tcp_output.c 104.5 KB
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/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
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 * Authors:	Ross Biro
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 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

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

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#define pr_fmt(fmt) "TCP: " fmt

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#include <net/tcp.h>

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

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

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

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

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

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

	return (__u16)mss;
}

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

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

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

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

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	tp->lsndtime = now;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	if (unlikely(opts->num_sack_blocks)) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ?
			tp->duplicate_sack : tp->selective_acks;
S
Stephen Hemminger 已提交
496 497 498 499 500
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
501
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
502
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
503

A
Adam Langley 已提交
504 505
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
506 507 508
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
509

510
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
511
	}
Y
Yuchung Cheng 已提交
512 513 514

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
515 516 517 518 519 520 521 522 523 524 525 526 527
		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
528

529 530 531 532
		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
533
		}
534
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
535
	}
A
Adam Langley 已提交
536 537
}

538 539 540
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
541
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
542
				struct tcp_out_options *opts,
543 544
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
545
	struct tcp_sock *tp = tcp_sk(sk);
546
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
547
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
548

549
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
550 551 552
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
553
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
554
	}
A
Adam Langley 已提交
555 556
#else
	*md5 = NULL;
557
#endif
A
Adam Langley 已提交
558 559 560 561 562 563 564 565 566 567 568

	/* 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);
569
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
570

571
	if (likely(sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
572
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
573
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
574
		opts->tsecr = tp->rx_opt.ts_recent;
575
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
576
	}
577
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
578
		opts->ws = tp->rx_opt.rcv_wscale;
579
		opts->options |= OPTION_WSCALE;
580
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
581
	}
582
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
583
		opts->options |= OPTION_SACK_ADVERTISE;
584
		if (unlikely(!(OPTION_TS & opts->options)))
585
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
586 587
	}

588
	if (fastopen && fastopen->cookie.len >= 0) {
589 590 591 592
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
593 594 595 596 597 598
		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;
599
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
600 601
		}
	}
602 603

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
604 605
}

606
/* Set up TCP options for SYN-ACKs. */
607 608 609 610 611
static unsigned int tcp_synack_options(struct request_sock *req,
				       unsigned int mss, struct sk_buff *skb,
				       struct tcp_out_options *opts,
				       const struct tcp_md5sig_key *md5,
				       struct tcp_fastopen_cookie *foc)
612
{
A
Adam Langley 已提交
613
	struct inet_request_sock *ireq = inet_rsk(req);
614
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
615

616
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
617
	if (md5) {
A
Adam Langley 已提交
618
		opts->options |= OPTION_MD5;
619 620 621 622 623 624 625
		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
626
		ireq->tstamp_ok &= !ireq->sack_ok;
627 628
	}
#endif
A
Adam Langley 已提交
629

630
	/* We always send an MSS option. */
A
Adam Langley 已提交
631
	opts->mss = mss;
632
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
633 634 635

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
636
		opts->options |= OPTION_WSCALE;
637
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
638
	}
E
Eric Dumazet 已提交
639
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
640
		opts->options |= OPTION_TS;
641
		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
A
Adam Langley 已提交
642
		opts->tsecr = req->ts_recent;
643
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
644 645 646
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
647
		if (unlikely(!ireq->tstamp_ok))
648
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
649
	}
650 651 652 653 654
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
655 656 657 658 659 660 661
		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
662

663
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
664 665
}

666 667 668
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
669
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
670
					struct tcp_out_options *opts,
671 672
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
673
	struct tcp_sock *tp = tcp_sk(sk);
674
	unsigned int size = 0;
675
	unsigned int eff_sacks;
A
Adam Langley 已提交
676

677 678
	opts->options = 0;

A
Adam Langley 已提交
679 680 681 682 683 684 685 686 687 688 689 690
#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
691
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
692 693 694 695
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

696 697
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
698
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
699
		opts->num_sack_blocks =
700
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
701 702 703 704 705 706 707
			      (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
708
}
L
Linus Torvalds 已提交
709

E
Eric Dumazet 已提交
710 711 712 713 714 715 716 717 718

/* 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
719
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
720 721 722 723 724 725 726 727 728 729 730
 *
 * 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);

731 732 733 734
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
735 736 737 738 739 740 741 742
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK)) {
		struct tcp_sock *tp = tcp_sk(sk);

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

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

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

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

		sk = (struct sock *)tp;
770
		smp_mb__before_atomic();
771 772
		clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);

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

		sk_free(sk);
	}
}

E
Eric Dumazet 已提交
787 788 789 790
#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED |		\
			  TCPF_WRITE_TIMER_DEFERRED |	\
			  TCPF_DELACK_TIMER_DEFERRED |	\
			  TCPF_MTU_REDUCED_DEFERRED)
E
Eric Dumazet 已提交
791 792 793 794 795 796 797 798 799
/**
 * 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)
{
800
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
801

802 803
	/* perform an atomic operation only if at least one flag is set */
	do {
804
		flags = sk->sk_tsq_flags;
805 806 807
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
808
	} while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
809

E
Eric Dumazet 已提交
810
	if (flags & TCPF_TSQ_DEFERRED)
811 812
		tcp_tsq_handler(sk);

813 814 815 816 817 818 819 820 821 822 823
	/* Here begins the tricky part :
	 * We are called from release_sock() with :
	 * 1) BH disabled
	 * 2) sk_lock.slock spinlock held
	 * 3) socket owned by us (sk->sk_lock.owned == 1)
	 *
	 * But following code is meant to be called from BH handlers,
	 * so we should keep BH disabled, but early release socket ownership
	 */
	sock_release_ownership(sk);

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

880
	for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
E
Eric Dumazet 已提交
881
		struct tsq_tasklet *tsq;
882
		bool empty;
E
Eric Dumazet 已提交
883

884 885 886
		if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
			goto out;

887
		nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
888
		nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
889 890 891
		if (nval != oval)
			continue;

E
Eric Dumazet 已提交
892 893
		/* queue this socket to tasklet queue */
		local_irq_save(flags);
894
		tsq = this_cpu_ptr(&tsq_tasklet);
895
		empty = list_empty(&tsq->head);
E
Eric Dumazet 已提交
896
		list_add(&tp->tsq_node, &tsq->head);
897 898
		if (empty)
			tasklet_schedule(&tsq->tasklet);
E
Eric Dumazet 已提交
899
		local_irq_restore(flags);
900
		return;
E
Eric Dumazet 已提交
901
	}
902 903
out:
	sk_free(sk);
E
Eric Dumazet 已提交
904 905
}

L
Linus Torvalds 已提交
906 907 908 909 910 911 912 913 914 915 916
/* 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.
 */
917 918
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
919
{
920 921 922 923
	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
924
	struct tcp_out_options opts;
925
	unsigned int tcp_options_size, tcp_header_size;
926
	struct tcp_md5sig_key *md5;
927 928 929 930
	struct tcphdr *th;
	int err;

