tcp_output.c 101.0 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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unsigned int sysctl_tcp_notsent_lowat __read_mostly = UINT_MAX;
EXPORT_SYMBOL(sysctl_tcp_notsent_lowat);

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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".
 * This is the first part of cwnd validation mechanism. */
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static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
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{
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	struct tcp_sock *tp = tcp_sk(sk);
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	s32 delta = tcp_time_stamp - tp->lsndtime;
	u32 restart_cwnd = tcp_init_cwnd(tp, dst);
	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 (sysctl_tcp_slow_start_after_idle &&
	    (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
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		tcp_cwnd_restart(sk, __sk_dst_get(sk));
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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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		 */
		space = max_t(u32, sysctl_tcp_rmem[2], 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
tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th,
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		    struct sock *sk)
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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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		if (tcp_ca_needs_ecn(sk))
			INET_ECN_xmit(sk);
	}
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}

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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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				int tcp_header_len)
{
	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;
				tcp_hdr(skb)->cwr = 1;
				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)
			tcp_hdr(skb)->ece = 1;
	}
}

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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);
	}

495
	if (unlikely(OPTION_WSCALE & options)) {
A
Adam Langley 已提交
496 497 498 499 500 501 502 503 504
		*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
505 506 507 508 509
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
510
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
511
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
512

A
Adam Langley 已提交
513 514
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
515 516 517
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
518

519
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
520
	}
Y
Yuchung Cheng 已提交
521 522 523

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
524 525 526 527 528 529 530 531 532 533 534 535 536
		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
537

538 539 540 541
		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
542
		}
543
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
544
	}
A
Adam Langley 已提交
545 546
}

547 548 549
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
550
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
551
				struct tcp_out_options *opts,
552 553
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
554
	struct tcp_sock *tp = tcp_sk(sk);
555
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
556
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
557

558
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
559 560 561
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
562
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
563
	}
A
Adam Langley 已提交
564 565
#else
	*md5 = NULL;
566
#endif
A
Adam Langley 已提交
567 568 569 570 571 572 573 574 575 576 577

	/* 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);
578
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
579

580
	if (likely(sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
581
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
582
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
583
		opts->tsecr = tp->rx_opt.ts_recent;
584
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
585
	}
586
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
587
		opts->ws = tp->rx_opt.rcv_wscale;
588
		opts->options |= OPTION_WSCALE;
589
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
590
	}
591
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
592
		opts->options |= OPTION_SACK_ADVERTISE;
593
		if (unlikely(!(OPTION_TS & opts->options)))
594
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
595 596
	}

597
	if (fastopen && fastopen->cookie.len >= 0) {
598 599 600 601
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
602 603 604 605 606 607
		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;
608
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
609 610
		}
	}
611 612

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
613 614
}

615
/* Set up TCP options for SYN-ACKs. */
616
static unsigned int tcp_synack_options(struct sock *sk,
A
Adam Langley 已提交
617
				   struct request_sock *req,
618
				   unsigned int mss, struct sk_buff *skb,
A
Adam Langley 已提交
619
				   struct tcp_out_options *opts,
E
Eric Dumazet 已提交
620
				   const struct tcp_md5sig_key *md5,
621
				   struct tcp_fastopen_cookie *foc)
622
{
A
Adam Langley 已提交
623
	struct inet_request_sock *ireq = inet_rsk(req);
624
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
625

626
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
627
	if (md5) {
A
Adam Langley 已提交
628
		opts->options |= OPTION_MD5;
629 630 631 632 633 634 635
		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
636
		ireq->tstamp_ok &= !ireq->sack_ok;
637 638
	}
#endif
A
Adam Langley 已提交
639

640
	/* We always send an MSS option. */
A
Adam Langley 已提交
641
	opts->mss = mss;
642
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
643 644 645

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
646
		opts->options |= OPTION_WSCALE;
647
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
648
	}
E
Eric Dumazet 已提交
649
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
650
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
651
		opts->tsval = tcp_skb_timestamp(skb);
A
Adam Langley 已提交
652
		opts->tsecr = req->ts_recent;
653
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
654 655 656
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
657
		if (unlikely(!ireq->tstamp_ok))
658
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
659
	}
660 661 662 663 664
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
665 666 667 668 669 670 671
		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
672

673
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
674 675
}

676 677 678
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
679
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
680
					struct tcp_out_options *opts,
681 682
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
683
	struct tcp_sock *tp = tcp_sk(sk);
684
	unsigned int size = 0;
685
	unsigned int eff_sacks;
A
Adam Langley 已提交
686

687 688
	opts->options = 0;

A
Adam Langley 已提交
689 690 691 692 693 694 695 696 697 698 699 700
#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
701
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
702 703 704 705
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

706 707
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
708
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
709
		opts->num_sack_blocks =
710
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
711 712 713 714 715 716 717
			      (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
718
}
L
Linus Torvalds 已提交
719

E
Eric Dumazet 已提交
720 721 722 723 724 725 726 727 728

/* 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
729
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
730 731 732 733 734 735 736 737 738 739 740
 *
 * 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);

741 742 743 744 745
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK))
J
John Ogness 已提交
746 747
		tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle,
			       0, GFP_ATOMIC);
748
}
E
Eric Dumazet 已提交
749
/*
S
stephen hemminger 已提交
750
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
751
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
752
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775
 * interrupt us (non NAPI drivers)
 */
static void tcp_tasklet_func(unsigned long data)
{
	struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
	LIST_HEAD(list);
	unsigned long flags;
	struct list_head *q, *n;
	struct tcp_sock *tp;
	struct sock *sk;

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

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

		sk = (struct sock *)tp;
		bh_lock_sock(sk);

		if (!sock_owned_by_user(sk)) {
776
			tcp_tsq_handler(sk);
E
Eric Dumazet 已提交
777 778
		} else {
			/* defer the work to tcp_release_cb() */
779
			set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
E
Eric Dumazet 已提交
780 781 782 783 784 785 786 787
		}
		bh_unlock_sock(sk);

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

788 789
#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) |		\
			  (1UL << TCP_WRITE_TIMER_DEFERRED) |	\
790 791
			  (1UL << TCP_DELACK_TIMER_DEFERRED) |	\
			  (1UL << TCP_MTU_REDUCED_DEFERRED))
E
Eric Dumazet 已提交
792 793 794 795 796 797 798 799 800 801
/**
 * 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)
{
	struct tcp_sock *tp = tcp_sk(sk);
802
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
803

804 805 806 807 808 809 810 811 812 813 814
	/* perform an atomic operation only if at least one flag is set */
	do {
		flags = tp->tsq_flags;
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
	} while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);

	if (flags & (1UL << TCP_TSQ_DEFERRED))
		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);

