tcp_output.c 73.7 KB
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/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Implementation of the Transmission Control Protocol(TCP).
 *
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 * Authors:	Ross Biro
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 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

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

#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 tcp_event_new_data_sent(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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	unsigned int prior_packets = tp->packets_out;
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	tcp_advance_send_head(sk, skb);
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	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
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	/* Don't override Nagle indefinately with F-RTO */
	if (tp->frto_counter == 2)
		tp->frto_counter = 3;
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	tp->packets_out += tcp_skb_pcount(skb);
	if (!prior_packets)
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
					  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
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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(tcp_wnd_end(tp), tp->snd_nxt))
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		return tp->snd_nxt;
	else
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		return tcp_wnd_end(tp);
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}

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

	/* 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.
		 */
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		new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
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	}
	tp->rcv_wnd = new_win;
	tp->rcv_wup = tp->rcv_nxt;

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

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

	/* If we advertise zero window, disable fast path. */
	if (new_win == 0)
		tp->pred_flags = 0;

	return new_win;
}

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static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb)
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{
	TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR;
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	if (!(tp->ecn_flags & TCP_ECN_OK))
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		TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE;
}

static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);

	tp->ecn_flags = 0;
	if (sysctl_tcp_ecn) {
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		TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ECE | TCPCB_FLAG_CWR;
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		tp->ecn_flags = TCP_ECN_OK;
	}
}

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

static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
				int tcp_header_len)
{
	struct tcp_sock *tp = tcp_sk(sk);

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

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

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

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

	TCP_SKB_CB(skb)->seq = seq;
	if (flags & (TCPCB_FLAG_SYN | TCPCB_FLAG_FIN))
		seq++;
	TCP_SKB_CB(skb)->end_seq = seq;
}

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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);
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		*md5_hash = (__u8 *)ptr;
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	}
#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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Stephen Hemminger 已提交
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		if (sysctl_tcp_timestamps) {
513 514
			tcp_header_size += TCPOLEN_TSTAMP_ALIGNED;
			sysctl_flags |= SYSCTL_FLAG_TSTAMPS;
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		}
516 517 518
		if (sysctl_tcp_window_scaling) {
			tcp_header_size += TCPOLEN_WSCALE_ALIGNED;
			sysctl_flags |= SYSCTL_FLAG_WSCALE;
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		}
520 521 522 523
		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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		}
525 526 527 528 529 530 531 532
	} 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));
	}
533

534 535 536
	if (tcp_packets_in_flight(tp) == 0)
		tcp_ca_event(sk, CA_EVENT_TX_START);

537 538 539 540 541 542 543 544 545 546
#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

547 548
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
549
	skb_set_owner_w(skb, sk);
550 551

	/* Build TCP header and checksum it. */
552
	th = tcp_hdr(skb);
553 554 555 556
	th->source		= inet->sport;
	th->dest		= inet->dport;
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
557
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
558 559 560 561 562 563
					tcb->flags);

	if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
564
		th->window	= htons(min(tp->rcv_wnd, 65535U));
565 566 567 568 569
	} else {
		th->window	= htons(tcp_select_window(sk));
	}
	th->check		= 0;
	th->urg_ptr		= 0;
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571
	if (unlikely(tp->urg_mode &&
572 573
		     between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF))) {
		th->urg_ptr		= htons(tp->snd_up - tcb->seq);
574 575
		th->urg			= 1;
	}
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577
	if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
578
		tcp_syn_build_options((__be32 *)(th + 1),
579 580 581 582 583 584
				      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,
585 586 587 588 589 590
				      tp->rx_opt.ts_recent,

#ifdef CONFIG_TCP_MD5SIG
				      md5 ? &md5_hash_location :
#endif
				      NULL);
591
	} else {
592
		tcp_build_and_update_options((__be32 *)(th + 1),
593 594 595 596 597
					     tp, tcb->when,
#ifdef CONFIG_TCP_MD5SIG
					     md5 ? &md5_hash_location :
#endif
					     NULL);
598
		TCP_ECN_send(sk, skb, tcp_header_size);
599
	}
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601 602 603 604 605 606
#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,
607
					       tcp_hdr(skb),
608 609 610 611
					       skb->len);
	}
#endif

612
	icsk->icsk_af_ops->send_check(sk, skb->len, skb);
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614 615
	if (likely(tcb->flags & TCPCB_FLAG_ACK))
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
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616

617 618
	if (skb->len != tcp_header_size)
		tcp_event_data_sent(tp, skb, sk);
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620
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
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Pavel Emelyanov 已提交
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		TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
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623
	err = icsk->icsk_af_ops->queue_xmit(skb, 0);
624
	if (likely(err <= 0))
625 626
		return err;

627
	tcp_enter_cwr(sk, 1);
628

629
	return net_xmit_eval(err);
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#undef SYSCTL_FLAG_TSTAMPS
#undef SYSCTL_FLAG_WSCALE
#undef SYSCTL_FLAG_SACK
}

636
/* 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);
648
	tcp_add_write_queue_tail(sk, skb);
649 650
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
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}

653 654
static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb,
				 unsigned int mss_now)
655
{
656
	if (skb->len <= mss_now || !sk_can_gso(sk)) {
657 658 659
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
660 661 662
		skb_shinfo(skb)->gso_segs = 1;
		skb_shinfo(skb)->gso_size = 0;
		skb_shinfo(skb)->gso_type = 0;
663
	} else {
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Ilpo Järvinen 已提交
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		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
665
		skb_shinfo(skb)->gso_size = mss_now;
666
		skb_shinfo(skb)->gso_type = sk->sk_gso_type;
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	}
}

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/* When a modification to fackets out becomes necessary, we need to check
671
 * skb is counted to fackets_out or not.
I
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 */
673
static void tcp_adjust_fackets_out(struct sock *sk, struct sk_buff *skb,
I
Ilpo Järvinen 已提交
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				   int decr)
{
676 677
	struct tcp_sock *tp = tcp_sk(sk);

