_write_queue_head(sk))
2963 2964 2965
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2966 2967 2968
	}
}

2969 2970
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2971 2972
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2973 2974
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2975
 */
2976
void sk_forced_mem_schedule(struct sock *sk, int size)
2977
{
2978
	int amt;
2979 2980 2981 2982 2983

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2984 2985
	sk_memory_allocated_add(sk, amt);

2986 2987
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
2988 2989
}

2990 2991
/* 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
2992 2993 2994
 */
void tcp_send_fin(struct sock *sk)
{
2995
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2996 2997
	struct tcp_sock *tp = tcp_sk(sk);

2998 2999 3000 3001
	/* 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
3002
	 */
3003
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
3004 3005 3006
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
3007
		tp->write_seq++;
3008 3009 3010 3011 3012 3013 3014 3015 3016 3017
		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
3018
	} else {
3019 3020 3021 3022 3023
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3024
		}
3025
		skb_reserve(skb, MAX_TCP_HEADER);
3026
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3027
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3028
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3029
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3030 3031
		tcp_queue_skb(sk, skb);
	}
3032
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3033 3034 3035 3036 3037
}

/* 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
3038
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3039
 */
A
Al Viro 已提交
3040
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3041 3042 3043 3044 3045 3046
{
	struct sk_buff *skb;

	/* NOTE: No TCP options attached and we never retransmit this. */
	skb = alloc_skb(MAX_TCP_HEADER, priority);
	if (!skb) {
P
Pavel Emelyanov 已提交
3047
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3048 3049 3050 3051 3052
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3053
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3054
			     TCPHDR_ACK | TCPHDR_RST);
3055
	skb_mstamp_get(&skb->skb_mstamp);
L
Linus Torvalds 已提交
3056
	/* Send it off. */
3057
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3058
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3059

P
Pavel Emelyanov 已提交
3060
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
3061 3062
}

3063 3064
/* 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
3065 3066 3067 3068 3069 3070
 * 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)
{
3071
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3072

3073
	skb = tcp_write_queue_head(sk);
3074
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3075
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3076 3077
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3078
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3079 3080
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
3081
			if (!nskb)
L
Linus Torvalds 已提交
3082
				return -ENOMEM;
3083
			tcp_unlink_write_queue(skb, sk);
3084
			__skb_header_release(nskb);
3085
			__tcp_add_write_queue_head(sk, nskb);
3086 3087 3088
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3089 3090 3091
			skb = nskb;
		}

E
Eric Dumazet 已提交
3092
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3093
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3094
	}
3095
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3096 3097
}

3098 3099 3100 3101 3102 3103 3104 3105 3106
/**
 * 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.
 */
3107
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3108
				struct request_sock *req,
3109
				struct tcp_fastopen_cookie *foc,
3110
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3111
{
3112
	struct inet_request_sock *ireq = inet_rsk(req);
3113
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3114
	struct tcp_md5sig_key *md5 = NULL;
3115 3116
	struct tcp_out_options opts;
	struct sk_buff *skb;
3117
	int tcp_header_size;
3118 3119
	struct tcphdr *th;
	u16 user_mss;
3120
	int mss;
L
Linus Torvalds 已提交
3121

3122
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3123 3124
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3125
		return NULL;
3126
	}
L
Linus Torvalds 已提交
3127 3128 3129
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3130 3131
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3132
		skb_set_owner_w(skb, req_to_sk(req));
3133 3134 3135 3136 3137 3138 3139
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3140 3141 3142 3143 3144
		/* 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);
3145
		break;
3146
	}
3147
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3148

3149
	mss = dst_metric_advmss(dst);
3150 3151 3152
	user_mss = READ_ONCE(tp->rx_opt.user_mss);
	if (user_mss && user_mss < mss)
		mss = user_mss;
3153

A
Adam Langley 已提交
3154
	memset(&opts, 0, sizeof(opts));
3155 3156
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
3157
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3158 3159
	else
#endif
E
Eric Dumazet 已提交
3160
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
3161 3162 3163

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3164
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3165
#endif
3166
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3167 3168
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3169