826
	if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
827
		tcp_write_timer_handler(sk);
828 829 830
		__sock_put(sk);
	}
	if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
831
		tcp_delack_timer_handler(sk);
832 833 834
		__sock_put(sk);
	}
	if (flags & (1UL << TCP_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);
864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
	int wmem;

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

	/* If this softirq is serviced by ksoftirqd, we are likely under stress.
	 * Wait until our queues (qdisc + devices) are drained.
	 * This gives :
	 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
	 * - chance for incoming ACK (processed by another cpu maybe)
	 *   to migrate this flow (skb->ooo_okay will be eventually set)
	 */
	if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
		goto out;
E
Eric Dumazet 已提交
880 881 882 883 884 885 886 887

	if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
	    !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
		unsigned long flags;
		struct tsq_tasklet *tsq;

		/* queue this socket to tasklet queue */
		local_irq_save(flags);
888
		tsq = this_cpu_ptr(&tsq_tasklet);
E
Eric Dumazet 已提交
889 890 891
		list_add(&tp->tsq_node, &tsq->head);
		tasklet_schedule(&tsq->tasklet);
		local_irq_restore(flags);
892
		return;
E
Eric Dumazet 已提交
893
	}
894 895
out:
	sk_free(sk);
E
Eric Dumazet 已提交
896 897
}

L
Linus Torvalds 已提交
898 899 900 901 902 903 904 905 906 907 908
/* 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.
 */
909 910
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
911
{
912 913 914 915
	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
916
	struct tcp_out_options opts;
917
	unsigned int tcp_options_size, tcp_header_size;
918
	struct tcp_md5sig_key *md5;
919 920 921 922 923
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));

924
	if (clone_it) {
925
		skb_mstamp_get(&skb->skb_mstamp);
926

927 928 929 930 931 932 933
		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
934

935 936 937
	inet = inet_sk(sk);
	tp = tcp_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
938
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
939

E
Eric Dumazet 已提交
940
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
941 942 943 944 945
		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);
946

E
Eric Dumazet 已提交
947
	if (tcp_packets_in_flight(tp) == 0)
948
		tcp_ca_event(sk, CA_EVENT_TX_START);
E
Eric Dumazet 已提交
949 950

	/* if no packet is in qdisc/device queue, then allow XPS to select
951 952 953 954 955
	 * 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
956
	 */
957
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
958

959 960
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
961 962 963

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
964
	skb->destructor = skb_is_tcp_pure_ack(skb) ? sock_wfree : tcp_wfree;
965
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
966
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
967 968

	/* Build TCP header and checksum it. */
969
	th = tcp_hdr(skb);
E
Eric Dumazet 已提交
970 971
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
972 973
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
974
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
975
					tcb->tcp_flags);
976

E
Eric Dumazet 已提交
977
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
978 979 980
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
981
		th->window	= htons(min(tp->rcv_wnd, 65535U));
982 983 984 985 986
	} else {
		th->window	= htons(tcp_select_window(sk));
	}
	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
987

I
Ilpo Järvinen 已提交
988
	/* The urg_mode check is necessary during a below snd_una win probe */
989 990 991 992 993
	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)) {
994
			th->urg_ptr = htons(0xFFFF);
995 996
			th->urg = 1;
		}
997
	}
L
Linus Torvalds 已提交
998

999
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
1000
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
E
Eric Dumazet 已提交
1001
	if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
1002
		tcp_ecn_send(sk, skb, tcp_header_size);
L
Linus Torvalds 已提交
1003

1004 1005 1006
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1007
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1008
		tp->af_specific->calc_md5_hash(opts.hash_location,
1009
					       md5, sk, skb);
1010 1011 1012
	}
#endif

1013
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1014

E
Eric Dumazet 已提交
1015
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1016
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1017

1018
	if (skb->len != tcp_header_size)
1019
		tcp_event_data_sent(tp, sk);
L
Linus Torvalds 已提交
1020

1021
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1022 1023
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1024

1025
	tp->segs_out += tcp_skb_pcount(skb);
1026
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1027
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1028
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1029

E
Eric Dumazet 已提交
1030 1031
	/* Our usage of tstamp should remain private */
	skb->tstamp.tv64 = 0;
1032 1033 1034 1035 1036

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

1037
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1038

1039
	if (likely(err <= 0))
1040 1041
		return err;

1042
	tcp_enter_cwr(sk);
1043

1044
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1045 1046
}

1047
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1048 1049 1050 1051 1052 1053 1054 1055 1056 1057
 *
 * 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;
1058
	__skb_header_release(skb);
1059
	tcp_add_write_queue_tail(sk, skb);
1060 1061
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1062 1063
}

1064
/* Initialize TSO segments for a packet. */
1065
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1066
{
1067
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1068 1069 1070
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1071
		tcp_skb_pcount_set(skb, 1);
1072
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1073
	} else {
1074
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1075
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1076 1077 1078
	}
}

I
Ilpo Järvinen 已提交
1079
/* When a modification to fackets out becomes necessary, we need to check
1080
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1081
 */
1082
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1083 1084
				   int decr)
{
1085 1086
	struct tcp_sock *tp = tcp_sk(sk);

1087
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1088 1089
		return;

1090
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1091 1092 1093
		tp->fackets_out -= decr;
}

1094 1095 1096
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1097
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117
{
	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) &&
1118
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1119 1120 1121 1122 1123
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

	if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) &&
	    !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);
	}
}

L
Linus Torvalds 已提交
1139 1140
/* 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
1141
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1142 1143
 * Remember, these are still headerless SKBs at this point.
 */
1144
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1145
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1146 1147 1148
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1149
	int nsize, old_factor;
1150
	int nlen;
1151
	u8 flags;
L
Linus Torvalds 已提交
1152

1153 1154
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1155

L
Linus Torvalds 已提交
1156 1157 1158 1159
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1160
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1161 1162 1163
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1164
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1165
	if (!buff)
L
Linus Torvalds 已提交
1166
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1167

1168 1169
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1170 1171 1172
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1173 1174 1175 1176 1177 1178 1179

	/* 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
1180 1181 1182
	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;
1183
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
1184

1185
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1186
		/* Copy and checksum data tail into the new buffer. */
1187 1188
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1189 1190 1191 1192 1193 1194
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1195
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1196 1197 1198 1199 1200
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1201
	buff->tstamp = skb->tstamp;
1202
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1203

1204 1205
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1206
	/* Fix up tso_factor for both original and new SKB.  */
1207 1208
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1209

1210 1211 1212
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1213
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1214 1215
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1216

1217 1218
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1219 1220 1221
	}

	/* Link BUFF into the send queue. */
1222
	__skb_header_release(buff);
1223
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1224 1225 1226 1227 1228 1229 1230 1231