678
	if (!tp->sacked_out || tcp_is_reno(tp))
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Ilpo Järvinen 已提交
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		return;

681
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
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Ilpo Järvinen 已提交
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		tp->fackets_out -= decr;
}

L
Linus Torvalds 已提交
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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
687
 * 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.
 */
690 691
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
		 unsigned int mss_now)
L
Linus Torvalds 已提交
692 693 694
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
695
	int nsize, old_factor;
696
	int nlen;
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	u16 flags;

699
	BUG_ON(len > skb->len);
700

701
	tcp_clear_retrans_hints_partial(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. */
H
Herbert Xu 已提交
715

716 717
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
718 719 720
	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;
729
	TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH);
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	TCP_SKB_CB(buff)->flags = flags;
731
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
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733
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
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		/* Copy and checksum data tail into the new buffer. */
735 736
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
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						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
743
		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;
753
	buff->tstamp = skb->tstamp;
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755 756
	old_factor = tcp_skb_pcount(skb);

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	/* Fix up tso_factor for both original and new SKB.  */
758 759
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
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761 762 763
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
764
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
765 766
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
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768
		tp->packets_out -= diff;
769 770 771 772 773 774

		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;

775
		if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
776
			tp->lost_out -= diff;
777

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		/* Adjust Reno SACK estimate. */
		if (tcp_is_reno(tp) && diff > 0) {
			tcp_dec_pcount_approx_int(&tp->sacked_out, diff);
			tcp_verify_left_out(tp);
782
		}
783
		tcp_adjust_fackets_out(sk, skb, diff);
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	}

	/* Link BUFF into the send queue. */
787
	skb_header_release(buff);
788
	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.
 */
797
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
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{
	int i, k, eat;

	eat = len;
	k = 0;
803
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
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		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;

819
	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)
{
826
	if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
L
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827 828
		return -ENOMEM;

829 830
	/* If len == headlen, we avoid __skb_pull to preserve alignment. */
	if (unlikely(len < skb_headlen(skb)))
L
Linus Torvalds 已提交
831
		__skb_pull(skb, len);
832 833
	else
		__pskb_trim_head(skb, len - skb_headlen(skb));
L
Linus Torvalds 已提交
834 835

	TCP_SKB_CB(skb)->seq += len;
836
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
837 838 839

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
840
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
841 842 843 844 845 846
	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)
847
		tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
L
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848 849 850 851

	return 0;
}

J
John Heffner 已提交
852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902
/* 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) +
903
			       icsk->icsk_af_ops->net_header_len;
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John Heffner 已提交
904 905 906 907
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
	icsk->icsk_mtup.probe_size = 0;
}

908 909 910 911 912 913 914 915 916
/* Bound MSS / TSO packet size with the half of the window */
static int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
{
	if (tp->max_window && pktsize > (tp->max_window >> 1))
		return max(tp->max_window >> 1, 68U - tp->tcp_header_len);
	else
		return pktsize;
}

L
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917 918 919 920 921 922
/* This function synchronize snd mss to current pmtu/exthdr set.

   tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
   for TCP options, but includes only bare TCP header.

   tp->rx_opt.mss_clamp is mss negotiated at connection setup.
S
Stephen Hemminger 已提交
923
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
924 925
   It also does not include TCP options.

926
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
927 928 929 930 931 932 933 934 935

   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.

936 937
   NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
   are READ ONLY outside this function.		--ANK (980731)
L
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938 939 940 941
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
942
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
943
	int mss_now;
L
Linus Torvalds 已提交
944

J
John Heffner 已提交
945 946
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
947

J
John Heffner 已提交
948
	mss_now = tcp_mtu_to_mss(sk, pmtu);
949
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
950 951

	/* And store cached results */
952
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
953 954
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
955
	tp->mss_cache = mss_now;
L
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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.
 */
967
unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
L
Linus Torvalds 已提交
968 969 970
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct dst_entry *dst = __sk_dst_get(sk);
971 972 973 974 975 976
	u32 mss_now;
	u16 xmit_size_goal;
	int doing_tso = 0;

	mss_now = tp->mss_cache;

977
	if (large_allowed && sk_can_gso(sk) && !tp->urg_mode)
978
		doing_tso = 1;
L
Linus Torvalds 已提交
979 980 981

	if (dst) {
		u32 mtu = dst_mtu(dst);
982
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
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983 984 985
			mss_now = tcp_sync_mss(sk, mtu);
	}

986 987 988
	if (tp->rx_opt.eff_sacks)
		mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
			    (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
L
Linus Torvalds 已提交
989

990 991 992 993 994
#ifdef CONFIG_TCP_MD5SIG
	if (tp->af_specific->md5_lookup(sk, sk))
		mss_now -= TCPOLEN_MD5SIG_ALIGNED;
#endif

995
	xmit_size_goal = mss_now;
L
Linus Torvalds 已提交
996

997
	if (doing_tso) {
998
		xmit_size_goal = ((sk->sk_gso_max_size - 1) -
999
				  inet_csk(sk)->icsk_af_ops->net_header_len -
1000 1001
				  inet_csk(sk)->icsk_ext_hdr_len -
				  tp->tcp_header_len);
L
Linus Torvalds 已提交
1002

1003
		xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal);
1004
		xmit_size_goal -= (xmit_size_goal % mss_now);
L
Linus Torvalds 已提交
1005
	}
1006
	tp->xmit_size_goal = xmit_size_goal;
L
Linus Torvalds 已提交
1007 1008 1009 1010

	return mss_now;
}

1011
/* Congestion window validation. (RFC2861) */
1012
static void tcp_cwnd_validate(struct sock *sk)
1013
{
1014
	struct tcp_sock *tp = tcp_sk(sk);
1015

1016
	if (tp->packets_out >= tp->snd_cwnd) {
1017 1018 1019 1020 1021 1022 1023 1024
		/* 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;

1025 1026
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1027 1028 1029 1030
			tcp_cwnd_application_limited(sk);
	}
}