3170 3171
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3172

3173
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3174 3175 3176
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3177
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3178
	th->source = htons(ireq->ir_num);
3179
	th->dest = ireq->ir_rmt_port;
3180 3181 3182 3183
	/* 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
3184
			     TCPHDR_SYN | TCPHDR_ACK);
3185

L
Linus Torvalds 已提交
3186
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3187 3188
	/* 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
3189 3190

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3191
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3192
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3193
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3194
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3195 3196 3197

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3198
	if (md5)
3199
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3200
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3201
	rcu_read_unlock();
3202 3203
#endif

3204 3205
	/* Do not fool tcpdump (if any), clean our debris */
	skb->tstamp.tv64 = 0;
L
Linus Torvalds 已提交
3206 3207
	return skb;
}
E
Eric Dumazet 已提交
3208
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3209

3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228
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();
}

3229
/* Do all connect socket setups that can be done AF independent. */
3230
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3231
{
3232
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3233 3234 3235 3236 3237 3238 3239
	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) +
3240
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3241

3242
#ifdef CONFIG_TCP_MD5SIG
3243
	if (tp->af_specific->md5_lookup(sk, sk))
3244 3245 3246
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3247 3248 3249 3250
	/* 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
3251
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3252 3253
	tcp_sync_mss(sk, dst_mtu(dst));

3254 3255
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3256 3257
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3258
	tp->advmss = dst_metric_advmss(dst);
3259 3260 3261
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
		tp->advmss = tp->rx_opt.user_mss;

L
Linus Torvalds 已提交
3262 3263
	tcp_initialize_rcv_mss(sk);

3264 3265 3266 3267 3268
	/* 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
3269 3270 3271 3272
	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,
3273
				  sysctl_tcp_window_scaling,
3274 3275
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3276 3277 3278 3279 3280 3281 3282

	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;
3283
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3284 3285
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3286
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3287
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3288 3289 3290

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3291 3292
	else
		tp->rcv_tstamp = tcp_time_stamp;
P
Pavel Emelyanov 已提交
3293 3294
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3295

3296 3297
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3298 3299 3300
	tcp_clear_retrans(tp);
}

3301 3302 3303 3304 3305 3306
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;
3307
	__skb_header_release(skb);
3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325
	__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;
3326
	int syn_loss = 0, space, err = 0;
3327
	unsigned long last_syn_loss = 0;
3328
	struct sk_buff *syn_data;
3329

3330
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3331 3332 3333 3334 3335 3336 3337 3338
	tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
			       &syn_loss, &last_syn_loss);
	/* Recurring FO SYN losses: revert to regular handshake temporarily */
	if (syn_loss > 1 &&
	    time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
		fo->cookie.len = -1;
		goto fallback;
	}
3339

3340 3341 3342
	if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
		fo->cookie.len = -1;
	else if (fo->cookie.len <= 0)
3343 3344 3345 3346 3347 3348 3349 3350
		goto fallback;

	/* MSS for SYN-data is based on cached MSS and bounded by PMTU and
	 * user-MSS. Reserve maximum option space for middleboxes that add
	 * private TCP options. The cost is reduced data space in SYN :(
	 */
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3351
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3352 3353
		MAX_TCP_OPTION_SPACE;

3354 3355 3356 3357 3358
	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));

3359
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3360
	if (!syn_data)
3361
		goto fallback;
3362 3363
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374
	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;
		}
3375
	}
3376 3377 3378 3379
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3380

3381
	tcp_connect_queue_skb(sk, syn_data);
3382 3383
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3384

3385
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3386

3387
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3388

3389 3390 3391 3392 3393 3394 3395 3396
	/* 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) {
3397
		tp->syn_data = (fo->copied > 0);
3398
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413
		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;
}

3414
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3415 3416 3417 3418
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3419
	int err;
L
Linus Torvalds 已提交
3420 3421 3422

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3423 3424 3425 3426 3427
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3428
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3429
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3430 3431
		return -ENOBUFS;

C
Changli Gao 已提交
3432
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
E
Eric Dumazet 已提交
3433
	tp->retrans_stamp = tcp_time_stamp;
3434
	tcp_connect_queue_skb(sk, buff);
3435
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3436

