tcp_output.c 91.6 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 two TSO segments */
int sysctl_tcp_limit_output_bytes __read_mostly = 131072;

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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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int sysctl_tcp_mtu_probing __read_mostly = 0;
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int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
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/* By default, RFC2861 behavior.  */
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int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
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static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp);
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/* Account for new data that has been sent to the network. */
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static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
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{
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	struct inet_connection_sock *icsk = inet_csk(sk);
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	struct tcp_sock *tp = tcp_sk(sk);
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	unsigned int prior_packets = tp->packets_out;
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	tcp_advance_send_head(sk, skb);
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	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
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	tp->packets_out += tcp_skb_pcount(skb);
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	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
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	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
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		tcp_rearm_rto(sk);
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	}
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}

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

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

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

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

	return (__u16)mss;
}

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

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

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

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/* Congestion state accounting after a packet has been sent. */
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static void tcp_event_data_sent(struct tcp_sock *tp,
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				struct sock *sk)
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{
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	struct inet_connection_sock *icsk = inet_csk(sk);
	const u32 now = tcp_time_stamp;
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	const struct dst_entry *dst = __sk_dst_get(sk);
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	if (sysctl_tcp_slow_start_after_idle &&
	    (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
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		tcp_cwnd_restart(sk, __sk_dst_get(sk));
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	tp->lsndtime = now;

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

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

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

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

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

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

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

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

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

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

	/* Set the clamp no higher than max representable value */
	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
}
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EXPORT_SYMBOL(tcp_select_initial_window);
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/* Chose a new window to advertise, update state in tcp_sock for the
 * socket, and return result with RFC1323 scaling applied.  The return
 * value can be stuffed directly into th->window for an outgoing
 * frame.
 */
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static u16 tcp_select_window(struct sock *sk)
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{
	struct tcp_sock *tp = tcp_sk(sk);
	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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		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. */
	if (new_win == 0)
		tp->pred_flags = 0;

	return new_win;
}

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/* Packet ECN state for a SYN-ACK */
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static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
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{
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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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}

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/* Packet ECN state for a SYN.  */
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static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);

	tp->ecn_flags = 0;
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	if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) {
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		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
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		tp->ecn_flags = TCP_ECN_OK;
	}
}

static __inline__ void
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TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
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{
	if (inet_rsk(req)->ecn_ok)
		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 inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
				int tcp_header_len)
{
	struct tcp_sock *tp = tcp_sk(sk);

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

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

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

	skb_shinfo(skb)->gso_segs = 1;
	skb_shinfo(skb)->gso_size = 0;
	skb_shinfo(skb)->gso_type = 0;

	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
 * inter-operatibility perspective it seems that we're somewhat stuck with
 * 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;
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		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
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			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
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						     TCPOLEN_SACK_PERBLOCK)));
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		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
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			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
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		tp->rx_opt.dsack = 0;
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	}
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	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;

		*ptr++ = htonl((TCPOPT_EXP << 24) |
			       ((TCPOLEN_EXP_FASTOPEN_BASE + foc->len) << 16) |
			       TCPOPT_FASTOPEN_MAGIC);

		memcpy(ptr, foc->val, foc->len);
		if ((foc->len & 3) == 2) {
			u8 *align = ((u8 *)ptr) + foc->len;
			align[0] = align[1] = TCPOPT_NOP;
		}
		ptr += (foc->len + 3) >> 2;
	}
A
Adam Langley 已提交
498 499
}

500 501 502
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
503
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
504
				struct tcp_out_options *opts,
505 506
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
507
	struct tcp_sock *tp = tcp_sk(sk);
508
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
509
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
510

511
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
512 513 514
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
515
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
516
	}
A
Adam Langley 已提交
517 518
#else
	*md5 = NULL;
519
#endif
A
Adam Langley 已提交
520 521 522 523 524 525 526 527 528 529 530

	/* 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);
531
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
532

533
	if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
A
Adam Langley 已提交
534
		opts->options |= OPTION_TS;
535
		opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset;
A
Adam Langley 已提交
536
		opts->tsecr = tp->rx_opt.ts_recent;
537
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
538
	}
539
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
540
		opts->ws = tp->rx_opt.rcv_wscale;
541
		opts->options |= OPTION_WSCALE;
542
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
543
	}
544
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
545
		opts->options |= OPTION_SACK_ADVERTISE;
546
		if (unlikely(!(OPTION_TS & opts->options)))
547
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
548 549
	}

550 551 552 553 554 555 556 557 558 559
	if (fastopen && fastopen->cookie.len >= 0) {
		u32 need = TCPOLEN_EXP_FASTOPEN_BASE + fastopen->cookie.len;
		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;
		}
	}
560 561

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
562 563
}

564
/* Set up TCP options for SYN-ACKs. */
565
static unsigned int tcp_synack_options(struct sock *sk,
A
Adam Langley 已提交
566
				   struct request_sock *req,
567
				   unsigned int mss, struct sk_buff *skb,
A
Adam Langley 已提交
568
				   struct tcp_out_options *opts,
569
				   struct tcp_md5sig_key **md5,
570
				   struct tcp_fastopen_cookie *foc)
571
{
A
Adam Langley 已提交
572
	struct inet_request_sock *ireq = inet_rsk(req);
573
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
574

575
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
576 577 578
	*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
	if (*md5) {
		opts->options |= OPTION_MD5;
579 580 581 582 583 584 585
		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
586
		ireq->tstamp_ok &= !ireq->sack_ok;
587
	}
A
Adam Langley 已提交
588 589
#else
	*md5 = NULL;
590
#endif
A
Adam Langley 已提交
591

592
	/* We always send an MSS option. */
A
Adam Langley 已提交
593
	opts->mss = mss;
594
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
595 596 597

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
598
		opts->options |= OPTION_WSCALE;
599
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
600
	}
E
Eric Dumazet 已提交
601
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
602 603 604
		opts->options |= OPTION_TS;
		opts->tsval = TCP_SKB_CB(skb)->when;
		opts->tsecr = req->ts_recent;
605
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
606 607 608
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
609
		if (unlikely(!ireq->tstamp_ok))
610
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
611
	}
612 613 614 615 616 617 618 619 620
	if (foc != NULL) {
		u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
		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
621

622
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
623 624
}

625 626 627
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
628
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
629
					struct tcp_out_options *opts,
630 631
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
632 633
	struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
	struct tcp_sock *tp = tcp_sk(sk);
634
	unsigned int size = 0;
635
	unsigned int eff_sacks;
A
Adam Langley 已提交
636 637 638 639 640 641 642 643 644 645 646 647 648

#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;
649
		opts->tsval = tcb ? tcb->when + tp->tsoffset : 0;
A
Adam Langley 已提交
650 651 652 653
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

654 655
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
656
		const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
A
Adam Langley 已提交
657
		opts->num_sack_blocks =
658
			min_t(unsigned int, eff_sacks,
A
Adam Langley 已提交
659 660 661 662 663 664 665
			      (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
666
}
L
Linus Torvalds 已提交
667

E
Eric Dumazet 已提交
668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688

/* 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.
 * The invariant being skb->truesize substracted from sk->sk_wmem_alloc
 *
 * 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);

689 690 691 692 693 694 695
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK))
		tcp_write_xmit(sk, tcp_current_mss(sk), 0, 0, GFP_ATOMIC);
}
E
Eric Dumazet 已提交
696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722
/*
 * One tasklest per cpu tries to send more skbs.
 * We run in tasklet context but need to disable irqs when
 * transfering tsq->head because tcp_wfree() might
 * interrupt us (non NAPI drivers)
 */
static void tcp_tasklet_func(unsigned long data)
{
	struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
	LIST_HEAD(list);
	unsigned long flags;
	struct list_head *q, *n;
	struct tcp_sock *tp;
	struct sock *sk;