1031 1032 1033 1034
/* Returns the portion of skb which can be sent right away without
 * introducing MSS oddities to segment boundaries. In rare cases where
 * mss_now != mss_cache, we will request caller to create a small skb
 * per input skb which could be mostly avoided here (if desired).
1035 1036 1037 1038 1039 1040 1041
 *
 * We explicitly want to create a request for splitting write queue tail
 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
 * thus all the complexity (cwnd_len is always MSS multiple which we
 * return whenever allowed by the other factors). Basically we need the
 * modulo only when the receiver window alone is the limiting factor or
 * when we would be allowed to send the split-due-to-Nagle skb fully.
1042 1043
 */
static unsigned int tcp_mss_split_point(struct sock *sk, struct sk_buff *skb,
1044
					unsigned int mss_now, unsigned int cwnd)
1045
{
1046 1047
	struct tcp_sock *tp = tcp_sk(sk);
	u32 needed, window, cwnd_len;
1048

1049
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1050
	cwnd_len = mss_now * cwnd;
1051 1052 1053 1054

	if (likely(cwnd_len <= window && skb != tcp_write_queue_tail(sk)))
		return cwnd_len;

1055 1056
	needed = min(skb->len, window);

1057
	if (cwnd_len <= needed)
1058 1059 1060
		return cwnd_len;

	return needed - needed % mss_now;
1061 1062 1063 1064 1065
}

/* 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.
 */
1066 1067
static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp,
					 struct sk_buff *skb)
1068 1069 1070 1071
{
	u32 in_flight, cwnd;

	/* Don't be strict about the congestion window for the final FIN.  */
1072 1073
	if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086
		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.
 */
1087 1088
static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb,
			     unsigned int mss_now)
1089 1090 1091
{
	int tso_segs = tcp_skb_pcount(skb);

1092
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1093
		tcp_set_skb_tso_segs(sk, skb, mss_now);
1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112
		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,
1113
				  const struct sk_buff *skb,
1114 1115 1116
				  unsigned mss_now, int nonagle)
{
	return (skb->len < mss_now &&
1117 1118
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp))));
1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135
}

/* 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;

1136 1137 1138 1139
	/* 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) ||
1140 1141 1142 1143 1144 1145 1146 1147 1148 1149
	    (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? */
1150 1151
static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb,
				   unsigned int cur_mss)
1152 1153 1154 1155 1156 1157
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1158
	return !after(end_seq, tcp_wnd_end(tp));
1159 1160
}

1161
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1162 1163 1164 1165 1166 1167 1168 1169 1170
 * 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;

1171
	tcp_init_tso_segs(sk, skb, cur_mss);
1172 1173 1174 1175 1176

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1177
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1178 1179 1180 1181 1182
		cwnd_quota = 0;

	return cwnd_quota;
}

1183
int tcp_may_send_now(struct sock *sk)
1184
{
1185
	struct tcp_sock *tp = tcp_sk(sk);
1186
	struct sk_buff *skb = tcp_send_head(sk);
1187 1188 1189 1190

	return (skb &&
		tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
			     (tcp_skb_is_last(sk, skb) ?
1191
			      tp->nonagle : TCP_NAGLE_PUSH)));
1192 1193 1194 1195 1196 1197 1198 1199 1200
}

/* 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).
 */
1201 1202
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
			unsigned int mss_now)
1203 1204 1205 1206 1207 1208
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
	u16 flags;

	/* All of a TSO frame must be composed of paged data.  */
1209 1210
	if (skb->len != skb->data_len)
		return tcp_fragment(sk, skb, len, mss_now);
1211

1212
	buff = sk_stream_alloc_skb(sk, 0, GFP_ATOMIC);
1213 1214 1215
	if (unlikely(buff == NULL))
		return -ENOMEM;

1216 1217
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1218
	buff->truesize += nlen;
1219 1220 1221 1222 1223 1224 1225 1226 1227
	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;
1228
	TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH);
1229 1230 1231 1232 1233
	TCP_SKB_CB(buff)->flags = flags;

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

1234
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1235 1236 1237
	skb_split(skb, buff, len);

	/* Fix up tso_factor for both original and new SKB.  */
1238 1239
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
1240 1241 1242

	/* Link BUFF into the send queue. */
	skb_header_release(buff);
1243
	tcp_insert_write_queue_after(skb, buff, sk);
1244 1245 1246 1247 1248 1249 1250 1251 1252

	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.
 */
1253
static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1254
{
1255
	struct tcp_sock *tp = tcp_sk(sk);
1256
	const struct inet_connection_sock *icsk = inet_csk(sk);
1257 1258 1259
	u32 send_win, cong_win, limit, in_flight;

	if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
J
John Heffner 已提交
1260
		goto send_now;
1261

1262
	if (icsk->icsk_ca_state != TCP_CA_Open)
J
John Heffner 已提交
1263 1264 1265
		goto send_now;

	/* Defer for less than two clock ticks. */
I
Ilpo Järvinen 已提交
1266 1267
	if (tp->tso_deferred &&
	    ((jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
J
John Heffner 已提交
1268
		goto send_now;
1269

1270 1271
	in_flight = tcp_packets_in_flight(tp);

1272
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1273

1274
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1275 1276 1277 1278 1279 1280

	/* 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);

1281
	/* If a full-sized TSO skb can be sent, do it. */
1282
	if (limit >= sk->sk_gso_max_size)
J
John Heffner 已提交
1283
		goto send_now;
1284

1285 1286 1287 1288 1289 1290 1291 1292
	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
1293
			goto send_now;
1294 1295 1296 1297 1298 1299 1300
	} 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
1301
			goto send_now;
1302 1303 1304
	}

	/* Ok, it looks like it is advisable to defer.  */
1305
	tp->tso_deferred = 1 | (jiffies << 1);
J
John Heffner 已提交
1306

