tcp_output.c 106.3 KB
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/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
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 * Authors:	Ross Biro
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 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

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

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#define pr_fmt(fmt) "TCP: " fmt

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#include <net/tcp.h>

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

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

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

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

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

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

	return (__u16)mss;
}

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

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

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

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

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	tp->lsndtime = now;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

679 680
	opts->options = 0;

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

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

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

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

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

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

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

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

		tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
J
John Ogness 已提交
745
			       0, GFP_ATOMIC);
746
	}
747
}
E
Eric Dumazet 已提交
748
/*
S
stephen hemminger 已提交
749
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
750
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
751
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771
 * interrupt us (non NAPI drivers)
 */
static void tcp_tasklet_func(unsigned long data)
{
	struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
	LIST_HEAD(list);
	unsigned long flags;
	struct list_head *q, *n;
	struct tcp_sock *tp;
	struct sock *sk;

	local_irq_save(flags);
	list_splice_init(&tsq->head, &list);
	local_irq_restore(flags);

	list_for_each_safe(q, n, &list) {
		tp = list_entry(q, struct tcp_sock, tsq_node);
		list_del(&tp->tsq_node);

		sk = (struct sock *)tp;
772
		smp_mb__before_atomic();
773 774
		clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);

775
		if (!sk->sk_lock.owned &&
776
		    test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) {
777 778
			bh_lock_sock(sk);
			if (!sock_owned_by_user(sk)) {
779
				clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
780 781 782
				tcp_tsq_handler(sk);
			}
			bh_unlock_sock(sk);
E
Eric Dumazet 已提交
783 784 785 786 787 788
		}

		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
789 790 791 792
#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
793 794 795 796 797 798 799 800 801
/**
 * 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)
{
802
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
803

804 805
	/* perform an atomic operation only if at least one flag is set */
	do {
806
		flags = sk->sk_tsq_flags;
807 808 809
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
810
	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
811

E
Eric Dumazet 已提交
812
	if (flags & TCPF_TSQ_DEFERRED)
813 814
		tcp_tsq_handler(sk);

815 816 817 818 819 820 821 822 823 824 825
	/* 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
826
	if (flags & TCPF_WRITE_TIMER_DEFERRED) {
827
		tcp_write_timer_handler(sk);
828 829
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
830
	if (flags & TCPF_DELACK_TIMER_DEFERRED) {
831
		tcp_delack_timer_handler(sk);
832 833
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
834
	if (flags & TCPF_MTU_REDUCED_DEFERRED) {
835
		inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
836 837
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856
}
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
857
 * We can't xmit new skbs from this context, as we might already
E
Eric Dumazet 已提交
858 859
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
860
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
861 862 863
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);
864
	unsigned long flags, nval, oval;
865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880
	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
881

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

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

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

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

L
Linus Torvalds 已提交
908 909 910 911 912 913 914 915 916 917 918
/* 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.
 */
919 920
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
921
{
922 923 924 925
	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
926
	struct tcp_out_options opts;
927
	unsigned int tcp_options_size, tcp_header_size;
928
	struct tcp_md5sig_key *md5;
929 930 931 932
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
933
	tp = tcp_sk(sk);
934

935
	if (clone_it) {
936
		skb_mstamp_get(&skb->skb_mstamp);
937 938
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
939
		tcp_rate_skb_sent(sk, skb);
940

941 942 943 944 945 946 947
		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
948

949 950
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
951
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
952

E
Eric Dumazet 已提交
953
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
954 955 956 957 958
		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);
959

E
Eric Dumazet 已提交
960
	/* if no packet is in qdisc/device queue, then allow XPS to select
961 962 963 964 965
	 * 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
966
	 */
967
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
968

969 970
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
971 972 973

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
974
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
975
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
976
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
977 978

	/* Build TCP header and checksum it. */
979
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
980 981
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
982 983
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
984
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
985
					tcb->tcp_flags);
986 987 988

	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
989

I
Ilpo Järvinen 已提交
990
	/* The urg_mode check is necessary during a below snd_una win probe */
991 992 993 994 995
	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)) {
996
			th->urg_ptr = htons(0xFFFF);
997 998
			th->urg = 1;
		}
999
	}
L
Linus Torvalds 已提交
1000

1001
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1002
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1003 1004 1005 1006 1007 1008 1009 1010 1011
	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));
	}
1012 1013 1014
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1015
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1016
		tp->af_specific->calc_md5_hash(opts.hash_location,
1017
					       md5, sk, skb);
1018 1019 1020
	}
#endif

1021
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1022

E
Eric Dumazet 已提交
1023
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1024
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1025

1026
	if (skb->len != tcp_header_size) {
1027
		tcp_event_data_sent(tp, sk);
1028 1029
		tp->data_segs_out += tcp_skb_pcount(skb);
	}
L
Linus Torvalds 已提交
1030

1031
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1032 1033
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1034

1035
	tp->segs_out += tcp_skb_pcount(skb);
1036
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1037
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1038
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1039

E
Eric Dumazet 已提交
1040
	/* Our usage of tstamp should remain private */
T
Thomas Gleixner 已提交
1041
	skb->tstamp = 0;
1042 1043 1044 1045 1046

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

1047
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1048

1049
	if (likely(err <= 0))
1050 1051
		return err;

1052
	tcp_enter_cwr(sk);
1053

1054
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1055 1056
}

1057
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1058 1059 1060 1061 1062 1063 1064 1065 1066 1067
 *
 * 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;
1068
	__skb_header_release(skb);
1069
	tcp_add_write_queue_tail(sk, skb);
1070 1071
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1072 1073
}