	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.
 */
1232
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1233
{
1234
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1235 1236
	int i, k, eat;

E
Eric Dumazet 已提交
1237 1238 1239 1240 1241 1242 1243
	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
1244 1245
	eat = len;
	k = 0;
1246 1247 1248
	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
1249 1250

		if (size <= eat) {
1251
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1252
			eat -= size;
L
Linus Torvalds 已提交
1253
		} else {
1254
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1255
			if (eat) {
1256 1257
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1258 1259 1260 1261 1262
				eat = 0;
			}
			k++;
		}
	}
1263
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1264

1265
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1266 1267 1268 1269
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1270
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1271 1272
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1273
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1274 1275
		return -ENOMEM;

E
Eric Dumazet 已提交
1276
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1277 1278

	TCP_SKB_CB(skb)->seq += len;
1279
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1280 1281 1282

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1283
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1284 1285
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1286
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1287
	if (tcp_skb_pcount(skb) > 1)
1288
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1289 1290 1291 1292

	return 0;
}

1293 1294
/* 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
1295
{
1296 1297
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1298 1299 1300 1301 1302 1303 1304
	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);

1305 1306 1307 1308 1309 1310 1311 1312
	/* 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
1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325
	/* 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;
}

1326 1327 1328 1329 1330 1331 1332 1333
/* 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
1334
/* Inverse of above */
1335
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1336
{
1337 1338
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1339 1340 1341 1342 1343 1344 1345
	int mtu;

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

1346 1347 1348 1349 1350 1351 1352
	/* 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
1353 1354 1355
	return mtu;
}

1356
/* MTU probing init per socket */
J
John Heffner 已提交
1357 1358 1359 1360
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
1361
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1362

F
Fan Du 已提交
1363
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1364
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1365
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1366
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1367
	icsk->icsk_mtup.probe_size = 0;
1368 1369
	if (icsk->icsk_mtup.enabled)
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
J
John Heffner 已提交
1370
}
E
Eric Dumazet 已提交
1371
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1372

L
Linus Torvalds 已提交
1373 1374 1375 1376 1377 1378
/* 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
1379
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1380 1381
   It also does not include TCP options.

1382
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1383 1384 1385 1386 1387 1388 1389 1390 1391

   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.

1392 1393
   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
1394 1395 1396 1397
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1398
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1399
	int mss_now;
L
Linus Torvalds 已提交
1400

J
John Heffner 已提交
1401 1402
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1403

J
John Heffner 已提交
1404
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1405
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1406 1407

	/* And store cached results */
1408
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1409 1410
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1411
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1412 1413 1414

	return mss_now;
}
E
Eric Dumazet 已提交
1415
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1416 1417 1418 1419

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1420
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1421
{
1422 1423
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1424
	u32 mss_now;
1425
	unsigned int header_len;
A
Adam Langley 已提交
1426 1427
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1428 1429 1430

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1431 1432
	if (dst) {
		u32 mtu = dst_mtu(dst);
1433
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1434 1435 1436
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1437 1438 1439 1440 1441 1442 1443 1444 1445 1446
	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;
	}
1447

L
Linus Torvalds 已提交
1448 1449 1450
	return mss_now;
}

1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472
/* 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;
}

1473
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1474
{
1475
	struct tcp_sock *tp = tcp_sk(sk);
1476

1477 1478 1479 1480 1481 1482 1483 1484 1485
	/* 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;
	}
1486

1487
	if (tcp_is_cwnd_limited(sk)) {
1488 1489 1490 1491 1492 1493 1494 1495
		/* 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;

1496 1497
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1498 1499 1500 1501
			tcp_cwnd_application_limited(sk);
	}
}

E
Eric Dumazet 已提交
1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515
/* 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
1516
 */
E
Eric Dumazet 已提交
1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531
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,
1532
			    int nonagle)
E
Eric Dumazet 已提交
1533 1534 1535 1536 1537
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now)
{
	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.
	 */
	segs = max_t(u32, bytes / mss_now, sysctl_tcp_min_tso_segs);

	return min_t(u32, segs, sk->sk_gso_max_segs);
}

E
Eric Dumazet 已提交
1559 1560 1561 1562 1563 1564
/* 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)
1565
{
1566
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1567
	u32 partial, needed, window, max_len;
1568

1569
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1570
	max_len = mss_now * max_segs;
1571

1572 1573
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1574

1575 1576
	needed = min(skb->len, window);

1577 1578
	if (max_len <= needed)
		return max_len;
1579

E
Eric Dumazet 已提交
1580 1581 1582 1583 1584
	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
	 */
1585
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1586 1587 1588
		return needed - partial;

	return needed;
1589 1590 1591 1592 1593
}

/* 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.
 */
1594 1595
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1596
{
E
Eric Dumazet 已提交
1597
	u32 in_flight, cwnd, halfcwnd;
1598 1599

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1600 1601
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1602 1603 1604 1605
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1606 1607
	if (in_flight >= cwnd)
		return 0;
1608

E
Eric Dumazet 已提交
1609 1610 1611 1612 1613
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1614 1615
}

1616
/* Initialize TSO state of a skb.
1617
 * This must be invoked the first time we consider transmitting
1618 1619
 * SKB onto the wire.
 */
1620
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1621 1622 1623
{
	int tso_segs = tcp_skb_pcount(skb);

1624
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1625
		tcp_set_skb_tso_segs(skb, mss_now);
1626 1627 1628 1629 1630 1631
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1632
/* Return true if the Nagle test allows this packet to be
1633 1634
 * sent now.
 */
E
Eric Dumazet 已提交
1635 1636
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1637 1638 1639 1640 1641 1642 1643 1644
{
	/* 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
1645
		return true;
1646

Y
Yuchung Cheng 已提交
1647 1648
	/* 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
1649
		return true;
1650

1651
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1652
		return true;
1653

E
Eric Dumazet 已提交
1654
	return false;
1655 1656 1657
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1658 1659 1660
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1661 1662 1663 1664 1665 1666
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1667
	return !after(end_seq, tcp_wnd_end(tp));
1668 1669
}

1670
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1671 1672 1673
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1674
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1675 1676
				 unsigned int cur_mss, int nonagle)
{
1677
	const struct tcp_sock *tp = tcp_sk(sk);
1678 1679
	unsigned int cwnd_quota;

1680
	tcp_init_tso_segs(skb, cur_mss);
1681 1682 1683 1684 1685

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1686
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1687 1688 1689 1690 1691
		cwnd_quota = 0;

	return cwnd_quota;
}

1692
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1693
bool tcp_may_send_now(struct sock *sk)
1694
{
1695
	const struct tcp_sock *tp = tcp_sk(sk);
1696
	struct sk_buff *skb = tcp_send_head(sk);
1697

