tcp_output.c 102.1 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7
/*
 * 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).
 *
8
 * Authors:	Ross Biro
L
Linus Torvalds 已提交
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
 *		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
 *
 */

37 38
#define pr_fmt(fmt) "TCP: " fmt

L
Linus Torvalds 已提交
39 40 41
#include <net/tcp.h>

#include <linux/compiler.h>
42
#include <linux/gfp.h>
L
Linus Torvalds 已提交
43 44 45
#include <linux/module.h>

/* People can turn this off for buggy TCP's found in printers etc. */
46
int sysctl_tcp_retrans_collapse __read_mostly = 1;
L
Linus Torvalds 已提交
47

48
/* People can turn this on to work with those rare, broken TCPs that
49 50
 * interpret the window field as a signed quantity.
 */
51
int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
52

53 54
/* Default TSQ limit of four TSO segments */
int sysctl_tcp_limit_output_bytes __read_mostly = 262144;
E
Eric Dumazet 已提交
55

L
Linus Torvalds 已提交
56 57 58 59
/* 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.
 */
60
int sysctl_tcp_tso_win_divisor __read_mostly = 3;
L
Linus Torvalds 已提交
61

62
/* By default, RFC2861 behavior.  */
63
int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
64

E
Eric Dumazet 已提交
65 66
static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp);
67

68
/* Account for new data that has been sent to the network. */
69
static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
L
Linus Torvalds 已提交
70
{
N
Nandita Dukkipati 已提交
71
	struct inet_connection_sock *icsk = inet_csk(sk);
72
	struct tcp_sock *tp = tcp_sk(sk);
73
	unsigned int prior_packets = tp->packets_out;
74

75
	tcp_advance_send_head(sk, skb);
L
Linus Torvalds 已提交
76
	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
77

78
	tp->packets_out += tcp_skb_pcount(skb);
N
Nandita Dukkipati 已提交
79
	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
80
	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
81
		tcp_rearm_rto(sk);
82
	}
83

84 85
	NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
		      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
86 87 88 89 90 91 92 93
}

/* 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:
 */
94
static inline __u32 tcp_acceptable_seq(const struct sock *sk)
L
Linus Torvalds 已提交
95
{
96
	const struct tcp_sock *tp = tcp_sk(sk);
97

98
	if (!before(tcp_wnd_end(tp), tp->snd_nxt))
L
Linus Torvalds 已提交
99 100
		return tp->snd_nxt;
	else
101
		return tcp_wnd_end(tp);
L
Linus Torvalds 已提交
102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
}

/* 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);
121
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
122 123
	int mss = tp->advmss;

124 125 126 127 128 129 130
	if (dst) {
		unsigned int metric = dst_metric_advmss(dst);

		if (metric < mss) {
			mss = metric;
			tp->advmss = mss;
		}
L
Linus Torvalds 已提交
131 132 133 134 135 136
	}

	return (__u16)mss;
}

/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
137 138 139
 * This is the first part of cwnd validation mechanism.
 */
void tcp_cwnd_restart(struct sock *sk, s32 delta)
L
Linus Torvalds 已提交
140
{
141
	struct tcp_sock *tp = tcp_sk(sk);
142
	u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
L
Linus Torvalds 已提交
143 144
	u32 cwnd = tp->snd_cwnd;

145
	tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
L
Linus Torvalds 已提交
146

147
	tp->snd_ssthresh = tcp_current_ssthresh(sk);
L
Linus Torvalds 已提交
148 149
	restart_cwnd = min(restart_cwnd, cwnd);

150
	while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
L
Linus Torvalds 已提交
151 152 153 154 155 156
		cwnd >>= 1;
	tp->snd_cwnd = max(cwnd, restart_cwnd);
	tp->snd_cwnd_stamp = tcp_time_stamp;
	tp->snd_cwnd_used = 0;
}

157
/* Congestion state accounting after a packet has been sent. */
S
Stephen Hemminger 已提交
158
static void tcp_event_data_sent(struct tcp_sock *tp,
159
				struct sock *sk)
L
Linus Torvalds 已提交
160
{
161 162
	struct inet_connection_sock *icsk = inet_csk(sk);
	const u32 now = tcp_time_stamp;
L
Linus Torvalds 已提交
163

164 165 166
	if (tcp_packets_in_flight(tp) == 0)
		tcp_ca_event(sk, CA_EVENT_TX_START);

L
Linus Torvalds 已提交
167 168 169 170 171
	tp->lsndtime = now;

	/* If it is a reply for ato after last received
	 * packet, enter pingpong mode.
	 */
172 173
	if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
		icsk->icsk_ack.pingpong = 1;
L
Linus Torvalds 已提交
174 175
}

176
/* Account for an ACK we sent. */
S
Stephen Hemminger 已提交
177
static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
L
Linus Torvalds 已提交
178
{
179 180
	tcp_dec_quickack_mode(sk, pkts);
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
L
Linus Torvalds 已提交
181 182
}

183 184 185 186

u32 tcp_default_init_rwnd(u32 mss)
{
	/* Initial receive window should be twice of TCP_INIT_CWND to
W
Weiping Pan 已提交
187
	 * enable proper sending of new unsent data during fast recovery
188 189 190 191 192 193 194 195 196 197
	 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
	 * limit when mss is larger than 1460.
	 */
	u32 init_rwnd = TCP_INIT_CWND * 2;

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

L
Linus Torvalds 已提交
198 199 200 201 202 203 204 205 206
/* 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,
207 208
			       int wscale_ok, __u8 *rcv_wscale,
			       __u32 init_rcv_wnd)
L
Linus Torvalds 已提交
209 210 211 212 213 214 215 216 217 218 219 220 221
{
	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
222 223 224 225 226 227
	 * 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.
L
Linus Torvalds 已提交
228
	 */
229 230 231 232 233
	if (sysctl_tcp_workaround_signed_windows)
		(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
	else
		(*rcv_wnd) = space;

L
Linus Torvalds 已提交
234 235 236
	(*rcv_wscale) = 0;
	if (wscale_ok) {
		/* Set window scaling on max possible window
237
		 * See RFC1323 for an explanation of the limit to 14
L
Linus Torvalds 已提交
238 239
		 */
		space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
240
		space = min_t(u32, space, *window_clamp);
L
Linus Torvalds 已提交
241 242 243 244 245 246
		while (space > 65535 && (*rcv_wscale) < 14) {
			space >>= 1;
			(*rcv_wscale)++;
		}
	}

247
	if (mss > (1 << *rcv_wscale)) {
248 249 250
		if (!init_rcv_wnd) /* Use default unless specified otherwise */
			init_rcv_wnd = tcp_default_init_rwnd(mss);
		*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
L
Linus Torvalds 已提交
251 252 253 254 255
	}

	/* Set the clamp no higher than max representable value */
	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
}
E
Eric Dumazet 已提交
256
EXPORT_SYMBOL(tcp_select_initial_window);
L
Linus Torvalds 已提交
257 258 259 260 261 262

/* 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.
 */
S
Stephen Hemminger 已提交
263
static u16 tcp_select_window(struct sock *sk)
L
Linus Torvalds 已提交
264 265
{
	struct tcp_sock *tp = tcp_sk(sk);
266
	u32 old_win = tp->rcv_wnd;
L
Linus Torvalds 已提交
267 268 269 270
	u32 cur_win = tcp_receive_window(tp);
	u32 new_win = __tcp_select_window(sk);