1074
/* Initialize TSO segments for a packet. */
1075
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1076
{
1077
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1078 1079 1080
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1081
		tcp_skb_pcount_set(skb, 1);
1082
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1083
	} else {
1084
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1085
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1086 1087 1088
	}
}

I
Ilpo Järvinen 已提交
1089
/* When a modification to fackets out becomes necessary, we need to check
1090
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1091
 */
1092
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1093 1094
				   int decr)
{
1095 1096
	struct tcp_sock *tp = tcp_sk(sk);

1097
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1098 1099
		return;

1100
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1101 1102 1103
		tp->fackets_out -= decr;
}

1104 1105 1106
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1107
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127
{
	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) &&
1128
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1129 1130 1131 1132 1133
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1134 1135 1136 1137 1138 1139
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);
}

1140 1141 1142 1143
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1144
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1145 1146 1147 1148 1149 1150 1151
	    !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);
1152 1153
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1154 1155 1156
	}
}

1157 1158 1159 1160 1161 1162
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
1163 1164
/* 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
1165
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1166 1167
 * Remember, these are still headerless SKBs at this point.
 */
1168
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1169
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1170 1171 1172
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1173
	int nsize, old_factor;
1174
	int nlen;
1175
	u8 flags;
L
Linus Torvalds 已提交
1176

1177 1178
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1179

L
Linus Torvalds 已提交
1180 1181 1182 1183
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1184
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1185 1186 1187
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1188
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1189
	if (!buff)
L
Linus Torvalds 已提交
1190
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1191

1192 1193
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1194 1195 1196
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1197 1198 1199 1200 1201 1202 1203

	/* 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
1204 1205 1206
	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;
1207
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1208
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1209

1210
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1211
		/* Copy and checksum data tail into the new buffer. */
1212 1213
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1214 1215 1216 1217 1218 1219
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1220
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1221 1222 1223 1224 1225
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1226
	buff->tstamp = skb->tstamp;
1227
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1228

1229 1230
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1231
	/* Fix up tso_factor for both original and new SKB.  */
1232 1233
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1234

1235 1236 1237
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1238 1239 1240
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1241
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1242 1243
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1244

1245 1246
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1247 1248 1249
	}

	/* Link BUFF into the send queue. */
1250
	__skb_header_release(buff);
1251
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1252 1253 1254 1255 1256 1257 1258 1259

	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.
 */
1260
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1261
{
1262
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1263 1264
	int i, k, eat;

E
Eric Dumazet 已提交
1265 1266 1267 1268 1269 1270 1271
	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
1272 1273
	eat = len;
	k = 0;
1274 1275 1276
	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
1277 1278

		if (size <= eat) {
1279
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1280
			eat -= size;
L
Linus Torvalds 已提交
1281
		} else {
1282
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1283
			if (eat) {
1284 1285
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1286 1287 1288 1289 1290
				eat = 0;
			}
			k++;
		}
	}
1291
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1292

1293
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1294 1295 1296 1297
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1298
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1299 1300
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1301
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1302 1303
		return -ENOMEM;

E
Eric Dumazet 已提交
1304
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1305 1306

	TCP_SKB_CB(skb)->seq += len;
1307
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1308 1309 1310

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1311
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1312 1313
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1314
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1315
	if (tcp_skb_pcount(skb) > 1)
1316
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1317 1318 1319 1320

	return 0;
}

1321 1322
/* 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
1323
{
1324 1325
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1326 1327 1328 1329 1330 1331 1332
	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);

1333 1334 1335 1336 1337 1338 1339 1340
	/* 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
1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353
	/* 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;
}

1354 1355 1356 1357 1358 1359 1360 1361
/* 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
1362
/* Inverse of above */
1363
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1364
{
1365 1366
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1367 1368 1369 1370 1371 1372 1373
	int mtu;

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

1374 1375 1376 1377 1378 1379 1380
	/* 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
1381 1382
	return mtu;
}
1383
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1384

1385
/* MTU probing init per socket */
J
John Heffner 已提交
1386 1387 1388 1389
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
1390
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1391

F
Fan Du 已提交
1392
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1393
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1394
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1395
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1396
	icsk->icsk_mtup.probe_size = 0;
1397 1398
	if (icsk->icsk_mtup.enabled)
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
J
John Heffner 已提交
1399
}
E
Eric Dumazet 已提交
1400
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1401

L
Linus Torvalds 已提交
1402 1403 1404 1405 1406 1407
/* 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
1408
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1409 1410
   It also does not include TCP options.

1411
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1412 1413 1414 1415 1416 1417 1418 1419 1420

   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.

1421 1422
   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
1423 1424 1425 1426
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1427
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1428
	int mss_now;
L
Linus Torvalds 已提交
1429

J
John Heffner 已提交
1430 1431
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1432

J
John Heffner 已提交
1433
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1434
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1435 1436

	/* And store cached results */
1437
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1438 1439
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1440
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1441 1442 1443

	return mss_now;
}
E
Eric Dumazet 已提交
1444
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1445 1446 1447 1448

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1449
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1450
{
1451 1452
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1453
	u32 mss_now;
1454
	unsigned int header_len;
A
Adam Langley 已提交
1455 1456
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1457 1458 1459

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1460 1461
	if (dst) {
		u32 mtu = dst_mtu(dst);
1462
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1463 1464 1465
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1466 1467 1468 1469 1470 1471 1472 1473 1474 1475
	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;
	}
1476

L
Linus Torvalds 已提交
1477 1478 1479
	return mss_now;
}

1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501
/* 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;
}