1307
	return 1;
J
John Heffner 已提交
1308 1309 1310 1311

send_now:
	tp->tso_deferred = 0;
	return 0;
1312 1313
}

J
John Heffner 已提交
1314 1315 1316
/* 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,
1317 1318
 *         -1 otherwise
 */
J
John Heffner 已提交
1319 1320 1321 1322 1323 1324 1325
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;
1326
	int size_needed;
J
John Heffner 已提交
1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342
	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);
1343
	probe_size = 2 * tp->mss_cache;
1344
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
J
John Heffner 已提交
1345 1346 1347 1348 1349 1350
	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? */
1351
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1352 1353
		return -1;

1354 1355
	if (tp->snd_wnd < size_needed)
		return -1;
1356
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1357
		return 0;
J
John Heffner 已提交
1358

1359 1360 1361
	/* Do we need to wait to drain cwnd? With none in flight, don't stall */
	if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
		if (!tcp_packets_in_flight(tp))
J
John Heffner 已提交
1362 1363 1364 1365 1366 1367 1368 1369
			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;
1370 1371
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
1372

1373
	skb = tcp_send_head(sk);
J
John Heffner 已提交
1374 1375 1376 1377 1378 1379

	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;
1380
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
1381

1382 1383
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
1384
	len = 0;
1385
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
1386 1387 1388 1389 1390
		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,
1391 1392
							    skb_put(nskb, copy),
							    copy, nskb->csum);
J
John Heffner 已提交
1393 1394 1395 1396 1397

		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;
1398
			tcp_unlink_write_queue(skb, sk);
1399
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
1400 1401
		} else {
			TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags &
1402
						   ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
J
John Heffner 已提交
1403 1404
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
1405
				if (skb->ip_summed != CHECKSUM_PARTIAL)
1406 1407
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
1408 1409 1410 1411 1412 1413 1414 1415
			} else {
				__pskb_trim_head(skb, copy);
				tcp_set_skb_tso_segs(sk, skb, mss_now);
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
1416 1417 1418

		if (len >= probe_size)
			break;
J
John Heffner 已提交
1419 1420 1421 1422 1423 1424 1425 1426
	}
	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
1427
		 * effectively two packets. */
J
John Heffner 已提交
1428
		tp->snd_cwnd--;
1429
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
1430 1431

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1432 1433
		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
1434 1435 1436 1437 1438 1439 1440

		return 1;
	}

	return -1;
}

L
Linus Torvalds 已提交
1441 1442 1443 1444 1445 1446 1447
/* 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.
 */
1448
static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
L
Linus Torvalds 已提交
1449 1450
{
	struct tcp_sock *tp = tcp_sk(sk);
1451
	struct sk_buff *skb;
1452 1453
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
1454
	int result;
L
Linus Torvalds 已提交
1455 1456 1457 1458 1459

	/* 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.
	 */
1460 1461
	if (unlikely(sk->sk_state == TCP_CLOSE))
		return 0;
L
Linus Torvalds 已提交
1462

1463
	sent_pkts = 0;
J
John Heffner 已提交
1464 1465 1466 1467 1468 1469 1470 1471

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

1472
	while ((skb = tcp_send_head(sk))) {
1473 1474
		unsigned int limit;

1475
		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1476
		BUG_ON(!tso_segs);
1477

1478 1479 1480 1481 1482 1483 1484
		cwnd_quota = tcp_cwnd_test(tp, skb);
		if (!cwnd_quota)
			break;

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

1485 1486 1487 1488 1489 1490
		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 {
1491
			if (tcp_tso_should_defer(sk, skb))
1492 1493
				break;
		}
1494

1495
		limit = mss_now;
1496 1497 1498
		if (tso_segs > 1)
			limit = tcp_mss_split_point(sk, skb, mss_now,
						    cwnd_quota);
L
Linus Torvalds 已提交
1499

1500 1501 1502 1503
		if (skb->len > limit &&
		    unlikely(tso_fragment(sk, skb, limit, mss_now)))
			break;

1504
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
1505

1506
		if (unlikely(tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC)))
1507
			break;
L
Linus Torvalds 已提交
1508

1509 1510 1511
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
1512
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
1513

1514
		tcp_minshall_update(tp, mss_now, skb);
1515
		sent_pkts++;
1516
	}
L
Linus Torvalds 已提交
1517

1518
	if (likely(sent_pkts)) {
1519
		tcp_cwnd_validate(sk);
1520
		return 0;
L
Linus Torvalds 已提交
1521
	}
1522
	return !tp->packets_out && tcp_send_head(sk);
L
Linus Torvalds 已提交
1523 1524
}

1525 1526 1527 1528
/* 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.
 */
1529 1530
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
1531
{
1532
	struct sk_buff *skb = tcp_send_head(sk);
1533 1534

	if (skb) {
1535
		if (tcp_write_xmit(sk, cur_mss, nonagle))
1536
			tcp_check_probe_timer(sk);
1537 1538 1539
	}
}

1540 1541 1542 1543 1544
/* 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)
{
1545
	struct sk_buff *skb = tcp_send_head(sk);
1546 1547 1548 1549
	unsigned int tso_segs, cwnd_quota;

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

1550
	tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1551 1552 1553
	cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);

	if (likely(cwnd_quota)) {
1554 1555
		unsigned int limit;

1556 1557
		BUG_ON(!tso_segs);

1558
		limit = mss_now;
1559 1560 1561
		if (tso_segs > 1)
			limit = tcp_mss_split_point(sk, skb, mss_now,
						    cwnd_quota);
1562

1563 1564 1565 1566
		if (skb->len > limit &&
		    unlikely(tso_fragment(sk, skb, limit, mss_now)))
			return;

1567 1568 1569
		/* Send it out now. */
		TCP_SKB_CB(skb)->when = tcp_time_stamp;

1570
		if (likely(!tcp_transmit_skb(sk, skb, 1, sk->sk_allocation))) {
1571
			tcp_event_new_data_sent(sk, skb);
1572
			tcp_cwnd_validate(sk);
1573 1574 1575 1576 1577
			return;
		}
	}
}