	/* Never shrink the offered window */
S
Stephen Hemminger 已提交
271
	if (new_win < cur_win) {
L
Linus Torvalds 已提交
272 273 274 275 276 277 278
		/* 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.
		 */
279 280 281
		if (new_win == 0)
			NET_INC_STATS(sock_net(sk),
				      LINUX_MIB_TCPWANTZEROWINDOWADV);
282
		new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
L
Linus Torvalds 已提交
283 284 285 286 287 288 289
	}
	tp->rcv_wnd = new_win;
	tp->rcv_wup = tp->rcv_nxt;

	/* Make sure we do not exceed the maximum possible
	 * scaled window.
	 */
290
	if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
L
Linus Torvalds 已提交
291 292 293 294 295 296 297 298
		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. */
299
	if (new_win == 0) {
L
Linus Torvalds 已提交
300
		tp->pred_flags = 0;
301 302 303 304 305 306
		if (old_win)
			NET_INC_STATS(sock_net(sk),
				      LINUX_MIB_TCPTOZEROWINDOWADV);
	} else if (old_win == 0) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
	}
L
Linus Torvalds 已提交
307 308 309 310

	return new_win;
}

311
/* Packet ECN state for a SYN-ACK */
312
static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
313
{
314 315
	const struct tcp_sock *tp = tcp_sk(sk);

E
Eric Dumazet 已提交
316
	TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
317
	if (!(tp->ecn_flags & TCP_ECN_OK))
E
Eric Dumazet 已提交
318
		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
319 320
	else if (tcp_ca_needs_ecn(sk))
		INET_ECN_xmit(sk);
321 322
}

323
/* Packet ECN state for a SYN.  */
324
static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
325 326
{
	struct tcp_sock *tp = tcp_sk(sk);
327 328 329 330 331 332 333 334 335
	bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
		       tcp_ca_needs_ecn(sk);

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

		if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
			use_ecn = true;
	}
336 337

	tp->ecn_flags = 0;
338 339

	if (use_ecn) {
E
Eric Dumazet 已提交
340
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
341
		tp->ecn_flags = TCP_ECN_OK;
342 343
		if (tcp_ca_needs_ecn(sk))
			INET_ECN_xmit(sk);
344 345 346
	}
}

347 348 349 350 351 352 353 354 355
static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
{
	if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
		/* tp->ecn_flags are cleared at a later point in time when
		 * SYN ACK is ultimatively being received.
		 */
		TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
}

356
static void
357
tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
358
{
359
	if (inet_rsk(req)->ecn_ok)
360 361 362
		th->ece = 1;
}

363 364 365
/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
 * be sent.
 */
366
static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
367 368 369 370 371 372 373 374 375
				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);
376
			if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
377 378 379 380
				tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
				tcp_hdr(skb)->cwr = 1;
				skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
			}
381
		} else if (!tcp_ca_needs_ecn(sk)) {
382 383 384 385 386 387 388 389
			/* ACK or retransmitted segment: clear ECT|CE */
			INET_ECN_dontxmit(sk);
		}
		if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
			tcp_hdr(skb)->ece = 1;
	}
}

390 391 392 393 394
/* 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)
{
395
	skb->ip_summed = CHECKSUM_PARTIAL;
396 397
	skb->csum = 0;

E
Eric Dumazet 已提交
398
	TCP_SKB_CB(skb)->tcp_flags = flags;
399 400
	TCP_SKB_CB(skb)->sacked = 0;

401
	tcp_skb_pcount_set(skb, 1);
402 403

	TCP_SKB_CB(skb)->seq = seq;
C
Changli Gao 已提交
404
	if (flags & (TCPHDR_SYN | TCPHDR_FIN))
405 406 407 408
		seq++;
	TCP_SKB_CB(skb)->end_seq = seq;
}

E
Eric Dumazet 已提交
409
static inline bool tcp_urg_mode(const struct tcp_sock *tp)
I
Ilpo Järvinen 已提交
410 411 412 413
{
	return tp->snd_una != tp->snd_up;
}

A
Adam Langley 已提交
414 415 416
#define OPTION_SACK_ADVERTISE	(1 << 0)
#define OPTION_TS		(1 << 1)
#define OPTION_MD5		(1 << 2)
417
#define OPTION_WSCALE		(1 << 3)
Y
Yuchung Cheng 已提交
418
#define OPTION_FAST_OPEN_COOKIE	(1 << 8)
A
Adam Langley 已提交
419 420

struct tcp_out_options {
Y
Yuchung Cheng 已提交
421 422
	u16 options;		/* bit field of OPTION_* */
	u16 mss;		/* 0 to disable */
A
Adam Langley 已提交
423 424
	u8 ws;			/* window scale, 0 to disable */
	u8 num_sack_blocks;	/* number of SACK blocks to include */
425 426
	u8 hash_size;		/* bytes in hash_location */
	__u8 *hash_location;	/* temporary pointer, overloaded */
Y
Yuchung Cheng 已提交
427 428
	__u32 tsval, tsecr;	/* need to include OPTION_TS */
	struct tcp_fastopen_cookie *fastopen_cookie;	/* Fast open cookie */
A
Adam Langley 已提交
429 430
};

431 432 433
/* Write previously computed TCP options to the packet.
 *
 * Beware: Something in the Internet is very sensitive to the ordering of
434 435
 * TCP options, we learned this through the hard way, so be careful here.
 * Luckily we can at least blame others for their non-compliance but from
S
stephen hemminger 已提交
436
 * inter-operability perspective it seems that we're somewhat stuck with
437 438 439 440 441 442 443
 * the ordering which we have been using if we want to keep working with
 * those broken things (not that it currently hurts anybody as there isn't
 * particular reason why the ordering would need to be changed).
 *
 * At least SACK_PERM as the first option is known to lead to a disaster
 * (but it may well be that other scenarios fail similarly).
 */
A
Adam Langley 已提交
444
static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
445 446
			      struct tcp_out_options *opts)
{
Y
Yuchung Cheng 已提交
447
	u16 options = opts->options;	/* mungable copy */
448 449

	if (unlikely(OPTION_MD5 & options)) {
C
Christoph Paasch 已提交
450 451
		*ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
			       (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
452 453
		/* overload cookie hash location */
		opts->hash_location = (__u8 *)ptr;
A
Adam Langley 已提交
454
		ptr += 4;
S
Stephen Hemminger 已提交
455
	}
A
Adam Langley 已提交
456

457 458 459 460 461 462
	if (unlikely(opts->mss)) {
		*ptr++ = htonl((TCPOPT_MSS << 24) |
			       (TCPOLEN_MSS << 16) |
			       opts->mss);
	}

463 464
	if (likely(OPTION_TS & options)) {
		if (unlikely(OPTION_SACK_ADVERTISE & options)) {
A
Adam Langley 已提交
465 466 467 468
			*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
				       (TCPOLEN_SACK_PERM << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
469
			options &= ~OPTION_SACK_ADVERTISE;
A
Adam Langley 已提交
470 471 472 473 474 475 476 477 478 479
		} else {
			*ptr++ = htonl((TCPOPT_NOP << 24) |
				       (TCPOPT_NOP << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
		}
		*ptr++ = htonl(opts->tsval);
		*ptr++ = htonl(opts->tsecr);
	}

480
	if (unlikely(OPTION_SACK_ADVERTISE & options)) {
A
Adam Langley 已提交
481 482 483 484 485 486
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_SACK_PERM << 8) |
			       TCPOLEN_SACK_PERM);
	}

487
	if (unlikely(OPTION_WSCALE & options)) {
A
Adam Langley 已提交
488 489 490 491 492 493 494 495 496
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_WINDOW << 16) |
			       (TCPOLEN_WINDOW << 8) |
			       opts->ws);
	}

	if (unlikely(opts->num_sack_blocks)) {
		struct tcp_sack_block *sp = tp->rx_opt.dsack ?
			tp->duplicate_sack : tp->selective_acks;
S
Stephen Hemminger 已提交
497 498 499 500 501
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
502
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
503
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
504