1502
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1503
{
1504
	struct tcp_sock *tp = tcp_sk(sk);
1505

1506 1507 1508 1509 1510 1511 1512 1513 1514
	/* 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;
	}
1515

1516
	if (tcp_is_cwnd_limited(sk)) {
1517 1518 1519 1520 1521 1522 1523 1524
		/* 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;

1525 1526
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1527
			tcp_cwnd_application_limited(sk);
1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539

		/* 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);
1540 1541 1542
	}
}

E
Eric Dumazet 已提交
1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556
/* 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
1557
 */
E
Eric Dumazet 已提交
1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572
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,
1573
			    int nonagle)
E
Eric Dumazet 已提交
1574 1575 1576 1577 1578
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1579 1580 1581 1582

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1583 1584
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595
{
	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.
	 */
1596
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1597 1598 1599

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1600
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1601

1602 1603 1604 1605 1606 1607 1608 1609
/* 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;

1610 1611
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1612 1613
}

E
Eric Dumazet 已提交
1614 1615 1616 1617 1618 1619
/* 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)
1620
{
1621
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1622
	u32 partial, needed, window, max_len;
1623

1624
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1625
	max_len = mss_now * max_segs;
1626

1627 1628
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1629

1630 1631
	needed = min(skb->len, window);

1632 1633
	if (max_len <= needed)
		return max_len;
1634

E
Eric Dumazet 已提交
1635 1636 1637 1638 1639
	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
	 */
1640
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1641 1642 1643
		return needed - partial;

	return needed;
1644 1645 1646 1647 1648
}

/* 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.
 */
1649 1650
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1651
{
E
Eric Dumazet 已提交
1652
	u32 in_flight, cwnd, halfcwnd;
1653 1654

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1655 1656
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1657 1658 1659 1660
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1661 1662
	if (in_flight >= cwnd)
		return 0;
1663

E
Eric Dumazet 已提交
1664 1665 1666 1667 1668
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1669 1670
}

1671
/* Initialize TSO state of a skb.
1672
 * This must be invoked the first time we consider transmitting
1673 1674
 * SKB onto the wire.
 */
1675
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1676 1677 1678
{
	int tso_segs = tcp_skb_pcount(skb);

1679
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1680
		tcp_set_skb_tso_segs(skb, mss_now);
1681 1682 1683 1684 1685 1686
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1687
/* Return true if the Nagle test allows this packet to be
1688 1689
 * sent now.
 */
E
Eric Dumazet 已提交
1690 1691
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1692 1693 1694 1695 1696 1697 1698 1699
{
	/* 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
1700
		return true;
1701

Y
Yuchung Cheng 已提交
1702 1703
	/* 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
1704
		return true;
1705

1706
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1707
		return true;
1708

E
Eric Dumazet 已提交
1709
	return false;
1710 1711 1712
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1713 1714 1715
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1716 1717 1718 1719 1720 1721
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1722
	return !after(end_seq, tcp_wnd_end(tp));
1723 1724
}

1725
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1726 1727 1728
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1729
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1730 1731
				 unsigned int cur_mss, int nonagle)
{
1732
	const struct tcp_sock *tp = tcp_sk(sk);
1733 1734
	unsigned int cwnd_quota;

1735
	tcp_init_tso_segs(skb, cur_mss);
1736 1737 1738 1739 1740

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1741
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1742 1743 1744 1745 1746
		cwnd_quota = 0;

	return cwnd_quota;
}

1747
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1748
bool tcp_may_send_now(struct sock *sk)
1749
{
1750
	const struct tcp_sock *tp = tcp_sk(sk);
1751
	struct sk_buff *skb = tcp_send_head(sk);
1752

E
Eric Dumazet 已提交
1753
	return skb &&
I
Ilpo Järvinen 已提交
1754
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1755
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1756
			      tp->nonagle : TCP_NAGLE_PUSH));
1757 1758 1759 1760 1761 1762 1763 1764 1765
}

/* 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).
 */
1766
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1767
			unsigned int mss_now, gfp_t gfp)
1768 1769 1770
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1771
	u8 flags;
1772 1773

	/* All of a TSO frame must be composed of paged data.  */
1774
	if (skb->len != skb->data_len)
1775
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1776

1777
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1778
	if (unlikely(!buff))
1779 1780
		return -ENOMEM;

1781 1782
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1783
	buff->truesize += nlen;
1784 1785 1786 1787 1788 1789 1790 1791
	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
1792 1793 1794
	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;
1795 1796 1797 1798

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

1799 1800
	tcp_skb_fragment_eor(skb, buff);

1801
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1802
	skb_split(skb, buff, len);
1803
	tcp_fragment_tstamp(skb, buff);
1804 1805

	/* Fix up tso_factor for both original and new SKB.  */
1806 1807
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1808 1809

	/* Link BUFF into the send queue. */
1810
	__skb_header_release(buff);
1811
	tcp_insert_write_queue_after(skb, buff, sk);
1812 1813 1814 1815 1816 1817 1818 1819 1820

	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.
 */
1821
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1822
				 bool *is_cwnd_limited, u32 max_segs)
1823
{
1824
	const struct inet_connection_sock *icsk = inet_csk(sk);
1825 1826 1827 1828
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct skb_mstamp now;
	struct sk_buff *head;
1829
	int win_divisor;
1830

E
Eric Dumazet 已提交
1831
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1832
		goto send_now;
1833

1834
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1835 1836
		goto send_now;

E
Eric Dumazet 已提交
1837 1838 1839 1840
	/* 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
1841
		goto send_now;
1842

1843 1844
	in_flight = tcp_packets_in_flight(tp);