3437 3438 3439
	/* 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);
3440 3441
	if (err == -ECONNREFUSED)
		return err;
3442 3443 3444 3445 3446 3447

	/* 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
3448
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3449 3450

	/* Timer for repeating the SYN until an answer. */
3451 3452
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3453 3454
	return 0;
}
E
Eric Dumazet 已提交
3455
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3456 3457 3458 3459 3460 3461 3462

/* 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)
{
3463 3464
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3465 3466
	unsigned long timeout;

3467 3468
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3469
	if (ato > TCP_DELACK_MIN) {
3470
		const struct tcp_sock *tp = tcp_sk(sk);
3471
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3472

3473 3474
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3475 3476 3477 3478 3479
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3480
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3481 3482
		 * directly.
		 */
3483 3484 3485
		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
3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497

			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. */
3498
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3499 3500 3501
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3502 3503
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3504 3505 3506 3507
			tcp_send_ack(sk);
			return;
		}

3508 3509
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3510
	}
3511 3512 3513
	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
3514 3515 3516 3517 3518
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3519
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3520

3521 3522 3523
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3524

3525 3526
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3527 3528 3529 3530
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3531 3532 3533
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3534 3535 3536 3537 3538
		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
3539
	}
3540 3541 3542

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3543
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3544

E
Eric Dumazet 已提交
3545 3546 3547 3548 3549 3550 3551 3552
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 * We also avoid tcp_wfree() overhead (cache line miss accessing
	 * tp->tsq_flags) by using regular sock_wfree()
	 */
	skb_set_tcp_pure_ack(buff);

3553
	/* Send it off, this clears delayed acks for us. */
E
Eric Dumazet 已提交
3554
	skb_mstamp_get(&buff->skb_mstamp);
3555
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3556
}
3557
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569

/* 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.
 */
3570
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3571 3572 3573 3574 3575
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3576 3577
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3578
	if (!skb)
L
Linus Torvalds 已提交
3579 3580 3581 3582 3583 3584 3585 3586
		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
3587
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
E
Eric Dumazet 已提交
3588
	skb_mstamp_get(&skb->skb_mstamp);
3589
	NET_INC_STATS(sock_net(sk), mib);
3590
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3591 3592
}

P
Pavel Emelyanov 已提交
3593 3594 3595 3596
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;
3597
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3598 3599 3600
	}
}

3601
/* Initiate keepalive or window probe from timer. */
3602
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3603
{
3604 3605
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3606

3607 3608 3609
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3610 3611
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3612
		int err;
I
Ilpo Järvinen 已提交
3613
		unsigned int mss = tcp_current_mss(sk);
3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625
		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
3626
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3627
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3628 3629
				return -1;
		} else if (!tcp_skb_pcount(skb))
3630
			tcp_set_skb_tso_segs(skb, mss);
3631

E
Eric Dumazet 已提交
3632
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3633 3634 3635 3636 3637
		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
3638
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3639 3640
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3641 3642 3643 3644 3645 3646 3647 3648
	}
}

/* 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)
{
3649
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3650
	struct tcp_sock *tp = tcp_sk(sk);
3651
	struct net *net = sock_net(sk);
3652
	unsigned long probe_max;
L
Linus Torvalds 已提交
3653 3654
	int err;

3655
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3656

3657
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3658
		/* Cancel probe timer, if it is not required. */
3659
		icsk->icsk_probes_out = 0;
3660
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3661 3662 3663 3664
		return;
	}

	if (err <= 0) {
3665
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3666
			icsk->icsk_backoff++;
3667
		icsk->icsk_probes_out++;
3668
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3669 3670
	} else {
		/* If packet was not sent due to local congestion,
3671
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3672 3673 3674 3675
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3676 3677
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3678
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3679
	}
3680
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3681
				  tcp_probe0_when(sk, probe_max),
3682
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3683
}
3684

3685
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3686 3687 3688 3689 3690
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3691
	tcp_rsk(req)->txhash = net_tx_rndhash();
3692
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3693
	if (!res) {
E
Eric Dumazet 已提交
3694
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3695
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3696 3697
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3698 3699 3700 3701
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);