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

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

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

		if (!sock_owned_by_user(sk)) {
723
			tcp_tsq_handler(sk);
E
Eric Dumazet 已提交
724 725
		} else {
			/* defer the work to tcp_release_cb() */
726
			set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
E
Eric Dumazet 已提交
727 728 729 730 731 732 733 734
		}
		bh_unlock_sock(sk);

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

735 736
#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) |		\
			  (1UL << TCP_WRITE_TIMER_DEFERRED) |	\
737 738
			  (1UL << TCP_DELACK_TIMER_DEFERRED) |	\
			  (1UL << TCP_MTU_REDUCED_DEFERRED))
E
Eric Dumazet 已提交
739 740 741 742 743 744 745 746 747 748
/**
 * tcp_release_cb - tcp release_sock() callback
 * @sk: socket
 *
 * called from release_sock() to perform protocol dependent
 * actions before socket release.
 */
void tcp_release_cb(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
749
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
750

751 752 753 754 755 756 757 758 759 760 761
	/* perform an atomic operation only if at least one flag is set */
	do {
		flags = tp->tsq_flags;
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
	} while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);

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

762
	if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
763
		tcp_write_timer_handler(sk);
764 765 766
		__sock_put(sk);
	}
	if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
767
		tcp_delack_timer_handler(sk);
768 769 770
		__sock_put(sk);
	}
	if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
771
		sk->sk_prot->mtu_reduced(sk);
772 773
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
}
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.
 * We cant xmit new skbs from this context, as we might already
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
796
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);

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

		/* Keep a ref on socket.
		 * This last ref will be released in tcp_tasklet_func()
		 */
		atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc);

		/* queue this socket to tasklet queue */
		local_irq_save(flags);
		tsq = &__get_cpu_var(tsq_tasklet);
		list_add(&tp->tsq_node, &tsq->head);
		tasklet_schedule(&tsq->tasklet);
		local_irq_restore(flags);
	} else {
		sock_wfree(skb);
	}
}

L
Linus Torvalds 已提交
822 823 824 825 826 827 828 829 830 831 832
/* 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.
 */
833 834
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
835
{
836 837 838 839
	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
840
	struct tcp_out_options opts;
841
	unsigned int tcp_options_size, tcp_header_size;
842
	struct tcp_md5sig_key *md5;
843 844 845 846 847 848 849 850
	struct tcphdr *th;
	int err;

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

	/* If congestion control is doing timestamping, we must
	 * take such a timestamp before we potentially clone/copy.
	 */
851
	if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP)
852 853 854
		__net_timestamp(skb);

	if (likely(clone_it)) {
855 856 857 858 859 860 861
		const struct sk_buff *fclone = skb + 1;

		if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
			     fclone->fclone == SKB_FCLONE_CLONE))
			NET_INC_STATS_BH(sock_net(sk),
					 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);

862 863 864 865 866 867 868
		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
869

870 871 872
	inet = inet_sk(sk);
	tp = tcp_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
873
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
874

E
Eric Dumazet 已提交
875
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
876 877 878 879 880
		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);
881

E
Eric Dumazet 已提交
882
	if (tcp_packets_in_flight(tp) == 0)
883
		tcp_ca_event(sk, CA_EVENT_TX_START);
E
Eric Dumazet 已提交
884 885 886 887 888

	/* if no packet is in qdisc/device queue, then allow XPS to select
	 * another queue.
	 */
	skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
889

890 891
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
892 893 894 895 896 897

	skb_orphan(skb);
	skb->sk = sk;
	skb->destructor = (sysctl_tcp_limit_output_bytes > 0) ?
			  tcp_wfree : sock_wfree;
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
898 899

	/* Build TCP header and checksum it. */
900
	th = tcp_hdr(skb);
E
Eric Dumazet 已提交
901 902
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
903 904
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
905
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
906
					tcb->tcp_flags);
907

E
Eric Dumazet 已提交
908
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
909 910 911
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
912
		th->window	= htons(min(tp->rcv_wnd, 65535U));
913 914 915 916 917
	} else {
		th->window	= htons(tcp_select_window(sk));
	}
	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
918

I
Ilpo Järvinen 已提交
919
	/* The urg_mode check is necessary during a below snd_una win probe */
920 921 922 923 924
	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)) {
925
			th->urg_ptr = htons(0xFFFF);
926 927
			th->urg = 1;
		}
928
	}
L
Linus Torvalds 已提交
929

930
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
E
Eric Dumazet 已提交
931
	if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
932
		TCP_ECN_send(sk, skb, tcp_header_size);
L
Linus Torvalds 已提交
933

934 935 936
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
937
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
938
		tp->af_specific->calc_md5_hash(opts.hash_location,
939
					       md5, sk, NULL, skb);
940 941 942
	}
#endif

943
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
944

E
Eric Dumazet 已提交
945
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
946
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
947

948
	if (skb->len != tcp_header_size)
949
		tcp_event_data_sent(tp, sk);
L
Linus Torvalds 已提交
950

951
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
952 953
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
954

955
	err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl);
956
	if (likely(err <= 0))
957 958
		return err;

959
	tcp_enter_cwr(sk, 1);
960

961
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
962 963
}

964
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
965 966 967 968 969 970 971 972 973 974 975
 *
 * 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;
	skb_header_release(skb);
976
	tcp_add_write_queue_tail(sk, skb);
977 978
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
979 980
}

981
/* Initialize TSO segments for a packet. */
982
static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
983
				 unsigned int mss_now)
984
{
985 986
	if (skb->len <= mss_now || !sk_can_gso(sk) ||
	    skb->ip_summed == CHECKSUM_NONE) {
987 988 989
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
990 991
		skb_shinfo(skb)->gso_segs = 1;
		skb_shinfo(skb)->gso_size = 0;
992
		skb_shinfo(skb)->gso_type = 0;
993
	} else {
I
Ilpo Järvinen 已提交
994
		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
995
		skb_shinfo(skb)->gso_size = mss_now;
996
		skb_shinfo(skb)->gso_type = sk->sk_gso_type;
L
Linus Torvalds 已提交
997 998 999
	}
}

I
Ilpo Järvinen 已提交
1000
/* When a modification to fackets out becomes necessary, we need to check
1001
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1002
 */
1003
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1004 1005
				   int decr)
{
1006 1007
	struct tcp_sock *tp = tcp_sk(sk);

1008
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1009 1010
		return;

1011
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1012 1013 1014
		tp->fackets_out -= decr;
}

1015 1016 1017
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1018
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038
{
	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) &&
1039
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1040 1041 1042 1043 1044
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

L
Linus Torvalds 已提交
1045 1046
/* 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
1047
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1048 1049
 * Remember, these are still headerless SKBs at this point.
 */
1050 1051
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
		 unsigned int mss_now)
L
Linus Torvalds 已提交
1052 1053 1054
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1055
	int nsize, old_factor;
1056
	int nlen;
1057
	u8 flags;
L
Linus Torvalds 已提交
1058

1059 1060
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1061

L
Linus Torvalds 已提交
1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

	if (skb_cloned(skb) &&
	    skb_is_nonlinear(skb) &&
	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
		return -ENOMEM;

	/* Get a new skb... force flag on. */
	buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
	if (buff == NULL)
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1075

1076 1077
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1078 1079 1080
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1081 1082 1083 1084 1085 1086 1087

	/* 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
1088 1089 1090
	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;
1091
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
1092

1093
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1094
		/* Copy and checksum data tail into the new buffer. */
1095 1096
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1097 1098 1099 1100 1101 1102
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1103
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1104 1105 1106 1107 1108 1109 1110 1111 1112
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