A
Adam Langley 已提交
505 506
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
507 508 509
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
510

511
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
512
	}
Y
Yuchung Cheng 已提交
513 514 515

	if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
		struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
516 517 518 519 520 521 522 523 524 525 526 527 528
		u8 *p = (u8 *)ptr;
		u32 len; /* Fast Open option length */

		if (foc->exp) {
			len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
			*ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
				     TCPOPT_FASTOPEN_MAGIC);
			p += TCPOLEN_EXP_FASTOPEN_BASE;
		} else {
			len = TCPOLEN_FASTOPEN_BASE + foc->len;
			*p++ = TCPOPT_FASTOPEN;
			*p++ = len;
		}
Y
Yuchung Cheng 已提交
529

530 531 532 533
		memcpy(p, foc->val, foc->len);
		if ((len & 3) == 2) {
			p[foc->len] = TCPOPT_NOP;
			p[foc->len + 1] = TCPOPT_NOP;
Y
Yuchung Cheng 已提交
534
		}
535
		ptr += (len + 3) >> 2;
Y
Yuchung Cheng 已提交
536
	}
A
Adam Langley 已提交
537 538
}

539 540 541
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
542
static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
543
				struct tcp_out_options *opts,
544 545
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
546
	struct tcp_sock *tp = tcp_sk(sk);
547
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
548
	struct tcp_fastopen_request *fastopen = tp->fastopen_req;
A
Adam Langley 已提交
549

550
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
551 552 553
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
554
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
555
	}
A
Adam Langley 已提交
556 557
#else
	*md5 = NULL;
558
#endif
A
Adam Langley 已提交
559 560 561 562 563 564 565 566 567 568 569

	/* We always get an MSS option.  The option bytes which will be seen in
	 * normal data packets should timestamps be used, must be in the MSS
	 * advertised.  But we subtract them from tp->mss_cache so that
	 * calculations in tcp_sendmsg are simpler etc.  So account for this
	 * fact here if necessary.  If we don't do this correctly, as a
	 * receiver we won't recognize data packets as being full sized when we
	 * should, and thus we won't abide by the delayed ACK rules correctly.
	 * SACKs don't matter, we never delay an ACK when we have any of those
	 * going out.  */
	opts->mss = tcp_advertise_mss(sk);
570
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
571

572
	if (likely(sysctl_tcp_timestamps && !*md5)) {
A
Adam Langley 已提交
573
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
574
		opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
A
Adam Langley 已提交
575
		opts->tsecr = tp->rx_opt.ts_recent;
576
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
577
	}
578
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
579
		opts->ws = tp->rx_opt.rcv_wscale;
580
		opts->options |= OPTION_WSCALE;
581
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
582
	}
583
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
584
		opts->options |= OPTION_SACK_ADVERTISE;
585
		if (unlikely(!(OPTION_TS & opts->options)))
586
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
587 588
	}

589
	if (fastopen && fastopen->cookie.len >= 0) {
590 591 592 593
		u32 need = fastopen->cookie.len;

		need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
					       TCPOLEN_FASTOPEN_BASE;
594 595 596 597 598 599
		need = (need + 3) & ~3U;  /* Align to 32 bits */
		if (remaining >= need) {
			opts->options |= OPTION_FAST_OPEN_COOKIE;
			opts->fastopen_cookie = &fastopen->cookie;
			remaining -= need;
			tp->syn_fastopen = 1;
600
			tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
601 602
		}
	}
603 604

	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
605 606
}

607
/* Set up TCP options for SYN-ACKs. */
608 609 610 611 612
static unsigned int tcp_synack_options(struct request_sock *req,
				       unsigned int mss, struct sk_buff *skb,
				       struct tcp_out_options *opts,
				       const struct tcp_md5sig_key *md5,
				       struct tcp_fastopen_cookie *foc)
613
{
A
Adam Langley 已提交
614
	struct inet_request_sock *ireq = inet_rsk(req);
615
	unsigned int remaining = MAX_TCP_OPTION_SPACE;
A
Adam Langley 已提交
616

617
#ifdef CONFIG_TCP_MD5SIG
E
Eric Dumazet 已提交
618
	if (md5) {
A
Adam Langley 已提交
619
		opts->options |= OPTION_MD5;
620 621 622 623 624 625 626
		remaining -= TCPOLEN_MD5SIG_ALIGNED;

		/* We can't fit any SACK blocks in a packet with MD5 + TS
		 * options. There was discussion about disabling SACK
		 * rather than TS in order to fit in better with old,
		 * buggy kernels, but that was deemed to be unnecessary.
		 */
E
Eric Dumazet 已提交
627
		ireq->tstamp_ok &= !ireq->sack_ok;
628 629
	}
#endif
A
Adam Langley 已提交
630

631
	/* We always send an MSS option. */
A
Adam Langley 已提交
632
	opts->mss = mss;
633
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
634 635 636

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
637
		opts->options |= OPTION_WSCALE;
638
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
639
	}
E
Eric Dumazet 已提交
640
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
641
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
642
		opts->tsval = tcp_skb_timestamp(skb);
A
Adam Langley 已提交
643
		opts->tsecr = req->ts_recent;
644
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
645 646 647
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
648
		if (unlikely(!ireq->tstamp_ok))
649
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
650
	}
651 652 653 654 655
	if (foc != NULL && foc->len >= 0) {
		u32 need = foc->len;

		need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
				   TCPOLEN_FASTOPEN_BASE;
656 657 658 659 660 661 662
		need = (need + 3) & ~3U;  /* Align to 32 bits */
		if (remaining >= need) {
			opts->options |= OPTION_FAST_OPEN_COOKIE;
			opts->fastopen_cookie = foc;
			remaining -= need;
		}
	}
C
Christoph Paasch 已提交
663

664
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
665 666
}

667 668 669
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
670
static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
A
Adam Langley 已提交
671
					struct tcp_out_options *opts,
672 673
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
674
	struct tcp_sock *tp = tcp_sk(sk);
675
	unsigned int size = 0;
676
	unsigned int eff_sacks;
A
Adam Langley 已提交
677

678 679
	opts->options = 0;

A
Adam Langley 已提交
680 681 682 683 684 685 686 687 688 689 690 691
#ifdef CONFIG_TCP_MD5SIG
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (unlikely(*md5)) {
		opts->options |= OPTION_MD5;
		size += TCPOLEN_MD5SIG_ALIGNED;
	}
#else
	*md5 = NULL;
#endif

	if (likely(tp->rx_opt.tstamp_ok)) {
		opts->options |= OPTION_TS;
E
Eric Dumazet 已提交
692
		opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
A
Adam Langley 已提交
693 694 695 696
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

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

	return size;
S
Stephen Hemminger 已提交
709
}
L
Linus Torvalds 已提交
710

E
Eric Dumazet 已提交
711 712 713 714 715 716 717 718 719

/* TCP SMALL QUEUES (TSQ)
 *
 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
 * to reduce RTT and bufferbloat.
 * We do this using a special skb destructor (tcp_wfree).
 *
 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
 * needs to be reallocated in a driver.
S
stephen hemminger 已提交
720
 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
E
Eric Dumazet 已提交
721 722 723 724 725 726 727 728 729 730 731
 *
 * Since transmit from skb destructor is forbidden, we use a tasklet
 * to process all sockets that eventually need to send more skbs.
 * We use one tasklet per cpu, with its own queue of sockets.
 */
struct tsq_tasklet {
	struct tasklet_struct	tasklet;
	struct list_head	head; /* queue of tcp sockets */
};
static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);