L
Linus Torvalds 已提交
1578 1579
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
1580
 *
L
Linus Torvalds 已提交
1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598
 * 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.
1599
 *
L
Linus Torvalds 已提交
1600 1601
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
1602
 *
L
Linus Torvalds 已提交
1603
 * BSD seems to make the following compromise:
1604
 *
L
Linus Torvalds 已提交
1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631
 *	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)
{
1632
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1633
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
1634
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
1635 1636 1637 1638 1639
	 * 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
	 */
1640
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
1641 1642 1643 1644 1645
	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)
1646
		mss = full_space;
L
Linus Torvalds 已提交
1647

1648
	if (free_space < (full_space >> 1)) {
1649
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
1650 1651

		if (tcp_memory_pressure)
1652 1653
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685

		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)
1686
			window = (free_space / mss) * mss;
1687
		else if (mss == full_space &&
1688
			 free_space > window + (full_space >> 1))
1689
			window = free_space;
L
Linus Torvalds 已提交
1690 1691 1692 1693 1694 1695
	}

	return window;
}

/* Attempt to collapse two adjacent SKB's during retransmission. */
1696 1697
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb,
				     int mss_now)
L
Linus Torvalds 已提交
1698 1699
{
	struct tcp_sock *tp = tcp_sk(sk);
1700
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
1701 1702
	int skb_size, next_skb_size;
	u16 flags;
L
Linus Torvalds 已提交
1703 1704 1705 1706

	/* The first test we must make is that neither of these two
	 * SKB's are still referenced by someone else.
	 */
1707 1708
	if (skb_cloned(skb) || skb_cloned(next_skb))
		return;
L
Linus Torvalds 已提交
1709

1710 1711 1712
	skb_size = skb->len;
	next_skb_size = next_skb->len;
	flags = TCP_SKB_CB(skb)->flags;
L
Linus Torvalds 已提交
1713

1714 1715 1716
	/* Also punt if next skb has been SACK'd. */
	if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED)
		return;
L
Linus Torvalds 已提交
1717

1718 1719 1720
	/* Next skb is out of window. */
	if (after(TCP_SKB_CB(next_skb)->end_seq, tcp_wnd_end(tp)))
		return;
L
Linus Torvalds 已提交
1721

1722 1723 1724 1725 1726 1727 1728
	/* 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;
L
Linus Torvalds 已提交
1729

1730
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
1731

1732
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
1733

1734 1735
	/* Ok.	We will be able to collapse the packet. */
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
1736

1737 1738
	skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
				  next_skb_size);
L
Linus Torvalds 已提交
1739

1740 1741
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1742

1743 1744
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
1745

1746 1747
	/* Update sequence range on original skb. */
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
L
Linus Torvalds 已提交
1748

1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771
	/* 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;
	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);
	/* Reno case is special. Sigh... */
	if (tcp_is_reno(tp) && tp->sacked_out)
		tcp_dec_pcount_approx(&tp->sacked_out, next_skb);

	tcp_adjust_fackets_out(sk, next_skb, tcp_skb_pcount(next_skb));
	tp->packets_out -= tcp_skb_pcount(next_skb);

	/* changed transmit queue under us so clear hints */
	tcp_clear_retrans_hints_partial(tp);

	sk_wmem_free_skb(sk, next_skb);
L
Linus Torvalds 已提交
1772 1773 1774
}

/* Do a simple retransmit without using the backoff mechanisms in
1775
 * tcp_timer. This is used for path mtu discovery.
L
Linus Torvalds 已提交
1776
 * The socket is already locked here.
1777
 */
L
Linus Torvalds 已提交
1778 1779
void tcp_simple_retransmit(struct sock *sk)
{
1780
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1781 1782 1783 1784 1785
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
	unsigned int mss = tcp_current_mss(sk, 0);
	int lost = 0;

1786 1787 1788
	tcp_for_write_queue(skb, sk) {
		if (skb == tcp_send_head(sk))
			break;
1789
		if (skb->len > mss &&
1790 1791
		    !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
			if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
L
Linus Torvalds 已提交
1792 1793 1794
				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
				tp->retrans_out -= tcp_skb_pcount(skb);
			}
1795
			if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST)) {
L
Linus Torvalds 已提交
1796 1797 1798 1799 1800 1801 1802
				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
				tp->lost_out += tcp_skb_pcount(skb);
				lost = 1;
			}
		}
	}

1803
	tcp_clear_all_retrans_hints(tp);
1804

L
Linus Torvalds 已提交
1805 1806 1807
	if (!lost)
		return;

1808 1809 1810
	if (tcp_is_reno(tp))
		tcp_limit_reno_sacked(tp);

1811
	tcp_verify_left_out(tp);
L
Linus Torvalds 已提交
1812

1813
	/* Don't muck with the congestion window here.
L
Linus Torvalds 已提交
1814 1815 1816 1817
	 * Reason is that we do not increase amount of _data_
	 * in network, but units changed and effective
	 * cwnd/ssthresh really reduced now.
	 */
1818
	if (icsk->icsk_ca_state != TCP_CA_Loss) {
L
Linus Torvalds 已提交
1819
		tp->high_seq = tp->snd_nxt;
1820
		tp->snd_ssthresh = tcp_current_ssthresh(sk);
L
Linus Torvalds 已提交
1821 1822
		tp->prior_ssthresh = 0;
		tp->undo_marker = 0;
1823
		tcp_set_ca_state(sk, TCP_CA_Loss);
L
Linus Torvalds 已提交
1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834
	}
	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
1835
	struct inet_connection_sock *icsk = inet_csk(sk);
1836
	unsigned int cur_mss;
L
Linus Torvalds 已提交
1837 1838
	int err;

J
John Heffner 已提交
1839 1840 1841 1842 1843
	/* Inconslusive MTU probe */
	if (icsk->icsk_mtup.probe_size) {
		icsk->icsk_mtup.probe_size = 0;
	}