	/* Looks stupid, but our code really uses when of
	 * skbs, which it never sent before. --ANK
	 */
	TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1113
	buff->tstamp = skb->tstamp;
L
Linus Torvalds 已提交
1114

1115 1116
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1117
	/* Fix up tso_factor for both original and new SKB.  */
1118 1119
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
L
Linus Torvalds 已提交
1120

1121 1122 1123
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1124
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1125 1126
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1127

1128 1129
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1130 1131 1132
	}

	/* Link BUFF into the send queue. */
1133
	skb_header_release(buff);
1134
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1135 1136 1137 1138 1139 1140 1141 1142

	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.
 */
1143
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1144 1145 1146
{
	int i, k, eat;

E
Eric Dumazet 已提交
1147 1148 1149 1150 1151 1152 1153
	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
1154 1155
	eat = len;
	k = 0;
1156
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
E
Eric Dumazet 已提交
1157 1158 1159
		int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

		if (size <= eat) {
1160
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1161
			eat -= size;
L
Linus Torvalds 已提交
1162 1163 1164 1165
		} else {
			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
			if (eat) {
				skb_shinfo(skb)->frags[k].page_offset += eat;
E
Eric Dumazet 已提交
1166
				skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
L
Linus Torvalds 已提交
1167 1168 1169 1170 1171 1172 1173
				eat = 0;
			}
			k++;
		}
	}
	skb_shinfo(skb)->nr_frags = k;

1174
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1175 1176 1177 1178
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1179
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1180 1181
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1182
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1183 1184
		return -ENOMEM;

E
Eric Dumazet 已提交
1185
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1186 1187

	TCP_SKB_CB(skb)->seq += len;
1188
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1189 1190 1191

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1192
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1193 1194
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1195
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1196
	if (tcp_skb_pcount(skb) > 1)
1197
		tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1198 1199 1200 1201

	return 0;
}

1202 1203
/* 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
1204
{
1205 1206
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1207 1208 1209 1210 1211 1212 1213
	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);

1214 1215 1216 1217 1218 1219 1220 1221
	/* 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
1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234
	/* 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;
}

1235 1236 1237 1238 1239 1240 1241 1242
/* 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
1243
/* Inverse of above */
1244
int tcp_mss_to_mtu(struct sock *sk, int mss)
J
John Heffner 已提交
1245
{
1246 1247
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1248 1249 1250 1251 1252 1253 1254
	int mtu;

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

1255 1256 1257 1258 1259 1260 1261
	/* 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
1262 1263 1264
	return mtu;
}

1265
/* MTU probing init per socket */
J
John Heffner 已提交
1266 1267 1268 1269 1270 1271 1272
void tcp_mtup_init(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);

	icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1273
			       icsk->icsk_af_ops->net_header_len;
J
John Heffner 已提交
1274 1275 1276
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
	icsk->icsk_mtup.probe_size = 0;
}
E
Eric Dumazet 已提交
1277
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1278

L
Linus Torvalds 已提交
1279 1280 1281 1282 1283 1284
/* 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
1285
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1286 1287
   It also does not include TCP options.

1288
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1289 1290 1291 1292 1293 1294 1295 1296 1297

   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.

1298 1299
   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
1300 1301 1302 1303
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1304
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1305
	int mss_now;
L
Linus Torvalds 已提交
1306

J
John Heffner 已提交
1307 1308
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1309

J
John Heffner 已提交
1310
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1311
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1312 1313

	/* And store cached results */
1314
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1315 1316
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1317
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1318 1319 1320

	return mss_now;
}
E
Eric Dumazet 已提交
1321
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1322 1323 1324 1325

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1326
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1327
{
1328 1329
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1330
	u32 mss_now;
1331
	unsigned int header_len;
A
Adam Langley 已提交
1332 1333
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1334 1335 1336

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1337 1338
	if (dst) {
		u32 mtu = dst_mtu(dst);
1339
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1340 1341 1342
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1343 1344 1345 1346 1347 1348 1349 1350 1351 1352
	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;
	}
1353

L
Linus Torvalds 已提交
1354 1355 1356
	return mss_now;
}

1357
/* Congestion window validation. (RFC2861) */
1358
static void tcp_cwnd_validate(struct sock *sk)
1359
{
1360
	struct tcp_sock *tp = tcp_sk(sk);
1361

1362
	if (tp->packets_out >= tp->snd_cwnd) {
1363 1364 1365 1366 1367 1368 1369 1370
		/* 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;

1371 1372
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1373 1374 1375 1376
			tcp_cwnd_application_limited(sk);
	}
}

1377 1378 1379 1380
/* Returns the portion of skb which can be sent right away without
 * introducing MSS oddities to segment boundaries. In rare cases where
 * mss_now != mss_cache, we will request caller to create a small skb
 * per input skb which could be mostly avoided here (if desired).
1381 1382 1383 1384 1385 1386 1387
 *
 * We explicitly want to create a request for splitting write queue tail
 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
 * thus all the complexity (cwnd_len is always MSS multiple which we
 * return whenever allowed by the other factors). Basically we need the
 * modulo only when the receiver window alone is the limiting factor or
 * when we would be allowed to send the split-due-to-Nagle skb fully.
1388
 */
1389
static unsigned int tcp_mss_split_point(const struct sock *sk, const struct sk_buff *skb,
1390
					unsigned int mss_now, unsigned int max_segs)
1391
{
1392
	const struct tcp_sock *tp = tcp_sk(sk);
1393
	u32 needed, window, max_len;
1394

1395
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1396
	max_len = mss_now * max_segs;
1397

1398 1399
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1400

1401 1402
	needed = min(skb->len, window);

1403 1404
	if (max_len <= needed)
		return max_len;
1405 1406

	return needed - needed % mss_now;
1407 1408 1409 1410 1411
}

/* 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.
 */
1412 1413
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1414 1415 1416 1417
{
	u32 in_flight, cwnd;

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1418 1419
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1420 1421 1422 1423 1424 1425 1426 1427 1428 1429
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
	if (in_flight < cwnd)
		return (cwnd - in_flight);

	return 0;
}

1430
/* Initialize TSO state of a skb.
1431
 * This must be invoked the first time we consider transmitting
1432 1433
 * SKB onto the wire.
 */
1434
static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
1435
			     unsigned int mss_now)
1436 1437 1438
{
	int tso_segs = tcp_skb_pcount(skb);

1439
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1440
		tcp_set_skb_tso_segs(sk, skb, mss_now);
1441 1442 1443 1444 1445
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}

1446
/* Minshall's variant of the Nagle send check. */
E
Eric Dumazet 已提交
1447
static inline bool tcp_minshall_check(const struct tcp_sock *tp)
1448
{
1449
	return after(tp->snd_sml, tp->snd_una) &&
1450 1451 1452
		!after(tp->snd_sml, tp->snd_nxt);
}

E
Eric Dumazet 已提交
1453
/* Return false, if packet can be sent now without violation Nagle's rules:
1454 1455
 * 1. It is full sized.
 * 2. Or it contains FIN. (already checked by caller)
F
Feng King 已提交
1456
 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1457 1458 1459
 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
 *    With Minshall's modification: all sent small packets are ACKed.
 */
E
Eric Dumazet 已提交
1460
static inline bool tcp_nagle_check(const struct tcp_sock *tp,
1461
				  const struct sk_buff *skb,
1462
				  unsigned int mss_now, int nonagle)
1463
{
E
Eric Dumazet 已提交
1464
	return skb->len < mss_now &&
1465
		((nonagle & TCP_NAGLE_CORK) ||
E
Eric Dumazet 已提交
1466
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1467 1468
}

E
Eric Dumazet 已提交
1469
/* Return true if the Nagle test allows this packet to be
1470 1471
 * sent now.
 */
E
Eric Dumazet 已提交
1472 1473
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1474 1475 1476 1477 1478 1479 1480 1481
{
	/* 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
1482
		return true;
1483