732 733 734 735 736
static void tcp_tsq_handler(struct sock *sk)
{
	if ((1 << sk->sk_state) &
	    (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
	     TCPF_CLOSE_WAIT  | TCPF_LAST_ACK))
J
John Ogness 已提交
737 738
		tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle,
			       0, GFP_ATOMIC);
739
}
E
Eric Dumazet 已提交
740
/*
S
stephen hemminger 已提交
741
 * One tasklet per cpu tries to send more skbs.
E
Eric Dumazet 已提交
742
 * We run in tasklet context but need to disable irqs when
S
stephen hemminger 已提交
743
 * transferring tsq->head because tcp_wfree() might
E
Eric Dumazet 已提交
744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766
 * interrupt us (non NAPI drivers)
 */
static void tcp_tasklet_func(unsigned long data)
{
	struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
	LIST_HEAD(list);
	unsigned long flags;
	struct list_head *q, *n;
	struct tcp_sock *tp;
	struct sock *sk;

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

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

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

		if (!sock_owned_by_user(sk)) {
767
			tcp_tsq_handler(sk);
E
Eric Dumazet 已提交
768 769
		} else {
			/* defer the work to tcp_release_cb() */
770
			set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
E
Eric Dumazet 已提交
771 772 773 774 775 776 777 778
		}
		bh_unlock_sock(sk);

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

779 780
#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) |		\
			  (1UL << TCP_WRITE_TIMER_DEFERRED) |	\
781 782
			  (1UL << TCP_DELACK_TIMER_DEFERRED) |	\
			  (1UL << TCP_MTU_REDUCED_DEFERRED))
E
Eric Dumazet 已提交
783 784 785 786 787 788 789 790 791 792
/**
 * tcp_release_cb - tcp release_sock() callback
 * @sk: socket
 *
 * called from release_sock() to perform protocol dependent
 * actions before socket release.
 */
void tcp_release_cb(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
793
	unsigned long flags, nflags;
E
Eric Dumazet 已提交
794

795 796 797 798 799 800 801 802 803 804 805
	/* perform an atomic operation only if at least one flag is set */
	do {
		flags = tp->tsq_flags;
		if (!(flags & TCP_DEFERRED_ALL))
			return;
		nflags = flags & ~TCP_DEFERRED_ALL;
	} while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);

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

806 807 808 809 810 811 812 813 814 815 816
	/* Here begins the tricky part :
	 * We are called from release_sock() with :
	 * 1) BH disabled
	 * 2) sk_lock.slock spinlock held
	 * 3) socket owned by us (sk->sk_lock.owned == 1)
	 *
	 * But following code is meant to be called from BH handlers,
	 * so we should keep BH disabled, but early release socket ownership
	 */
	sock_release_ownership(sk);

817
	if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
818
		tcp_write_timer_handler(sk);
819 820 821
		__sock_put(sk);
	}
	if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
822
		tcp_delack_timer_handler(sk);
823 824 825
		__sock_put(sk);
	}
	if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
826
		inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
827 828
		__sock_put(sk);
	}
E
Eric Dumazet 已提交
829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847
}
EXPORT_SYMBOL(tcp_release_cb);

void __init tcp_tasklet_init(void)
{
	int i;

	for_each_possible_cpu(i) {
		struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);

		INIT_LIST_HEAD(&tsq->head);
		tasklet_init(&tsq->tasklet,
			     tcp_tasklet_func,
			     (unsigned long)tsq);
	}
}

/*
 * Write buffer destructor automatically called from kfree_skb.
S
stephen hemminger 已提交
848
 * We can't xmit new skbs from this context, as we might already
E
Eric Dumazet 已提交
849 850
 * hold qdisc lock.
 */
E
Eric Dumazet 已提交
851
void tcp_wfree(struct sk_buff *skb)
E
Eric Dumazet 已提交
852 853 854
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp = tcp_sk(sk);
855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870
	int wmem;

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

	/* If this softirq is serviced by ksoftirqd, we are likely under stress.
	 * Wait until our queues (qdisc + devices) are drained.
	 * This gives :
	 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
	 * - chance for incoming ACK (processed by another cpu maybe)
	 *   to migrate this flow (skb->ooo_okay will be eventually set)
	 */
	if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
		goto out;
E
Eric Dumazet 已提交
871 872 873 874 875 876 877 878

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

		/* queue this socket to tasklet queue */
		local_irq_save(flags);
879
		tsq = this_cpu_ptr(&tsq_tasklet);
E
Eric Dumazet 已提交
880 881 882
		list_add(&tp->tsq_node, &tsq->head);
		tasklet_schedule(&tsq->tasklet);
		local_irq_restore(flags);
883
		return;
E
Eric Dumazet 已提交
884
	}
885 886
out:
	sk_free(sk);
E
Eric Dumazet 已提交
887 888
}

L
Linus Torvalds 已提交
889 890 891 892 893 894 895 896 897 898 899
/* 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.
 */
900 901
static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
			    gfp_t gfp_mask)
L
Linus Torvalds 已提交
902
{
903 904 905 906
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct inet_sock *inet;
	struct tcp_sock *tp;
	struct tcp_skb_cb *tcb;
A
Adam Langley 已提交
907
	struct tcp_out_options opts;
908
	unsigned int tcp_options_size, tcp_header_size;
909
	struct tcp_md5sig_key *md5;
910 911 912 913 914
	struct tcphdr *th;
	int err;

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

915
	if (clone_it) {
916
		skb_mstamp_get(&skb->skb_mstamp);
917

918 919 920 921 922 923 924
		if (unlikely(skb_cloned(skb)))
			skb = pskb_copy(skb, gfp_mask);
		else
			skb = skb_clone(skb, gfp_mask);
		if (unlikely(!skb))
			return -ENOBUFS;
	}
L
Linus Torvalds 已提交
925

926 927 928
	inet = inet_sk(sk);
	tp = tcp_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
929
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
930

E
Eric Dumazet 已提交
931
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
932 933 934 935 936
		tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
	else
		tcp_options_size = tcp_established_options(sk, skb, &opts,
							   &md5);
	tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
937

E
Eric Dumazet 已提交
938
	/* if no packet is in qdisc/device queue, then allow XPS to select
939 940 941 942 943
	 * another queue. We can be called from tcp_tsq_handler()
	 * which holds one reference to sk_wmem_alloc.
	 *
	 * TODO: Ideally, in-flight pure ACK packets should not matter here.
	 * One way to get this would be to set skb->truesize = 2 on them.
E
Eric Dumazet 已提交
944
	 */
945
	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
946

947 948
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
E
Eric Dumazet 已提交
949 950 951

	skb_orphan(skb);
	skb->sk = sk;
E
Eric Dumazet 已提交
952
	skb->destructor = skb_is_tcp_pure_ack(skb) ? sock_wfree : tcp_wfree;
953
	skb_set_hash_from_sk(skb, sk);
E
Eric Dumazet 已提交
954
	atomic_add(skb->truesize, &sk->sk_wmem_alloc);
955 956

	/* Build TCP header and checksum it. */
957
	th = tcp_hdr(skb);
E
Eric Dumazet 已提交
958 959
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
960 961
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
962
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
963
					tcb->tcp_flags);
964

E
Eric Dumazet 已提交
965
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
966 967 968
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
969
		th->window	= htons(min(tp->rcv_wnd, 65535U));
970 971 972 973 974
	} else {
		th->window	= htons(tcp_select_window(sk));
	}
	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
975

I
Ilpo Järvinen 已提交
976
	/* The urg_mode check is necessary during a below snd_una win probe */
977 978 979 980 981
	if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
		if (before(tp->snd_up, tcb->seq + 0x10000)) {
			th->urg_ptr = htons(tp->snd_up - tcb->seq);
			th->urg = 1;
		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
982
			th->urg_ptr = htons(0xFFFF);
983 984
			th->urg = 1;
		}
985
	}
L
Linus Torvalds 已提交
986