	BUG_ON(!skb || !tcp_skb_pcount(skb));
931
	tp = tcp_sk(sk);
932

933
	if (clone_it) {
934
		skb_mstamp_get(&skb->skb_mstamp);
935 936
		TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
			- tp->snd_una;
937
		tcp_rate_skb_sent(sk, skb);
938

939 940 941 942 943 944 945
		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
946

947 948
	inet = inet_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
949
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
950

E
Eric Dumazet 已提交
951
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
952 953 954 955 956
		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);
957

E
Eric Dumazet 已提交
958
	/* if no packet is in qdisc/device queue, then allow XPS to select
959 960 961 962 963
	 * 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
964
	 */
965
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
966

967 968
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
969 970 971

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
972
	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
973
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
974
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
975 976

	/* Build TCP header and checksum it. */
977
	th = (struct tcphdr *)skb->data;
E
Eric Dumazet 已提交
978 979
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
980 981
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
982
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
983
					tcb->tcp_flags);
984 985 986

	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;
1001 1002 1003 1004 1005 1006 1007 1008 1009
	if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
		th->window      = htons(tcp_select_window(sk));
		tcp_ecn_send(sk, skb, th, tcp_header_size);
	} else {
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
		th->window	= htons(min(tp->rcv_wnd, 65535U));
	}
1010 1011 1012
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
1013
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1014
		tp->af_specific->calc_md5_hash(opts.hash_location,
1015
					       md5, sk, skb);
1016 1017 1018
	}
#endif

1019
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1020

E
Eric Dumazet 已提交
1021
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1022
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1023

1024
	if (skb->len != tcp_header_size) {
1025
		tcp_event_data_sent(tp, sk);
1026 1027
		tp->data_segs_out += tcp_skb_pcount(skb);
	}
L
Linus Torvalds 已提交
1028

1029
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1030 1031
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1032

1033
	tp->segs_out += tcp_skb_pcount(skb);
1034
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1035
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1036
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1037

E
Eric Dumazet 已提交
1038
	/* Our usage of tstamp should remain private */
T
Thomas Gleixner 已提交
1039
	skb->tstamp = 0;
1040 1041 1042 1043 1044

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

1045
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1046

1047
	if (likely(err <= 0))
1048 1049
		return err;

1050
	tcp_enter_cwr(sk);
1051

1052
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1053 1054
}

1055
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
 *
 * 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;
1066
	__skb_header_release(skb);
1067
	tcp_add_write_queue_tail(sk, skb);
1068 1069
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1070 1071
}

1072
/* Initialize TSO segments for a packet. */
1073
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1074
{
1075
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1076 1077 1078
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1079
		tcp_skb_pcount_set(skb, 1);
1080
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1081
	} else {
1082
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1083
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1084 1085 1086
	}
}

I
Ilpo Järvinen 已提交
1087
/* When a modification to fackets out becomes necessary, we need to check
1088
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1089
 */
1090
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1091 1092
				   int decr)
{
1093 1094
	struct tcp_sock *tp = tcp_sk(sk);

1095
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1096 1097
		return;

1098
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1099 1100 1101
		tp->fackets_out -= decr;
}

1102 1103 1104
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1105
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
{
	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) &&
1126
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1127 1128 1129 1130 1131
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1132 1133 1134 1135 1136 1137
static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
{
	return TCP_SKB_CB(skb)->txstamp_ack ||
		(skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
}

1138 1139 1140 1141
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

1142
	if (unlikely(tcp_has_tx_tstamp(skb)) &&
1143 1144 1145 1146 1147 1148 1149
	    !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);
1150 1151
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1152 1153 1154
	}
}

1155 1156 1157 1158 1159 1160
static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
{
	TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
	TCP_SKB_CB(skb)->eor = 0;
}

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

1175 1176
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1177

L
Linus Torvalds 已提交
1178 1179 1180 1181
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1182
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1183 1184 1185
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1186
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1187
	if (!buff)
L
Linus Torvalds 已提交
1188
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1189

1190 1191
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1192 1193 1194
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1195 1196 1197 1198 1199 1200 1201

	/* 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
1202 1203 1204
	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;
1205
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1206
	tcp_skb_fragment_eor(skb, buff);
L
Linus Torvalds 已提交
1207

1208
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1209
		/* Copy and checksum data tail into the new buffer. */
1210 1211
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1212 1213 1214 1215 1216 1217
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1218
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1219 1220 1221 1222 1223
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1224
	buff->tstamp = skb->tstamp;
1225
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1226

1227 1228
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1229
	/* Fix up tso_factor for both original and new SKB.  */
1230 1231
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1232

1233 1234 1235
	/* Update delivered info for the new segment */
	TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;

1236 1237 1238
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1239
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1240 1241
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1242

1243 1244
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1245 1246 1247
	}

	/* Link BUFF into the send queue. */
1248
	__skb_header_release(buff);
1249
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1250 1251 1252 1253 1254 1255 1256 1257

	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.
 */
1258
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1259
{
1260
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1261 1262
	int i, k, eat;

E
Eric Dumazet 已提交
1263 1264 1265 1266 1267 1268 1269
	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
1270 1271
	eat = len;
	k = 0;
1272 1273 1274
	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
1275 1276

		if (size <= eat) {
1277
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1278
			eat -= size;
L
Linus Torvalds 已提交
1279
		} else {
1280
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1281
			if (eat) {
1282 1283
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1284 1285 1286 1287 1288
				eat = 0;
			}
			k++;
		}
	}
1289
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1290

1291
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1292 1293 1294 1295
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1296
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1297 1298
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1299
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1300 1301
		return -ENOMEM;

E
Eric Dumazet 已提交
1302
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1303 1304

	TCP_SKB_CB(skb)->seq += len;
1305
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1306 1307 1308

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1309
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1310 1311
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1312
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1313
	if (tcp_skb_pcount(skb) > 1)
1314
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1315 1316 1317 1318

	return 0;
}

1319 1320
/* 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
1321
{
1322 1323
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1324 1325 1326 1327 1328 1329 1330
	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);

1331 1332 1333 1334 1335 1336 1337 1338
	/* 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
1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351
	/* 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;
}

1352 1353 1354 1355 1356 1357 1358 1359
/* 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
1360
/* Inverse of above */
1361
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1362
{
1363 1364
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1365 1366 1367 1368 1369 1370 1371
	int mtu;

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

1372 1373 1374 1375 1376 1377 1378
	/* 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
1379 1380
	return mtu;
}
1381
EXPORT_SYMBOL(tcp_mss_to_mtu);
J
John Heffner 已提交
1382

1383
/* MTU probing init per socket */
J
John Heffner 已提交
1384 1385 1386 1387
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
1388
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1389

F
Fan Du 已提交
1390
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1391
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1392
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1393
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1394
	icsk->icsk_mtup.probe_size = 0;
1395 1396
	if (icsk->icsk_mtup.enabled)
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
J
John Heffner 已提交
1397
}
E
Eric Dumazet 已提交
1398
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1399

L
Linus Torvalds 已提交
1400 1401 1402 1403 1404 1405
/* 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
1406
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1407 1408
   It also does not include TCP options.