1845
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1846

1847
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1848 1849 1850 1851 1852 1853

	/* 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);

1854
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1855
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1856
		goto send_now;
1857

1858 1859 1860 1861
	/* 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;

1862 1863
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1864 1865 1866 1867 1868
		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.
		 */
1869
		chunk /= win_divisor;
1870
		if (limit >= chunk)
J
John Heffner 已提交
1871
			goto send_now;
1872 1873 1874 1875 1876 1877
	} 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.
		 */
1878
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1879
			goto send_now;
1880 1881
	}

1882 1883 1884 1885 1886 1887 1888
	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
1889
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1890

1891
	if (cong_win < send_win && cong_win <= skb->len)
1892 1893
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1894
	return true;
J
John Heffner 已提交
1895 1896

send_now:
E
Eric Dumazet 已提交
1897
	return false;
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 1924
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
1925
/* Create a new MTU probe if we are ready.
1926 1927 1928 1929
 * 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
1930 1931
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1932 1933
 *         -1 otherwise
 */
J
John Heffner 已提交
1934 1935 1936
static int tcp_mtu_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
1937
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
1938
	struct sk_buff *skb, *nskb, *next;
1939
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1940
	int probe_size;
1941
	int size_needed;
1942
	int copy, len;
J
John Heffner 已提交
1943
	int mss_now;
1944
	int interval;
J
John Heffner 已提交
1945 1946 1947 1948

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
1949 1950 1951 1952 1953 1954 1955
	 * not SACKing (the variable headers throw things off)
	 */
	if (likely(!icsk->icsk_mtup.enabled ||
		   icsk->icsk_mtup.probe_size ||
		   inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
		   tp->snd_cwnd < 11 ||
		   tp->rx_opt.num_sacks || tp->rx_opt.dsack))
J
John Heffner 已提交
1956 1957
		return -1;

1958 1959 1960 1961
	/* 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
1962
	mss_now = tcp_current_mss(sk);
1963 1964
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
1965
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1966
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1967 1968 1969 1970
	/* 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.
	 */
1971
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1972 1973 1974 1975 1976
		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
1977 1978 1979 1980
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1981
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1982 1983
		return -1;

1984 1985
	if (tp->snd_wnd < size_needed)
		return -1;
1986
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1987
		return 0;
J
John Heffner 已提交
1988

1989 1990 1991
	/* 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
1992 1993 1994 1995 1996 1997
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
1998
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1999
	if (!nskb)
J
John Heffner 已提交
2000
		return -1;
2001 2002
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2003

2004
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2005 2006 2007

	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
2008
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2009 2010
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2011
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2012

2013 2014
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2015
	len = 0;
2016
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2017
		copy = min_t(int, skb->len, probe_size - len);
2018
		if (nskb->ip_summed) {
J
John Heffner 已提交
2019
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2020 2021 2022 2023 2024 2025
		} 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
2026 2027 2028 2029

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2030
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2031
			tcp_unlink_write_queue(skb, sk);
2032
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2033
		} else {
E
Eric Dumazet 已提交
2034
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2035
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2036 2037
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2038
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2039 2040
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2041 2042
			} else {
				__pskb_trim_head(skb, copy);
2043
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2044 2045 2046 2047 2048
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2049 2050 2051

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2052
	}
2053
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2054 2055

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2056 2057
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2058 2059
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2060
		 * effectively two packets. */
J
John Heffner 已提交
2061
		tp->snd_cwnd--;
2062
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2063 2064

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2065 2066
		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
2067 2068 2069 2070 2071 2072 2073

		return 1;
	}

	return -1;
}

2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094
/* 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) {
2095 2096 2097 2098 2099 2100 2101 2102 2103
		/* 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;

2104
		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115
		/* 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;
}

2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130
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
2131 2132
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2133 2134 2135 2136 2137 2138 2139 2140 2141 2142
	 * 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);

2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154

	/* 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);
2155 2156
}

L
Linus Torvalds 已提交
2157 2158 2159 2160
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2161 2162 2163 2164
 * 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
2165 2166 2167
 * 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
2168 2169
 * 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
2170
 */
E
Eric Dumazet 已提交
2171 2172
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
2173 2174
{
	struct tcp_sock *tp = tcp_sk(sk);
2175
	struct sk_buff *skb;
2176 2177
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2178
	int result;
2179
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2180
	u32 max_segs;
L
Linus Torvalds 已提交
2181

2182
	sent_pkts = 0;
J
John Heffner 已提交
2183

2184 2185 2186 2187
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2188
			return false;
2189 2190 2191
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2192 2193
	}

2194
	max_segs = tcp_tso_segs(sk, mss_now);
2195
	while ((skb = tcp_send_head(sk))) {
2196 2197
		unsigned int limit;

2198
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2199
		BUG_ON(!tso_segs);
2200

2201
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2202 2203
			/* "skb_mstamp" is used as a start point for the retransmit timer */
			skb_mstamp_get(&skb->skb_mstamp);
2204
			goto repair; /* Skip network transmission */
2205
		}
2206

2207
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2208 2209 2210 2211 2212 2213 2214
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2215

2216 2217
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2218
			break;
2219
		}
2220

2221
		if (tso_segs == 1) {
2222 2223 2224 2225 2226
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2227
			if (!push_one &&
E
Eric Dumazet 已提交
2228 2229
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2230 2231
				break;
		}
2232

E
Eric Dumazet 已提交
2233
		limit = mss_now;
2234
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2235 2236 2237 2238 2239 2240 2241 2242 2243 2244
			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;

2245 2246
		if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
			clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
2247 2248
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2249

