tcp_output.c 71.8 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).
 *
 * Version:	$Id: tcp_output.c,v 1.146 2002/02/01 22:01:04 davem Exp $
 *
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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
 *
 */

#include <net/tcp.h>

#include <linux/compiler.h>
#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
 * 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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/* 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;
int sysctl_tcp_base_mss __read_mostly = 512;
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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 void update_send_head(struct sock *sk, struct sk_buff *skb)
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{
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	struct tcp_sock *tp = tcp_sk(sk);

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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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	tcp_packets_out_inc(sk, skb);
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}

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

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	if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt))
		return tp->snd_nxt;
	else
		return tp->snd_una+tp->snd_wnd;
}

/* 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);
	struct dst_entry *dst = __sk_dst_get(sk);
	int mss = tp->advmss;

	if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) {
		mss = dst_metric(dst, RTAX_ADVMSS);
		tp->advmss = mss;
	}

	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, 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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static void tcp_event_data_sent(struct tcp_sock *tp,
				struct sk_buff *skb, struct sock *sk)
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{
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	struct inet_connection_sock *icsk = inet_csk(sk);
	const u32 now = tcp_time_stamp;
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	if (sysctl_tcp_slow_start_after_idle &&
	    (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
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		tcp_cwnd_restart(sk, __sk_dst_get(sk));
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	tp->lsndtime = now;

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

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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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}

/* 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,
			       int wscale_ok, __u8 *rcv_wscale)
{
	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)++;
		}
	}

	/* Set initial window to value enough for senders,
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	 * following RFC2414. Senders, not following this RFC,
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	 * will be satisfied with 2.
	 */
	if (mss > (1<<*rcv_wscale)) {
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		int init_cwnd = 4;
		if (mss > 1460*3)
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			init_cwnd = 2;
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		else if (mss > 1460)
			init_cwnd = 3;
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		if (*rcv_wnd > init_cwnd*mss)
			*rcv_wnd = init_cwnd*mss;
	}

	/* Set the clamp no higher than max representable value */
	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
}

/* 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.
		 */
		new_win = cur_win;
	}
	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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static void tcp_build_and_update_options(__be32 *ptr, struct tcp_sock *tp,
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					 __u32 tstamp, __u8 **md5_hash)
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{
	if (tp->rx_opt.tstamp_ok) {
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		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_TIMESTAMP << 8) |
			       TCPOLEN_TIMESTAMP);
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		*ptr++ = htonl(tstamp);
		*ptr++ = htonl(tp->rx_opt.ts_recent);
	}
	if (tp->rx_opt.eff_sacks) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ? tp->duplicate_sack : tp->selective_acks;
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
			       (TCPOLEN_SACK_BASE + (tp->rx_opt.eff_sacks *
						     TCPOLEN_SACK_PERBLOCK)));
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		for (this_sack = 0; this_sack < tp->rx_opt.eff_sacks; this_sack++) {
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			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
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		if (tp->rx_opt.dsack) {
			tp->rx_opt.dsack = 0;
			tp->rx_opt.eff_sacks--;
		}
	}
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#ifdef CONFIG_TCP_MD5SIG
	if (md5_hash) {
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_MD5SIG << 8) |
			       TCPOLEN_MD5SIG);
		*md5_hash = (__u8 *)ptr;
	}
#endif
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}

/* Construct a tcp options header for a SYN or SYN_ACK packet.
 * If this is every changed make sure to change the definition of
 * MAX_SYN_SIZE to match the new maximum number of options that you
 * can generate.
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 *
 * Note - that with the RFC2385 TCP option, we make room for the
 * 16 byte MD5 hash. This will be filled in later, so the pointer for the
 * location to be filled is passed back up.
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 */
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static void tcp_syn_build_options(__be32 *ptr, int mss, int ts, int sack,
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				  int offer_wscale, int wscale, __u32 tstamp,
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				  __u32 ts_recent, __u8 **md5_hash)
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{
	/* 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.
	 */
	*ptr++ = htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | mss);
	if (ts) {
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		if (sack)
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			*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
				       (TCPOLEN_SACK_PERM << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
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		else
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			*ptr++ = htonl((TCPOPT_NOP << 24) |
				       (TCPOPT_NOP << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
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		*ptr++ = htonl(tstamp);		/* TSVAL */
		*ptr++ = htonl(ts_recent);	/* TSECR */
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	} else if (sack)
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		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_SACK_PERM << 8) |
			       TCPOLEN_SACK_PERM);
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	if (offer_wscale)
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		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_WINDOW << 16) |
			       (TCPOLEN_WINDOW << 8) |
			       (wscale));
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#ifdef CONFIG_TCP_MD5SIG
	/*
	 * If MD5 is enabled, then we set the option, and include the size
	 * (always 18). The actual MD5 hash is added just before the
	 * packet is sent.
	 */
	if (md5_hash) {
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_MD5SIG << 8) |
			       TCPOLEN_MD5SIG);
		*md5_hash = (__u8 *) ptr;
	}
#endif
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}
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/* 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.
 */
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static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, gfp_t gfp_mask)
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{
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	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct inet_sock *inet;
	struct tcp_sock *tp;
	struct tcp_skb_cb *tcb;
	int tcp_header_size;
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#ifdef CONFIG_TCP_MD5SIG
	struct tcp_md5sig_key *md5;
	__u8 *md5_hash_location;
#endif
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	struct tcphdr *th;
	int sysctl_flags;
	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.
	 */
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	if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP)
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		__net_timestamp(skb);

	if (likely(clone_it)) {
		if (unlikely(skb_cloned(skb)))
			skb = pskb_copy(skb, gfp_mask);
		else
			skb = skb_clone(skb, gfp_mask);
		if (unlikely(!skb))
			return -ENOBUFS;
	}
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	inet = inet_sk(sk);
	tp = tcp_sk(sk);
	tcb = TCP_SKB_CB(skb);
	tcp_header_size = tp->tcp_header_len;
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#define SYSCTL_FLAG_TSTAMPS	0x1
#define SYSCTL_FLAG_WSCALE	0x2
#define SYSCTL_FLAG_SACK	0x4

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	sysctl_flags = 0;
	if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
		tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS;
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		if (sysctl_tcp_timestamps) {
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			tcp_header_size += TCPOLEN_TSTAMP_ALIGNED;
			sysctl_flags |= SYSCTL_FLAG_TSTAMPS;
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		}
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		if (sysctl_tcp_window_scaling) {
			tcp_header_size += TCPOLEN_WSCALE_ALIGNED;
			sysctl_flags |= SYSCTL_FLAG_WSCALE;
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		}
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		if (sysctl_tcp_sack) {
			sysctl_flags |= SYSCTL_FLAG_SACK;
			if (!(sysctl_flags & SYSCTL_FLAG_TSTAMPS))
				tcp_header_size += TCPOLEN_SACKPERM_ALIGNED;
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		}
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	} else if (unlikely(tp->rx_opt.eff_sacks)) {
		/* A SACK is 2 pad bytes, a 2 byte header, plus
		 * 2 32-bit sequence numbers for each SACK block.
		 */
		tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED +
				    (tp->rx_opt.eff_sacks *
				     TCPOLEN_SACK_PERBLOCK));
	}
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	if (tcp_packets_in_flight(tp) == 0)
		tcp_ca_event(sk, CA_EVENT_TX_START);