L
Linus Torvalds 已提交
1844
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
1845
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857
	 */
	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;
	}

1858 1859 1860 1861 1862
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

	cur_mss = tcp_current_mss(sk, 0);

L
Linus Torvalds 已提交
1863 1864 1865 1866 1867
	/* 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.
	 */
1868
	if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))
L
Linus Torvalds 已提交
1869 1870 1871 1872
	    && TCP_SKB_CB(skb)->seq != tp->snd_una)
		return -EAGAIN;

	if (skb->len > cur_mss) {
1873
		if (tcp_fragment(sk, skb, cur_mss, cur_mss))
L
Linus Torvalds 已提交
1874 1875 1876 1877
			return -ENOMEM; /* We'll try again later. */
	}

	/* Collapse two adjacent packets if worthwhile and we can. */
S
Stephen Hemminger 已提交
1878 1879 1880 1881
	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)) &&
1882 1883 1884 1885
	    (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) &&
S
Stephen Hemminger 已提交
1886
	    (sysctl_tcp_retrans_collapse != 0))
L
Linus Torvalds 已提交
1887 1888 1889 1890 1891 1892
		tcp_retrans_try_collapse(sk, skb, cur_mss);

	/* 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
1893 1894 1895
	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
1896
		if (!pskb_trim(skb, 0)) {
1897 1898 1899
			/* Reuse, even though it does some unnecessary work */
			tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1,
					     TCP_SKB_CB(skb)->flags);
L
Linus Torvalds 已提交
1900 1901 1902 1903 1904 1905 1906 1907 1908
			skb->ip_summed = CHECKSUM_NONE;
		}
	}

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

1909
	err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
1910 1911 1912

	if (err == 0) {
		/* Update global TCP statistics. */
P
Pavel Emelyanov 已提交
1913
		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
L
Linus Torvalds 已提交
1914 1915 1916 1917

		tp->total_retrans++;

#if FASTRETRANS_DEBUG > 0
1918
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
L
Linus Torvalds 已提交
1919 1920 1921 1922
			if (net_ratelimit())
				printk(KERN_DEBUG "retrans_out leaked.\n");
		}
#endif
1923 1924
		if (!tp->retrans_out)
			tp->lost_retrans_low = tp->snd_nxt;
L
Linus Torvalds 已提交
1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951
		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)
{
1952
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1953 1954
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
1955 1956 1957 1958 1959
	int packet_cnt;

	if (tp->retransmit_skb_hint) {
		skb = tp->retransmit_skb_hint;
		packet_cnt = tp->retransmit_cnt_hint;
1960
	} else {
1961
		skb = tcp_write_queue_head(sk);
1962 1963
		packet_cnt = 0;
	}
L
Linus Torvalds 已提交
1964 1965

	/* First pass: retransmit lost packets. */
1966
	if (tp->lost_out) {
1967
		tcp_for_write_queue_from(skb, sk) {
L
Linus Torvalds 已提交
1968 1969
			__u8 sacked = TCP_SKB_CB(skb)->sacked;

1970 1971
			if (skb == tcp_send_head(sk))
				break;
1972 1973 1974 1975
			/* 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
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
			/* 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;

1986
			if (sacked & TCPCB_LOST) {
1987
				if (!(sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
1988 1989
					int mib_idx;

1990 1991
					if (tcp_retransmit_skb(sk, skb)) {
						tp->retransmit_skb_hint = NULL;
L
Linus Torvalds 已提交
1992
						return;
1993
					}
1994
					if (icsk->icsk_ca_state != TCP_CA_Loss)
1995
						mib_idx = LINUX_MIB_TCPFASTRETRANS;
L
Linus Torvalds 已提交
1996
					else
1997 1998
						mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
					NET_INC_STATS_BH(mib_idx);
L
Linus Torvalds 已提交
1999

2000
					if (skb == tcp_write_queue_head(sk))
2001
						inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2002 2003
									  inet_csk(sk)->icsk_rto,
									  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2004 2005
				}

2006 2007
				packet_cnt += tcp_skb_pcount(skb);
				if (packet_cnt >= tp->lost_out)
L
Linus Torvalds 已提交
2008 2009 2010 2011 2012 2013 2014 2015
					break;
			}
		}
	}

	/* OK, demanded retransmission is finished. */

	/* Forward retransmissions are possible only during Recovery. */
2016
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
L
Linus Torvalds 已提交
2017 2018 2019
		return;

	/* No forward retransmissions in Reno are possible. */
2020
	if (tcp_is_reno(tp))
L
Linus Torvalds 已提交
2021 2022 2023 2024 2025 2026
		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
2027 2028
	 * segments to send. In the other cases, follow rule 3 for
	 * NextSeg() specified in RFC3517.
L
Linus Torvalds 已提交
2029 2030
	 */

2031
	if (tcp_may_send_now(sk))
L
Linus Torvalds 已提交
2032 2033
		return;

2034 2035 2036 2037 2038
	/* If nothing is SACKed, highest_sack in the loop won't be valid */
	if (!tp->sacked_out)
		return;

	if (tp->forward_skb_hint)
2039
		skb = tp->forward_skb_hint;
2040
	else
2041
		skb = tcp_write_queue_head(sk);
2042

2043 2044 2045
	tcp_for_write_queue_from(skb, sk) {
		if (skb == tcp_send_head(sk))
			break;
2046
		tp->forward_skb_hint = skb;
L
Linus Torvalds 已提交
2047

2048
		if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
L
Linus Torvalds 已提交
2049 2050 2051 2052 2053 2054 2055 2056 2057
			break;

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

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

		/* Ok, retransmit it. */
2058 2059
		if (tcp_retransmit_skb(sk, skb)) {
			tp->forward_skb_hint = NULL;
L
Linus Torvalds 已提交
2060
			break;
2061
		}
L
Linus Torvalds 已提交
2062

2063
		if (skb == tcp_write_queue_head(sk))
2064 2065 2066
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2067 2068 2069 2070 2071 2072 2073 2074 2075 2076