1409
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1410 1411 1412 1413 1414 1415 1416 1417 1418

   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.

1419 1420
   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
1421 1422 1423 1424
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1425
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1426
	int mss_now;
L
Linus Torvalds 已提交
1427

J
John Heffner 已提交
1428 1429
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1430

J
John Heffner 已提交
1431
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1432
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1433 1434

	/* And store cached results */
1435
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1436 1437
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1438
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1439 1440 1441

	return mss_now;
}
E
Eric Dumazet 已提交
1442
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1443 1444 1445 1446

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1447
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1448
{
1449 1450
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1451
	u32 mss_now;
1452
	unsigned int header_len;
A
Adam Langley 已提交
1453 1454
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1455 1456 1457

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1458 1459
	if (dst) {
		u32 mtu = dst_mtu(dst);
1460
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1461 1462 1463
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1464 1465 1466 1467 1468 1469 1470 1471 1472 1473
	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;
	}
1474

L
Linus Torvalds 已提交
1475 1476 1477
	return mss_now;
}

1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499
/* 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;
}

1500
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1501
{
1502
	struct tcp_sock *tp = tcp_sk(sk);
1503

1504 1505 1506 1507 1508 1509 1510 1511 1512
	/* 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;
	}
1513

1514
	if (tcp_is_cwnd_limited(sk)) {
1515 1516 1517 1518 1519 1520 1521 1522
		/* 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;

1523 1524
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1525
			tcp_cwnd_application_limited(sk);
1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537

		/* The following conditions together indicate the starvation
		 * is caused by insufficient sender buffer:
		 * 1) just sent some data (see tcp_write_xmit)
		 * 2) not cwnd limited (this else condition)
		 * 3) no more data to send (null tcp_send_head )
		 * 4) application is hitting buffer limit (SOCK_NOSPACE)
		 */
		if (!tcp_send_head(sk) && sk->sk_socket &&
		    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
		    (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
			tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1538 1539 1540
	}
}

E
Eric Dumazet 已提交
1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554
/* 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
1555
 */
E
Eric Dumazet 已提交
1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570
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,
1571
			    int nonagle)
E
Eric Dumazet 已提交
1572 1573 1574 1575 1576
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1577 1578 1579 1580

/* Return how many segs we'd like on a TSO packet,
 * to send one TSO packet per ms
 */
1581 1582
u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
		     int min_tso_segs)
E
Eric Dumazet 已提交
1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593
{
	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.
	 */
1594
	segs = max_t(u32, bytes / mss_now, min_tso_segs);
E
Eric Dumazet 已提交
1595 1596 1597

	return min_t(u32, segs, sk->sk_gso_max_segs);
}
1598
EXPORT_SYMBOL(tcp_tso_autosize);
E
Eric Dumazet 已提交
1599

1600 1601 1602 1603 1604 1605 1606 1607
/* Return the number of segments we want in the skb we are transmitting.
 * See if congestion control module wants to decide; otherwise, autosize.
 */
static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
{
	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
	u32 tso_segs = ca_ops->tso_segs_goal ? ca_ops->tso_segs_goal(sk) : 0;

1608 1609
	return tso_segs ? :
		tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
1610 1611
}

E
Eric Dumazet 已提交
1612 1613 1614 1615 1616 1617
/* 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)
1618
{
1619
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1620
	u32 partial, needed, window, max_len;
1621

1622
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1623
	max_len = mss_now * max_segs;
1624

1625 1626
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1627

1628 1629
	needed = min(skb->len, window);

1630 1631
	if (max_len <= needed)
		return max_len;
1632

E
Eric Dumazet 已提交
1633 1634 1635 1636 1637
	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
	 */
1638
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1639 1640 1641
		return needed - partial;

	return needed;
1642 1643 1644 1645 1646
}

/* 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.
 */
1647 1648
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1649
{
E
Eric Dumazet 已提交
1650
	u32 in_flight, cwnd, halfcwnd;
1651 1652

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1653 1654
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1655 1656 1657 1658
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1659 1660
	if (in_flight >= cwnd)
		return 0;
1661

E
Eric Dumazet 已提交
1662 1663 1664 1665 1666
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1667 1668
}

1669
/* Initialize TSO state of a skb.
1670
 * This must be invoked the first time we consider transmitting
1671 1672
 * SKB onto the wire.
 */
1673
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1674 1675 1676
{
	int tso_segs = tcp_skb_pcount(skb);

1677
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1678
		tcp_set_skb_tso_segs(skb, mss_now);
1679 1680 1681 1682 1683 1684
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1685
/* Return true if the Nagle test allows this packet to be
1686 1687
 * sent now.
 */
E
Eric Dumazet 已提交
1688 1689
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1690 1691 1692 1693 1694 1695 1696 1697
{
	/* 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
1698
		return true;
1699

Y
Yuchung Cheng 已提交
1700 1701
	/* 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
1702
		return true;
1703

1704
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1705
		return true;
1706

E
Eric Dumazet 已提交
1707
	return false;
1708 1709 1710
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1711 1712 1713
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1714 1715 1716 1717 1718 1719
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1720
	return !after(end_seq, tcp_wnd_end(tp));
1721 1722
}

1723
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1724 1725 1726
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1727
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1728 1729
				 unsigned int cur_mss, int nonagle)
{
1730
	const struct tcp_sock *tp = tcp_sk(sk);
1731 1732
	unsigned int cwnd_quota;

1733
	tcp_init_tso_segs(skb, cur_mss);
1734 1735 1736 1737 1738

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1739
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1740 1741 1742 1743 1744
		cwnd_quota = 0;

	return cwnd_quota;
}

1745
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1746
bool tcp_may_send_now(struct sock *sk)
1747
{
1748
	const struct tcp_sock *tp = tcp_sk(sk);
1749
	struct sk_buff *skb = tcp_send_head(sk);
1750

E
Eric Dumazet 已提交
1751
	return skb &&
I
Ilpo Järvinen 已提交
1752
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1753
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1754
			      tp->nonagle : TCP_NAGLE_PUSH));
1755 1756 1757 1758 1759 1760 1761 1762 1763
}

/* 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).
 */
1764
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1765
			unsigned int mss_now, gfp_t gfp)
1766 1767 1768
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1769
	u8 flags;
1770 1771