E
Eric Dumazet 已提交
1698
	return skb &&
I
Ilpo Järvinen 已提交
1699
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1700
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1701
			      tp->nonagle : TCP_NAGLE_PUSH));
1702 1703 1704 1705 1706 1707 1708 1709 1710
}

/* 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).
 */
1711
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1712
			unsigned int mss_now, gfp_t gfp)
1713 1714 1715
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1716
	u8 flags;
1717 1718

	/* All of a TSO frame must be composed of paged data.  */
1719
	if (skb->len != skb->data_len)
1720
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1721

1722
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1723
	if (unlikely(!buff))
1724 1725
		return -ENOMEM;

1726 1727
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1728
	buff->truesize += nlen;
1729 1730 1731 1732 1733 1734 1735 1736
	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
1737 1738 1739
	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;
1740 1741 1742 1743

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

1744
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1745
	skb_split(skb, buff, len);
1746
	tcp_fragment_tstamp(skb, buff);
1747 1748

	/* Fix up tso_factor for both original and new SKB.  */
1749 1750
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1751 1752

	/* Link BUFF into the send queue. */
1753
	__skb_header_release(buff);
1754
	tcp_insert_write_queue_after(skb, buff, sk);
1755 1756 1757 1758 1759 1760 1761 1762 1763

	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.
 */
1764
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1765
				 bool *is_cwnd_limited, u32 max_segs)
1766
{
1767
	const struct inet_connection_sock *icsk = inet_csk(sk);
1768 1769 1770 1771
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct skb_mstamp now;
	struct sk_buff *head;
1772
	int win_divisor;
1773

E
Eric Dumazet 已提交
1774
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1775
		goto send_now;
1776

1777
	if (!((1 << icsk->icsk_ca_state) & (TCPF_CA_Open | TCPF_CA_CWR)))
J
John Heffner 已提交
1778 1779
		goto send_now;

E
Eric Dumazet 已提交
1780 1781 1782 1783
	/* 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
1784
		goto send_now;
1785

1786 1787
	in_flight = tcp_packets_in_flight(tp);

1788
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1789

1790
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1791 1792 1793 1794 1795 1796

	/* 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);

1797
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1798
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1799
		goto send_now;
1800

1801 1802 1803 1804
	/* 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;

1805 1806
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1807 1808 1809 1810 1811
		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.
		 */
1812
		chunk /= win_divisor;
1813
		if (limit >= chunk)
J
John Heffner 已提交
1814
			goto send_now;
1815 1816 1817 1818 1819 1820
	} 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.
		 */
1821
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1822
			goto send_now;
1823 1824
	}

1825 1826 1827 1828 1829 1830 1831
	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
1832
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1833

1834 1835 1836
	if (cong_win < send_win && cong_win < skb->len)
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1837
	return true;
J
John Heffner 已提交
1838 1839

send_now:
E
Eric Dumazet 已提交
1840
	return false;
1841 1842
}

1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867
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
1868
/* Create a new MTU probe if we are ready.
1869 1870 1871 1872
 * 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
1873 1874
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1875 1876
 *         -1 otherwise
 */
J
John Heffner 已提交
1877 1878 1879 1880 1881
static int tcp_mtu_probe(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct sk_buff *skb, *nskb, *next;
1882
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1883 1884
	int len;
	int probe_size;
1885
	int size_needed;
J
John Heffner 已提交
1886 1887
	int copy;
	int mss_now;
1888
	int interval;
J
John Heffner 已提交
1889 1890 1891 1892 1893 1894 1895 1896 1897

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
	 * not SACKing (the variable headers throw things off) */
	if (!icsk->icsk_mtup.enabled ||
	    icsk->icsk_mtup.probe_size ||
	    inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
	    tp->snd_cwnd < 11 ||
1898
	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
J
John Heffner 已提交
1899 1900
		return -1;

1901 1902 1903 1904
	/* 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
1905
	mss_now = tcp_current_mss(sk);
1906 1907
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
1908
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1909
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1910 1911 1912 1913
	/* 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.
	 */
1914
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1915 1916 1917 1918 1919
		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
1920 1921 1922 1923
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1924
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1925 1926
		return -1;

1927 1928
	if (tp->snd_wnd < size_needed)
		return -1;
1929
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1930
		return 0;
J
John Heffner 已提交
1931

1932 1933 1934
	/* 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
1935 1936 1937 1938 1939 1940
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
1941
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1942
	if (!nskb)
J
John Heffner 已提交
1943
		return -1;
1944 1945
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
1946

1947
	skb = tcp_send_head(sk);
J
John Heffner 已提交
1948 1949 1950

	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
1951
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
1952 1953
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
1954
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
1955

1956 1957
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
1958
	len = 0;
1959
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
1960 1961 1962 1963 1964
		copy = min_t(int, skb->len, probe_size - len);
		if (nskb->ip_summed)
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
		else
			nskb->csum = skb_copy_and_csum_bits(skb, 0,
1965 1966
							    skb_put(nskb, copy),
							    copy, nskb->csum);
J
John Heffner 已提交
1967 1968 1969 1970

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
1971
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1972
			tcp_unlink_write_queue(skb, sk);
1973
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
1974
		} else {
E
Eric Dumazet 已提交
1975
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
1976
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
1977 1978
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
1979
				if (skb->ip_summed != CHECKSUM_PARTIAL)
1980 1981
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
1982 1983
			} else {
				__pskb_trim_head(skb, copy);
1984
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
1985 1986 1987 1988 1989
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
1990 1991 1992

		if (len >= probe_size)
			break;
J
John Heffner 已提交
1993
	}
1994
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
1995 1996

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
1997 1998
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
1999 2000
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2001
		 * effectively two packets. */
J
John Heffner 已提交
2002
		tp->snd_cwnd--;
2003
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2004 2005

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2006 2007
		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
2008 2009 2010 2011 2012 2013 2014

		return 1;
	}

	return -1;
}

L
Linus Torvalds 已提交
2015 2016 2017 2018
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2019 2020 2021 2022
 * 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
2023 2024 2025
 * 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
2026 2027
 * 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
2028
 */
E
Eric Dumazet 已提交
2029 2030
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
2031 2032
{
	struct tcp_sock *tp = tcp_sk(sk);
2033
	struct sk_buff *skb;
2034 2035
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2036
	int result;
2037
	bool is_cwnd_limited = false;
E
Eric Dumazet 已提交
2038
	u32 max_segs;
L
Linus Torvalds 已提交
2039

2040
	sent_pkts = 0;
J
John Heffner 已提交
2041

2042 2043 2044 2045
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2046
			return false;
2047 2048 2049
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2050 2051
	}

E
Eric Dumazet 已提交
2052
	max_segs = tcp_tso_autosize(sk, mss_now);
2053
	while ((skb = tcp_send_head(sk))) {
2054 2055
		unsigned int limit;