		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)
{
2077
	struct tcp_sock *tp = tcp_sk(sk);
2078
	struct sk_buff *skb = tcp_write_queue_tail(sk);
L
Linus Torvalds 已提交
2079
	int mss_now;
2080

L
Linus Torvalds 已提交
2081 2082 2083 2084 2085 2086
	/* 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);

2087
	if (tcp_send_head(sk) != NULL) {
L
Linus Torvalds 已提交
2088 2089 2090 2091 2092 2093
		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 (;;) {
2094
			skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL);
L
Linus Torvalds 已提交
2095 2096 2097 2098 2099 2100 2101 2102
			if (skb)
				break;
			yield();
		}

		/* Reserve space for headers and prepare control bits. */
		skb_reserve(skb, MAX_TCP_HEADER);
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2103 2104
		tcp_init_nondata_skb(skb, tp->write_seq,
				     TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
L
Linus Torvalds 已提交
2105 2106
		tcp_queue_skb(sk, skb);
	}
2107
	__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
2108 2109 2110 2111 2112
}

/* 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
2113
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2114
 */
A
Al Viro 已提交
2115
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127
{
	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);
2128 2129
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
			     TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
L
Linus Torvalds 已提交
2130 2131
	/* Send it off. */
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2132
	if (tcp_transmit_skb(sk, skb, 0, priority))
L
Linus Torvalds 已提交
2133
		NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
2134

P
Pavel Emelyanov 已提交
2135
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
2136 2137 2138 2139 2140 2141 2142 2143 2144
}

/* 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)
{
2145
	struct sk_buff *skb;
L
Linus Torvalds 已提交
2146

2147
	skb = tcp_write_queue_head(sk);
2148
	if (skb == NULL || !(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN)) {
L
Linus Torvalds 已提交
2149 2150 2151
		printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
		return -EFAULT;
	}
2152
	if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_ACK)) {
L
Linus Torvalds 已提交
2153 2154 2155 2156
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
			if (nskb == NULL)
				return -ENOMEM;
2157
			tcp_unlink_write_queue(skb, sk);
L
Linus Torvalds 已提交
2158
			skb_header_release(nskb);
2159
			__tcp_add_write_queue_head(sk, nskb);
2160 2161 2162
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
2163 2164 2165 2166 2167 2168 2169
			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;
2170
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
2171 2172 2173 2174 2175
}

/*
 * Prepare a SYN-ACK.
 */
2176 2177
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
				struct request_sock *req)
L
Linus Torvalds 已提交
2178
{
2179
	struct inet_request_sock *ireq = inet_rsk(req);
L
Linus Torvalds 已提交
2180 2181 2182 2183
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcphdr *th;
	int tcp_header_size;
	struct sk_buff *skb;
2184 2185 2186 2187
#ifdef CONFIG_TCP_MD5SIG
	struct tcp_md5sig_key *md5;
	__u8 *md5_hash_location;
#endif
L
Linus Torvalds 已提交
2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198

	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 +
2199 2200
			   (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
			   (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
L
Linus Torvalds 已提交
2201
			   /* SACK_PERM is in the place of NOP NOP of TS */
2202
			   ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
2203 2204 2205 2206 2207 2208 2209

#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
2210 2211
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
2212

2213
	th = tcp_hdr(skb);
L
Linus Torvalds 已提交
2214 2215 2216 2217 2218
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
	TCP_ECN_make_synack(req, th);
	th->source = inet_sk(sk)->sport;
2219
	th->dest = ireq->rmt_port;
2220 2221 2222 2223 2224
	/* Setting of flags are superfluous here for callers (and ECE is
	 * not even correctly set)
	 */
	tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
			     TCPCB_FLAG_SYN | TCPCB_FLAG_ACK);
L
Linus Torvalds 已提交
2225
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
2226
	th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
L
Linus Torvalds 已提交
2227
	if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2228
		__u8 rcv_wscale;
L
Linus Torvalds 已提交
2229 2230 2231
		/* 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 */
2232
		tcp_select_initial_window(tcp_full_space(sk),
2233
			dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
L
Linus Torvalds 已提交
2234 2235
			&req->rcv_wnd,
			&req->window_clamp,
2236
			ireq->wscale_ok,
L
Linus Torvalds 已提交
2237
			&rcv_wscale);
2238
		ireq->rcv_wscale = rcv_wscale;
L
Linus Torvalds 已提交
2239 2240 2241
	}

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2242
	th->window = htons(min(req->rcv_wnd, 65535U));
2243 2244 2245 2246 2247
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
		TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
	else
#endif
L
Linus Torvalds 已提交
2248
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2249
	tcp_syn_build_options((__be32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
2250
			      ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
L
Linus Torvalds 已提交
2251
			      TCP_SKB_CB(skb)->when,
2252 2253 2254 2255 2256 2257 2258
			      req->ts_recent,
			      (
#ifdef CONFIG_TCP_MD5SIG
			       md5 ? &md5_hash_location :
#endif
			       NULL)
			      );
L
Linus Torvalds 已提交
2259 2260

	th->doff = (tcp_header_size >> 2);
P
Pavel Emelyanov 已提交
2261
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
2262 2263 2264 2265 2266 2267 2268

#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,
2269
					       tcp_hdr(skb),
2270 2271 2272 2273
					       skb->len);
	}
#endif

L
Linus Torvalds 已提交
2274 2275 2276
	return skb;
}

2277
/*
L
Linus Torvalds 已提交
2278
 * Do all connect socket setups that can be done AF independent.
2279
 */
S
Stephen Hemminger 已提交
2280
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291
{
	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);

2292 2293 2294 2295 2296
#ifdef CONFIG_TCP_MD5SIG
	if (tp->af_specific->md5_lookup(sk, sk) != NULL)
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
2297 2298 2299 2300
	/* If user gave his TCP_MAXSEG, record it to clamp */
	if (tp->rx_opt.user_mss)
		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
	tp->max_window = 0;
J
John Heffner 已提交
2301
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328
	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;