	/* All of a TSO frame must be composed of paged data.  */
1772
	if (skb->len != skb->data_len)
1773
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1774

1775
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1776
	if (unlikely(!buff))
1777 1778
		return -ENOMEM;

1779 1780
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1781
	buff->truesize += nlen;
1782 1783 1784 1785 1786 1787 1788 1789
	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
1790 1791 1792
	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;
1793 1794 1795 1796

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

1797 1798
	tcp_skb_fragment_eor(skb, buff);

1799
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1800
	skb_split(skb, buff, len);
1801
	tcp_fragment_tstamp(skb, buff);
1802 1803

	/* Fix up tso_factor for both original and new SKB.  */
1804 1805
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1806 1807

	/* Link BUFF into the send queue. */
1808
	__skb_header_release(buff);
1809
	tcp_insert_write_queue_after(skb, buff, sk);
1810 1811 1812 1813 1814 1815 1816 1817 1818

	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.
 */
1819
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1820
				 bool *is_cwnd_limited, u32 max_segs)
1821
{
1822
	const struct inet_connection_sock *icsk = inet_csk(sk);
1823 1824 1825 1826
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct skb_mstamp now;
	struct sk_buff *head;
1827
	int win_divisor;
1828

E
Eric Dumazet 已提交
1829
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1830
		goto send_now;
1831

1832
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1833 1834
		goto send_now;

E
Eric Dumazet 已提交
1835 1836 1837 1838
	/* 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
1839
		goto send_now;
1840

1841 1842
	in_flight = tcp_packets_in_flight(tp);

1843
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1844

1845
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1846 1847 1848 1849 1850 1851

	/* 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);

1852
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1853
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1854
		goto send_now;
1855

1856 1857 1858 1859
	/* 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;

1860 1861
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1862 1863 1864 1865 1866
		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.
		 */
1867
		chunk /= win_divisor;
1868
		if (limit >= chunk)
J
John Heffner 已提交
1869
			goto send_now;
1870 1871 1872 1873 1874 1875
	} 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.
		 */
1876
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1877
			goto send_now;
1878 1879
	}

1880 1881 1882 1883 1884 1885 1886
	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
1887
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1888

1889
	if (cong_win < send_win && cong_win <= skb->len)
1890 1891
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1892
	return true;
J
John Heffner 已提交
1893 1894

send_now:
E
Eric Dumazet 已提交
1895
	return false;
1896 1897
}

1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922
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
1923
/* Create a new MTU probe if we are ready.
1924 1925 1926 1927
 * 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
1928 1929
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1930 1931
 *         -1 otherwise
 */
J
John Heffner 已提交
1932 1933 1934
static int tcp_mtu_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
1935
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
1936
	struct sk_buff *skb, *nskb, *next;
1937
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1938
	int probe_size;
1939
	int size_needed;
1940
	int copy, len;
J
John Heffner 已提交
1941
	int mss_now;
1942
	int interval;
J
John Heffner 已提交
1943 1944 1945 1946

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
1947 1948 1949 1950 1951 1952 1953
	 * not SACKing (the variable headers throw things off)
	 */
	if (likely(!icsk->icsk_mtup.enabled ||
		   icsk->icsk_mtup.probe_size ||
		   inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
		   tp->snd_cwnd < 11 ||
		   tp->rx_opt.num_sacks || tp->rx_opt.dsack))
J
John Heffner 已提交
1954 1955
		return -1;

1956 1957 1958 1959
	/* 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
1960
	mss_now = tcp_current_mss(sk);
1961 1962
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
1963
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1964
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1965 1966 1967 1968
	/* 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.
	 */
1969
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1970 1971 1972 1973 1974
		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
1975 1976 1977 1978
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1979
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1980 1981
		return -1;

1982 1983
	if (tp->snd_wnd < size_needed)
		return -1;
1984
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1985
		return 0;
J
John Heffner 已提交
1986

1987 1988 1989
	/* 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
1990 1991 1992 1993 1994 1995
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
1996
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1997
	if (!nskb)
J
John Heffner 已提交
1998
		return -1;
1999 2000
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
2001

2002
	skb = tcp_send_head(sk);
J
John Heffner 已提交
2003 2004 2005

	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
2006
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
2007 2008
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
2009
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
2010

2011 2012
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
2013
	len = 0;
2014
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
2015
		copy = min_t(int, skb->len, probe_size - len);
2016
		if (nskb->ip_summed) {
J
John Heffner 已提交
2017
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2018 2019 2020 2021 2022 2023
		} else {
			__wsum csum = skb_copy_and_csum_bits(skb, 0,
							     skb_put(nskb, copy),
							     copy, 0);
			nskb->csum = csum_block_add(nskb->csum, csum, len);
		}
J
John Heffner 已提交
2024 2025 2026 2027

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
2028
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2029
			tcp_unlink_write_queue(skb, sk);
2030
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
2031
		} else {
E
Eric Dumazet 已提交
2032
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
2033
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
2034 2035
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
2036
				if (skb->ip_summed != CHECKSUM_PARTIAL)
2037 2038
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
2039 2040
			} else {
				__pskb_trim_head(skb, copy);
2041
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
2042 2043 2044 2045 2046
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
2047 2048 2049

		if (len >= probe_size)
			break;
J
John Heffner 已提交
2050
	}
2051
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
2052 2053

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
2054 2055
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
2056 2057
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
2058
		 * effectively two packets. */
J
John Heffner 已提交
2059
		tp->snd_cwnd--;
2060
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
2061 2062

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2063 2064
		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
2065 2066 2067 2068 2069 2070 2071

		return 1;
	}

	return -1;
}

2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092
/* TCP Small Queues :
 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
 * (These limits are doubled for retransmits)
 * This allows for :
 *  - better RTT estimation and ACK scheduling
 *  - faster recovery
 *  - high rates
 * Alas, some drivers / subsystems require a fair amount
 * of queued bytes to ensure line rate.
 * One example is wifi aggregation (802.11 AMPDU)
 */
static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
				  unsigned int factor)
{
	unsigned int limit;

	limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
	limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
	limit <<= factor;

	if (atomic_read(&sk->sk_wmem_alloc) > limit) {
2093 2094 2095 2096 2097 2098 2099 2100 2101
		/* Always send the 1st or 2nd skb in write queue.
		 * No need to wait for TX completion to call us back,
		 * after softirq/tasklet schedule.
		 * This helps when TX completions are delayed too much.
		 */
		if (skb == sk->sk_write_queue.next ||
		    skb->prev == sk->sk_write_queue.next)
			return false;

2102
		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113
		/* It is possible TX completion already happened
		 * before we set TSQ_THROTTLED, so we must
		 * test again the condition.
		 */
		smp_mb__after_atomic();
		if (atomic_read(&sk->sk_wmem_alloc) > limit)
			return true;
	}
	return false;
}