Y
Yuchung Cheng 已提交
1484 1485
	/* 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
1486
		return true;
1487 1488

	if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
E
Eric Dumazet 已提交
1489
		return true;
1490

E
Eric Dumazet 已提交
1491
	return false;
1492 1493 1494
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1495 1496 1497
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1498 1499 1500 1501 1502 1503
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1504
	return !after(end_seq, tcp_wnd_end(tp));
1505 1506
}

1507
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1508 1509 1510
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1511
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1512 1513
				 unsigned int cur_mss, int nonagle)
{
1514
	const struct tcp_sock *tp = tcp_sk(sk);
1515 1516
	unsigned int cwnd_quota;

1517
	tcp_init_tso_segs(sk, skb, cur_mss);
1518 1519 1520 1521 1522

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1523
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1524 1525 1526 1527 1528
		cwnd_quota = 0;

	return cwnd_quota;
}

1529
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1530
bool tcp_may_send_now(struct sock *sk)
1531
{
1532
	const struct tcp_sock *tp = tcp_sk(sk);
1533
	struct sk_buff *skb = tcp_send_head(sk);
1534

E
Eric Dumazet 已提交
1535
	return skb &&
I
Ilpo Järvinen 已提交
1536
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1537
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1538
			      tp->nonagle : TCP_NAGLE_PUSH));
1539 1540 1541 1542 1543 1544 1545 1546 1547
}

/* 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).
 */
1548
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1549
			unsigned int mss_now, gfp_t gfp)
1550 1551 1552
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1553
	u8 flags;
1554 1555

	/* All of a TSO frame must be composed of paged data.  */
1556 1557
	if (skb->len != skb->data_len)
		return tcp_fragment(sk, skb, len, mss_now);
1558

1559
	buff = sk_stream_alloc_skb(sk, 0, gfp);
1560 1561 1562
	if (unlikely(buff == NULL))
		return -ENOMEM;

1563 1564
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1565
	buff->truesize += nlen;
1566 1567 1568 1569 1570 1571 1572 1573
	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
1574 1575 1576
	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;
1577 1578 1579 1580

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

1581
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1582 1583 1584
	skb_split(skb, buff, len);

	/* Fix up tso_factor for both original and new SKB.  */
1585 1586
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
1587 1588 1589

	/* Link BUFF into the send queue. */
	skb_header_release(buff);
1590
	tcp_insert_write_queue_after(skb, buff, sk);
1591 1592 1593 1594 1595 1596 1597 1598 1599

	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.
 */
E
Eric Dumazet 已提交
1600
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1601
{
1602
	struct tcp_sock *tp = tcp_sk(sk);
1603
	const struct inet_connection_sock *icsk = inet_csk(sk);
1604
	u32 send_win, cong_win, limit, in_flight;
1605
	int win_divisor;
1606

E
Eric Dumazet 已提交
1607
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1608
		goto send_now;
1609

1610
	if (icsk->icsk_ca_state != TCP_CA_Open)
J
John Heffner 已提交
1611 1612 1613
		goto send_now;

	/* Defer for less than two clock ticks. */
I
Ilpo Järvinen 已提交
1614
	if (tp->tso_deferred &&
1615
	    (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
J
John Heffner 已提交
1616
		goto send_now;
1617

1618 1619
	in_flight = tcp_packets_in_flight(tp);

1620
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1621

1622
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1623 1624 1625 1626 1627 1628

	/* 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);

1629
	/* If a full-sized TSO skb can be sent, do it. */
1630 1631
	if (limit >= min_t(unsigned int, sk->sk_gso_max_size,
			   sk->sk_gso_max_segs * tp->mss_cache))
J
John Heffner 已提交
1632
		goto send_now;
1633

1634 1635 1636 1637
	/* 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;

1638 1639
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1640 1641 1642 1643 1644
		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.
		 */
1645
		chunk /= win_divisor;
1646
		if (limit >= chunk)
J
John Heffner 已提交
1647
			goto send_now;
1648 1649 1650 1651 1652 1653
	} 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.
		 */
1654
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1655
			goto send_now;
1656 1657
	}

E
Eric Dumazet 已提交
1658 1659 1660 1661 1662
	/* Ok, it looks like it is advisable to defer.
	 * Do not rearm the timer if already set to not break TCP ACK clocking.
	 */
	if (!tp->tso_deferred)
		tp->tso_deferred = 1 | (jiffies << 1);
J
John Heffner 已提交
1663

E
Eric Dumazet 已提交
1664
	return true;
J
John Heffner 已提交
1665 1666 1667

send_now:
	tp->tso_deferred = 0;
E
Eric Dumazet 已提交
1668
	return false;
1669 1670
}

J
John Heffner 已提交
1671
/* Create a new MTU probe if we are ready.
1672 1673 1674 1675
 * 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
1676 1677
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1678 1679
 *         -1 otherwise
 */
J
John Heffner 已提交
1680 1681 1682 1683 1684 1685 1686
static int tcp_mtu_probe(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct sk_buff *skb, *nskb, *next;
	int len;
	int probe_size;
1687
	int size_needed;
J
John Heffner 已提交
1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698
	int copy;
	int mss_now;

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
	 * not SACKing (the variable headers throw things off) */
	if (!icsk->icsk_mtup.enabled ||
	    icsk->icsk_mtup.probe_size ||
	    inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
	    tp->snd_cwnd < 11 ||
1699
	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
J
John Heffner 已提交
1700 1701 1702
		return -1;

	/* Very simple search strategy: just double the MSS. */
I
Ilpo Järvinen 已提交
1703
	mss_now = tcp_current_mss(sk);
1704
	probe_size = 2 * tp->mss_cache;
1705
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
J
John Heffner 已提交
1706 1707 1708 1709 1710 1711
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
		/* TODO: set timer for probe_converge_event */
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1712
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1713 1714
		return -1;

1715 1716
	if (tp->snd_wnd < size_needed)
		return -1;
1717
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1718
		return 0;
J
John Heffner 已提交
1719

1720 1721 1722
	/* 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
1723 1724 1725 1726 1727 1728 1729 1730
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
	if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
		return -1;
1731 1732
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
1733

1734
	skb = tcp_send_head(sk);
J
John Heffner 已提交
1735 1736 1737

	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
1738
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
1739 1740
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
1741
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
1742

1743 1744
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
1745
	len = 0;
1746
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
1747 1748 1749 1750 1751
		copy = min_t(int, skb->len, probe_size - len);
		if (nskb->ip_summed)
			skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
		else
			nskb->csum = skb_copy_and_csum_bits(skb, 0,
1752 1753
							    skb_put(nskb, copy),
							    copy, nskb->csum);
J
John Heffner 已提交
1754 1755 1756 1757

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
1758
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1759
			tcp_unlink_write_queue(skb, sk);
1760
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
1761
		} else {
E
Eric Dumazet 已提交
1762
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
1763
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
1764 1765
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
1766
				if (skb->ip_summed != CHECKSUM_PARTIAL)
1767 1768
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
1769 1770 1771 1772 1773 1774 1775 1776
			} else {
				__pskb_trim_head(skb, copy);
				tcp_set_skb_tso_segs(sk, skb, mss_now);
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
1777 1778 1779

		if (len >= probe_size)
			break;
J
John Heffner 已提交
1780 1781 1782 1783 1784 1785 1786 1787
	}
	tcp_init_tso_segs(sk, nskb, nskb->len);

	/* We're ready to send.  If this fails, the probe will
	 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
	TCP_SKB_CB(nskb)->when = tcp_time_stamp;
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
1788
		 * effectively two packets. */
J
John Heffner 已提交
1789
		tp->snd_cwnd--;
1790
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
1791 1792