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#ifdef CONFIG_TCP_MD5SIG
	/*
	 * Are we doing MD5 on this segment? If so - make
	 * room for it.
	 */
	md5 = tp->af_specific->md5_lookup(sk, sk);
	if (md5)
		tcp_header_size += TCPOLEN_MD5SIG_ALIGNED;
#endif

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	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
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	skb_set_owner_w(skb, sk);
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	/* Build TCP header and checksum it. */
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	th = tcp_hdr(skb);
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	th->source		= inet->sport;
	th->dest		= inet->dport;
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
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	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
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					tcb->flags);

	if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
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		th->window	= htons(min(tp->rcv_wnd, 65535U));
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	} else {
		th->window	= htons(tcp_select_window(sk));
	}
	th->check		= 0;
	th->urg_ptr		= 0;
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	if (unlikely(tp->urg_mode &&
		     between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF))) {
		th->urg_ptr		= htons(tp->snd_up-tcb->seq);
		th->urg			= 1;
	}
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	if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
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		tcp_syn_build_options((__be32 *)(th + 1),
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				      tcp_advertise_mss(sk),
				      (sysctl_flags & SYSCTL_FLAG_TSTAMPS),
				      (sysctl_flags & SYSCTL_FLAG_SACK),
				      (sysctl_flags & SYSCTL_FLAG_WSCALE),
				      tp->rx_opt.rcv_wscale,
				      tcb->when,
508 509 510 511 512 513
				      tp->rx_opt.ts_recent,

#ifdef CONFIG_TCP_MD5SIG
				      md5 ? &md5_hash_location :
#endif
				      NULL);
514
	} else {
515
		tcp_build_and_update_options((__be32 *)(th + 1),
516 517 518 519 520
					     tp, tcb->when,
#ifdef CONFIG_TCP_MD5SIG
					     md5 ? &md5_hash_location :
#endif
					     NULL);
521
		TCP_ECN_send(sk, skb, tcp_header_size);
522
	}
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524 525 526 527 528 529
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
		tp->af_specific->calc_md5_hash(md5_hash_location,
					       md5,
					       sk, NULL, NULL,
530
					       tcp_hdr(skb),
531 532 533 534 535
					       sk->sk_protocol,
					       skb->len);
	}
#endif

536
	icsk->icsk_af_ops->send_check(sk, skb->len, skb);
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538 539
	if (likely(tcb->flags & TCPCB_FLAG_ACK))
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
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541 542
	if (skb->len != tcp_header_size)
		tcp_event_data_sent(tp, skb, sk);
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544 545
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
		TCP_INC_STATS(TCP_MIB_OUTSEGS);
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547
	err = icsk->icsk_af_ops->queue_xmit(skb, 0);
548
	if (likely(err <= 0))
549 550
		return err;

551
	tcp_enter_cwr(sk, 1);
552

553
	return net_xmit_eval(err);
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#undef SYSCTL_FLAG_TSTAMPS
#undef SYSCTL_FLAG_WSCALE
#undef SYSCTL_FLAG_SACK
}


561
/* This routine just queue's the buffer
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 *
 * 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);
573
	tcp_add_write_queue_tail(sk, skb);
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	sk_charge_skb(sk, skb);
}

577
static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
578
{
579
	if (skb->len <= mss_now || !sk_can_gso(sk)) {
580 581 582
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
583 584 585
		skb_shinfo(skb)->gso_segs = 1;
		skb_shinfo(skb)->gso_size = 0;
		skb_shinfo(skb)->gso_type = 0;
586 587 588
	} else {
		unsigned int factor;

589 590
		factor = skb->len + (mss_now - 1);
		factor /= mss_now;
591 592
		skb_shinfo(skb)->gso_segs = factor;
		skb_shinfo(skb)->gso_size = mss_now;
593
		skb_shinfo(skb)->gso_type = sk->sk_gso_type;
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	}
}

/* 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
599
 * packet to the list.  This won't be called frequently, I hope.
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 * Remember, these are still headerless SKBs at this point.
 */
602
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now)
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{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
606
	int nsize, old_factor;
607
	int nlen;
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	u16 flags;

610
	BUG_ON(len > skb->len);
611

612
	clear_all_retrans_hints(tp);
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	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. */
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627 628 629 630
	sk_charge_skb(sk, buff);
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
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	/* 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. */
	flags = TCP_SKB_CB(skb)->flags;
	TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
	TCP_SKB_CB(buff)->flags = flags;
641
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
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	TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;

644
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
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		/* Copy and checksum data tail into the new buffer. */
		buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize),
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
653
		skb->ip_summed = CHECKSUM_PARTIAL;
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		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;
663
	buff->tstamp = skb->tstamp;
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665 666
	old_factor = tcp_skb_pcount(skb);

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	/* Fix up tso_factor for both original and new SKB.  */
668 669
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
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671 672 673
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
674
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
675 676
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
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678
		tp->packets_out -= diff;
679 680 681 682 683 684

		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
			tp->sacked_out -= diff;
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
			tp->retrans_out -= diff;

685 686 687 688
		if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
			tp->lost_out -= diff;
			tp->left_out -= diff;
		}
689

690
		if (diff > 0) {
691 692 693 694 695 696 697 698
			/* Adjust Reno SACK estimate. */
			if (!tp->rx_opt.sack_ok) {
				tp->sacked_out -= diff;
				if ((int)tp->sacked_out < 0)
					tp->sacked_out = 0;
				tcp_sync_left_out(tp);
			}

699 700 701 702
			tp->fackets_out -= diff;
			if ((int)tp->fackets_out < 0)
				tp->fackets_out = 0;
		}
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	}

	/* Link BUFF into the send queue. */
706
	skb_header_release(buff);
707
	tcp_insert_write_queue_after(skb, buff, sk);
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	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.
 */
716
static void __pskb_trim_head(struct sk_buff *skb, int len)
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{
	int i, k, eat;

	eat = len;
	k = 0;
	for (i=0; i<skb_shinfo(skb)->nr_frags; i++) {
		if (skb_shinfo(skb)->frags[i].size <= eat) {
			put_page(skb_shinfo(skb)->frags[i].page);
			eat -= skb_shinfo(skb)->frags[i].size;
		} else {
			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
			if (eat) {
				skb_shinfo(skb)->frags[k].page_offset += eat;
				skb_shinfo(skb)->frags[k].size -= eat;
				eat = 0;
			}
			k++;
		}
	}
	skb_shinfo(skb)->nr_frags = k;

738
	skb_reset_tail_pointer(skb);
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	skb->data_len -= len;
	skb->len = skb->data_len;
}

int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
	if (skb_cloned(skb) &&
	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
		return -ENOMEM;

749 750
	/* If len == headlen, we avoid __skb_pull to preserve alignment. */
	if (unlikely(len < skb_headlen(skb)))
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		__skb_pull(skb, len);
752 753
	else
		__pskb_trim_head(skb, len - skb_headlen(skb));
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	TCP_SKB_CB(skb)->seq += len;
756
	skb->ip_summed = CHECKSUM_PARTIAL;
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	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
	sk->sk_forward_alloc += len;
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

	/* Any change of skb->len requires recalculation of tso
	 * factor and mss.
	 */
	if (tcp_skb_pcount(skb) > 1)
767
		tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
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	return 0;
}

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/* Not accounting for SACKs here. */
int tcp_mtu_to_mss(struct sock *sk, int pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	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);

	/* 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;

	/* Now subtract TCP options size, not including SACKs */
	mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);

	return mss_now;
}

/* Inverse of above */
int tcp_mss_to_mtu(struct sock *sk, int mss)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	int mtu;

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

	return mtu;
}

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) +
823
			       icsk->icsk_af_ops->net_header_len;
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	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
	icsk->icsk_mtup.probe_size = 0;
}

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/* 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.
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   It is minimum of user_mss and mss received with SYN.
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   It also does not include TCP options.