2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
	const u32 now = tcp_time_stamp;

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

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

	/* If there are multiple conditions worthy of tracking in a
2129 2130
	 * chronograph then the highest priority enum takes precedence
	 * over the other conditions. So that if something "more interesting"
2131 2132 2133 2134 2135 2136 2137 2138 2139 2140
	 * starts happening, stop the previous chrono and start a new one.
	 */
	if (type > tp->chrono_type)
		tcp_chrono_set(tp, type);
}

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

2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152

	/* There are multiple conditions worthy of tracking in a
	 * chronograph, so that the highest priority enum takes
	 * precedence over the other conditions (see tcp_chrono_start).
	 * If a condition stops, we only stop chrono tracking if
	 * it's the "most interesting" or current chrono we are
	 * tracking and starts busy chrono if we have pending data.
	 */
	if (tcp_write_queue_empty(sk))
		tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
	else if (type == tp->chrono_type)
		tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2153 2154
}

L
Linus Torvalds 已提交
2155 2156 2157 2158
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2159 2160 2161 2162
 * 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
2163 2164 2165
 * 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
2166 2167
 * 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
2168
 */
E
Eric Dumazet 已提交
2169 2170
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
2171 2172
{
	struct tcp_sock *tp = tcp_sk(sk);
2173
	struct sk_buff *skb;
2174 2175
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2176
	int result;
2177
	bool is_cwnd_limited = false, is_rwnd_limited = false;
E
Eric Dumazet 已提交
2178
	u32 max_segs;
L
Linus Torvalds 已提交
2179

2180
	sent_pkts = 0;
J
John Heffner 已提交
2181

2182 2183 2184 2185
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2186
			return false;
2187 2188 2189
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2190 2191
	}

2192
	max_segs = tcp_tso_segs(sk, mss_now);
2193
	while ((skb = tcp_send_head(sk))) {
2194 2195
		unsigned int limit;

2196
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2197
		BUG_ON(!tso_segs);
2198

2199
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2200 2201
			/* "skb_mstamp" is used as a start point for the retransmit timer */
			skb_mstamp_get(&skb->skb_mstamp);
2202
			goto repair; /* Skip network transmission */
2203
		}
2204

2205
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2206 2207 2208 2209 2210 2211 2212
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2213

2214 2215
		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
			is_rwnd_limited = true;
2216
			break;
2217
		}
2218

2219
		if (tso_segs == 1) {
2220 2221 2222 2223 2224
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2225
			if (!push_one &&
E
Eric Dumazet 已提交
2226 2227
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2228 2229
				break;
		}
2230

E
Eric Dumazet 已提交
2231
		limit = mss_now;
2232
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2233 2234 2235 2236 2237 2238 2239 2240 2241 2242
			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;

2243 2244
		if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
			clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
2245 2246
		if (tcp_small_queue_check(sk, skb, 0))
			break;
E
Eric Dumazet 已提交
2247

2248
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2249
			break;
L
Linus Torvalds 已提交
2250

2251
repair:
2252 2253 2254
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2255
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2256

2257
		tcp_minshall_update(tp, mss_now, skb);
2258
		sent_pkts += tcp_skb_pcount(skb);
2259 2260 2261

		if (push_one)
			break;
2262
	}
L
Linus Torvalds 已提交
2263

2264 2265 2266 2267 2268
	if (is_rwnd_limited)
		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
	else
		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);

2269
	if (likely(sent_pkts)) {
2270 2271
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2272 2273 2274 2275

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2276
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2277
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2278
		return false;
L
Linus Torvalds 已提交
2279
	}
2280
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2281 2282 2283 2284 2285 2286 2287
}

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;
2288
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2289 2290 2291 2292 2293 2294 2295 2296 2297

	/* 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.
	 */
2298
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2299 2300 2301 2302 2303 2304 2305 2306 2307
		return false;

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

	/* Schedule a loss probe in 2*RTT for SACK capable connections
	 * in Open state, that are either limited by cwnd or application.
	 */
Y
Yuchung Cheng 已提交
2308 2309 2310
	if ((sysctl_tcp_early_retrans != 3 && sysctl_tcp_early_retrans != 4) ||
	    !tp->packets_out || !tcp_is_sack(tp) ||
	    icsk->icsk_ca_state != TCP_CA_Open)
N
Nandita Dukkipati 已提交
2311 2312 2313 2314 2315 2316 2317
		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
2318 2319
	 * for delayed ack when there's one outstanding packet. If no RTT
	 * sample is available then probe after TCP_TIMEOUT_INIT.
N
Nandita Dukkipati 已提交
2320
	 */
2321
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340
	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;
}

2341 2342 2343 2344 2345 2346 2347
/* Thanks to skb fast clones, we can detect if a prior transmit of
 * a packet is still in a qdisc or driver queue.
 * In this case, there is very little point doing a retransmit !
 */
static bool skb_still_in_host_queue(const struct sock *sk,
				    const struct sk_buff *skb)
{
2348
	if (unlikely(skb_fclone_busy(sk, skb))) {
2349 2350
		NET_INC_STATS(sock_net(sk),
			      LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2351 2352 2353 2354 2355
		return true;
	}
	return false;
}

2356
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2357 2358 2359 2360
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2361
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2362 2363 2364 2365
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377
	skb = tcp_send_head(sk);
	if (skb) {
		if (tcp_snd_wnd_test(tp, skb, mss)) {
			pcount = tp->packets_out;
			tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
			if (tp->packets_out > pcount)
				goto probe_sent;
			goto rearm_timer;
		}
		skb = tcp_write_queue_prev(sk, skb);
	} else {
		skb = tcp_write_queue_tail(sk);
N
Nandita Dukkipati 已提交
2378 2379
	}

N
Nandita Dukkipati 已提交
2380 2381 2382 2383
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2384 2385 2386 2387
	/* Retransmit last segment. */
	if (WARN_ON(!skb))
		goto rearm_timer;

2388 2389 2390
	if (skb_still_in_host_queue(sk, skb))
		goto rearm_timer;

N
Nandita Dukkipati 已提交
2391 2392 2393 2394 2395
	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2396 2397
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
					  GFP_ATOMIC)))
N
Nandita Dukkipati 已提交
2398
			goto rearm_timer;
2399
		skb = tcp_write_queue_next(sk, skb);
N
Nandita Dukkipati 已提交
2400 2401 2402 2403 2404
	}

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

2405
	if (__tcp_retransmit_skb(sk, skb, 1))
2406
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2407

N
Nandita Dukkipati 已提交
2408
	/* Record snd_nxt for loss detection. */
2409
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2410

2411
probe_sent:
2412
	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2413 2414
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2415
rearm_timer:
2416
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2417 2418
}