2250
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2251
			break;
L
Linus Torvalds 已提交
2252

2253
repair:
2254 2255 2256
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2257
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2258

2259
		tcp_minshall_update(tp, mss_now, skb);
2260
		sent_pkts += tcp_skb_pcount(skb);
2261 2262 2263

		if (push_one)
			break;
2264
	}
L
Linus Torvalds 已提交
2265

2266 2267 2268 2269 2270
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2271
	if (likely(sent_pkts)) {
2272 2273
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2274 2275 2276 2277

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2278
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2279
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2280
		return false;
L
Linus Torvalds 已提交
2281
	}
2282
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2283 2284 2285 2286 2287 2288 2289
}

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;
2290
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301

	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.
	 */
2302
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2303 2304 2305 2306 2307 2308 2309 2310 2311
		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.
	 */
2312
	if (sysctl_tcp_early_retrans < 3 || !tp->packets_out ||
N
Nandita Dukkipati 已提交
2313 2314 2315 2316 2317 2318 2319 2320
	    !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
2321 2322
	 * 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
2323
	 */
2324
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343
	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;
}

2344 2345 2346 2347 2348 2349 2350
/* 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)
{
2351
	if (unlikely(skb_fclone_busy(sk, skb))) {
2352 2353
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2354 2355 2356 2357 2358
		return true;
	}
	return false;
}

2359
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2360 2361 2362 2363
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2364
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2365 2366 2367 2368
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380
	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
2381 2382
	}

N
Nandita Dukkipati 已提交
2383 2384 2385 2386
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2387 2388 2389 2390
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2391 2392 2393
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2394 2395 2396 2397 2398
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2399 2400
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2401
			goto rearm_timer;
2402
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2403 2404 2405 2406 2407
	}

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

2408
	if (__tcp_retransmit_skb(sk, skb, 1))
2409
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2410

N
Nandita Dukkipati 已提交
2411
	/* Record snd_nxt for loss detection. */
2412
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2413

2414
probe_sent:
2415
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2416 2417
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2418
rearm_timer:
2419
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2420 2421
}

2422 2423 2424 2425
/* 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.
 */
2426 2427
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2428
{
2429 2430 2431 2432 2433 2434 2435
	/* 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;

2436
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2437
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2438
		tcp_check_probe_timer(sk);
2439 2440
}

2441 2442 2443 2444 2445
/* 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)
{
2446
	struct sk_buff *skb = tcp_send_head(sk);
2447 2448 2449

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

2450
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2451 2452
}

L
Linus Torvalds 已提交
2453 2454
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2455
 *
L
Linus Torvalds 已提交
2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473
 * 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.
2474
 *
L
Linus Torvalds 已提交
2475 2476
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2477
 *
L
Linus Torvalds 已提交
2478
 * BSD seems to make the following compromise:
2479
 *
L
Linus Torvalds 已提交
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 2506
 *	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)
{
2507
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2508
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2509
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2510 2511 2512 2513 2514
	 * 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
	 */
2515
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2516
	int free_space = tcp_space(sk);
2517 2518
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2519 2520 2521
	int window;

	if (mss > full_space)
2522
		mss = full_space;
L
Linus Torvalds 已提交
2523

2524
	if (free_space < (full_space >> 1)) {
2525
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2526

2527
		if (tcp_under_memory_pressure(sk))
2528 2529
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2530

2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543
		/* 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
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 2573
			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)
2574
			window = (free_space / mss) * mss;
2575
		else if (mss == full_space &&
2576
			 free_space > window + (full_space >> 1))
2577
			window = free_space;
L
Linus Torvalds 已提交
2578 2579 2580 2581 2582
	}

	return window;
}

2583 2584
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2585
{
2586 2587 2588
	if (unlikely(tcp_has_tx_tstamp(next_skb))) {
		const struct skb_shared_info *next_shinfo =
			skb_shinfo(next_skb);
2589 2590
		struct skb_shared_info *shinfo = skb_shinfo(skb);

2591
		shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2592
		shinfo->tskey = next_shinfo->tskey;
2593 2594
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2595 2596 2597
	}
}

2598
/* Collapses two adjacent SKB's during retransmission. */
2599
static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2600 2601
{
	struct tcp_sock *tp = tcp_sk(sk);
2602
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2603
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2604

2605 2606
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2607

2608
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2609

2610 2611 2612 2613 2614 2615 2616
	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;
	}
2617
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2618

2619
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2620

2621 2622
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2623

2624 2625
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2626

2627 2628
	/* 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
2629

2630
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2631
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2632 2633 2634 2635 2636

	/* 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;
2637
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2638 2639

	/* changed transmit queue under us so clear hints */
2640 2641 2642
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2643

2644 2645
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2646 2647
	tcp_skb_collapse_tstamp(skb, next_skb);

2648
	sk_wmem_free_skb(sk, next_skb);
2649
	return true;
L
Linus Torvalds 已提交
2650 2651
}

2652
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2653
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2654 2655
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2656
		return false;
2657
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2658
		return false;
2659
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2660
		return false;
E
Eric Dumazet 已提交
2661
	/* Some heuristics for collapsing over SACK'd could be invented */
2662
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2663
		return false;
2664

E
Eric Dumazet 已提交
2665
	return true;
2666 2667
}

2668 2669 2670
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2671 2672 2673 2674 2675
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
2676
	bool first = true;
2677 2678 2679

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2680
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2681 2682 2683 2684 2685 2686
		return;

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

2687 2688 2689
		if (!tcp_skb_can_collapse_to(to))
			break;