837
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
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   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.

847 848
   NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
   are READ ONLY outside this function.		--ANK (980731)
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 */

unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
854
	struct inet_connection_sock *icsk = inet_csk(sk);
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	int mss_now;
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	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
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	mss_now = tcp_mtu_to_mss(sk, pmtu);
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	/* Bound mss with half of window */
	if (tp->max_window && mss_now > (tp->max_window>>1))
		mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len);

	/* And store cached results */
867
	icsk->icsk_pmtu_cookie = pmtu;
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	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
870
	tp->mss_cache = mss_now;
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	return mss_now;
}

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 *
 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
 * cannot be large. However, taking into account rare use of URG, this
 * is not a big flaw.
 */
882
unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
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{
	struct tcp_sock *tp = tcp_sk(sk);
	struct dst_entry *dst = __sk_dst_get(sk);
886 887 888 889 890 891
	u32 mss_now;
	u16 xmit_size_goal;
	int doing_tso = 0;

	mss_now = tp->mss_cache;

892
	if (large_allowed && sk_can_gso(sk) && !tp->urg_mode)
893
		doing_tso = 1;
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	if (dst) {
		u32 mtu = dst_mtu(dst);
897
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
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			mss_now = tcp_sync_mss(sk, mtu);
	}

901 902 903
	if (tp->rx_opt.eff_sacks)
		mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
			    (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
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905 906 907 908 909
#ifdef CONFIG_TCP_MD5SIG
	if (tp->af_specific->md5_lookup(sk, sk))
		mss_now -= TCPOLEN_MD5SIG_ALIGNED;
#endif

910
	xmit_size_goal = mss_now;
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912
	if (doing_tso) {
913 914
		xmit_size_goal = (65535 -
				  inet_csk(sk)->icsk_af_ops->net_header_len -
915 916
				  inet_csk(sk)->icsk_ext_hdr_len -
				  tp->tcp_header_len);
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918 919 920 921
		if (tp->max_window &&
		    (xmit_size_goal > (tp->max_window >> 1)))
			xmit_size_goal = max((tp->max_window >> 1),
					     68U - tp->tcp_header_len);
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923
		xmit_size_goal -= (xmit_size_goal % mss_now);
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	}
925
	tp->xmit_size_goal = xmit_size_goal;
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	return mss_now;
}

930 931
/* Congestion window validation. (RFC2861) */

932
static void tcp_cwnd_validate(struct sock *sk)
933
{
934
	struct tcp_sock *tp = tcp_sk(sk);
935 936 937 938 939 940 941 942 943 944 945
	__u32 packets_out = tp->packets_out;

	if (packets_out >= tp->snd_cwnd) {
		/* 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;

946 947
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
948 949 950 951
			tcp_cwnd_application_limited(sk);
	}
}

952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968
static unsigned int tcp_window_allows(struct tcp_sock *tp, struct sk_buff *skb, unsigned int mss_now, unsigned int cwnd)
{
	u32 window, cwnd_len;

	window = (tp->snd_una + tp->snd_wnd - TCP_SKB_CB(skb)->seq);
	cwnd_len = mss_now * cwnd;
	return min(window, cwnd_len);
}

/* 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.
 */
static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *skb)
{
	u32 in_flight, cwnd;

	/* Don't be strict about the congestion window for the final FIN.  */
969 970
	if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
	    tcp_skb_pcount(skb) == 1)
971 972 973 974 975 976 977 978 979 980 981 982 983
		return 1;

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

	return 0;
}

/* This must be invoked the first time we consider transmitting
 * SKB onto the wire.
 */
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static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
985 986 987
{
	int tso_segs = tcp_skb_pcount(skb);

988 989
	if (!tso_segs ||
	    (tso_segs > 1 &&
990
	     tcp_skb_mss(skb) != mss_now)) {
991
		tcp_set_skb_tso_segs(sk, skb, mss_now);
992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}

static inline int tcp_minshall_check(const struct tcp_sock *tp)
{
	return after(tp->snd_sml,tp->snd_una) &&
		!after(tp->snd_sml, tp->snd_nxt);
}

/* Return 0, if packet can be sent now without violation Nagle's rules:
 * 1. It is full sized.
 * 2. Or it contains FIN. (already checked by caller)
 * 3. Or TCP_NODELAY was set.
 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
 *    With Minshall's modification: all sent small packets are ACKed.
 */

static inline int tcp_nagle_check(const struct tcp_sock *tp,
1012
				  const struct sk_buff *skb,
1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036
				  unsigned mss_now, int nonagle)
{
	return (skb->len < mss_now &&
		((nonagle&TCP_NAGLE_CORK) ||
		 (!nonagle &&
		  tp->packets_out &&
		  tcp_minshall_check(tp))));
}

/* Return non-zero if the Nagle test allows this packet to be
 * sent now.
 */
static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb,
				 unsigned int cur_mss, int nonagle)
{
	/* 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)
		return 1;

1037 1038 1039 1040
	/* Don't use the nagle rule for urgent data (or for the final FIN).
	 * Nagle can be ignored during F-RTO too (see RFC4138).
	 */
	if (tp->urg_mode || (tp->frto_counter == 2) ||
1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060
	    (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
		return 1;

	if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
		return 1;

	return 0;
}

/* Does at least the first segment of SKB fit into the send window? */
static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, unsigned int cur_mss)
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

	return !after(end_seq, tp->snd_una + tp->snd_wnd);
}

1061
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1062 1063 1064 1065 1066 1067 1068 1069 1070
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
				 unsigned int cur_mss, int nonagle)
{
	struct tcp_sock *tp = tcp_sk(sk);
	unsigned int cwnd_quota;

1071
	tcp_init_tso_segs(sk, skb, cur_mss);
1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
	if (cwnd_quota &&
	    !tcp_snd_wnd_test(tp, skb, cur_mss))
		cwnd_quota = 0;

	return cwnd_quota;
}

1084
int tcp_may_send_now(struct sock *sk)
1085
{
1086
	struct tcp_sock *tp = tcp_sk(sk);
1087
	struct sk_buff *skb = tcp_send_head(sk);
1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102

	return (skb &&
		tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
			     (tcp_skb_is_last(sk, skb) ?
			      TCP_NAGLE_PUSH :
			      tp->nonagle)));
}

/* 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).
 */
1103
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now)
1104 1105 1106 1107 1108 1109
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
	u16 flags;