2419 2420 2421 2422
/* 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.
 */
2423 2424
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2425
{
2426 2427 2428 2429 2430 2431 2432
	/* 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;

2433
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2434
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2435
		tcp_check_probe_timer(sk);
2436 2437
}

2438 2439 2440 2441 2442
/* 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)
{
2443
	struct sk_buff *skb = tcp_send_head(sk);
2444 2445 2446

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

2447
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2448 2449
}

L
Linus Torvalds 已提交
2450 2451
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2452
 *
L
Linus Torvalds 已提交
2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470
 * 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.
2471
 *
L
Linus Torvalds 已提交
2472 2473
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2474
 *
L
Linus Torvalds 已提交
2475
 * BSD seems to make the following compromise:
2476
 *
L
Linus Torvalds 已提交
2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503
 *	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)
{
2504
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2505
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2506
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2507 2508 2509 2510 2511
	 * 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
	 */
2512
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2513
	int free_space = tcp_space(sk);
2514 2515
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2516 2517
	int window;

2518
	if (unlikely(mss > full_space)) {
2519
		mss = full_space;
2520 2521 2522
		if (mss <= 0)
			return 0;
	}
2523
	if (free_space < (full_space >> 1)) {
2524
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2525

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

2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542
		/* free_space might become our new window, make sure we don't
		 * increase it due to wscale.
		 */
		free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);

		/* if free space is less than mss estimate, or is below 1/16th
		 * of the maximum allowed, try to move to zero-window, else
		 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
		 * new incoming data is dropped due to memory limits.
		 * With large window, mss test triggers way too late in order
		 * to announce zero window in time before rmem limit kicks in.
		 */
		if (free_space < (allowed_space >> 4) || free_space < mss)
L
Linus Torvalds 已提交
2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572
			return 0;
	}

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

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

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

	return window;
}

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

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

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

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

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

2609 2610 2611 2612 2613 2614 2615
	if (next_skb_size) {
		if (next_skb_size <= skb_availroom(skb))
			skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
				      next_skb_size);
		else if (!skb_shift(skb, next_skb, next_skb_size))
			return false;
	}
2616
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2617

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

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

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

2626 2627
	/* Update sequence range on original skb. */
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
L
Linus Torvalds 已提交
2628

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

	/* All done, get rid of second SKB and account for it so
	 * packet counting does not break.
	 */
	TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2636
	TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2637 2638

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

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

2645 2646
	tcp_skb_collapse_tstamp(skb, next_skb);

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

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

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

2667 2668 2669
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2670 2671 2672 2673 2674
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
				     int space)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb = to, *tmp;
E
Eric Dumazet 已提交
2675
	bool first = true;
2676 2677 2678

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

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

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

2689 2690 2691
		space -= skb->len;

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

		if (space < 0)
			break;

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

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

L
Linus Torvalds 已提交
2707 2708 2709 2710
/* This retransmits one SKB.  Policy decisions and retransmit queue
 * state updates are done by the caller.  Returns non-zero if an
 * error occurred which prevented the send.
 */
2711
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
L
Linus Torvalds 已提交
2712
{
J
John Heffner 已提交
2713
	struct inet_connection_sock *icsk = inet_csk(sk);
2714
	struct tcp_sock *tp = tcp_sk(sk);
2715
	unsigned int cur_mss;
2716 2717
	int diff, len, err;

L
Linus Torvalds 已提交
2718

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

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

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

L
Linus Torvalds 已提交
2734 2735 2736 2737 2738 2739 2740
	if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
		if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
			BUG();
		if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
			return -ENOMEM;
	}

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

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

L
Linus Torvalds 已提交
2746 2747 2748 2749 2750
	/* If receiver has shrunk his window, and skb is out of
	 * new window, do not retransmit it. The exception is the
	 * case, when window is shrunk to zero. In this case
	 * our retransmit serves as a zero window probe.
	 */
2751 2752
	if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
	    TCP_SKB_CB(skb)->seq != tp->snd_una)
L
Linus Torvalds 已提交
2753 2754
		return -EAGAIN;

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

2763 2764 2765 2766 2767 2768 2769
		diff = tcp_skb_pcount(skb);
		tcp_set_skb_tso_segs(skb, cur_mss);
		diff -= tcp_skb_pcount(skb);
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
		if (skb->len < cur_mss)
			tcp_retrans_try_collapse(sk, skb, cur_mss);
L
Linus Torvalds 已提交
2770 2771
	}

2772 2773 2774 2775
	/* RFC3168, section 6.1.1.1. ECN fallback */
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
		tcp_ecn_clear_syn(sk, skb);

2776 2777 2778 2779 2780 2781 2782
	/* Update global and local TCP statistics. */
	segs = tcp_skb_pcount(skb);
	TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
	tp->total_retrans += segs;

2783 2784 2785 2786 2787 2788
	/* 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)) {
2789 2790 2791 2792
		struct sk_buff *nskb;

		skb_mstamp_get(&skb->skb_mstamp);
		nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2793 2794
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2795
	} else {
2796
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2797
	}
2798

2799
	if (likely(!err)) {
2800
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2801 2802
	} else if (err != -EBUSY) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2803
	}
2804
	return err;
2805 2806
}

2807
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2808 2809
{
	struct tcp_sock *tp = tcp_sk(sk);
2810
	int err = __tcp_retransmit_skb(sk, skb, segs);
L
Linus Torvalds 已提交
2811 2812 2813

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

		/* Save stamp of the first retransmit. */
		if (!tp->retrans_stamp)
E
Eric Dumazet 已提交
2823
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2824 2825

	}
Y
Yuchung Cheng 已提交
2826 2827 2828 2829

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842
	return err;
}

/* This gets called after a retransmit timeout, and the initially
 * retransmitted data is acknowledged.  It tries to continue
 * resending the rest of the retransmit queue, until either
 * we've sent it all or the congestion window limit is reached.
 * If doing SACK, the first ACK which comes back for a timeout
 * based retransmit packet might feed us FACK information again.
 * If so, we use it to avoid unnecessarily retransmissions.
 */
void tcp_xmit_retransmit_queue(struct sock *sk)
{
2843
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2844 2845
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2846
	struct sk_buff *hole = NULL;
2847
	u32 max_segs;
2848
	int mib_idx;
2849

2850 2851 2852
	if (!tp->packets_out)
		return;

2853
	if (tp->retransmit_skb_hint) {
2854
		skb = tp->retransmit_skb_hint;
2855
	} else {
2856
		skb = tcp_write_queue_head(sk);
2857
	}
L
Linus Torvalds 已提交
2858

2859
	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2860
	tcp_for_write_queue_from(skb, sk) {
E
Eric Dumazet 已提交
2861
		__u8 sacked;
2862
		int segs;
L
Linus Torvalds 已提交
2863