2690 2691 2692
		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2693
			first = false;
2694 2695 2696 2697 2698 2699 2700 2701 2702
			continue;
		}

		if (space < 0)
			break;

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

2703 2704
		if (!tcp_collapse_retrans(sk, to))
			break;
2705 2706 2707
	}
}

L
Linus Torvalds 已提交
2708 2709 2710 2711
/* 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.
 */
2712
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2713
{
J
John Heffner 已提交
2714
	struct inet_connection_sock *icsk = inet_csk(sk);
2715
	struct tcp_sock *tp = tcp_sk(sk);
2716
	unsigned int cur_mss;
2717 2718
	int diff, len, err;

L
Linus Torvalds 已提交
2719

2720 2721
	/* Inconclusive MTU probe */
	if (icsk->icsk_mtup.probe_size)
J
John Heffner 已提交
2722 2723
		icsk->icsk_mtup.probe_size = 0;

L
Linus Torvalds 已提交
2724
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2725
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2726 2727
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
2728 2729
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
L
Linus Torvalds 已提交
2730 2731
		return -EAGAIN;

2732 2733 2734
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2735 2736 2737 2738 2739 2740 2741
	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;
	}

2742 2743 2744
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2745
	cur_mss = tcp_current_mss(sk);
2746

L
Linus Torvalds 已提交
2747 2748 2749 2750 2751
	/* 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.
	 */
2752 2753
	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
2754 2755
		return -EAGAIN;

2756 2757 2758
	len = cur_mss * segs;
	if (skb->len > len) {
		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2759
			return -ENOMEM; /* We'll try again later. */
2760
	} else {
2761 2762
		if (skb_unclone(skb, GFP_ATOMIC))
			return -ENOMEM;
2763

2764 2765 2766 2767 2768 2769 2770
		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
2771 2772
	}

2773 2774 2775 2776
	/* 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);

2777 2778 2779 2780 2781 2782
	/* 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)) {
2783 2784 2785 2786
		struct sk_buff *nskb;

		skb_mstamp_get(&skb->skb_mstamp);
		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2787 2788
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2789
	} else {
2790
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2791
	}
2792

2793
	if (likely(!err)) {
2794 2795
		segs = tcp_skb_pcount(skb);

2796
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2797
		/* Update global TCP statistics. */
2798
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
2799
		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2800
			__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2801
		tp->total_retrans += segs;
2802
	}
2803
	return err;
2804 2805
}

2806
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2807 2808
{
	struct tcp_sock *tp = tcp_sk(sk);
2809
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2810 2811 2812

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2813
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2814
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2815 2816 2817 2818 2819 2820 2821
		}
#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
2822
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2823

2824
	} else if (err != -EBUSY) {
2825
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
L
Linus Torvalds 已提交
2826
	}
Y
Yuchung Cheng 已提交
2827 2828 2829 2830

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2831 2832 2833
	return err;
}

2834 2835 2836
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
E
Eric Dumazet 已提交
2837
static bool tcp_can_forward_retransmit(struct sock *sk)
2838 2839
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2840
	const struct tcp_sock *tp = tcp_sk(sk);
2841 2842 2843

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
E
Eric Dumazet 已提交
2844
		return false;
2845 2846 2847

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
E
Eric Dumazet 已提交
2848
		return false;
2849 2850 2851 2852 2853 2854 2855 2856 2857 2858

	/* 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
2859
		return false;
2860

E
Eric Dumazet 已提交
2861
	return true;
2862 2863
}

L
Linus Torvalds 已提交
2864 2865 2866 2867 2868 2869 2870 2871 2872 2873
/* 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)
{
2874
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2875 2876
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2877
	struct sk_buff *hole = NULL;
2878
	u32 max_segs, last_lost;
2879
	int mib_idx;
2880
	int fwd_rexmitting = 0;
2881

2882 2883 2884
	if (!tp->packets_out)
		return;

2885 2886 2887
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2888
	if (tp->retransmit_skb_hint) {
2889
		skb = tp->retransmit_skb_hint;
2890 2891 2892 2893
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2894
		skb = tcp_write_queue_head(sk);
2895 2896
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2897

2898
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2899
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2900
		__u8 sacked;
2901
		int segs;
L
Linus Torvalds 已提交
2902

2903 2904 2905
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2906
		if (!hole)
2907
			tp->retransmit_skb_hint = skb;
2908

2909 2910
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2911
			return;
E
Eric Dumazet 已提交
2912
		sacked = TCP_SKB_CB(skb)->sacked;
2913 2914 2915 2916
		/* 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
2917

2918 2919 2920 2921 2922
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2923

2924
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2925
			tp->retransmit_high = last_lost;
2926 2927 2928
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
2929
			if (hole) {
2930 2931 2932 2933 2934
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2935

2936
		} else if (!(sacked & TCPCB_LOST)) {
2937
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2938 2939
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2940

2941
		} else {
2942
			last_lost = TCP_SKB_CB(skb)->end_seq;
2943 2944 2945 2946 2947
			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
2948

2949
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2950 2951
			continue;

2952 2953 2954
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2955
		if (tcp_retransmit_skb(sk, skb, segs))
2956
			return;
2957

2958
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2959

2960
		if (tcp_in_cwnd_reduction(sk))
2961 2962
			tp->prr_out += tcp_skb_pcount(skb);

2963
		if (skb == tcp_write_queue_head(sk))
2964 2965 2966
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2967 2968 2969
	}
}

2970 2971
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2972 2973
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2974 2975
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2976
 */
2977
void sk_forced_mem_schedule(struct sock *sk, int size)
2978
{
2979
	int amt;
2980 2981 2982 2983 2984