987
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
988
	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
E
Eric Dumazet 已提交
989
	if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
990
		tcp_ecn_send(sk, skb, tcp_header_size);
L
Linus Torvalds 已提交
991

992 993 994
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
995
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
996
		tp->af_specific->calc_md5_hash(opts.hash_location,
997
					       md5, sk, skb);
998 999 1000
	}
#endif

1001
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
1002

E
Eric Dumazet 已提交
1003
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
1004
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1005

1006
	if (skb->len != tcp_header_size) {
1007
		tcp_event_data_sent(tp, sk);
1008 1009
		tp->data_segs_out += tcp_skb_pcount(skb);
	}
L
Linus Torvalds 已提交
1010

1011
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1012 1013
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
1014

1015
	tp->segs_out += tcp_skb_pcount(skb);
1016
	/* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1017
	skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1018
	skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1019

E
Eric Dumazet 已提交
1020 1021
	/* Our usage of tstamp should remain private */
	skb->tstamp.tv64 = 0;
1022 1023 1024 1025 1026

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

1027
	err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
E
Eric Dumazet 已提交
1028

1029
	if (likely(err <= 0))
1030 1031
		return err;

1032
	tcp_enter_cwr(sk);
1033

1034
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
1035 1036
}

1037
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
1038 1039 1040 1041 1042 1043 1044 1045 1046 1047
 *
 * 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;
1048
	__skb_header_release(skb);
1049
	tcp_add_write_queue_tail(sk, skb);
1050 1051
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
1052 1053
}

1054
/* Initialize TSO segments for a packet. */
1055
static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1056
{
1057
	if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1058 1059 1060
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
1061
		tcp_skb_pcount_set(skb, 1);
1062
		TCP_SKB_CB(skb)->tcp_gso_size = 0;
1063
	} else {
1064
		tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1065
		TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
L
Linus Torvalds 已提交
1066 1067 1068
	}
}

I
Ilpo Järvinen 已提交
1069
/* When a modification to fackets out becomes necessary, we need to check
1070
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
1071
 */
1072
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
1073 1074
				   int decr)
{
1075 1076
	struct tcp_sock *tp = tcp_sk(sk);

1077
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
1078 1079
		return;

1080
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
1081 1082 1083
		tp->fackets_out -= decr;
}

1084 1085 1086
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
1087
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107
{
	struct tcp_sock *tp = tcp_sk(sk);

	tp->packets_out -= decr;

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

	/* Reno case is special. Sigh... */
	if (tcp_is_reno(tp) && decr > 0)
		tp->sacked_out -= min_t(u32, tp->sacked_out, decr);

	tcp_adjust_fackets_out(sk, skb, decr);

	if (tp->lost_skb_hint &&
	    before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1108
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1109 1110 1111 1112 1113
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
{
	struct skb_shared_info *shinfo = skb_shinfo(skb);

	if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) &&
	    !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
		struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
		u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;

		shinfo->tx_flags &= ~tsflags;
		shinfo2->tx_flags |= tsflags;
		swap(shinfo->tskey, shinfo2->tskey);
1126 1127
		TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
		TCP_SKB_CB(skb)->txstamp_ack = 0;
1128 1129 1130
	}
}

L
Linus Torvalds 已提交
1131 1132
/* 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
1133
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
1134 1135
 * Remember, these are still headerless SKBs at this point.
 */
1136
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1137
		 unsigned int mss_now, gfp_t gfp)
L
Linus Torvalds 已提交
1138 1139 1140
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1141
	int nsize, old_factor;
1142
	int nlen;
1143
	u8 flags;
L
Linus Torvalds 已提交
1144

1145 1146
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1147

L
Linus Torvalds 已提交
1148 1149 1150 1151
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

1152
	if (skb_unclone(skb, gfp))
L
Linus Torvalds 已提交
1153 1154 1155
		return -ENOMEM;

	/* Get a new skb... force flag on. */
1156
	buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1157
	if (!buff)
L
Linus Torvalds 已提交
1158
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1159

1160 1161
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1162 1163 1164
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1165 1166 1167 1168 1169 1170 1171

	/* Correct the sequence numbers. */
	TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
	TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;

	/* PSH and FIN should only be set in the second packet. */
E
Eric Dumazet 已提交
1172 1173 1174
	flags = TCP_SKB_CB(skb)->tcp_flags;
	TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
	TCP_SKB_CB(buff)->tcp_flags = flags;
1175
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
1176

1177
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1178
		/* Copy and checksum data tail into the new buffer. */
1179 1180
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1181 1182 1183 1184 1185 1186
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1187
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1188 1189 1190 1191 1192
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

1193
	buff->tstamp = skb->tstamp;
1194
	tcp_fragment_tstamp(skb, buff);
L
Linus Torvalds 已提交
1195

1196 1197
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1198
	/* Fix up tso_factor for both original and new SKB.  */
1199 1200
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
L
Linus Torvalds 已提交
1201

1202 1203 1204
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1205
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1206 1207
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1208

1209 1210
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1211 1212 1213
	}

	/* Link BUFF into the send queue. */
1214
	__skb_header_release(buff);
1215
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1216 1217 1218 1219 1220 1221 1222 1223

	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.
 */
1224
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1225
{
1226
	struct skb_shared_info *shinfo;
L
Linus Torvalds 已提交
1227 1228
	int i, k, eat;

E
Eric Dumazet 已提交
1229 1230 1231 1232 1233 1234 1235
	eat = min_t(int, len, skb_headlen(skb));
	if (eat) {
		__skb_pull(skb, eat);
		len -= eat;
		if (!len)
			return;
	}
L
Linus Torvalds 已提交
1236 1237
	eat = len;
	k = 0;
1238 1239 1240
	shinfo = skb_shinfo(skb);
	for (i = 0; i < shinfo->nr_frags; i++) {
		int size = skb_frag_size(&shinfo->frags[i]);
E
Eric Dumazet 已提交
1241 1242

		if (size <= eat) {
1243
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1244
			eat -= size;
L
Linus Torvalds 已提交
1245
		} else {
1246
			shinfo->frags[k] = shinfo->frags[i];
L
Linus Torvalds 已提交
1247
			if (eat) {
1248 1249
				shinfo->frags[k].page_offset += eat;
				skb_frag_size_sub(&shinfo->frags[k], eat);
L
Linus Torvalds 已提交
1250 1251 1252 1253 1254
				eat = 0;
			}
			k++;
		}
	}
1255
	shinfo->nr_frags = k;
L
Linus Torvalds 已提交
1256

1257
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1258 1259 1260 1261
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1262
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1263 1264
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1265
	if (skb_unclone(skb, GFP_ATOMIC))
L
Linus Torvalds 已提交
1266 1267
		return -ENOMEM;

E
Eric Dumazet 已提交
1268
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1269 1270

	TCP_SKB_CB(skb)->seq += len;
1271
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1272 1273 1274

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1275
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1276 1277
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1278
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1279
	if (tcp_skb_pcount(skb) > 1)
1280
		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1281 1282 1283 1284

	return 0;
}

1285 1286
/* Calculate MSS not accounting any TCP options.  */
static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
J
John Heffner 已提交
1287
{
1288 1289
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1290 1291 1292 1293 1294 1295 1296
	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);

1297 1298 1299 1300 1301 1302 1303 1304
	/* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
	if (icsk->icsk_af_ops->net_frag_header_len) {
		const struct dst_entry *dst = __sk_dst_get(sk);

		if (dst && dst_allfrag(dst))
			mss_now -= icsk->icsk_af_ops->net_frag_header_len;
	}