	/* All of a TSO frame must be composed of paged data.  */
1110 1111
	if (skb->len != skb->data_len)
		return tcp_fragment(sk, skb, len, mss_now);
1112 1113 1114 1115 1116

	buff = sk_stream_alloc_pskb(sk, 0, 0, GFP_ATOMIC);
	if (unlikely(buff == NULL))
		return -ENOMEM;

1117 1118
	sk_charge_skb(sk, buff);
	buff->truesize += nlen;
1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133
	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. */
	flags = TCP_SKB_CB(skb)->flags;
	TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
	TCP_SKB_CB(buff)->flags = flags;

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

1134
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1135 1136 1137
	skb_split(skb, buff, len);

	/* Fix up tso_factor for both original and new SKB.  */
1138 1139
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
1140 1141 1142

	/* Link BUFF into the send queue. */
	skb_header_release(buff);
1143
	tcp_insert_write_queue_after(skb, buff, sk);
1144 1145 1146 1147 1148 1149 1150 1151 1152

	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.
 */
1153
static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1154
{
1155
	struct tcp_sock *tp = tcp_sk(sk);
1156
	const struct inet_connection_sock *icsk = inet_csk(sk);
1157 1158 1159
	u32 send_win, cong_win, limit, in_flight;

	if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
J
John Heffner 已提交
1160
		goto send_now;
1161

1162
	if (icsk->icsk_ca_state != TCP_CA_Open)
J
John Heffner 已提交
1163 1164 1165 1166 1167
		goto send_now;

	/* Defer for less than two clock ticks. */
	if (!tp->tso_deferred && ((jiffies<<1)>>1) - (tp->tso_deferred>>1) > 1)
		goto send_now;
1168

1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180
	in_flight = tcp_packets_in_flight(tp);

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

	send_win = (tp->snd_una + tp->snd_wnd) - TCP_SKB_CB(skb)->seq;

	/* 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);

1181 1182
	/* If a full-sized TSO skb can be sent, do it. */
	if (limit >= 65536)
J
John Heffner 已提交
1183
		goto send_now;
1184

1185 1186 1187 1188 1189 1190 1191 1192
	if (sysctl_tcp_tso_win_divisor) {
		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.
		 */
		chunk /= sysctl_tcp_tso_win_divisor;
		if (limit >= chunk)
J
John Heffner 已提交
1193
			goto send_now;
1194 1195 1196 1197 1198 1199 1200
	} 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.
		 */
		if (limit > tcp_max_burst(tp) * tp->mss_cache)
J
John Heffner 已提交
1201
			goto send_now;
1202 1203 1204
	}

	/* Ok, it looks like it is advisable to defer.  */
J
John Heffner 已提交
1205 1206
	tp->tso_deferred = 1 | (jiffies<<1);

1207
	return 1;
J
John Heffner 已提交
1208 1209 1210 1211

send_now:
	tp->tso_deferred = 0;
	return 0;
1212 1213
}

J
John Heffner 已提交
1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249
/* Create a new MTU probe if we are ready.
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
 *         -1 otherwise */
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;
	unsigned int pif;
	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 ||
	    tp->rx_opt.eff_sacks)
		return -1;

	/* Very simple search strategy: just double the MSS. */
	mss_now = tcp_current_mss(sk, 0);
	probe_size = 2*tp->mss_cache;
	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? */
	len = 0;
1250
	if ((skb = tcp_send_head(sk)) == NULL)
J
John Heffner 已提交
1251 1252
		return -1;
	while ((len += skb->len) < probe_size && !tcp_skb_is_last(sk, skb))
1253
		skb = tcp_write_queue_next(sk, skb);
J
John Heffner 已提交
1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279
	if (len < probe_size)
		return -1;

	/* Receive window check. */
	if (after(TCP_SKB_CB(skb)->seq + probe_size, tp->snd_una + tp->snd_wnd)) {
		if (tp->snd_wnd < probe_size)
			return -1;
		else
			return 0;
	}

	/* Do we need to wait to drain cwnd? */
	pif = tcp_packets_in_flight(tp);
	if (pif + 2 > tp->snd_cwnd) {
		/* With no packets in flight, don't stall. */
		if (pif == 0)
			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;
	sk_charge_skb(sk, nskb);

1280 1281 1282
	skb = tcp_send_head(sk);
	tcp_insert_write_queue_before(nskb, skb, sk);
	tcp_advance_send_head(sk, skb);
J
John Heffner 已提交
1283 1284 1285 1286 1287 1288

	TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
	TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
	TCP_SKB_CB(nskb)->flags = TCPCB_FLAG_ACK;
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
1289
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
1290 1291 1292

	len = 0;
	while (len < probe_size) {
1293
		next = tcp_write_queue_next(sk, skb);
J
John Heffner 已提交
1294 1295 1296 1297 1298 1299

		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,
1300
					 skb_put(nskb, copy), copy, nskb->csum);
J
John Heffner 已提交
1301 1302 1303 1304 1305

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
			TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags;
1306
			tcp_unlink_write_queue(skb, sk);
J
John Heffner 已提交
1307 1308 1309
			sk_stream_free_skb(sk, skb);
		} else {
			TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags &
1310
						   ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
J
John Heffner 已提交
1311 1312
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
1313
				if (skb->ip_summed != CHECKSUM_PARTIAL)
J
John Heffner 已提交
1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333
					skb->csum = csum_partial(skb->data, skb->len, 0);
			} else {
				__pskb_trim_head(skb, copy);
				tcp_set_skb_tso_segs(sk, skb, mss_now);
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
		skb = next;
	}
	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
		* effectively two packets. */
		tp->snd_cwnd--;
1334
		update_send_head(sk, nskb);
J
John Heffner 已提交
1335 1336

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1337 1338
		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
1339 1340 1341 1342 1343 1344 1345 1346

		return 1;
	}

	return -1;
}


L
Linus Torvalds 已提交
1347 1348 1349 1350 1351 1352 1353
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
 * Returns 1, if no segments are in flight and we have queued segments, but
 * cannot send anything now because of SWS or another problem.
 */
1354
static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
L
Linus Torvalds 已提交
1355 1356
{
	struct tcp_sock *tp = tcp_sk(sk);
1357
	struct sk_buff *skb;
1358 1359
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
1360
	int result;
L
Linus Torvalds 已提交
1361 1362 1363 1364 1365

	/* 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.
	 */
1366 1367
	if (unlikely(sk->sk_state == TCP_CLOSE))
		return 0;
L
Linus Torvalds 已提交
1368

1369
	sent_pkts = 0;
J
John Heffner 已提交
1370 1371 1372 1373 1374 1375 1376 1377

	/* Do MTU probing. */
	if ((result = tcp_mtu_probe(sk)) == 0) {
		return 0;
	} else if (result > 0) {
		sent_pkts = 1;
	}

1378
	while ((skb = tcp_send_head(sk))) {
1379 1380
		unsigned int limit;

1381
		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1382
		BUG_ON(!tso_segs);
1383

1384 1385 1386 1387 1388 1389 1390
		cwnd_quota = tcp_cwnd_test(tp, skb);
		if (!cwnd_quota)
			break;

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

1391 1392 1393 1394 1395 1396
		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 {
1397
			if (tcp_tso_should_defer(sk, skb))
1398 1399
				break;
		}
1400