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1793 1794
		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
1795 1796 1797 1798 1799 1800 1801

		return 1;
	}

	return -1;
}

L
Linus Torvalds 已提交
1802 1803 1804 1805
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
1806 1807 1808 1809
 * 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
1810 1811 1812
 * 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
1813 1814
 * 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
1815
 */
E
Eric Dumazet 已提交
1816 1817
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
1818 1819
{
	struct tcp_sock *tp = tcp_sk(sk);
1820
	struct sk_buff *skb;
1821 1822
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
1823
	int result;
L
Linus Torvalds 已提交
1824

1825
	sent_pkts = 0;
J
John Heffner 已提交
1826

1827 1828 1829 1830
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
1831
			return false;
1832 1833 1834
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
1835 1836
	}

1837
	while ((skb = tcp_send_head(sk))) {
1838 1839
		unsigned int limit;

E
Eric Dumazet 已提交
1840

1841
		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1842
		BUG_ON(!tso_segs);
1843

1844 1845 1846
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
			goto repair; /* Skip network transmission */

1847
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
1848 1849 1850 1851 1852 1853 1854
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
1855 1856 1857 1858

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

1859 1860 1861 1862 1863 1864
		if (tso_segs == 1) {
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
1865
			if (!push_one && tcp_tso_should_defer(sk, skb))
1866 1867
				break;
		}
1868

E
Eric Dumazet 已提交
1869 1870 1871 1872 1873 1874 1875
		/* TSQ : sk_wmem_alloc accounts skb truesize,
		 * including skb overhead. But thats OK.
		 */
		if (atomic_read(&sk->sk_wmem_alloc) >= sysctl_tcp_limit_output_bytes) {
			set_bit(TSQ_THROTTLED, &tp->tsq_flags);
			break;
		}
1876
		limit = mss_now;
1877
		if (tso_segs > 1 && !tcp_urg_mode(tp))
1878
			limit = tcp_mss_split_point(sk, skb, mss_now,
1879 1880 1881
						    min_t(unsigned int,
							  cwnd_quota,
							  sk->sk_gso_max_segs));
L
Linus Torvalds 已提交
1882

1883
		if (skb->len > limit &&
1884
		    unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
1885 1886
			break;

1887
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
1888

1889
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1890
			break;
L
Linus Torvalds 已提交
1891

1892
repair:
1893 1894 1895
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
1896
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
1897

1898
		tcp_minshall_update(tp, mss_now, skb);
1899
		sent_pkts += tcp_skb_pcount(skb);
1900 1901 1902

		if (push_one)
			break;
1903
	}
L
Linus Torvalds 已提交
1904

1905
	if (likely(sent_pkts)) {
1906 1907
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
1908 1909 1910 1911

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
1912
		tcp_cwnd_validate(sk);
E
Eric Dumazet 已提交
1913
		return false;
L
Linus Torvalds 已提交
1914
	}
N
Nandita Dukkipati 已提交
1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980
	return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk));
}

bool tcp_schedule_loss_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	u32 timeout, tlp_time_stamp, rto_time_stamp;
	u32 rtt = tp->srtt >> 3;

	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
		return false;
	/* No consecutive loss probes. */
	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
		tcp_rearm_rto(sk);
		return false;
	}
	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
	if (sk->sk_state == TCP_SYN_RECV)
		return false;

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

	/* Schedule a loss probe in 2*RTT for SACK capable connections
	 * in Open state, that are either limited by cwnd or application.
	 */
	if (sysctl_tcp_early_retrans < 3 || !rtt || !tp->packets_out ||
	    !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
		return false;

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

	/* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
	 * for delayed ack when there's one outstanding packet.
	 */
	timeout = rtt << 1;
	if (tp->packets_out == 1)
		timeout = max_t(u32, timeout,
				(rtt + (rtt >> 1) + TCP_DELACK_MAX));
	timeout = max_t(u32, timeout, msecs_to_jiffies(10));

	/* If RTO is shorter, just schedule TLP in its place. */
	tlp_time_stamp = tcp_time_stamp + timeout;
	rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
	if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
		s32 delta = rto_time_stamp - tcp_time_stamp;
		if (delta > 0)
			timeout = delta;
	}

	inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
				  TCP_RTO_MAX);
	return true;
}

/* When probe timeout (PTO) fires, send a new segment if one exists, else
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
1981
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
1982 1983 1984 1985 1986 1987 1988 1989 1990 1991
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);
	int err = -1;

	if (tcp_send_head(sk) != NULL) {
		err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
		goto rearm_timer;
	}

N
Nandita Dukkipati 已提交
1992 1993 1994 1995
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

N
Nandita Dukkipati 已提交
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
	/* Retransmit last segment. */
	skb = tcp_write_queue_tail(sk);
	if (WARN_ON(!skb))
		goto rearm_timer;

	pcount = tcp_skb_pcount(skb);
	if (WARN_ON(!pcount))
		goto rearm_timer;

	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss)))
			goto rearm_timer;
		skb = tcp_write_queue_tail(sk);
	}

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

	/* Probe with zero data doesn't trigger fast recovery. */
	if (skb->len > 0)
		err = __tcp_retransmit_skb(sk, skb);

N
Nandita Dukkipati 已提交
2018 2019 2020 2021
	/* Record snd_nxt for loss detection. */
	if (likely(!err))
		tp->tlp_high_seq = tp->snd_nxt;

N
Nandita Dukkipati 已提交
2022 2023 2024 2025 2026 2027 2028 2029 2030
rearm_timer:
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto,
				  TCP_RTO_MAX);

	if (likely(!err))
		NET_INC_STATS_BH(sock_net(sk),
				 LINUX_MIB_TCPLOSSPROBES);
	return;
L
Linus Torvalds 已提交
2031 2032
}

2033 2034 2035 2036
/* 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.
 */
2037 2038
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2039
{
2040 2041 2042 2043 2044 2045 2046
	/* 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;

2047 2048
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
			   sk_gfp_atomic(sk, GFP_ATOMIC)))
2049
		tcp_check_probe_timer(sk);
2050 2051
}

2052 2053 2054 2055 2056
/* 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)
{
2057
	struct sk_buff *skb = tcp_send_head(sk);
2058 2059 2060

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

2061
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2062 2063
}

L
Linus Torvalds 已提交
2064 2065
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2066
 *
L
Linus Torvalds 已提交
2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084
 * 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.
2085
 *
L
Linus Torvalds 已提交
2086 2087
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2088
 *
L
Linus Torvalds 已提交
2089
 * BSD seems to make the following compromise:
2090
 *
L
Linus Torvalds 已提交
2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117
 *	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)
{
2118
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2119
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2120
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2121 2122 2123 2124 2125
	 * 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
	 */
2126
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2127 2128 2129 2130 2131
	int free_space = tcp_space(sk);
	int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
	int window;

	if (mss > full_space)
2132
		mss = full_space;
L
Linus Torvalds 已提交
2133

2134
	if (free_space < (full_space >> 1)) {
2135
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2136

2137
		if (sk_under_memory_pressure(sk))
2138 2139
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171

		if (free_space < mss)
			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)
2172
			window = (free_space / mss) * mss;
2173
		else if (mss == full_space &&
2174
			 free_space > window + (full_space >> 1))
2175
			window = free_space;
L
Linus Torvalds 已提交
2176 2177 2178 2179 2180
	}

	return window;
}

2181 2182
/* Collapses two adjacent SKB's during retransmission. */
static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2183 2184
{
	struct tcp_sock *tp = tcp_sk(sk);
2185
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2186
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2187

2188 2189
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2190

2191
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2192

2193
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2194

2195
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2196

2197 2198
	skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
				  next_skb_size);
L
Linus Torvalds 已提交
2199