J
John Heffner 已提交
1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317
	/* Clamp it (mss_clamp does not include tcp options) */
	if (mss_now > tp->rx_opt.mss_clamp)
		mss_now = tp->rx_opt.mss_clamp;

	/* Now subtract optional transport overhead */
	mss_now -= icsk->icsk_ext_hdr_len;

	/* Then reserve room for full set of TCP options and 8 bytes of data */
	if (mss_now < 48)
		mss_now = 48;
	return mss_now;
}

1318 1319 1320 1321 1322 1323 1324 1325
/* Calculate MSS. Not accounting for SACKs here.  */
int tcp_mtu_to_mss(struct sock *sk, int pmtu)
{
	/* Subtract TCP options size, not including SACKs */
	return __tcp_mtu_to_mss(sk, pmtu) -
	       (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
}

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

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

1338 1339 1340 1341 1342 1343 1344
	/* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
	if (icsk->icsk_af_ops->net_frag_header_len) {
		const struct dst_entry *dst = __sk_dst_get(sk);

		if (dst && dst_allfrag(dst))
			mtu += icsk->icsk_af_ops->net_frag_header_len;
	}
J
John Heffner 已提交
1345 1346 1347
	return mtu;
}

1348
/* MTU probing init per socket */
J
John Heffner 已提交
1349 1350 1351 1352
void tcp_mtup_init(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
F
Fan Du 已提交
1353
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1354

F
Fan Du 已提交
1355
	icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
J
John Heffner 已提交
1356
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1357
			       icsk->icsk_af_ops->net_header_len;
F
Fan Du 已提交
1358
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
J
John Heffner 已提交
1359
	icsk->icsk_mtup.probe_size = 0;
1360 1361
	if (icsk->icsk_mtup.enabled)
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
J
John Heffner 已提交
1362
}
E
Eric Dumazet 已提交
1363
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1364

L
Linus Torvalds 已提交
1365 1366 1367 1368 1369 1370
/* 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
1371
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1372 1373
   It also does not include TCP options.

1374
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1375 1376 1377 1378 1379 1380 1381 1382 1383

   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.

1384 1385
   NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
   are READ ONLY outside this function.		--ANK (980731)
L
Linus Torvalds 已提交
1386 1387 1388 1389
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1390
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1391
	int mss_now;
L
Linus Torvalds 已提交
1392

J
John Heffner 已提交
1393 1394
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1395

J
John Heffner 已提交
1396
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1397
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1398 1399

	/* And store cached results */
1400
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1401 1402
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1403
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1404 1405 1406

	return mss_now;
}
E
Eric Dumazet 已提交
1407
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1408 1409 1410 1411

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1412
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1413
{
1414 1415
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1416
	u32 mss_now;
1417
	unsigned int header_len;
A
Adam Langley 已提交
1418 1419
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1420 1421 1422

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1423 1424
	if (dst) {
		u32 mtu = dst_mtu(dst);
1425
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1426 1427 1428
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1429 1430 1431 1432 1433 1434 1435 1436 1437 1438
	header_len = tcp_established_options(sk, NULL, &opts, &md5) +
		     sizeof(struct tcphdr);
	/* The mss_cache is sized based on tp->tcp_header_len, which assumes
	 * some common options. If this is an odd packet (because we have SACK
	 * blocks etc) then our calculated header_len will be different, and
	 * we have to adjust mss_now correspondingly */
	if (header_len != tp->tcp_header_len) {
		int delta = (int) header_len - tp->tcp_header_len;
		mss_now -= delta;
	}
1439

L
Linus Torvalds 已提交
1440 1441 1442
	return mss_now;
}

1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464
/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
 * As additional protections, we do not touch cwnd in retransmission phases,
 * and if application hit its sndbuf limit recently.
 */
static void tcp_cwnd_application_limited(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
	    sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
		/* Limited by application or receiver window. */
		u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
		u32 win_used = max(tp->snd_cwnd_used, init_win);
		if (win_used < tp->snd_cwnd) {
			tp->snd_ssthresh = tcp_current_ssthresh(sk);
			tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
		}
		tp->snd_cwnd_used = 0;
	}
	tp->snd_cwnd_stamp = tcp_time_stamp;
}

1465
static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1466
{
1467
	struct tcp_sock *tp = tcp_sk(sk);
1468

1469 1470 1471 1472 1473 1474 1475 1476 1477
	/* Track the maximum number of outstanding packets in each
	 * window, and remember whether we were cwnd-limited then.
	 */
	if (!before(tp->snd_una, tp->max_packets_seq) ||
	    tp->packets_out > tp->max_packets_out) {
		tp->max_packets_out = tp->packets_out;
		tp->max_packets_seq = tp->snd_nxt;
		tp->is_cwnd_limited = is_cwnd_limited;
	}
1478

1479
	if (tcp_is_cwnd_limited(sk)) {
1480 1481 1482 1483 1484 1485 1486 1487
		/* 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;

1488 1489
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1490 1491 1492 1493
			tcp_cwnd_application_limited(sk);
	}
}

E
Eric Dumazet 已提交
1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507
/* Minshall's variant of the Nagle send check. */
static bool tcp_minshall_check(const struct tcp_sock *tp)
{
	return after(tp->snd_sml, tp->snd_una) &&
		!after(tp->snd_sml, tp->snd_nxt);
}

/* Update snd_sml if this skb is under mss
 * Note that a TSO packet might end with a sub-mss segment
 * The test is really :
 * if ((skb->len % mss) != 0)
 *        tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
 * But we can avoid doing the divide again given we already have
 *  skb_pcount = skb->len / mss_now
1508
 */
E
Eric Dumazet 已提交
1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523
static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
				const struct sk_buff *skb)
{
	if (skb->len < tcp_skb_pcount(skb) * mss_now)
		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
}

/* Return false, if packet can be sent now without violation Nagle's rules:
 * 1. It is full sized. (provided by caller in %partial bool)
 * 2. Or it contains FIN. (already checked by caller)
 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
 *    With Minshall's modification: all sent small packets are ACKed.
 */
static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1524
			    int nonagle)
E
Eric Dumazet 已提交
1525 1526 1527 1528 1529
{
	return partial &&
		((nonagle & TCP_NAGLE_CORK) ||
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
}
E
Eric Dumazet 已提交
1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550

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

	bytes = min(sk->sk_pacing_rate >> 10,
		    sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);

	/* Goal is to send at least one packet per ms,
	 * not one big TSO packet every 100 ms.
	 * This preserves ACK clocking and is consistent
	 * with tcp_tso_should_defer() heuristic.
	 */
	segs = max_t(u32, bytes / mss_now, sysctl_tcp_min_tso_segs);

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

E
Eric Dumazet 已提交
1551 1552 1553 1554 1555 1556
/* Returns the portion of skb which can be sent right away */
static unsigned int tcp_mss_split_point(const struct sock *sk,
					const struct sk_buff *skb,
					unsigned int mss_now,
					unsigned int max_segs,
					int nonagle)
1557
{
1558
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
1559
	u32 partial, needed, window, max_len;
1560

1561
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1562
	max_len = mss_now * max_segs;
1563

1564 1565
	if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
		return max_len;
1566

1567 1568
	needed = min(skb->len, window);

1569 1570
	if (max_len <= needed)
		return max_len;
1571

E
Eric Dumazet 已提交
1572 1573 1574 1575 1576
	partial = needed % mss_now;
	/* If last segment is not a full MSS, check if Nagle rules allow us
	 * to include this last segment in this skb.
	 * Otherwise, we'll split the skb at last MSS boundary
	 */
1577
	if (tcp_nagle_check(partial != 0, tp, nonagle))
E
Eric Dumazet 已提交
1578 1579 1580
		return needed - partial;

	return needed;
1581 1582 1583 1584 1585
}

/* 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.
 */
1586 1587
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1588
{
E
Eric Dumazet 已提交
1589
	u32 in_flight, cwnd, halfcwnd;
1590 1591