1401
		limit = mss_now;
1402
		if (tso_segs > 1) {
1403 1404
			limit = tcp_window_allows(tp, skb,
						  mss_now, cwnd_quota);
1405 1406 1407

			if (skb->len < limit) {
				unsigned int trim = skb->len % mss_now;
1408

1409 1410 1411
				if (trim)
					limit = skb->len - trim;
			}
1412
		}
L
Linus Torvalds 已提交
1413

1414 1415 1416 1417
		if (skb->len > limit &&
		    unlikely(tso_fragment(sk, skb, limit, mss_now)))
			break;

1418
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
1419

1420
		if (unlikely(tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC)))
1421
			break;
L
Linus Torvalds 已提交
1422

1423 1424 1425
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
1426
		update_send_head(sk, skb);
L
Linus Torvalds 已提交
1427

1428
		tcp_minshall_update(tp, mss_now, skb);
1429
		sent_pkts++;
1430
	}
L
Linus Torvalds 已提交
1431

1432
	if (likely(sent_pkts)) {
1433
		tcp_cwnd_validate(sk);
1434
		return 0;
L
Linus Torvalds 已提交
1435
	}
1436
	return !tp->packets_out && tcp_send_head(sk);
L
Linus Torvalds 已提交
1437 1438
}

1439 1440 1441 1442
/* 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.
 */
1443 1444
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
1445
{
1446
	struct sk_buff *skb = tcp_send_head(sk);
1447 1448

	if (skb) {
1449
		if (tcp_write_xmit(sk, cur_mss, nonagle))
1450
			tcp_check_probe_timer(sk);
1451 1452 1453
	}
}

1454 1455 1456 1457 1458 1459
/* 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)
{
	struct tcp_sock *tp = tcp_sk(sk);
1460
	struct sk_buff *skb = tcp_send_head(sk);
1461 1462 1463 1464
	unsigned int tso_segs, cwnd_quota;

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

1465
	tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1466 1467 1468
	cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);

	if (likely(cwnd_quota)) {
1469 1470
		unsigned int limit;

1471 1472
		BUG_ON(!tso_segs);

1473
		limit = mss_now;
1474
		if (tso_segs > 1) {
1475 1476
			limit = tcp_window_allows(tp, skb,
						  mss_now, cwnd_quota);
1477 1478 1479 1480 1481 1482 1483 1484 1485

			if (skb->len < limit) {
				unsigned int trim = skb->len % mss_now;

				if (trim)
					limit = skb->len - trim;
			}
		}

1486 1487 1488 1489
		if (skb->len > limit &&
		    unlikely(tso_fragment(sk, skb, limit, mss_now)))
			return;

1490 1491 1492
		/* Send it out now. */
		TCP_SKB_CB(skb)->when = tcp_time_stamp;

1493
		if (likely(!tcp_transmit_skb(sk, skb, 1, sk->sk_allocation))) {
1494 1495
			update_send_head(sk, skb);
			tcp_cwnd_validate(sk);
1496 1497 1498 1499 1500
			return;
		}
	}
}

L
Linus Torvalds 已提交
1501 1502
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
1503
 *
L
Linus Torvalds 已提交
1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521
 * 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.
1522
 *
L
Linus Torvalds 已提交
1523 1524
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
1525
 *
L
Linus Torvalds 已提交
1526
 * BSD seems to make the following compromise:
1527
 *
L
Linus Torvalds 已提交
1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554
 *	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)
{
1555
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1556
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
1557
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
1558 1559 1560 1561 1562
	 * 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
	 */
1563
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
1564 1565 1566 1567 1568
	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)
1569
		mss = full_space;
L
Linus Torvalds 已提交
1570 1571

	if (free_space < full_space/2) {
1572
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608

		if (tcp_memory_pressure)
			tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss);

		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)
			window = (free_space/mss)*mss;
1609 1610 1611
		else if (mss == full_space &&
		         free_space > window + full_space/2)
			window = free_space;
L
Linus Torvalds 已提交
1612 1613 1614 1615 1616 1617 1618 1619 1620
	}

	return window;
}

/* Attempt to collapse two adjacent SKB's during retransmission. */
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now)
{
	struct tcp_sock *tp = tcp_sk(sk);
1621
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
L
Linus Torvalds 已提交
1622 1623 1624 1625 1626 1627 1628 1629 1630

	/* The first test we must make is that neither of these two
	 * SKB's are still referenced by someone else.
	 */
	if (!skb_cloned(skb) && !skb_cloned(next_skb)) {
		int skb_size = skb->len, next_skb_size = next_skb->len;
		u16 flags = TCP_SKB_CB(skb)->flags;

		/* Also punt if next skb has been SACK'd. */
S
Stephen Hemminger 已提交
1631
		if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED)
L
Linus Torvalds 已提交
1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648
			return;

		/* Next skb is out of window. */
		if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd))
			return;

		/* Punt if not enough space exists in the first SKB for
		 * the data in the second, or the total combined payload
		 * would exceed the MSS.
		 */
		if ((next_skb_size > skb_tailroom(skb)) ||
		    ((skb_size + next_skb_size) > mss_now))
			return;

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

1649 1650 1651 1652
		/* changing transmit queue under us so clear hints */
		clear_all_retrans_hints(tp);

		/* Ok.	We will be able to collapse the packet. */
1653
		tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
1654

1655 1656 1657
		skb_copy_from_linear_data(next_skb,
					  skb_put(skb, next_skb_size),
					  next_skb_size);
L
Linus Torvalds 已提交
1658

1659 1660
		if (next_skb->ip_summed == CHECKSUM_PARTIAL)
			skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1661

1662
		if (skb->ip_summed != CHECKSUM_PARTIAL)
L
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1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697
			skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);

		/* Update sequence range on original skb. */
		TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;

		/* Merge over control information. */
		flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */
		TCP_SKB_CB(skb)->flags = flags;

		/* 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|TCPCB_AT_TAIL);
		if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS)
			tp->retrans_out -= tcp_skb_pcount(next_skb);
		if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) {
			tp->lost_out -= tcp_skb_pcount(next_skb);
			tp->left_out -= tcp_skb_pcount(next_skb);
		}
		/* Reno case is special. Sigh... */
		if (!tp->rx_opt.sack_ok && tp->sacked_out) {
			tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
			tp->left_out -= tcp_skb_pcount(next_skb);
		}

		/* Not quite right: it can be > snd.fack, but
		 * it is better to underestimate fackets.
		 */
		tcp_dec_pcount_approx(&tp->fackets_out, next_skb);
		tcp_packets_out_dec(tp, next_skb);
		sk_stream_free_skb(sk, next_skb);
	}
}

/* Do a simple retransmit without using the backoff mechanisms in
1698
 * tcp_timer. This is used for path mtu discovery.
L
Linus Torvalds 已提交
1699
 * The socket is already locked here.
1700
 */
L
Linus Torvalds 已提交
1701 1702
void tcp_simple_retransmit(struct sock *sk)
{
1703
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1704 1705 1706 1707 1708
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
	unsigned int mss = tcp_current_mss(sk, 0);
	int lost = 0;