2056
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2057
		BUG_ON(!tso_segs);
2058

2059
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2060 2061
			/* "skb_mstamp" is used as a start point for the retransmit timer */
			skb_mstamp_get(&skb->skb_mstamp);
2062
			goto repair; /* Skip network transmission */
2063
		}
2064

2065
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2066
		if (!cwnd_quota) {
2067
			is_cwnd_limited = true;
N
Nandita Dukkipati 已提交
2068 2069 2070 2071 2072 2073
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2074 2075 2076 2077

		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
			break;

2078
		if (tso_segs == 1) {
2079 2080 2081 2082 2083
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2084
			if (!push_one &&
E
Eric Dumazet 已提交
2085 2086
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2087 2088
				break;
		}
2089

E
Eric Dumazet 已提交
2090
		limit = mss_now;
2091
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2092 2093 2094 2095 2096 2097 2098 2099 2100 2101
			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;

E
Eric Dumazet 已提交
2102 2103 2104 2105 2106 2107
		/* TCP Small Queues :
		 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
		 * This allows for :
		 *  - better RTT estimation and ACK scheduling
		 *  - faster recovery
		 *  - high rates
2108 2109 2110
		 * Alas, some drivers / subsystems require a fair amount
		 * of queued bytes to ensure line rate.
		 * One example is wifi aggregation (802.11 AMPDU)
E
Eric Dumazet 已提交
2111
		 */
E
Eric Dumazet 已提交
2112 2113
		limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
		limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
E
Eric Dumazet 已提交
2114 2115

		if (atomic_read(&sk->sk_wmem_alloc) > limit) {
E
Eric Dumazet 已提交
2116
			set_bit(TSQ_THROTTLED, &tp->tsq_flags);
J
John Ogness 已提交
2117 2118 2119 2120
			/* It is possible TX completion already happened
			 * before we set TSQ_THROTTLED, so we must
			 * test again the condition.
			 */
2121
			smp_mb__after_atomic();
J
John Ogness 已提交
2122 2123
			if (atomic_read(&sk->sk_wmem_alloc) > limit)
				break;
E
Eric Dumazet 已提交
2124
		}
E
Eric Dumazet 已提交
2125

2126
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2127
			break;
L
Linus Torvalds 已提交
2128

2129
repair:
2130 2131 2132
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2133
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2134

2135
		tcp_minshall_update(tp, mss_now, skb);
2136
		sent_pkts += tcp_skb_pcount(skb);
2137 2138 2139

		if (push_one)
			break;
2140
	}
L
Linus Torvalds 已提交
2141

2142
	if (likely(sent_pkts)) {
2143 2144
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2145 2146 2147 2148

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2149
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2150
		return false;
L
Linus Torvalds 已提交
2151
	}
N
Nandita Dukkipati 已提交
2152 2153 2154 2155 2156 2157 2158 2159
	return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk));
}

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;
2160
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181

	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.
	 */
	if (sk->sk_state == TCP_SYN_RECV)
		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.
	 */
2182
	if (sysctl_tcp_early_retrans < 3 || !tp->srtt_us || !tp->packets_out ||
N
Nandita Dukkipati 已提交
2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212
	    !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
	 * for delayed ack when there's one outstanding packet.
	 */
	timeout = rtt << 1;
	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;
}

2213 2214 2215 2216 2217 2218 2219 2220
/* 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 !
 * Note: This is called from BH context only.
 */
static bool skb_still_in_host_queue(const struct sock *sk,
				    const struct sk_buff *skb)
{
2221
	if (unlikely(skb_fclone_busy(sk, skb))) {
2222 2223 2224 2225 2226 2227 2228
		NET_INC_STATS_BH(sock_net(sk),
				 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
		return true;
	}
	return false;
}

N
Nandita Dukkipati 已提交
2229 2230 2231 2232 2233
/* When probe timeout (PTO) fires, send a new segment if one exists, else
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2234
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2235 2236 2237 2238 2239
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);
	int err = -1;

2240
	if (tcp_send_head(sk)) {
N
Nandita Dukkipati 已提交
2241 2242 2243 2244
		err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
		goto rearm_timer;
	}

N
Nandita Dukkipati 已提交
2245 2246 2247 2248
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2249 2250 2251 2252 2253
	/* Retransmit last segment. */
	skb = tcp_write_queue_tail(sk);
	if (WARN_ON(!skb))
		goto rearm_timer;

2254 2255 2256
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2257 2258 2259 2260 2261
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2262 2263
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2264 2265 2266 2267 2268 2269 2270
			goto rearm_timer;
		skb = tcp_write_queue_tail(sk);
	}

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

P
Per Hurtig 已提交
2271
	err = __tcp_retransmit_skb(sk, skb);
N
Nandita Dukkipati 已提交
2272

N
Nandita Dukkipati 已提交
2273 2274 2275 2276
	/* Record snd_nxt for loss detection. */
	if (likely(!err))
		tp->tlp_high_seq = tp->snd_nxt;

N
Nandita Dukkipati 已提交
2277 2278 2279 2280 2281 2282 2283 2284
rearm_timer:
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto,
				  TCP_RTO_MAX);

	if (likely(!err))
		NET_INC_STATS_BH(sock_net(sk),
				 LINUX_MIB_TCPLOSSPROBES);
L
Linus Torvalds 已提交
2285 2286
}

2287 2288 2289 2290
/* 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.
 */
2291 2292
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2293
{
2294 2295 2296 2297 2298 2299 2300
	/* 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;

2301 2302
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
			   sk_gfp_atomic(sk, GFP_ATOMIC)))
2303
		tcp_check_probe_timer(sk);
2304 2305
}

2306 2307 2308 2309 2310
/* 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)
{
2311
	struct sk_buff *skb = tcp_send_head(sk);
2312 2313 2314

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

2315
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2316 2317
}

L
Linus Torvalds 已提交
2318 2319
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2320
 *
L
Linus Torvalds 已提交
2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338
 * 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.
2339
 *
L
Linus Torvalds 已提交
2340 2341
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2342
 *
L
Linus Torvalds 已提交
2343
 * BSD seems to make the following compromise:
2344
 *
L
Linus Torvalds 已提交
2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371
 *	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)
{
2372
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2373
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2374
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2375 2376 2377 2378 2379
	 * 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
	 */
2380
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2381
	int free_space = tcp_space(sk);
2382 2383
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2384 2385 2386
	int window;

	if (mss > full_space)
2387
		mss = full_space;
L
Linus Torvalds 已提交
2388

2389
	if (free_space < (full_space >> 1)) {
2390
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2391

2392
		if (tcp_under_memory_pressure(sk))
2393 2394
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2395