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1592 1593
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1594 1595 1596 1597
		return 1;

	in_flight = tcp_packets_in_flight(tp);
	cwnd = tp->snd_cwnd;
E
Eric Dumazet 已提交
1598 1599
	if (in_flight >= cwnd)
		return 0;
1600

E
Eric Dumazet 已提交
1601 1602 1603 1604 1605
	/* For better scheduling, ensure we have at least
	 * 2 GSO packets in flight.
	 */
	halfcwnd = max(cwnd >> 1, 1U);
	return min(halfcwnd, cwnd - in_flight);
1606 1607
}

1608
/* Initialize TSO state of a skb.
1609
 * This must be invoked the first time we consider transmitting
1610 1611
 * SKB onto the wire.
 */
1612
static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1613 1614 1615
{
	int tso_segs = tcp_skb_pcount(skb);

1616
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1617
		tcp_set_skb_tso_segs(skb, mss_now);
1618 1619 1620 1621 1622 1623
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}


E
Eric Dumazet 已提交
1624
/* Return true if the Nagle test allows this packet to be
1625 1626
 * sent now.
 */
E
Eric Dumazet 已提交
1627 1628
static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
				  unsigned int cur_mss, int nonagle)
1629 1630 1631 1632 1633 1634 1635 1636
{
	/* Nagle rule does not apply to frames, which sit in the middle of the
	 * write_queue (they have no chances to get new data).
	 *
	 * This is implemented in the callers, where they modify the 'nonagle'
	 * argument based upon the location of SKB in the send queue.
	 */
	if (nonagle & TCP_NAGLE_PUSH)
E
Eric Dumazet 已提交
1637
		return true;
1638

Y
Yuchung Cheng 已提交
1639 1640
	/* Don't use the nagle rule for urgent data (or for the final FIN). */
	if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
E
Eric Dumazet 已提交
1641
		return true;
1642

1643
	if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
E
Eric Dumazet 已提交
1644
		return true;
1645

E
Eric Dumazet 已提交
1646
	return false;
1647 1648 1649
}

/* Does at least the first segment of SKB fit into the send window? */
E
Eric Dumazet 已提交
1650 1651 1652
static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
			     const struct sk_buff *skb,
			     unsigned int cur_mss)
1653 1654 1655 1656 1657 1658
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1659
	return !after(end_seq, tcp_wnd_end(tp));
1660 1661
}

1662
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1663 1664 1665
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1666
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1667 1668
				 unsigned int cur_mss, int nonagle)
{
1669
	const struct tcp_sock *tp = tcp_sk(sk);
1670 1671
	unsigned int cwnd_quota;

1672
	tcp_init_tso_segs(skb, cur_mss);
1673 1674 1675 1676 1677

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1678
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1679 1680 1681 1682 1683
		cwnd_quota = 0;

	return cwnd_quota;
}

1684
/* Test if sending is allowed right now. */
E
Eric Dumazet 已提交
1685
bool tcp_may_send_now(struct sock *sk)
1686
{
1687
	const struct tcp_sock *tp = tcp_sk(sk);
1688
	struct sk_buff *skb = tcp_send_head(sk);
1689

E
Eric Dumazet 已提交
1690
	return skb &&
I
Ilpo Järvinen 已提交
1691
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1692
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1693
			      tp->nonagle : TCP_NAGLE_PUSH));
1694 1695 1696 1697 1698 1699 1700 1701 1702
}

/* 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).
 */
1703
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1704
			unsigned int mss_now, gfp_t gfp)
1705 1706 1707
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1708
	u8 flags;
1709 1710

	/* All of a TSO frame must be composed of paged data.  */
1711
	if (skb->len != skb->data_len)
1712
		return tcp_fragment(sk, skb, len, mss_now, gfp);
1713

1714
	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1715
	if (unlikely(!buff))
1716 1717
		return -ENOMEM;

1718 1719
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1720
	buff->truesize += nlen;
1721 1722 1723 1724 1725 1726 1727 1728
	skb->truesize -= nlen;

	/* Correct the sequence numbers. */
	TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
	TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;

	/* PSH and FIN should only be set in the second packet. */
E
Eric Dumazet 已提交
1729 1730 1731
	flags = TCP_SKB_CB(skb)->tcp_flags;
	TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
	TCP_SKB_CB(buff)->tcp_flags = flags;
1732 1733 1734 1735

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

1736
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1737
	skb_split(skb, buff, len);
1738
	tcp_fragment_tstamp(skb, buff);
1739 1740

	/* Fix up tso_factor for both original and new SKB.  */
1741 1742
	tcp_set_skb_tso_segs(skb, mss_now);
	tcp_set_skb_tso_segs(buff, mss_now);
1743 1744

	/* Link BUFF into the send queue. */
1745
	__skb_header_release(buff);
1746
	tcp_insert_write_queue_after(skb, buff, sk);
1747 1748 1749 1750 1751 1752 1753 1754 1755

	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.
 */
1756
static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
E
Eric Dumazet 已提交
1757
				 bool *is_cwnd_limited, u32 max_segs)
1758
{
1759
	const struct inet_connection_sock *icsk = inet_csk(sk);
1760 1761 1762 1763
	u32 age, send_win, cong_win, limit, in_flight;
	struct tcp_sock *tp = tcp_sk(sk);
	struct skb_mstamp now;
	struct sk_buff *head;
1764
	int win_divisor;
1765

E
Eric Dumazet 已提交
1766
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1767
		goto send_now;
1768

1769
	if (icsk->icsk_ca_state >= TCP_CA_Recovery)
J
John Heffner 已提交
1770 1771
		goto send_now;

E
Eric Dumazet 已提交
1772 1773 1774 1775
	/* Avoid bursty behavior by allowing defer
	 * only if the last write was recent.
	 */
	if ((s32)(tcp_time_stamp - tp->lsndtime) > 0)
J
John Heffner 已提交
1776
		goto send_now;
1777

1778 1779
	in_flight = tcp_packets_in_flight(tp);

1780
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1781

1782
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1783 1784 1785 1786 1787 1788

	/* 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);

1789
	/* If a full-sized TSO skb can be sent, do it. */
E
Eric Dumazet 已提交
1790
	if (limit >= max_segs * tp->mss_cache)
J
John Heffner 已提交
1791
		goto send_now;
1792

1793 1794 1795 1796
	/* Middle in queue won't get any more data, full sendable already? */
	if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
		goto send_now;

1797 1798
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1799 1800 1801 1802 1803
		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.
		 */
1804
		chunk /= win_divisor;
1805
		if (limit >= chunk)
J
John Heffner 已提交
1806
			goto send_now;
1807 1808 1809 1810 1811 1812
	} 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.
		 */
1813
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1814
			goto send_now;
1815 1816
	}

1817 1818 1819 1820 1821 1822 1823
	head = tcp_write_queue_head(sk);
	skb_mstamp_get(&now);
	age = skb_mstamp_us_delta(&now, &head->skb_mstamp);
	/* If next ACK is likely to come too late (half srtt), do not defer */
	if (age < (tp->srtt_us >> 4))
		goto send_now;

E
Eric Dumazet 已提交
1824
	/* Ok, it looks like it is advisable to defer. */
J
John Heffner 已提交
1825

1826
	if (cong_win < send_win && cong_win <= skb->len)
1827 1828
		*is_cwnd_limited = true;