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2985 2986
	sk_memory_allocated_add(sk, amt);

2987 2988
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
2989 2990
}

2991 2992
/* 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
2993 2994 2995
 */
void tcp_send_fin(struct sock *sk)
{
2996
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2997 2998
	struct tcp_sock *tp = tcp_sk(sk);

2999 3000 3001 3002
	/* 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
3003
	 */
3004
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
3005 3006 3007
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
3008
		tp->write_seq++;
3009 3010 3011 3012 3013 3014 3015 3016 3017 3018
		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
3019
	} else {
3020 3021 3022 3023 3024
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
3025
		}
3026
		skb_reserve(skb, MAX_TCP_HEADER);
3027
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
3028
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3029
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
3030
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
3031 3032
		tcp_queue_skb(sk, skb);
	}
3033
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
3034 3035 3036 3037 3038
}

/* 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
3039
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
3040
 */
A
Al Viro 已提交
3041
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
3042 3043 3044 3045 3046 3047
{
	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
3048
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
3049 3050 3051 3052 3053
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
3054
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3055
			     TCPHDR_ACK | TCPHDR_RST);
3056
	skb_mstamp_get(&skb->skb_mstamp);
L
Linus Torvalds 已提交
3057
	/* Send it off. */
3058
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3059
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3060

P
Pavel Emelyanov 已提交
3061
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
3062 3063
}

3064 3065
/* 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
3066 3067 3068 3069 3070 3071
 * 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)
{
3072
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3073

3074
	skb = tcp_write_queue_head(sk);
3075
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3076
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3077 3078
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3079
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3080 3081
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
3082
			if (!nskb)
L
Linus Torvalds 已提交
3083
				return -ENOMEM;
3084
			tcp_unlink_write_queue(skb, sk);
3085
			__skb_header_release(nskb);
3086
			__tcp_add_write_queue_head(sk, nskb);
3087 3088 3089
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3090 3091 3092
			skb = nskb;
		}

E
Eric Dumazet 已提交
3093
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3094
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3095
	}
3096
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3097 3098
}

3099 3100 3101 3102 3103 3104 3105 3106 3107
/**
 * 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.
 */
3108
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3109
				struct request_sock *req,
3110
				struct tcp_fastopen_cookie *foc,
3111
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3112
{
3113
	struct inet_request_sock *ireq = inet_rsk(req);
3114
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3115
	struct tcp_md5sig_key *md5 = NULL;
3116 3117
	struct tcp_out_options opts;
	struct sk_buff *skb;
3118
	int tcp_header_size;
3119 3120
	struct tcphdr *th;
	u16 user_mss;
3121
	int mss;
L
Linus Torvalds 已提交
3122

3123
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3124 3125
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3126
		return NULL;
3127
	}
L
Linus Torvalds 已提交
3128 3129 3130
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3131 3132
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3133
		skb_set_owner_w(skb, req_to_sk(req));
3134 3135 3136 3137 3138 3139 3140
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3141 3142 3143 3144 3145
		/* 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);
3146
		break;
3147
	}
3148
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3149

3150
	mss = dst_metric_advmss(dst);
3151 3152 3153
	user_mss = READ_ONCE(tp->rx_opt.user_mss);
	if (user_mss && user_mss < mss)
		mss = user_mss;
3154

A
Adam Langley 已提交
3155
	memset(&opts, 0, sizeof(opts));
3156 3157
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
3158
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3159 3160
	else
#endif
E
Eric Dumazet 已提交
3161
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
3162 3163 3164

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3165
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3166
#endif
3167
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3168 3169
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3170

3171 3172
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3173

3174
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3175 3176 3177
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3178
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3179
	th->source = htons(ireq->ir_num);
3180
	th->dest = ireq->ir_rmt_port;
3181 3182 3183 3184
	/* 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
3185
			     TCPHDR_SYN | TCPHDR_ACK);
3186

L
Linus Torvalds 已提交
3187
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3188 3189
	/* 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
3190 3191

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3192
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3193
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3194
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3195
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3196 3197 3198

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3199
	if (md5)
3200
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3201
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3202
	rcu_read_unlock();
3203 3204
#endif

3205
	/* Do not fool tcpdump (if any), clean our debris */
T
Thomas Gleixner 已提交
3206
	skb->tstamp = 0;
L
Linus Torvalds 已提交
3207 3208
	return skb;
}
E
Eric Dumazet 已提交
3209
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3210

3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229
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();
}

3230
/* Do all connect socket setups that can be done AF independent. */
3231
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3232
{
3233
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3234 3235 3236 3237 3238 3239 3240
	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) +
3241
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3242

3243
#ifdef CONFIG_TCP_MD5SIG
3244
	if (tp->af_specific->md5_lookup(sk, sk))
3245 3246 3247
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3248 3249 3250 3251
	/* 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
3252
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3253 3254
	tcp_sync_mss(sk, dst_mtu(dst));

3255 3256
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3257 3258
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3259
	tp->advmss = dst_metric_advmss(dst);
3260 3261 3262
	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
3263 3264
	tcp_initialize_rcv_mss(sk);

3265 3266 3267 3268 3269
	/* 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
3270 3271 3272 3273
	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,
3274
				  sysctl_tcp_window_scaling,
3275 3276
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3277 3278 3279 3280 3281 3282 3283

	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;
3284
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3285 3286
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3287
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3288
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3289 3290 3291

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3292 3293
	else
		tp->rcv_tstamp = tcp_time_stamp;
P
Pavel Emelyanov 已提交
3294 3295
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3296