2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408
		/* 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
2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438
			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)
2439
			window = (free_space / mss) * mss;
2440
		else if (mss == full_space &&
2441
			 free_space > window + (full_space >> 1))
2442
			window = free_space;
L
Linus Torvalds 已提交
2443 2444 2445 2446 2447
	}

	return window;
}

2448 2449
/* Collapses two adjacent SKB's during retransmission. */
static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2450 2451
{
	struct tcp_sock *tp = tcp_sk(sk);
2452
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2453
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2454

2455 2456
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2457

2458
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2459

2460
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2461

2462
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2463

2464 2465
	skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
				  next_skb_size);
L
Linus Torvalds 已提交
2466

2467 2468
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2469

2470 2471
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2472

2473 2474
	/* 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
2475

2476
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2477
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2478 2479 2480 2481 2482 2483 2484

	/* 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;

	/* changed transmit queue under us so clear hints */
2485 2486 2487
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2488

2489 2490
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2491
	sk_wmem_free_skb(sk, next_skb);
L
Linus Torvalds 已提交
2492 2493
}

2494
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2495
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2496 2497
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2498
		return false;
2499 2500
	/* TODO: SACK collapsing could be used to remove this condition */
	if (skb_shinfo(skb)->nr_frags != 0)
E
Eric Dumazet 已提交
2501
		return false;
2502
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2503
		return false;
2504
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2505
		return false;
2506 2507
	/* Some heurestics for collapsing over SACK'd could be invented */
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2508
		return false;
2509

E
Eric Dumazet 已提交
2510
	return true;
2511 2512
}

2513 2514 2515
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2516 2517 2518 2519 2520
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
2521
	bool first = true;
2522 2523 2524

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2525
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2526 2527 2528 2529 2530 2531 2532 2533 2534
		return;

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

		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2535
			first = false;
2536 2537 2538 2539 2540 2541 2542 2543
			continue;
		}

		if (space < 0)
			break;
		/* Punt if not enough space exists in the first SKB for
		 * the data in the second
		 */
2544
		if (skb->len > skb_availroom(to))
2545 2546 2547 2548 2549 2550 2551 2552 2553
			break;

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

		tcp_collapse_retrans(sk, to);
	}
}

L
Linus Torvalds 已提交
2554 2555 2556 2557
/* 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.
 */
2558
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2559 2560
{
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2561
	struct inet_connection_sock *icsk = inet_csk(sk);
2562
	unsigned int cur_mss;
2563
	int err;
L
Linus Torvalds 已提交
2564

J
John Heffner 已提交
2565 2566 2567 2568 2569
	/* Inconslusive MTU probe */
	if (icsk->icsk_mtup.probe_size) {
		icsk->icsk_mtup.probe_size = 0;
	}

L
Linus Torvalds 已提交
2570
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2571
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2572 2573 2574 2575 2576
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
	    min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
		return -EAGAIN;

2577 2578 2579
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2580 2581 2582 2583 2584 2585 2586
	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;
	}

2587 2588 2589
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2590
	cur_mss = tcp_current_mss(sk);
2591

L
Linus Torvalds 已提交
2592 2593 2594 2595 2596
	/* 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.
	 */
2597 2598
	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
2599 2600 2601
		return -EAGAIN;

	if (skb->len > cur_mss) {
2602
		if (tcp_fragment(sk, skb, cur_mss, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2603
			return -ENOMEM; /* We'll try again later. */
2604
	} else {
2605 2606 2607
		int oldpcount = tcp_skb_pcount(skb);

		if (unlikely(oldpcount > 1)) {
2608 2609
			if (skb_unclone(skb, GFP_ATOMIC))
				return -ENOMEM;
2610
			tcp_init_tso_segs(skb, cur_mss);
2611 2612
			tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
		}
L
Linus Torvalds 已提交
2613 2614
	}

2615 2616 2617 2618
	/* 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);

2619
	tcp_retrans_try_collapse(sk, skb, cur_mss);
L
Linus Torvalds 已提交
2620 2621 2622 2623 2624

	/* Make a copy, if the first transmission SKB clone we made
	 * is still in somebody's hands, else make a clone.
	 */

2625 2626 2627 2628 2629 2630
	/* 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)) {
E
Eric Dumazet 已提交
2631 2632
		struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
						   GFP_ATOMIC);
2633 2634
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2635
	} else {
2636
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2637
	}
2638

2639
	if (likely(!err)) {
2640
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2641 2642 2643 2644 2645 2646
		/* Update global TCP statistics. */
		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
		tp->total_retrans++;
	}
2647
	return err;
2648 2649 2650 2651 2652 2653
}

int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
	int err = __tcp_retransmit_skb(sk, skb);
L
Linus Torvalds 已提交
2654 2655 2656

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2657
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2658
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2659 2660
		}
#endif
2661 2662
		if (!tp->retrans_out)
			tp->lost_retrans_low = tp->snd_nxt;
L
Linus Torvalds 已提交
2663 2664 2665 2666 2667
		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
2668
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2669 2670 2671 2672 2673

		/* snd_nxt is stored to detect loss of retransmitted segment,
		 * see tcp_input.c tcp_sacktag_write_queue().
		 */
		TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
2674
	} else if (err != -EBUSY) {
2675
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
L
Linus Torvalds 已提交
2676
	}
Y
Yuchung Cheng 已提交
2677 2678 2679 2680

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2681 2682 2683
	return err;
}

2684 2685 2686
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
E
Eric Dumazet 已提交
2687
static bool tcp_can_forward_retransmit(struct sock *sk)
2688 2689
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2690
	const struct tcp_sock *tp = tcp_sk(sk);
2691 2692 2693

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
E
Eric Dumazet 已提交
2694
		return false;
2695 2696 2697

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
E
Eric Dumazet 已提交
2698
		return false;
2699 2700 2701 2702 2703 2704 2705 2706 2707 2708

	/* 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
2709
		return false;
2710

E
Eric Dumazet 已提交
2711
	return true;
2712 2713
}

L
Linus Torvalds 已提交
2714 2715 2716 2717 2718 2719 2720 2721 2722 2723
/* 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)
{
2724
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2725 2726
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2727
	struct sk_buff *hole = NULL;
2728
	u32 last_lost;
2729
	int mib_idx;
2730
	int fwd_rexmitting = 0;
2731

2732 2733 2734
	if (!tp->packets_out)
		return;

2735 2736 2737
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2738
	if (tp->retransmit_skb_hint) {
2739
		skb = tp->retransmit_skb_hint;
2740 2741 2742 2743
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2744
		skb = tcp_write_queue_head(sk);
2745 2746
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2747

2748 2749
	tcp_for_write_queue_from(skb, sk) {
		__u8 sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
2750