2200 2201
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2202

2203 2204
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2205

2206 2207
	/* 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
2208

2209
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2210
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2211 2212 2213 2214 2215 2216 2217

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

	/* changed transmit queue under us so clear hints */
2218 2219 2220
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2221

2222 2223
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2224
	sk_wmem_free_skb(sk, next_skb);
L
Linus Torvalds 已提交
2225 2226
}

2227
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2228
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2229 2230
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2231
		return false;
2232 2233
	/* TODO: SACK collapsing could be used to remove this condition */
	if (skb_shinfo(skb)->nr_frags != 0)
E
Eric Dumazet 已提交
2234
		return false;
2235
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2236
		return false;
2237
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2238
		return false;
2239 2240
	/* Some heurestics for collapsing over SACK'd could be invented */
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2241
		return false;
2242

E
Eric Dumazet 已提交
2243
	return true;
2244 2245
}

2246 2247 2248
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2249 2250 2251 2252 2253
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
2254
	bool first = true;
2255 2256 2257

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2258
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2259 2260 2261 2262 2263 2264 2265 2266 2267
		return;

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

		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2268
			first = false;
2269 2270 2271 2272 2273 2274 2275 2276
			continue;
		}

		if (space < 0)
			break;
		/* Punt if not enough space exists in the first SKB for
		 * the data in the second
		 */
2277
		if (skb->len > skb_availroom(to))
2278 2279 2280 2281 2282 2283 2284 2285 2286
			break;

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

		tcp_collapse_retrans(sk, to);
	}
}

L
Linus Torvalds 已提交
2287 2288 2289 2290
/* 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.
 */
2291
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2292 2293
{
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2294
	struct inet_connection_sock *icsk = inet_csk(sk);
2295
	unsigned int cur_mss;
L
Linus Torvalds 已提交
2296

J
John Heffner 已提交
2297 2298 2299 2300 2301
	/* Inconslusive MTU probe */
	if (icsk->icsk_mtup.probe_size) {
		icsk->icsk_mtup.probe_size = 0;
	}

L
Linus Torvalds 已提交
2302
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2303
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
	    min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
		return -EAGAIN;

	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;
	}

2316 2317 2318
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2319
	cur_mss = tcp_current_mss(sk);
2320

L
Linus Torvalds 已提交
2321 2322 2323 2324 2325
	/* 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.
	 */
2326 2327
	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
2328 2329 2330
		return -EAGAIN;

	if (skb->len > cur_mss) {
2331
		if (tcp_fragment(sk, skb, cur_mss, cur_mss))
L
Linus Torvalds 已提交
2332
			return -ENOMEM; /* We'll try again later. */
2333
	} else {
2334 2335 2336 2337 2338 2339
		int oldpcount = tcp_skb_pcount(skb);

		if (unlikely(oldpcount > 1)) {
			tcp_init_tso_segs(sk, skb, cur_mss);
			tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
		}
L
Linus Torvalds 已提交
2340 2341
	}

2342
	tcp_retrans_try_collapse(sk, skb, cur_mss);
L
Linus Torvalds 已提交
2343 2344 2345 2346 2347

	/* Some Solaris stacks overoptimize and ignore the FIN on a
	 * retransmit when old data is attached.  So strip it off
	 * since it is cheap to do so and saves bytes on the network.
	 */
S
Stephen Hemminger 已提交
2348
	if (skb->len > 0 &&
E
Eric Dumazet 已提交
2349
	    (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
S
Stephen Hemminger 已提交
2350
	    tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
L
Linus Torvalds 已提交
2351
		if (!pskb_trim(skb, 0)) {
2352 2353
			/* Reuse, even though it does some unnecessary work */
			tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1,
E
Eric Dumazet 已提交
2354
					     TCP_SKB_CB(skb)->tcp_flags);
L
Linus Torvalds 已提交
2355 2356 2357 2358 2359 2360 2361 2362 2363
			skb->ip_summed = CHECKSUM_NONE;
		}
	}

	/* Make a copy, if the first transmission SKB clone we made
	 * is still in somebody's hands, else make a clone.
	 */
	TCP_SKB_CB(skb)->when = tcp_time_stamp;

2364 2365 2366 2367 2368 2369
	/* make sure skb->data is aligned on arches that require it
	 * and check if ack-trimming & collapsing extended the headroom
	 * beyond what csum_start can cover.
	 */
	if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
		     skb_headroom(skb) >= 0xFFFF)) {
E
Eric Dumazet 已提交
2370 2371
		struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
						   GFP_ATOMIC);
2372 2373
		return nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			      -ENOBUFS;
E
Eric Dumazet 已提交
2374
	} else {
2375
		return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2376
	}
2377 2378 2379 2380 2381 2382
}

int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
	int err = __tcp_retransmit_skb(sk, skb);
L
Linus Torvalds 已提交
2383 2384 2385

	if (err == 0) {
		/* Update global TCP statistics. */
P
Pavel Emelyanov 已提交
2386
		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
L
Linus Torvalds 已提交
2387 2388 2389 2390

		tp->total_retrans++;

#if FASTRETRANS_DEBUG > 0
2391
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2392
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2393 2394
		}
#endif
2395 2396
		if (!tp->retrans_out)
			tp->lost_retrans_low = tp->snd_nxt;
L
Linus Torvalds 已提交
2397 2398 2399 2400 2401 2402 2403
		TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
		tp->retrans_out += tcp_skb_pcount(skb);

		/* Save stamp of the first retransmit. */
		if (!tp->retrans_stamp)
			tp->retrans_stamp = TCP_SKB_CB(skb)->when;

Y
Yuchung Cheng 已提交
2404
		tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2405 2406 2407 2408 2409 2410 2411 2412 2413

		/* snd_nxt is stored to detect loss of retransmitted segment,
		 * see tcp_input.c tcp_sacktag_write_queue().
		 */
		TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
	}
	return err;
}

2414 2415 2416
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
E
Eric Dumazet 已提交
2417
static bool tcp_can_forward_retransmit(struct sock *sk)
2418 2419
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2420
	const struct tcp_sock *tp = tcp_sk(sk);
2421 2422 2423

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
E
Eric Dumazet 已提交
2424
		return false;
2425 2426 2427

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
E
Eric Dumazet 已提交
2428
		return false;
2429 2430 2431 2432 2433 2434 2435 2436 2437 2438

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

	if (tcp_may_send_now(sk))
E
Eric Dumazet 已提交
2439
		return false;
2440

E
Eric Dumazet 已提交
2441
	return true;
2442 2443
}

L
Linus Torvalds 已提交
2444 2445 2446 2447 2448 2449 2450 2451 2452 2453
/* 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)
{
2454
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2455 2456
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2457
	struct sk_buff *hole = NULL;
2458
	u32 last_lost;
2459
	int mib_idx;
2460
	int fwd_rexmitting = 0;
2461

2462 2463 2464
	if (!tp->packets_out)
		return;

2465 2466 2467
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2468
	if (tp->retransmit_skb_hint) {
2469
		skb = tp->retransmit_skb_hint;
2470 2471 2472 2473
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2474
		skb = tcp_write_queue_head(sk);
2475 2476
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2477

2478 2479
	tcp_for_write_queue_from(skb, sk) {
		__u8 sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
2480

2481 2482 2483
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2484 2485
		if (hole == NULL)
			tp->retransmit_skb_hint = skb;
2486 2487 2488 2489 2490 2491 2492 2493 2494 2495

		/* Assume this retransmit will generate
		 * only one packet for congestion window
		 * calculation purposes.  This works because
		 * tcp_retransmit_skb() will chop up the
		 * packet to be MSS sized and all the
		 * packet counting works out.
		 */
		if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
			return;
L
Linus Torvalds 已提交
2496

2497 2498 2499 2500 2501
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2502