1709 1710 1711
	tcp_for_write_queue(skb, sk) {
		if (skb == tcp_send_head(sk))
			break;
1712
		if (skb->len > mss &&
L
Linus Torvalds 已提交
1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725
		    !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
			if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
				tp->retrans_out -= tcp_skb_pcount(skb);
			}
			if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) {
				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
				tp->lost_out += tcp_skb_pcount(skb);
				lost = 1;
			}
		}
	}

1726 1727
	clear_all_retrans_hints(tp);

L
Linus Torvalds 已提交
1728 1729 1730 1731 1732
	if (!lost)
		return;

	tcp_sync_left_out(tp);

1733
	/* Don't muck with the congestion window here.
L
Linus Torvalds 已提交
1734 1735 1736 1737
	 * Reason is that we do not increase amount of _data_
	 * in network, but units changed and effective
	 * cwnd/ssthresh really reduced now.
	 */
1738
	if (icsk->icsk_ca_state != TCP_CA_Loss) {
L
Linus Torvalds 已提交
1739
		tp->high_seq = tp->snd_nxt;
1740
		tp->snd_ssthresh = tcp_current_ssthresh(sk);
L
Linus Torvalds 已提交
1741 1742
		tp->prior_ssthresh = 0;
		tp->undo_marker = 0;
1743
		tcp_set_ca_state(sk, TCP_CA_Loss);
L
Linus Torvalds 已提交
1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754
	}
	tcp_xmit_retransmit_queue(sk);
}

/* 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.
 */
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
1755
	struct inet_connection_sock *icsk = inet_csk(sk);
1756
	unsigned int cur_mss = tcp_current_mss(sk, 0);
L
Linus Torvalds 已提交
1757 1758
	int err;

J
John Heffner 已提交
1759 1760 1761 1762 1763
	/* Inconslusive MTU probe */
	if (icsk->icsk_mtup.probe_size) {
		icsk->icsk_mtup.probe_size = 0;
	}

L
Linus Torvalds 已提交
1764
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
1765
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787
	 */
	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;
	}

	/* 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.
	 */
	if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)
	    && TCP_SKB_CB(skb)->seq != tp->snd_una)
		return -EAGAIN;

	if (skb->len > cur_mss) {
1788
		if (tcp_fragment(sk, skb, cur_mss, cur_mss))
L
Linus Torvalds 已提交
1789 1790 1791 1792
			return -ENOMEM; /* We'll try again later. */
	}

	/* Collapse two adjacent packets if worthwhile and we can. */
S
Stephen Hemminger 已提交
1793 1794 1795 1796 1797 1798 1799
	if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) &&
	    (skb->len < (cur_mss >> 1)) &&
	    (tcp_write_queue_next(sk, skb) != tcp_send_head(sk)) &&
	    (!tcp_skb_is_last(sk, skb)) &&
	    (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(tcp_write_queue_next(sk, skb))->nr_frags == 0) &&
	    (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(tcp_write_queue_next(sk, skb)) == 1) &&
	    (sysctl_tcp_retrans_collapse != 0))
L
Linus Torvalds 已提交
1800 1801
		tcp_retrans_try_collapse(sk, skb, cur_mss);

1802
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
L
Linus Torvalds 已提交
1803 1804 1805 1806 1807 1808
		return -EHOSTUNREACH; /* Routing failure or similar. */

	/* 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
1809 1810 1811
	if (skb->len > 0 &&
	    (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
	    tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
L
Linus Torvalds 已提交
1812 1813
		if (!pskb_trim(skb, 0)) {
			TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1;
1814 1815 1816
			skb_shinfo(skb)->gso_segs = 1;
			skb_shinfo(skb)->gso_size = 0;
			skb_shinfo(skb)->gso_type = 0;
L
Linus Torvalds 已提交
1817 1818 1819 1820 1821 1822 1823 1824 1825 1826
			skb->ip_summed = CHECKSUM_NONE;
			skb->csum = 0;
		}
	}

	/* 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;

1827
	err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
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1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867

	if (err == 0) {
		/* Update global TCP statistics. */
		TCP_INC_STATS(TCP_MIB_RETRANSSEGS);

		tp->total_retrans++;

#if FASTRETRANS_DEBUG > 0
		if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
			if (net_ratelimit())
				printk(KERN_DEBUG "retrans_out leaked.\n");
		}
#endif
		TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
		tp->retrans_out += tcp_skb_pcount(skb);

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

		tp->undo_retrans++;

		/* 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;
}

/* 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)
{
1868
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1869 1870
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
1871 1872 1873 1874 1875 1876
	int packet_cnt;

	if (tp->retransmit_skb_hint) {
		skb = tp->retransmit_skb_hint;
		packet_cnt = tp->retransmit_cnt_hint;
	}else{
1877
		skb = tcp_write_queue_head(sk);
1878 1879
		packet_cnt = 0;
	}
L
Linus Torvalds 已提交
1880 1881

	/* First pass: retransmit lost packets. */
1882
	if (tp->lost_out) {
1883
		tcp_for_write_queue_from(skb, sk) {
L
Linus Torvalds 已提交
1884 1885
			__u8 sacked = TCP_SKB_CB(skb)->sacked;

1886 1887
			if (skb == tcp_send_head(sk))
				break;
1888 1889 1890 1891
			/* we could do better than to assign each time */
			tp->retransmit_skb_hint = skb;
			tp->retransmit_cnt_hint = packet_cnt;

L
Linus Torvalds 已提交
1892 1893 1894 1895 1896 1897 1898 1899 1900 1901
			/* 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;

1902
			if (sacked & TCPCB_LOST) {
L
Linus Torvalds 已提交
1903
				if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
1904 1905
					if (tcp_retransmit_skb(sk, skb)) {
						tp->retransmit_skb_hint = NULL;
L
Linus Torvalds 已提交
1906
						return;
1907
					}
1908
					if (icsk->icsk_ca_state != TCP_CA_Loss)
L
Linus Torvalds 已提交
1909 1910 1911 1912
						NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS);
					else
						NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS);

1913
					if (skb == tcp_write_queue_head(sk))
1914
						inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1915 1916
									  inet_csk(sk)->icsk_rto,
									  TCP_RTO_MAX);
L
Linus Torvalds 已提交
1917 1918
				}

1919 1920
				packet_cnt += tcp_skb_pcount(skb);
				if (packet_cnt >= tp->lost_out)
L
Linus Torvalds 已提交
1921 1922 1923 1924 1925 1926 1927 1928
					break;
			}
		}
	}

	/* OK, demanded retransmission is finished. */

	/* Forward retransmissions are possible only during Recovery. */
1929
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
L
Linus Torvalds 已提交
1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942
		return;

	/* No forward retransmissions in Reno are possible. */
	if (!tp->rx_opt.sack_ok)
		return;

	/* 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.
	 */

1943
	if (tcp_may_send_now(sk))
L
Linus Torvalds 已提交
1944 1945
		return;

1946 1947 1948 1949
	if (tp->forward_skb_hint) {
		skb = tp->forward_skb_hint;
		packet_cnt = tp->forward_cnt_hint;
	} else{
1950
		skb = tcp_write_queue_head(sk);
1951 1952 1953
		packet_cnt = 0;
	}

1954 1955 1956
	tcp_for_write_queue_from(skb, sk) {
		if (skb == tcp_send_head(sk))
			break;
1957 1958
		tp->forward_cnt_hint = packet_cnt;
		tp->forward_skb_hint = skb;
L
Linus Torvalds 已提交
1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975