2329 2330
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
2331 2332 2333 2334 2335
	tcp_clear_retrans(tp);
}

/*
 * Build a SYN and send it off.
2336
 */
L
Linus Torvalds 已提交
2337 2338 2339 2340 2341 2342 2343
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;

	tcp_connect_init(sk);

2344
	buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
L
Linus Torvalds 已提交
2345 2346 2347 2348 2349 2350
	if (unlikely(buff == NULL))
		return -ENOBUFS;

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

2351
	tp->snd_nxt = tp->write_seq;
2352 2353
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPCB_FLAG_SYN);
	TCP_ECN_send_syn(sk, buff);
L
Linus Torvalds 已提交
2354 2355 2356 2357 2358

	/* Send it off. */
	TCP_SKB_CB(buff)->when = tcp_time_stamp;
	tp->retrans_stamp = TCP_SKB_CB(buff)->when;
	skb_header_release(buff);
2359
	__tcp_add_write_queue_tail(sk, buff);
2360 2361
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
L
Linus Torvalds 已提交
2362
	tp->packets_out += tcp_skb_pcount(buff);
2363
	tcp_transmit_skb(sk, buff, 1, GFP_KERNEL);
2364 2365 2366 2367 2368 2369

	/* We change tp->snd_nxt after the tcp_transmit_skb() call
	 * in order to make this packet get counted in tcpOutSegs.
	 */
	tp->snd_nxt = tp->write_seq;
	tp->pushed_seq = tp->write_seq;
P
Pavel Emelyanov 已提交
2370
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
2371 2372

	/* Timer for repeating the SYN until an answer. */
2373 2374
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
2375 2376 2377 2378 2379 2380 2381 2382 2383
	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)
{
2384 2385
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
2386 2387 2388
	unsigned long timeout;

	if (ato > TCP_DELACK_MIN) {
2389
		const struct tcp_sock *tp = tcp_sk(sk);
2390
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
2391

2392 2393
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
2394 2395 2396 2397 2398
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
2399
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
2400 2401 2402
		 * directly.
		 */
		if (tp->srtt) {
2403
			int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN);
L
Linus Torvalds 已提交
2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415

			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. */
2416
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
2417 2418 2419
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
2420 2421
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
2422 2423 2424 2425
			tcp_send_ack(sk);
			return;
		}

2426 2427
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
2428
	}
2429 2430 2431
	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
	icsk->icsk_ack.timeout = timeout;
	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
L
Linus Torvalds 已提交
2432 2433 2434 2435 2436
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
2437
	struct sk_buff *buff;
L
Linus Torvalds 已提交
2438

2439 2440 2441
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
2442

2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453
	/* 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) {
		inet_csk_schedule_ack(sk);
		inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
					  TCP_DELACK_MAX, TCP_RTO_MAX);
		return;
L
Linus Torvalds 已提交
2454
	}
2455 2456 2457

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
2458
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPCB_FLAG_ACK);
2459 2460 2461 2462

	/* Send it off, this clears delayed acks for us. */
	TCP_SKB_CB(buff)->when = tcp_time_stamp;
	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);
2483
	if (skb == NULL)
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		return -1;

	/* Reserve space for headers and set control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
	/* Use a previous sequence.  This should cause the other
	 * end to send an ack.  Don't queue or clone SKB, just
	 * send it.
	 */
2492
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPCB_FLAG_ACK);
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	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2494
	return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
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}

int tcp_write_wakeup(struct sock *sk)
{
2499 2500
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
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2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520
	if (sk->sk_state == TCP_CLOSE)
		return -1;

	if ((skb = tcp_send_head(sk)) != NULL &&
	    before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
		int err;
		unsigned int mss = tcp_current_mss(sk, 0);
		unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;

		if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
			tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;

		/* We are probing the opening of a window
		 * but the window size is != 0
		 * must have been a result SWS avoidance ( sender )
		 */
		if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
		    skb->len > mss) {
			seg_size = min(seg_size, mss);
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			TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537
			if (tcp_fragment(sk, skb, seg_size, mss))
				return -1;
		} else if (!tcp_skb_pcount(skb))
			tcp_set_skb_tso_segs(sk, skb, mss);

		TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
		if (!err)
			tcp_event_new_data_sent(sk, skb);
		return err;
	} else {
		if (tp->urg_mode &&
		    between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
			tcp_xmit_probe_skb(sk, 1);
		return tcp_xmit_probe_skb(sk, 0);
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	}
}

/* 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)
{
2546
	struct inet_connection_sock *icsk = inet_csk(sk);
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	struct tcp_sock *tp = tcp_sk(sk);
	int err;

	err = tcp_write_wakeup(sk);

2552
	if (tp->packets_out || !tcp_send_head(sk)) {
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		/* Cancel probe timer, if it is not required. */
2554
		icsk->icsk_probes_out = 0;
2555
		icsk->icsk_backoff = 0;
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		return;
	}

	if (err <= 0) {
2560 2561
		if (icsk->icsk_backoff < sysctl_tcp_retries2)
			icsk->icsk_backoff++;
2562
		icsk->icsk_probes_out++;
2563
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2564 2565
					  min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
					  TCP_RTO_MAX);
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	} else {
		/* If packet was not sent due to local congestion,
2568
		 * do not backoff and do not remember icsk_probes_out.
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		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
2573 2574
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
2575
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2576
					  min(icsk->icsk_rto << icsk->icsk_backoff,
2577 2578
					      TCP_RESOURCE_PROBE_INTERVAL),
					  TCP_RTO_MAX);
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	}
}

2582
EXPORT_SYMBOL(tcp_select_initial_window);
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EXPORT_SYMBOL(tcp_connect);
EXPORT_SYMBOL(tcp_make_synack);
EXPORT_SYMBOL(tcp_simple_retransmit);
EXPORT_SYMBOL(tcp_sync_mss);
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EXPORT_SYMBOL(tcp_mtup_init);