3297 3298
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3299 3300 3301
	tcp_clear_retrans(tp);
}

3302 3303 3304 3305 3306 3307
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;
3308
	__skb_header_release(skb);
3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326
	__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;
3327
	int syn_loss = 0, space, err = 0;
3328
	unsigned long last_syn_loss = 0;
3329
	struct sk_buff *syn_data;
3330

3331
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3332 3333 3334 3335 3336 3337 3338 3339
	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;
	}
3340

3341 3342 3343
	if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
		fo->cookie.len = -1;
	else if (fo->cookie.len <= 0)
3344 3345 3346 3347 3348 3349 3350 3351
		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;
3352
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3353 3354
		MAX_TCP_OPTION_SPACE;

3355 3356 3357 3358 3359
	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));

3360
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3361
	if (!syn_data)
3362
		goto fallback;
3363 3364
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375
	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;
		}
3376
	}
3377 3378 3379 3380
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3381

3382
	tcp_connect_queue_skb(sk, syn_data);
3383 3384
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3385

3386
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3387

3388
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3389

3390 3391 3392 3393 3394 3395 3396 3397
	/* 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) {
3398
		tp->syn_data = (fo->copied > 0);
3399
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414
		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;
}

3415
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3416 3417 3418 3419
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3420
	int err;
L
Linus Torvalds 已提交
3421 3422 3423

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3424 3425 3426 3427 3428
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3429
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3430
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3431 3432
		return -ENOBUFS;

C
Changli Gao 已提交
3433
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
E
Eric Dumazet 已提交
3434
	tp->retrans_stamp = tcp_time_stamp;
3435
	tcp_connect_queue_skb(sk, buff);
3436
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3437

3438 3439 3440
	/* 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);
3441 3442
	if (err == -ECONNREFUSED)
		return err;
3443 3444 3445 3446 3447 3448

	/* 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
3449
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3450 3451

	/* Timer for repeating the SYN until an answer. */
3452 3453
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3454 3455
	return 0;
}
E
Eric Dumazet 已提交
3456
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3457 3458 3459 3460 3461 3462 3463

/* 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)
{
3464 3465
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3466 3467
	unsigned long timeout;

3468 3469
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3470
	if (ato > TCP_DELACK_MIN) {
3471
		const struct tcp_sock *tp = tcp_sk(sk);
3472
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3473

3474 3475
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3476 3477 3478 3479 3480
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3481
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3482 3483
		 * directly.
		 */
3484 3485 3486
		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
3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498

			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. */
3499
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3500 3501 3502
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3503 3504
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3505 3506 3507 3508
			tcp_send_ack(sk);
			return;
		}

3509 3510
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3511
	}
3512 3513 3514
	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
3515 3516 3517 3518 3519
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3520
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3521

3522 3523 3524
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3525

3526 3527
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3528 3529 3530 3531
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3532 3533 3534
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3535 3536 3537 3538 3539
		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
3540
	}
3541 3542 3543

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3544
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3545

E
Eric Dumazet 已提交
3546 3547 3548 3549 3550 3551
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 */
	skb_set_tcp_pure_ack(buff);

3552
	/* Send it off, this clears delayed acks for us. */
E
Eric Dumazet 已提交
3553
	skb_mstamp_get(&buff->skb_mstamp);
3554
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3555
}
3556
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568

/* 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.
 */
3569
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3570 3571 3572 3573 3574
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3575 3576
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3577
	if (!skb)
L
Linus Torvalds 已提交
3578 3579 3580 3581 3582 3583 3584 3585
		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
3586
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
E
Eric Dumazet 已提交
3587
	skb_mstamp_get(&skb->skb_mstamp);
3588
	NET_INC_STATS(sock_net(sk), mib);
3589
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3590 3591
}

P
Pavel Emelyanov 已提交
3592 3593 3594 3595
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;
3596
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3597 3598 3599
	}
}

3600
/* Initiate keepalive or window probe from timer. */
3601
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3602
{
3603 3604
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3605

3606 3607 3608
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3609 3610
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3611
		int err;
I
Ilpo Järvinen 已提交
3612
		unsigned int mss = tcp_current_mss(sk);
3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624
		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
3625
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3626
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3627 3628
				return -1;
		} else if (!tcp_skb_pcount(skb))
3629
			tcp_set_skb_tso_segs(skb, mss);
3630

E
Eric Dumazet 已提交
3631
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3632 3633 3634 3635 3636
		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
3637
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3638 3639
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3640 3641 3642 3643 3644 3645 3646 3647
	}
}

/* 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)
{
3648
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3649
	struct tcp_sock *tp = tcp_sk(sk);
3650
	struct net *net = sock_net(sk);
3651
	unsigned long probe_max;
L
Linus Torvalds 已提交
3652 3653
	int err;

3654
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3655

3656
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3657
		/* Cancel probe timer, if it is not required. */
3658
		icsk->icsk_probes_out = 0;
3659
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3660 3661 3662 3663
		return;
	}

	if (err <= 0) {
3664
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3665
			icsk->icsk_backoff++;
3666
		icsk->icsk_probes_out++;
3667
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3668 3669
	} else {
		/* If packet was not sent due to local congestion,
3670
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3671 3672 3673 3674
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3675 3676
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3677
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3678
	}
3679
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3680
				  tcp_probe0_when(sk, probe_max),
3681
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3682
}
3683

3684
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3685 3686 3687 3688 3689
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3690
	tcp_rsk(req)->txhash = net_tx_rndhash();
3691
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3692
	if (!res) {
E
Eric Dumazet 已提交
3693
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3694
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3695 3696
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3697 3698 3699 3700
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);