2864 2865 2866
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2867
		if (!hole)
2868
			tp->retransmit_skb_hint = skb;
2869

2870 2871
		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
		if (segs <= 0)
2872
			return;
E
Eric Dumazet 已提交
2873
		sacked = TCP_SKB_CB(skb)->sacked;
2874 2875 2876 2877
		/* In case tcp_shift_skb_data() have aggregated large skbs,
		 * we need to make sure not sending too bigs TSO packets
		 */
		segs = min_t(int, segs, max_segs);
L
Linus Torvalds 已提交
2878

2879 2880
		if (tp->retrans_out >= tp->lost_out) {
			break;
2881
		} else if (!(sacked & TCPCB_LOST)) {
2882
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2883 2884
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2885

2886 2887 2888 2889 2890 2891
		} else {
			if (icsk->icsk_ca_state != TCP_CA_Loss)
				mib_idx = LINUX_MIB_TCPFASTRETRANS;
			else
				mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
		}
L
Linus Torvalds 已提交
2892

2893
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2894 2895
			continue;

2896 2897 2898
		if (tcp_small_queue_check(sk, skb, 1))
			return;

2899
		if (tcp_retransmit_skb(sk, skb, segs))
2900
			return;
2901

2902
		NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
2903

2904
		if (tcp_in_cwnd_reduction(sk))
2905 2906
			tp->prr_out += tcp_skb_pcount(skb);

2907 2908
		if (skb == tcp_write_queue_head(sk) &&
		    icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
2909 2910 2911
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2912 2913 2914
	}
}

2915 2916
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2917 2918
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2919 2920
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2921
 */
2922
void sk_forced_mem_schedule(struct sock *sk, int size)
2923
{
2924
	int amt;
2925 2926 2927 2928 2929

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2930 2931
	sk_memory_allocated_add(sk, amt);

2932 2933
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
2934 2935
}

2936 2937
/* 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
2938 2939 2940
 */
void tcp_send_fin(struct sock *sk)
{
2941
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2942 2943
	struct tcp_sock *tp = tcp_sk(sk);

2944 2945 2946 2947
	/* 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
2948
	 */
2949
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
2950 2951 2952
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
2953
		tp->write_seq++;
2954 2955 2956 2957 2958 2959 2960 2961 2962 2963
		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
2964
	} else {
2965 2966 2967 2968 2969
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
2970
		}
2971
		skb_reserve(skb, MAX_TCP_HEADER);
2972
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
2973
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2974
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
2975
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
2976 2977
		tcp_queue_skb(sk, skb);
	}
2978
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
2979 2980 2981 2982 2983
}

/* 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
2984
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2985
 */
A
Al Viro 已提交
2986
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
2987 2988 2989 2990 2991 2992
{
	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
2993
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
2994 2995 2996 2997 2998
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
2999
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
3000
			     TCPHDR_ACK | TCPHDR_RST);
3001
	skb_mstamp_get(&skb->skb_mstamp);
L
Linus Torvalds 已提交
3002
	/* Send it off. */
3003
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
3004
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3005

P
Pavel Emelyanov 已提交
3006
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
3007 3008
}

3009 3010
/* 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
3011 3012 3013 3014 3015 3016
 * 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)
{
3017
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3018

3019
	skb = tcp_write_queue_head(sk);
3020
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3021
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
3022 3023
		return -EFAULT;
	}
E
Eric Dumazet 已提交
3024
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
3025 3026
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
3027
			if (!nskb)
L
Linus Torvalds 已提交
3028
				return -ENOMEM;
3029
			tcp_unlink_write_queue(skb, sk);
3030
			__skb_header_release(nskb);
3031
			__tcp_add_write_queue_head(sk, nskb);
3032 3033 3034
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
3035 3036 3037
			skb = nskb;
		}

E
Eric Dumazet 已提交
3038
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3039
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
3040
	}
3041
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
3042 3043
}

3044 3045 3046 3047 3048 3049 3050 3051 3052
/**
 * 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.
 */
3053
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3054
				struct request_sock *req,
3055
				struct tcp_fastopen_cookie *foc,
3056
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
3057
{
3058
	struct inet_request_sock *ireq = inet_rsk(req);
3059
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
3060
	struct tcp_md5sig_key *md5 = NULL;
3061 3062
	struct tcp_out_options opts;
	struct sk_buff *skb;
3063
	int tcp_header_size;
3064 3065
	struct tcphdr *th;
	u16 user_mss;
3066
	int mss;
L
Linus Torvalds 已提交
3067

3068
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3069 3070
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
3071
		return NULL;
3072
	}
L
Linus Torvalds 已提交
3073 3074 3075
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

3076 3077
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
3078
		skb_set_owner_w(skb, req_to_sk(req));
3079 3080 3081 3082 3083 3084 3085
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
3086 3087 3088 3089 3090
		/* sk is a const pointer, because we want to express multiple
		 * cpu might call us concurrently.
		 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
		 */
		skb_set_owner_w(skb, (struct sock *)sk);
3091
		break;
3092
	}
3093
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3094

3095
	mss = dst_metric_advmss(dst);
3096 3097 3098
	user_mss = READ_ONCE(tp->rx_opt.user_mss);
	if (user_mss && user_mss < mss)
		mss = user_mss;
3099

A
Adam Langley 已提交
3100
	memset(&opts, 0, sizeof(opts));
3101 3102
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
3103
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3104 3105
	else
#endif
E
Eric Dumazet 已提交
3106
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
3107 3108 3109

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3110
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3111
#endif
3112
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3113 3114
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3115

3116 3117
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3118

3119
	th = (struct tcphdr *)skb->data;
L
Linus Torvalds 已提交
3120 3121 3122
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3123
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3124
	th->source = htons(ireq->ir_num);
3125
	th->dest = ireq->ir_rmt_port;
3126 3127 3128 3129
	/* 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
3130
			     TCPHDR_SYN | TCPHDR_ACK);
3131

L
Linus Torvalds 已提交
3132
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3133 3134
	/* 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
3135 3136

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3137
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3138
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3139
	th->doff = (tcp_header_size >> 2);
E
Eric Dumazet 已提交
3140
	__TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3141 3142 3143

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3144
	if (md5)
3145
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3146
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3147
	rcu_read_unlock();
3148 3149
#endif

3150
	/* Do not fool tcpdump (if any), clean our debris */
T
Thomas Gleixner 已提交
3151
	skb->tstamp = 0;
L
Linus Torvalds 已提交
3152 3153
	return skb;
}
E
Eric Dumazet 已提交
3154
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3155

3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174
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();
}

3175
/* Do all connect socket setups that can be done AF independent. */
3176
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3177
{
3178
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3179 3180 3181 3182 3183 3184 3185
	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) +
3186
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3187