2751 2752 2753
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2754
		if (!hole)
2755
			tp->retransmit_skb_hint = skb;
2756 2757 2758 2759 2760 2761 2762 2763 2764 2765

		/* Assume this retransmit will generate
		 * only one packet for congestion window
		 * calculation purposes.  This works because
		 * tcp_retransmit_skb() will chop up the
		 * packet to be MSS sized and all the
		 * packet counting works out.
		 */
		if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
			return;
L
Linus Torvalds 已提交
2766

2767 2768 2769 2770 2771
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2772

2773
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2774
			tp->retransmit_high = last_lost;
2775 2776 2777
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
2778
			if (hole) {
2779 2780 2781 2782 2783
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2784

2785
		} else if (!(sacked & TCPCB_LOST)) {
2786
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2787 2788
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2789

2790
		} else {
2791
			last_lost = TCP_SKB_CB(skb)->end_seq;
2792 2793 2794 2795 2796
			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
2797

2798
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2799 2800
			continue;

2801
		if (tcp_retransmit_skb(sk, skb))
2802
			return;
2803

2804
		NET_INC_STATS_BH(sock_net(sk), mib_idx);
L
Linus Torvalds 已提交
2805

2806
		if (tcp_in_cwnd_reduction(sk))
2807 2808
			tp->prr_out += tcp_skb_pcount(skb);

2809
		if (skb == tcp_write_queue_head(sk))
2810 2811 2812
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2813 2814 2815
	}
}

2816 2817
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2818 2819
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2820 2821
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2822
 */
2823
void sk_forced_mem_schedule(struct sock *sk, int size)
2824 2825 2826 2827 2828 2829 2830 2831 2832 2833
{
	int amt, status;

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
	sk_memory_allocated_add(sk, amt, &status);
}

2834 2835
/* 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
2836 2837 2838
 */
void tcp_send_fin(struct sock *sk)
{
2839
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2840 2841
	struct tcp_sock *tp = tcp_sk(sk);

2842 2843 2844 2845
	/* 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
2846
	 */
2847
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
2848 2849 2850
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
2851
		tp->write_seq++;
2852 2853 2854 2855 2856 2857 2858 2859 2860 2861
		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
2862
	} else {
2863 2864 2865 2866 2867
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
2868
		}
2869
		skb_reserve(skb, MAX_TCP_HEADER);
2870
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
2871
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2872
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
2873
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
2874 2875
		tcp_queue_skb(sk, skb);
	}
2876
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
2877 2878 2879 2880 2881
}

/* 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
2882
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2883
 */
A
Al Viro 已提交
2884
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
2885 2886 2887 2888 2889 2890
{
	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
2891
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
2892 2893 2894 2895 2896
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
2897
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
2898
			     TCPHDR_ACK | TCPHDR_RST);
L
Linus Torvalds 已提交
2899
	/* Send it off. */
2900
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
2901
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2902

P
Pavel Emelyanov 已提交
2903
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
2904 2905
}

2906 2907
/* 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
2908 2909 2910 2911 2912 2913
 * 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)
{
2914
	struct sk_buff *skb;
L
Linus Torvalds 已提交
2915

2916
	skb = tcp_write_queue_head(sk);
2917
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2918
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
2919 2920
		return -EFAULT;
	}
E
Eric Dumazet 已提交
2921
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
2922 2923
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2924
			if (!nskb)
L
Linus Torvalds 已提交
2925
				return -ENOMEM;
2926
			tcp_unlink_write_queue(skb, sk);
2927
			__skb_header_release(nskb);
2928
			__tcp_add_write_queue_head(sk, nskb);
2929 2930 2931
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
2932 2933 2934
			skb = nskb;
		}

E
Eric Dumazet 已提交
2935
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2936
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
2937
	}
2938
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
2939 2940
}

2941 2942 2943 2944 2945 2946 2947 2948 2949
/**
 * 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.
 */
2950
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2951
				struct request_sock *req,
2952
				struct tcp_fastopen_cookie *foc)
L
Linus Torvalds 已提交
2953
{
2954
	struct tcp_out_options opts;
2955
	struct inet_request_sock *ireq = inet_rsk(req);
L
Linus Torvalds 已提交
2956 2957 2958
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcphdr *th;
	struct sk_buff *skb;
E
Eric Dumazet 已提交
2959
	struct tcp_md5sig_key *md5 = NULL;
2960
	int tcp_header_size;
2961
	int mss;
L
Linus Torvalds 已提交
2962

2963
	skb = sock_wmalloc(sk, MAX_TCP_HEADER, 1, GFP_ATOMIC);
2964 2965
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
2966
		return NULL;
2967
	}
L
Linus Torvalds 已提交
2968 2969 2970
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

2971
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
2972

2973
	mss = dst_metric_advmss(dst);
2974 2975 2976
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
		mss = tp->rx_opt.user_mss;

A
Adam Langley 已提交
2977
	memset(&opts, 0, sizeof(opts));
2978 2979
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
2980
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
2981 2982
	else
#endif
E
Eric Dumazet 已提交
2983
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
2984 2985 2986

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
2987
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
2988 2989
#endif
	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
C
Christoph Paasch 已提交
2990
					     foc) + sizeof(*th);
2991

2992 2993
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
2994

2995
	th = tcp_hdr(skb);
L
Linus Torvalds 已提交
2996 2997 2998
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
2999
	tcp_ecn_make_synack(req, th, sk);
E
Eric Dumazet 已提交
3000
	th->source = htons(ireq->ir_num);
3001
	th->dest = ireq->ir_rmt_port;
3002 3003 3004 3005
	/* 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
3006
			     TCPHDR_SYN | TCPHDR_ACK);
3007

L
Linus Torvalds 已提交
3008
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3009 3010
	/* 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
3011 3012

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3013
	th->window = htons(min(req->rcv_wnd, 65535U));
3014
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
L
Linus Torvalds 已提交
3015
	th->doff = (tcp_header_size >> 2);
3016
	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
3017 3018 3019

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3020
	if (md5)
3021
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3022
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3023
	rcu_read_unlock();
3024 3025
#endif

3026 3027
	/* Do not fool tcpdump (if any), clean our debris */
	skb->tstamp.tv64 = 0;
L
Linus Torvalds 已提交
3028 3029
	return skb;
}
E
Eric Dumazet 已提交
3030
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3031

3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050
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();
}

3051
/* Do all connect socket setups that can be done AF independent. */
3052
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3053
{
3054
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3055 3056 3057 3058 3059 3060 3061
	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) +
3062
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3063

3064
#ifdef CONFIG_TCP_MD5SIG
3065
	if (tp->af_specific->md5_lookup(sk, sk))
3066 3067 3068
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3069 3070 3071 3072
	/* 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
3073
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3074 3075
	tcp_sync_mss(sk, dst_mtu(dst));