		/* Similar to the retransmit loop above we
		 * can pretend that the retransmitted SKB
		 * we send out here will be composed of one
		 * real MSS sized packet because tcp_retransmit_skb()
		 * will fragment it if necessary.
		 */
		if (++packet_cnt > tp->fackets_out)
			break;

		if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
			break;

		if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
			continue;

		/* Ok, retransmit it. */
1976 1977
		if (tcp_retransmit_skb(sk, skb)) {
			tp->forward_skb_hint = NULL;
L
Linus Torvalds 已提交
1978
			break;
1979
		}
L
Linus Torvalds 已提交
1980

1981
		if (skb == tcp_write_queue_head(sk))
1982 1983 1984
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

		NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS);
	}
}


/* 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)
{
1996
	struct tcp_sock *tp = tcp_sk(sk);
1997
	struct sk_buff *skb = tcp_write_queue_tail(sk);
L
Linus Torvalds 已提交
1998
	int mss_now;
1999

L
Linus Torvalds 已提交
2000 2001 2002 2003 2004 2005
	/* Optimization, tack on the FIN if we have a queue of
	 * unsent frames.  But be careful about outgoing SACKS
	 * and IP options.
	 */
	mss_now = tcp_current_mss(sk, 1);

2006
	if (tcp_send_head(sk) != NULL) {
L
Linus Torvalds 已提交
2007 2008 2009 2010 2011 2012
		TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
		TCP_SKB_CB(skb)->end_seq++;
		tp->write_seq++;
	} else {
		/* Socket is locked, keep trying until memory is available. */
		for (;;) {
2013
			skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL);
L
Linus Torvalds 已提交
2014 2015 2016 2017 2018 2019 2020 2021 2022 2023
			if (skb)
				break;
			yield();
		}

		/* Reserve space for headers and prepare control bits. */
		skb_reserve(skb, MAX_TCP_HEADER);
		skb->csum = 0;
		TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
		TCP_SKB_CB(skb)->sacked = 0;
2024 2025 2026
		skb_shinfo(skb)->gso_segs = 1;
		skb_shinfo(skb)->gso_size = 0;
		skb_shinfo(skb)->gso_type = 0;
L
Linus Torvalds 已提交
2027 2028 2029 2030 2031 2032

		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
		TCP_SKB_CB(skb)->seq = tp->write_seq;
		TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
		tcp_queue_skb(sk, skb);
	}
2033
	__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
L
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2034 2035 2036 2037 2038
}

/* 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
2039
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2040
 */
A
Al Viro 已提交
2041
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
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Linus Torvalds 已提交
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{
	struct sk_buff *skb;

	/* NOTE: No TCP options attached and we never retransmit this. */
	skb = alloc_skb(MAX_TCP_HEADER, priority);
	if (!skb) {
		NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
	skb->csum = 0;
	TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
	TCP_SKB_CB(skb)->sacked = 0;
2057 2058 2059
	skb_shinfo(skb)->gso_segs = 1;
	skb_shinfo(skb)->gso_size = 0;
	skb_shinfo(skb)->gso_type = 0;
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	/* Send it off. */
2062
	TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk);
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	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2065
	if (tcp_transmit_skb(sk, skb, 0, priority))
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		NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
}

/* WARNING: This routine must only be called when we have already sent
 * 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)
{
	struct sk_buff* skb;

2078
	skb = tcp_write_queue_head(sk);
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	if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) {
		printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
		return -EFAULT;
	}
	if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) {
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
			if (nskb == NULL)
				return -ENOMEM;
2088
			tcp_unlink_write_queue(skb, sk);
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			skb_header_release(nskb);
2090
			__tcp_add_write_queue_head(sk, nskb);
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			sk_stream_free_skb(sk, skb);
			sk_charge_skb(sk, nskb);
			skb = nskb;
		}

		TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK;
		TCP_ECN_send_synack(tcp_sk(sk), skb);
	}
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2100
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
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}

/*
 * Prepare a SYN-ACK.
 */
struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2107
				 struct request_sock *req)
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{
2109
	struct inet_request_sock *ireq = inet_rsk(req);
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	struct tcp_sock *tp = tcp_sk(sk);
	struct tcphdr *th;
	int tcp_header_size;
	struct sk_buff *skb;
2114 2115 2116 2117
#ifdef CONFIG_TCP_MD5SIG
	struct tcp_md5sig_key *md5;
	__u8 *md5_hash_location;
#endif
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	skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
	if (skb == NULL)
		return NULL;

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

	skb->dst = dst_clone(dst);

	tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS +
2129 2130
			   (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
			   (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
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			   /* SACK_PERM is in the place of NOP NOP of TS */
2132
			   ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
2133 2134 2135 2136 2137 2138 2139

#ifdef CONFIG_TCP_MD5SIG
	/* Are we doing MD5 on this segment? If so - make room for it */
	md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
	if (md5)
		tcp_header_size += TCPOLEN_MD5SIG_ALIGNED;
#endif
2140 2141
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
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2143
	th = tcp_hdr(skb);
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	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
	TCP_ECN_make_synack(req, th);
	th->source = inet_sk(sk)->sport;
2149 2150
	th->dest = ireq->rmt_port;
	TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn;
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	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
	TCP_SKB_CB(skb)->sacked = 0;
2153 2154 2155
	skb_shinfo(skb)->gso_segs = 1;
	skb_shinfo(skb)->gso_size = 0;
	skb_shinfo(skb)->gso_type = 0;
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	th->seq = htonl(TCP_SKB_CB(skb)->seq);
2157
	th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
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	if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2159
		__u8 rcv_wscale;
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		/* Set this up on the first call only */
		req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
		/* tcp_full_space because it is guaranteed to be the first packet */
2163
		tcp_select_initial_window(tcp_full_space(sk),
2164
			dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
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			&req->rcv_wnd,
			&req->window_clamp,
2167
			ireq->wscale_ok,
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			&rcv_wscale);
2169
		ireq->rcv_wscale = rcv_wscale;
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	}

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2173
	th->window = htons(min(req->rcv_wnd, 65535U));
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	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2176
	tcp_syn_build_options((__be32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
2177
			      ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
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			      TCP_SKB_CB(skb)->when,
2179 2180 2181 2182 2183 2184 2185
			      req->ts_recent,
			      (
#ifdef CONFIG_TCP_MD5SIG
			       md5 ? &md5_hash_location :
#endif
			       NULL)
			      );
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	skb->csum = 0;
	th->doff = (tcp_header_size >> 2);
	TCP_INC_STATS(TCP_MIB_OUTSEGS);
2190 2191 2192 2193 2194 2195 2196

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
	if (md5) {
		tp->af_specific->calc_md5_hash(md5_hash_location,
					       md5,
					       NULL, dst, req,
2197
					       tcp_hdr(skb), sk->sk_protocol,
2198 2199 2200 2201
					       skb->len);
	}
#endif

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	return skb;
}

2205
/*
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 * Do all connect socket setups that can be done AF independent.
2207
 */
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static void tcp_connect_init(struct sock *sk)
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{
	struct dst_entry *dst = __sk_dst_get(sk);
	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) +
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);