3188
#ifdef CONFIG_TCP_MD5SIG
3189
	if (tp->af_specific->md5_lookup(sk, sk))
3190 3191 3192
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3193 3194 3195 3196
	/* 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
3197
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3198 3199
	tcp_sync_mss(sk, dst_mtu(dst));

3200 3201
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3202 3203
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3204
	tp->advmss = dst_metric_advmss(dst);
3205 3206 3207
	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
3208 3209
	tcp_initialize_rcv_mss(sk);

3210 3211 3212 3213 3214
	/* 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
3215 3216 3217 3218
	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,
3219
				  sysctl_tcp_window_scaling,
3220 3221
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3222 3223 3224 3225 3226 3227 3228

	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;
3229
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3230 3231
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3232
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3233
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3234 3235 3236

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3237 3238
	else
		tp->rcv_tstamp = tcp_time_stamp;
P
Pavel Emelyanov 已提交
3239 3240
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3241

3242 3243
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3244 3245 3246
	tcp_clear_retrans(tp);
}

3247 3248 3249 3250 3251 3252
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;
3253
	__skb_header_release(skb);
3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271
	__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;
3272
	int space, err = 0;
3273
	struct sk_buff *syn_data;
3274

3275
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3276
	if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3277 3278 3279 3280 3281 3282 3283 3284
		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;
3285
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3286 3287
		MAX_TCP_OPTION_SPACE;

3288 3289 3290 3291 3292
	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));

3293
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3294
	if (!syn_data)
3295
		goto fallback;
3296 3297
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308
	if (space) {
		int copied = copy_from_iter(skb_put(syn_data, space), space,
					    &fo->data->msg_iter);
		if (unlikely(!copied)) {
			kfree_skb(syn_data);
			goto fallback;
		}
		if (copied != space) {
			skb_trim(syn_data, copied);
			space = copied;
		}
3309
	}
3310 3311 3312 3313
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3314

3315
	tcp_connect_queue_skb(sk, syn_data);
3316 3317
	if (syn_data->len)
		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3318

3319
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3320

3321
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3322

3323 3324 3325 3326 3327 3328 3329 3330
	/* 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) {
3331
		tp->syn_data = (fo->copied > 0);
3332
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347
		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;
}

3348
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3349 3350 3351 3352
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3353
	int err;
L
Linus Torvalds 已提交
3354 3355 3356

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3357 3358 3359 3360 3361
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3362
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3363
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3364 3365
		return -ENOBUFS;

C
Changli Gao 已提交
3366
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
E
Eric Dumazet 已提交
3367
	tp->retrans_stamp = tcp_time_stamp;
3368
	tcp_connect_queue_skb(sk, buff);
3369
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3370

3371 3372 3373
	/* 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);
3374 3375
	if (err == -ECONNREFUSED)
		return err;
3376 3377 3378 3379 3380 3381

	/* 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
3382
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3383 3384

	/* Timer for repeating the SYN until an answer. */
3385 3386
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3387 3388
	return 0;
}
E
Eric Dumazet 已提交
3389
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3390 3391 3392 3393 3394 3395 3396

/* 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)
{
3397 3398
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3399 3400
	unsigned long timeout;

3401 3402
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3403
	if (ato > TCP_DELACK_MIN) {
3404
		const struct tcp_sock *tp = tcp_sk(sk);
3405
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3406

3407 3408
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3409 3410 3411 3412 3413
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3414
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3415 3416
		 * directly.
		 */
3417 3418 3419
		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
3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431

			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. */
3432
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3433 3434 3435
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3436 3437
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3438 3439 3440 3441
			tcp_send_ack(sk);
			return;
		}

3442 3443
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3444
	}
3445 3446 3447
	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
3448 3449 3450 3451 3452
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3453
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3454

3455 3456 3457
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3458

3459 3460
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3461 3462 3463 3464
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3465 3466 3467
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3468 3469 3470 3471 3472
		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
3473
	}
3474 3475 3476

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3477
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3478

E
Eric Dumazet 已提交
3479 3480 3481 3482 3483 3484
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 */
	skb_set_tcp_pure_ack(buff);

3485
	/* Send it off, this clears delayed acks for us. */
E
Eric Dumazet 已提交
3486
	skb_mstamp_get(&buff->skb_mstamp);
3487
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3488
}
3489
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501

/* 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.
 */
3502
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3503 3504 3505 3506 3507
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3508 3509
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3510
	if (!skb)
L
Linus Torvalds 已提交
3511 3512 3513 3514 3515 3516 3517 3518
		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
3519
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
E
Eric Dumazet 已提交
3520
	skb_mstamp_get(&skb->skb_mstamp);
3521
	NET_INC_STATS(sock_net(sk), mib);
3522
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3523 3524
}

P
Pavel Emelyanov 已提交
3525 3526 3527 3528
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;
3529
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3530 3531 3532
	}
}

3533
/* Initiate keepalive or window probe from timer. */
3534
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3535
{
3536 3537
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3538

3539 3540 3541
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3542 3543
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3544
		int err;
I
Ilpo Järvinen 已提交
3545
		unsigned int mss = tcp_current_mss(sk);
3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557
		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
3558
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3559
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3560 3561
				return -1;
		} else if (!tcp_skb_pcount(skb))
3562
			tcp_set_skb_tso_segs(skb, mss);
3563

E
Eric Dumazet 已提交
3564
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3565 3566 3567 3568 3569
		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
3570
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3571 3572
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3573 3574 3575 3576 3577 3578 3579 3580
	}
}

/* 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)
{
3581
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3582
	struct tcp_sock *tp = tcp_sk(sk);
3583
	struct net *net = sock_net(sk);
3584
	unsigned long probe_max;
L
Linus Torvalds 已提交
3585 3586
	int err;

3587
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3588

3589
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3590
		/* Cancel probe timer, if it is not required. */
3591
		icsk->icsk_probes_out = 0;
3592
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3593 3594 3595 3596
		return;
	}

	if (err <= 0) {
3597
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3598
			icsk->icsk_backoff++;
3599
		icsk->icsk_probes_out++;
3600
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3601 3602
	} else {
		/* If packet was not sent due to local congestion,
3603
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3604 3605 3606 3607
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3608 3609
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3610
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3611
	}
3612
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3613
				  tcp_probe0_when(sk, probe_max),
3614
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3615
}
3616

3617
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3618 3619 3620 3621 3622
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3623
	tcp_rsk(req)->txhash = net_tx_rndhash();
3624
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3625
	if (!res) {
E
Eric Dumazet 已提交
3626
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3627
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3628 3629
		if (unlikely(tcp_passive_fastopen(sk)))
			tcp_sk(sk)->total_retrans++;
3630 3631 3632 3633
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);