3076 3077
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3078 3079
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3080
	tp->advmss = dst_metric_advmss(dst);
3081 3082 3083
	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
3084 3085
	tcp_initialize_rcv_mss(sk);

3086 3087 3088 3089 3090
	/* 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
3091 3092 3093 3094
	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,
3095
				  sysctl_tcp_window_scaling,
3096 3097
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3098 3099 3100 3101 3102 3103 3104

	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;
3105
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3106 3107
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3108
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3109
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3110 3111 3112

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3113 3114
	else
		tp->rcv_tstamp = tcp_time_stamp;
P
Pavel Emelyanov 已提交
3115 3116
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3117

3118 3119
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3120 3121 3122
	tcp_clear_retrans(tp);
}

3123 3124 3125 3126 3127 3128
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;
3129
	__skb_header_release(skb);
3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147
	__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;
3148
	int syn_loss = 0, space, err = 0, copied;
3149
	unsigned long last_syn_loss = 0;
3150
	struct sk_buff *syn_data;
3151

3152
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3153 3154 3155 3156 3157 3158 3159 3160
	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;
	}
3161

3162 3163 3164
	if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
		fo->cookie.len = -1;
	else if (fo->cookie.len <= 0)
3165 3166 3167 3168 3169 3170 3171 3172
		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;
3173
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3174 3175
		MAX_TCP_OPTION_SPACE;

3176 3177 3178 3179 3180
	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));

3181
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3182
	if (!syn_data)
3183
		goto fallback;
3184 3185
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3186 3187 3188
	copied = copy_from_iter(skb_put(syn_data, space), space,
				&fo->data->msg_iter);
	if (unlikely(!copied)) {
3189 3190 3191
		kfree_skb(syn_data);
		goto fallback;
	}
3192 3193 3194 3195
	if (copied != space) {
		skb_trim(syn_data, copied);
		space = copied;
	}
3196

3197 3198 3199 3200
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3201

3202
	tcp_connect_queue_skb(sk, syn_data);
3203

3204
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3205

3206
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3207

3208 3209 3210 3211 3212 3213 3214 3215
	/* 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) {
3216
		tp->syn_data = (fo->copied > 0);
3217
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232
		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;
}

3233
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3234 3235 3236 3237
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3238
	int err;
L
Linus Torvalds 已提交
3239 3240 3241

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3242 3243 3244 3245 3246
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3247
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3248
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3249 3250
		return -ENOBUFS;

C
Changli Gao 已提交
3251
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
E
Eric Dumazet 已提交
3252
	tp->retrans_stamp = tcp_time_stamp;
3253
	tcp_connect_queue_skb(sk, buff);
3254
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3255

3256 3257 3258
	/* 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);
3259 3260
	if (err == -ECONNREFUSED)
		return err;
3261 3262 3263 3264 3265 3266

	/* 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
3267
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3268 3269

	/* Timer for repeating the SYN until an answer. */
3270 3271
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3272 3273
	return 0;
}
E
Eric Dumazet 已提交
3274
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3275 3276 3277 3278 3279 3280 3281

/* 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)
{
3282 3283
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3284 3285
	unsigned long timeout;

3286 3287
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3288
	if (ato > TCP_DELACK_MIN) {
3289
		const struct tcp_sock *tp = tcp_sk(sk);
3290
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3291

3292 3293
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3294 3295 3296 3297 3298
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3299
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3300 3301
		 * directly.
		 */
3302 3303 3304
		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
3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316

			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. */
3317
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3318 3319 3320
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3321 3322
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3323 3324 3325 3326
			tcp_send_ack(sk);
			return;
		}

3327 3328
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3329
	}
3330 3331 3332
	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
3333 3334 3335 3336 3337
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3338
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3339

3340 3341 3342
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3343

3344 3345
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3346 3347 3348 3349
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3350
	buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3351
	if (!buff) {
3352 3353 3354 3355 3356
		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
3357
	}
3358 3359 3360

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3361
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3362

E
Eric Dumazet 已提交
3363 3364 3365 3366 3367 3368 3369 3370
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 * We also avoid tcp_wfree() overhead (cache line miss accessing
	 * tp->tsq_flags) by using regular sock_wfree()
	 */
	skb_set_tcp_pure_ack(buff);

3371
	/* Send it off, this clears delayed acks for us. */
E
Eric Dumazet 已提交
3372
	skb_mstamp_get(&buff->skb_mstamp);
3373
	tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
L
Linus Torvalds 已提交
3374
}
3375
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387

/* 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.
 */
3388
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3389 3390 3391 3392 3393
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3394
	skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3395
	if (!skb)
L
Linus Torvalds 已提交
3396 3397 3398 3399 3400 3401 3402 3403
		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
3404
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
E
Eric Dumazet 已提交
3405
	skb_mstamp_get(&skb->skb_mstamp);
3406
	NET_INC_STATS_BH(sock_net(sk), mib);
3407
	return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
L
Linus Torvalds 已提交
3408 3409
}

P
Pavel Emelyanov 已提交
3410 3411 3412 3413
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;
3414
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3415 3416 3417
	}
}

3418
/* Initiate keepalive or window probe from timer. */
3419
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3420
{
3421 3422
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3423

3424 3425 3426
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3427 3428
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3429
		int err;
I
Ilpo Järvinen 已提交
3430
		unsigned int mss = tcp_current_mss(sk);
3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442
		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
3443
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3444
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3445 3446
				return -1;
		} else if (!tcp_skb_pcount(skb))
3447
			tcp_set_skb_tso_segs(skb, mss);
3448

E
Eric Dumazet 已提交
3449
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3450 3451 3452 3453 3454
		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
3455
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3456 3457
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3458 3459 3460 3461 3462 3463 3464 3465
	}
}

/* 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)
{
3466
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3467
	struct tcp_sock *tp = tcp_sk(sk);
3468
	unsigned long probe_max;
L
Linus Torvalds 已提交
3469 3470
	int err;

3471
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3472

3473
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3474
		/* Cancel probe timer, if it is not required. */
3475
		icsk->icsk_probes_out = 0;
3476
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3477 3478 3479 3480
		return;
	}

	if (err <= 0) {
3481 3482
		if (icsk->icsk_backoff < sysctl_tcp_retries2)
			icsk->icsk_backoff++;
3483
		icsk->icsk_probes_out++;
3484
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3485 3486
	} else {
		/* If packet was not sent due to local congestion,
3487
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3488 3489 3490 3491
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3492 3493
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3494
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3495
	}
3496
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3497
				  tcp_probe0_when(sk, probe_max),
3498
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3499
}
3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514

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

	res = af_ops->send_synack(sk, NULL, &fl, req, 0, NULL);
	if (!res) {
		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);