2503
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2504
			tp->retransmit_high = last_lost;
2505 2506 2507 2508 2509 2510 2511 2512 2513
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
			if (hole != NULL) {
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2514

2515
		} else if (!(sacked & TCPCB_LOST)) {
2516
			if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2517 2518
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2519

2520
		} else {
2521
			last_lost = TCP_SKB_CB(skb)->end_seq;
2522 2523 2524 2525 2526
			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
2527

2528
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2529 2530
			continue;

2531 2532
		if (tcp_retransmit_skb(sk, skb)) {
			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2533
			return;
2534
		}
2535
		NET_INC_STATS_BH(sock_net(sk), mib_idx);
L
Linus Torvalds 已提交
2536

2537
		if (tcp_in_cwnd_reduction(sk))
2538 2539
			tp->prr_out += tcp_skb_pcount(skb);

2540
		if (skb == tcp_write_queue_head(sk))
2541 2542 2543
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2544 2545 2546 2547 2548 2549 2550 2551
	}
}

/* Send a fin.  The caller locks the socket for us.  This cannot be
 * allowed to fail queueing a FIN frame under any circumstances.
 */
void tcp_send_fin(struct sock *sk)
{
2552
	struct tcp_sock *tp = tcp_sk(sk);
2553
	struct sk_buff *skb = tcp_write_queue_tail(sk);
L
Linus Torvalds 已提交
2554
	int mss_now;
2555

L
Linus Torvalds 已提交
2556 2557 2558 2559
	/* Optimization, tack on the FIN if we have a queue of
	 * unsent frames.  But be careful about outgoing SACKS
	 * and IP options.
	 */
I
Ilpo Järvinen 已提交
2560
	mss_now = tcp_current_mss(sk);
L
Linus Torvalds 已提交
2561

2562
	if (tcp_send_head(sk) != NULL) {
E
Eric Dumazet 已提交
2563
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
L
Linus Torvalds 已提交
2564 2565 2566 2567 2568
		TCP_SKB_CB(skb)->end_seq++;
		tp->write_seq++;
	} else {
		/* Socket is locked, keep trying until memory is available. */
		for (;;) {
2569 2570
			skb = alloc_skb_fclone(MAX_TCP_HEADER,
					       sk->sk_allocation);
L
Linus Torvalds 已提交
2571 2572 2573 2574 2575 2576 2577 2578
			if (skb)
				break;
			yield();
		}

		/* Reserve space for headers and prepare control bits. */
		skb_reserve(skb, MAX_TCP_HEADER);
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2579
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
2580
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
2581 2582
		tcp_queue_skb(sk, skb);
	}
2583
	__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
2584 2585 2586 2587 2588
}

/* 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
2589
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2590
 */
A
Al Viro 已提交
2591
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
2592 2593 2594 2595 2596 2597
{
	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
2598
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
2599 2600 2601 2602 2603
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
2604
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
2605
			     TCPHDR_ACK | TCPHDR_RST);
L
Linus Torvalds 已提交
2606 2607
	/* Send it off. */
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2608
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
2609
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2610

P
Pavel Emelyanov 已提交
2611
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
2612 2613
}

2614 2615
/* 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
2616 2617 2618 2619 2620 2621
 * 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)
{
2622
	struct sk_buff *skb;
L
Linus Torvalds 已提交
2623

2624
	skb = tcp_write_queue_head(sk);
E
Eric Dumazet 已提交
2625
	if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2626
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
2627 2628
		return -EFAULT;
	}
E
Eric Dumazet 已提交
2629
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
2630 2631 2632 2633
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
			if (nskb == NULL)
				return -ENOMEM;
2634
			tcp_unlink_write_queue(skb, sk);
L
Linus Torvalds 已提交
2635
			skb_header_release(nskb);
2636
			__tcp_add_write_queue_head(sk, nskb);
2637 2638 2639
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
2640 2641 2642
			skb = nskb;
		}

E
Eric Dumazet 已提交
2643
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
L
Linus Torvalds 已提交
2644 2645 2646
		TCP_ECN_send_synack(tcp_sk(sk), skb);
	}
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2647
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
2648 2649
}

2650 2651 2652 2653 2654 2655 2656 2657 2658
/**
 * 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.
 */
2659
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2660
				struct request_sock *req,
2661
				struct tcp_fastopen_cookie *foc)
L
Linus Torvalds 已提交
2662
{
2663
	struct tcp_out_options opts;
2664
	struct inet_request_sock *ireq = inet_rsk(req);
L
Linus Torvalds 已提交
2665 2666 2667
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcphdr *th;
	struct sk_buff *skb;
2668
	struct tcp_md5sig_key *md5;
2669
	int tcp_header_size;
2670
	int mss;
L
Linus Torvalds 已提交
2671

C
Christoph Paasch 已提交
2672
	skb = alloc_skb(MAX_TCP_HEADER + 15, sk_gfp_atomic(sk, GFP_ATOMIC));
2673 2674
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
2675
		return NULL;
2676
	}
L
Linus Torvalds 已提交
2677 2678 2679
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

2680
	skb_dst_set(skb, dst);
2681
	security_skb_owned_by(skb, sk);
L
Linus Torvalds 已提交
2682

2683
	mss = dst_metric_advmss(dst);
2684 2685 2686
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
		mss = tp->rx_opt.user_mss;

A
Adam Langley 已提交
2687 2688 2689 2690
	if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
		__u8 rcv_wscale;
		/* Set this up on the first call only */
		req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2691 2692 2693 2694 2695 2696

		/* limit the window selection if the user enforce a smaller rx buffer */
		if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
		    (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
			req->window_clamp = tcp_full_space(sk);

A
Adam Langley 已提交
2697 2698
		/* tcp_full_space because it is guaranteed to be the first packet */
		tcp_select_initial_window(tcp_full_space(sk),
2699
			mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
A
Adam Langley 已提交
2700 2701 2702
			&req->rcv_wnd,
			&req->window_clamp,
			ireq->wscale_ok,
2703 2704
			&rcv_wscale,
			dst_metric(dst, RTAX_INITRWND));
A
Adam Langley 已提交
2705 2706 2707 2708
		ireq->rcv_wscale = rcv_wscale;
	}

	memset(&opts, 0, sizeof(opts));
2709 2710 2711 2712 2713
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
		TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
	else
#endif
A
Adam Langley 已提交
2714
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
C
Christoph Paasch 已提交
2715 2716
	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
					     foc) + sizeof(*th);
2717

2718 2719
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
2720

2721
	th = tcp_hdr(skb);
L
Linus Torvalds 已提交
2722 2723 2724 2725
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
	TCP_ECN_make_synack(req, th);
2726
	th->source = ireq->loc_port;
2727
	th->dest = ireq->rmt_port;
2728 2729 2730 2731
	/* 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
2732
			     TCPHDR_SYN | TCPHDR_ACK);
2733

L
Linus Torvalds 已提交
2734
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
2735 2736
	/* 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
2737 2738

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2739
	th->window = htons(min(req->rcv_wnd, 65535U));
2740
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
L
Linus Torvalds 已提交
2741
	th->doff = (tcp_header_size >> 2);
2742
	TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb));
2743 2744 2745 2746

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
	if (md5) {
2747
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2748
					       md5, NULL, req, skb);
2749 2750 2751
	}
#endif

L
Linus Torvalds 已提交
2752 2753
	return skb;
}
E
Eric Dumazet 已提交
2754
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
2755

2756
/* Do all connect socket setups that can be done AF independent. */
P
Pavel Emelyanov 已提交
2757
void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
2758
{
2759
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
2760 2761 2762 2763 2764 2765 2766
	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) +
2767
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
2768