2220 2221 2222 2223 2224
#ifdef CONFIG_TCP_MD5SIG
	if (tp->af_specific->md5_lookup(sk, sk) != NULL)
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

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	/* 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;
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	tcp_mtup_init(sk);
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	tcp_sync_mss(sk, dst_mtu(dst));

	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
	tp->advmss = dst_metric(dst, RTAX_ADVMSS);
	tcp_initialize_rcv_mss(sk);

	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,
				  sysctl_tcp_window_scaling,
				  &rcv_wscale);

	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;
	tcp_init_wl(tp, tp->write_seq, 0);
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
	tp->rcv_nxt = 0;
	tp->rcv_wup = 0;
	tp->copied_seq = 0;

2257 2258
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
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	tcp_clear_retrans(tp);
}

/*
 * Build a SYN and send it off.
2264
 */
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int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;

	tcp_connect_init(sk);

2272
	buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
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	if (unlikely(buff == NULL))
		return -ENOBUFS;

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

	TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN;
2280
	TCP_ECN_send_syn(sk, buff);
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	TCP_SKB_CB(buff)->sacked = 0;
2282 2283 2284
	skb_shinfo(buff)->gso_segs = 1;
	skb_shinfo(buff)->gso_size = 0;
	skb_shinfo(buff)->gso_type = 0;
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	buff->csum = 0;
2286
	tp->snd_nxt = tp->write_seq;
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	TCP_SKB_CB(buff)->seq = tp->write_seq++;
	TCP_SKB_CB(buff)->end_seq = tp->write_seq;

	/* Send it off. */
	TCP_SKB_CB(buff)->when = tcp_time_stamp;
	tp->retrans_stamp = TCP_SKB_CB(buff)->when;
	skb_header_release(buff);
2294
	__tcp_add_write_queue_tail(sk, buff);
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	sk_charge_skb(sk, buff);
	tp->packets_out += tcp_skb_pcount(buff);
2297
	tcp_transmit_skb(sk, buff, 1, GFP_KERNEL);
2298 2299 2300 2301 2302 2303

	/* 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;
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	TCP_INC_STATS(TCP_MIB_ACTIVEOPENS);

	/* Timer for repeating the SYN until an answer. */
2307 2308
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
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	return 0;
}

/* 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)
{
2318 2319
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
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	unsigned long timeout;

	if (ato > TCP_DELACK_MIN) {
2323
		const struct tcp_sock *tp = tcp_sk(sk);
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		int max_ato = HZ/2;

2326
		if (icsk->icsk_ack.pingpong || (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
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			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
2332
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
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		 * directly.
		 */
		if (tp->srtt) {
			int rtt = max(tp->srtt>>3, TCP_DELACK_MIN);

			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. */
2349
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
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2350 2351 2352
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
2353 2354
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
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			tcp_send_ack(sk);
			return;
		}

2359 2360
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
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2361
	}
2362 2363 2364
	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
	icsk->icsk_ack.timeout = timeout;
	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
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}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
	/* If we have been reset, we may not send again. */
	if (sk->sk_state != TCP_CLOSE) {
		struct sk_buff *buff;

		/* We are not putting this on the write queue, so
		 * tcp_transmit_skb() will set the ownership to this
		 * sock.
		 */
		buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
		if (buff == NULL) {
2380 2381
			inet_csk_schedule_ack(sk);
			inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
2382 2383
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
						  TCP_DELACK_MAX, TCP_RTO_MAX);
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			return;
		}

		/* Reserve space for headers and prepare control bits. */
		skb_reserve(buff, MAX_TCP_HEADER);
		buff->csum = 0;
		TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK;
		TCP_SKB_CB(buff)->sacked = 0;
2392 2393 2394
		skb_shinfo(buff)->gso_segs = 1;
		skb_shinfo(buff)->gso_size = 0;
		skb_shinfo(buff)->gso_type = 0;
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		/* Send it off, this clears delayed acks for us. */
2397
		TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk);
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		TCP_SKB_CB(buff)->when = tcp_time_stamp;
2399
		tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC);
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	}
}

/* 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. */
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2421
	if (skb == NULL)
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		return -1;

	/* Reserve space for headers and set control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
	skb->csum = 0;
	TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
	TCP_SKB_CB(skb)->sacked = urgent;
2429 2430 2431
	skb_shinfo(skb)->gso_segs = 1;
	skb_shinfo(skb)->gso_size = 0;
	skb_shinfo(skb)->gso_type = 0;
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2432 2433 2434 2435 2436 2437 2438 2439

	/* Use a previous sequence.  This should cause the other
	 * end to send an ack.  Don't queue or clone SKB, just
	 * send it.
	 */
	TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1;
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2440
	return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
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}

int tcp_write_wakeup(struct sock *sk)
{
	if (sk->sk_state != TCP_CLOSE) {
		struct tcp_sock *tp = tcp_sk(sk);
		struct sk_buff *skb;

2449
		if ((skb = tcp_send_head(sk)) != NULL &&
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		    before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) {
			int err;
			unsigned int mss = tcp_current_mss(sk, 0);
			unsigned int seg_size = tp->snd_una+tp->snd_wnd-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);
				TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
2466
				if (tcp_fragment(sk, skb, seg_size, mss))
L
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2467 2468
					return -1;
			} else if (!tcp_skb_pcount(skb))
2469
				tcp_set_skb_tso_segs(sk, skb, mss);
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			TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
			TCP_SKB_CB(skb)->when = tcp_time_stamp;
2473
			err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
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2474
			if (!err) {
2475
				update_send_head(sk, skb);
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2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492
			}
			return err;
		} else {
			if (tp->urg_mode &&
			    between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF))
				tcp_xmit_probe_skb(sk, TCPCB_URG);
			return tcp_xmit_probe_skb(sk, 0);
		}
	}
	return -1;
}

/* 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)
{
2493
	struct inet_connection_sock *icsk = inet_csk(sk);
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2494 2495 2496 2497 2498
	struct tcp_sock *tp = tcp_sk(sk);
	int err;

	err = tcp_write_wakeup(sk);

2499
	if (tp->packets_out || !tcp_send_head(sk)) {
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2500
		/* Cancel probe timer, if it is not required. */
2501
		icsk->icsk_probes_out = 0;
2502
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
2503 2504 2505 2506
		return;
	}

	if (err <= 0) {
2507 2508
		if (icsk->icsk_backoff < sysctl_tcp_retries2)
			icsk->icsk_backoff++;
2509
		icsk->icsk_probes_out++;
2510
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2511 2512
					  min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2513 2514
	} else {
		/* If packet was not sent due to local congestion,
2515
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
2516 2517 2518 2519
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
2520 2521
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
2522
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2523
					  min(icsk->icsk_rto << icsk->icsk_backoff,
2524 2525
					      TCP_RESOURCE_PROBE_INTERVAL),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2526 2527 2528 2529 2530 2531 2532
	}
}

EXPORT_SYMBOL(tcp_connect);
EXPORT_SYMBOL(tcp_make_synack);
EXPORT_SYMBOL(tcp_simple_retransmit);
EXPORT_SYMBOL(tcp_sync_mss);
2533
EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor);
J
John Heffner 已提交
2534
EXPORT_SYMBOL(tcp_mtup_init);