2769 2770 2771 2772 2773
#ifdef CONFIG_TCP_MD5SIG
	if (tp->af_specific->md5_lookup(sk, sk) != NULL)
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
2774 2775 2776 2777
	/* 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
2778
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
2779 2780 2781 2782
	tcp_sync_mss(sk, dst_mtu(dst));

	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2783
	tp->advmss = dst_metric_advmss(dst);
2784 2785 2786
	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
2787 2788
	tcp_initialize_rcv_mss(sk);

2789 2790 2791 2792 2793
	/* 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
2794 2795 2796 2797
	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,
2798
				  sysctl_tcp_window_scaling,
2799 2800
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
2801 2802 2803 2804 2805 2806 2807

	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;
2808
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
2809 2810
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
2811
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
2812
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
2813 2814 2815 2816 2817

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
2818

2819 2820
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
2821 2822 2823
	tcp_clear_retrans(tp);
}

2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848
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;
	skb_header_release(skb);
	__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;
2849
	int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen;
2850
	struct sk_buff *syn_data = NULL, *data;
2851 2852
	unsigned long last_syn_loss = 0;

2853
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
2854 2855 2856 2857 2858 2859 2860 2861
	tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
			       &syn_loss, &last_syn_loss);
	/* Recurring FO SYN losses: revert to regular handshake temporarily */
	if (syn_loss > 1 &&
	    time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
		fo->cookie.len = -1;
		goto fallback;
	}
2862

2863 2864 2865
	if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
		fo->cookie.len = -1;
	else if (fo->cookie.len <= 0)
2866 2867 2868 2869 2870 2871 2872 2873
		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;
2874
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907
		MAX_TCP_OPTION_SPACE;

	syn_data = skb_copy_expand(syn, skb_headroom(syn), space,
				   sk->sk_allocation);
	if (syn_data == NULL)
		goto fallback;

	for (i = 0; i < iovlen && syn_data->len < space; ++i) {
		struct iovec *iov = &fo->data->msg_iov[i];
		unsigned char __user *from = iov->iov_base;
		int len = iov->iov_len;

		if (syn_data->len + len > space)
			len = space - syn_data->len;
		else if (i + 1 == iovlen)
			/* No more data pending in inet_wait_for_connect() */
			fo->data = NULL;

		if (skb_add_data(syn_data, from, len))
			goto fallback;
	}

	/* Queue a data-only packet after the regular SYN for retransmission */
	data = pskb_copy(syn_data, sk->sk_allocation);
	if (data == NULL)
		goto fallback;
	TCP_SKB_CB(data)->seq++;
	TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN;
	TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH);
	tcp_connect_queue_skb(sk, data);
	fo->copied = data->len;

	if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
2908
		tp->syn_data = (fo->copied > 0);
2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
		goto done;
	}
	syn_data = NULL;

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;
	kfree_skb(syn_data);
done:
	fo->cookie.len = -1;  /* Exclude Fast Open option for SYN retries */
	return err;
}

2927
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
2928 2929 2930 2931
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
2932
	int err;
L
Linus Torvalds 已提交
2933 2934 2935

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
2936 2937 2938 2939 2940
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

2941
	buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
L
Linus Torvalds 已提交
2942 2943 2944 2945 2946 2947
	if (unlikely(buff == NULL))
		return -ENOBUFS;

	/* Reserve space for headers. */
	skb_reserve(buff, MAX_TCP_HEADER);

C
Changli Gao 已提交
2948
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
2949 2950
	tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
	tcp_connect_queue_skb(sk, buff);
2951
	TCP_ECN_send_syn(sk, buff);
L
Linus Torvalds 已提交
2952

2953 2954 2955
	/* 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);
2956 2957
	if (err == -ECONNREFUSED)
		return err;
2958 2959 2960 2961 2962 2963

	/* 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
2964
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
2965 2966

	/* Timer for repeating the SYN until an answer. */
2967 2968
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
2969 2970
	return 0;
}
E
Eric Dumazet 已提交
2971
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
2972 2973 2974 2975 2976 2977 2978

/* 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)
{
2979 2980
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
2981 2982 2983
	unsigned long timeout;

	if (ato > TCP_DELACK_MIN) {
2984
		const struct tcp_sock *tp = tcp_sk(sk);
2985
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
2986

2987 2988
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
2989 2990 2991 2992 2993
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
2994
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
2995 2996 2997
		 * directly.
		 */
		if (tp->srtt) {
2998
			int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN);
L
Linus Torvalds 已提交
2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010

			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. */
3011
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3012 3013 3014
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3015 3016
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3017 3018 3019 3020
			tcp_send_ack(sk);
			return;
		}

3021 3022
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3023
	}
3024 3025 3026
	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
3027 3028 3029 3030 3031
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3032
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3033

3034 3035 3036
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3037

3038 3039 3040 3041
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3042
	buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3043 3044 3045 3046 3047 3048
	if (buff == NULL) {
		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
3049
	}
3050 3051 3052

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3053
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3054 3055 3056

	/* Send it off, this clears delayed acks for us. */
	TCP_SKB_CB(buff)->when = tcp_time_stamp;
3057
	tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
L
Linus Torvalds 已提交
3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076
}

/* 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.
 */
static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3077
	skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3078
	if (skb == NULL)
L
Linus Torvalds 已提交
3079 3080 3081 3082 3083 3084 3085 3086
		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
3087
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
L
Linus Torvalds 已提交
3088
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
3089
	return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
L
Linus Torvalds 已提交
3090 3091
}

P
Pavel Emelyanov 已提交
3092 3093 3094 3095
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;
P
Pavel Emelyanov 已提交
3096
		tcp_sk(sk)->snd_nxt = tcp_sk(sk)->write_seq;
P
Pavel Emelyanov 已提交
3097 3098 3099 3100
		tcp_xmit_probe_skb(sk, 0);
	}
}

3101
/* Initiate keepalive or window probe from timer. */
L
Linus Torvalds 已提交
3102 3103
int tcp_write_wakeup(struct sock *sk)
{
3104 3105
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3106

3107 3108 3109 3110 3111 3112
	if (sk->sk_state == TCP_CLOSE)
		return -1;

	if ((skb = tcp_send_head(sk)) != NULL &&
	    before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
		int err;
I
Ilpo Järvinen 已提交
3113
		unsigned int mss = tcp_current_mss(sk);
3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125
		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
3126
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3127 3128 3129 3130 3131
			if (tcp_fragment(sk, skb, seg_size, mss))
				return -1;
		} else if (!tcp_skb_pcount(skb))
			tcp_set_skb_tso_segs(sk, skb, mss);

E
Eric Dumazet 已提交
3132
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3133 3134 3135 3136 3137 3138
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
		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
3139
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3140 3141
			tcp_xmit_probe_skb(sk, 1);
		return tcp_xmit_probe_skb(sk, 0);
L
Linus Torvalds 已提交
3142 3143 3144 3145 3146 3147 3148 3149
	}
}

/* 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)
{
3150
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3151 3152 3153 3154 3155
	struct tcp_sock *tp = tcp_sk(sk);
	int err;

	err = tcp_write_wakeup(sk);

3156
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3157
		/* Cancel probe timer, if it is not required. */
3158
		icsk->icsk_probes_out = 0;
3159
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3160 3161 3162 3163
		return;
	}

	if (err <= 0) {
3164 3165
		if (icsk->icsk_backoff < sysctl_tcp_retries2)
			icsk->icsk_backoff++;
3166
		icsk->icsk_probes_out++;
3167
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3168 3169
					  min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3170 3171
	} else {
		/* If packet was not sent due to local congestion,
3172
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3173 3174 3175 3176
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3177 3178
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3179
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3180
					  min(icsk->icsk_rto << icsk->icsk_backoff,
3181 3182
					      TCP_RESOURCE_PROBE_INTERVAL),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3183 3184
	}
}