E
Eric Dumazet 已提交
1829
	return true;
J
John Heffner 已提交
1830 1831

send_now:
E
Eric Dumazet 已提交
1832
	return false;
1833 1834
}

1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859
static inline void tcp_mtu_check_reprobe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	struct net *net = sock_net(sk);
	u32 interval;
	s32 delta;

	interval = net->ipv4.sysctl_tcp_probe_interval;
	delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp;
	if (unlikely(delta >= interval * HZ)) {
		int mss = tcp_current_mss(sk);

		/* Update current search range */
		icsk->icsk_mtup.probe_size = 0;
		icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
			sizeof(struct tcphdr) +
			icsk->icsk_af_ops->net_header_len;
		icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);

		/* Update probe time stamp */
		icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
	}
}

J
John Heffner 已提交
1860
/* Create a new MTU probe if we are ready.
1861 1862 1863 1864
 * MTU probe is regularly attempting to increase the path MTU by
 * deliberately sending larger packets.  This discovers routing
 * changes resulting in larger path MTUs.
 *
J
John Heffner 已提交
1865 1866
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1867 1868
 *         -1 otherwise
 */
J
John Heffner 已提交
1869 1870 1871 1872 1873
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;
1874
	struct net *net = sock_net(sk);
J
John Heffner 已提交
1875 1876
	int len;
	int probe_size;
1877
	int size_needed;
J
John Heffner 已提交
1878 1879
	int copy;
	int mss_now;
1880
	int interval;
J
John Heffner 已提交
1881 1882 1883 1884 1885 1886 1887 1888 1889

	/* 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 ||
1890
	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
J
John Heffner 已提交
1891 1892
		return -1;

1893 1894 1895 1896
	/* Use binary search for probe_size between tcp_mss_base,
	 * and current mss_clamp. if (search_high - search_low)
	 * smaller than a threshold, backoff from probing.
	 */
I
Ilpo Järvinen 已提交
1897
	mss_now = tcp_current_mss(sk);
1898 1899
	probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
				    icsk->icsk_mtup.search_low) >> 1);
1900
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1901
	interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1902 1903 1904 1905
	/* When misfortune happens, we are reprobing actively,
	 * and then reprobe timer has expired. We stick with current
	 * probing process by not resetting search range to its orignal.
	 */
1906
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1907 1908 1909 1910 1911
		interval < net->ipv4.sysctl_tcp_probe_threshold) {
		/* Check whether enough time has elaplased for
		 * another round of probing.
		 */
		tcp_mtu_check_reprobe(sk);
J
John Heffner 已提交
1912 1913 1914 1915
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1916
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1917 1918
		return -1;

1919 1920
	if (tp->snd_wnd < size_needed)
		return -1;
1921
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1922
		return 0;
J
John Heffner 已提交
1923

1924 1925 1926
	/* 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
1927 1928 1929 1930 1931 1932
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
1933
	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1934
	if (!nskb)
J
John Heffner 已提交
1935
		return -1;
1936 1937
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
1938

1939
	skb = tcp_send_head(sk);
J
John Heffner 已提交
1940 1941 1942

	TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
	TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
E
Eric Dumazet 已提交
1943
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
1944 1945
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
1946
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
1947

1948 1949
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
1950
	len = 0;
1951
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
1952 1953 1954 1955 1956
		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,
1957 1958
							    skb_put(nskb, copy),
							    copy, nskb->csum);
J
John Heffner 已提交
1959 1960 1961 1962

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
1963
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1964
			tcp_unlink_write_queue(skb, sk);
1965
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
1966
		} else {
E
Eric Dumazet 已提交
1967
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
1968
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
1969 1970
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
1971
				if (skb->ip_summed != CHECKSUM_PARTIAL)
1972 1973
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
1974 1975
			} else {
				__pskb_trim_head(skb, copy);
1976
				tcp_set_skb_tso_segs(skb, mss_now);
J
John Heffner 已提交
1977 1978 1979 1980 1981
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
1982 1983 1984

		if (len >= probe_size)
			break;
J
John Heffner 已提交
1985
	}
1986
	tcp_init_tso_segs(nskb, nskb->len);
J
John Heffner 已提交
1987 1988

	/* We're ready to send.  If this fails, the probe will
E
Eric Dumazet 已提交
1989 1990
	 * be resegmented into mss-sized pieces by tcp_write_xmit().
	 */
J
John Heffner 已提交
1991 1992
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
1993
		 * effectively two packets. */
J
John Heffner 已提交
1994
		tp->snd_cwnd--;
1995
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
1996 1997

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1998 1999
		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
2000 2001 2002 2003 2004 2005 2006

		return 1;
	}

	return -1;
}

L
Linus Torvalds 已提交
2007 2008 2009 2010
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
2011 2012 2013 2014
 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
 * account rare use of URG, this is not a big flaw.
 *
N
Nandita Dukkipati 已提交
2015 2016 2017
 * Send at most one packet when push_one > 0. Temporarily ignore
 * cwnd limit to force at most one packet out when push_one == 2.

E
Eric Dumazet 已提交
2018 2019
 * Returns true, if no segments are in flight and we have queued segments,
 * but cannot send anything now because of SWS or another problem.
L
Linus Torvalds 已提交
2020
 */
E
Eric Dumazet 已提交
2021 2022
static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			   int push_one, gfp_t gfp)
L
Linus Torvalds 已提交
2023 2024
{
	struct tcp_sock *tp = tcp_sk(sk);
2025
	struct sk_buff *skb;
2026 2027
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
2028
	int result;
2029
	bool is_cwnd_limited = false;
E
Eric Dumazet 已提交
2030
	u32 max_segs;
L
Linus Torvalds 已提交
2031

2032
	sent_pkts = 0;
J
John Heffner 已提交
2033

2034 2035 2036 2037
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
E
Eric Dumazet 已提交
2038
			return false;
2039 2040 2041
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
2042 2043
	}

E
Eric Dumazet 已提交
2044
	max_segs = tcp_tso_autosize(sk, mss_now);
2045
	while ((skb = tcp_send_head(sk))) {
2046 2047
		unsigned int limit;

2048
		tso_segs = tcp_init_tso_segs(skb, mss_now);
2049
		BUG_ON(!tso_segs);
2050

2051
		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
E
Eric Dumazet 已提交
2052 2053
			/* "skb_mstamp" is used as a start point for the retransmit timer */
			skb_mstamp_get(&skb->skb_mstamp);
2054
			goto repair; /* Skip network transmission */
2055
		}
2056

2057
		cwnd_quota = tcp_cwnd_test(tp, skb);
N
Nandita Dukkipati 已提交
2058 2059 2060 2061 2062 2063 2064
		if (!cwnd_quota) {
			if (push_one == 2)
				/* Force out a loss probe pkt. */
				cwnd_quota = 1;
			else
				break;
		}
2065 2066 2067 2068

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

2069
		if (tso_segs == 1) {
2070 2071 2072 2073 2074
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
2075
			if (!push_one &&
E
Eric Dumazet 已提交
2076 2077
			    tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
						 max_segs))
2078 2079
				break;
		}
2080

E
Eric Dumazet 已提交
2081
		limit = mss_now;
2082
		if (tso_segs > 1 && !tcp_urg_mode(tp))
E
Eric Dumazet 已提交
2083 2084 2085 2086 2087 2088 2089 2090 2091 2092
			limit = tcp_mss_split_point(sk, skb, mss_now,
						    min_t(unsigned int,
							  cwnd_quota,
							  max_segs),
						    nonagle);

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

E
Eric Dumazet 已提交
2093 2094 2095 2096 2097 2098
		/* TCP Small Queues :
		 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
		 * This allows for :
		 *  - better RTT estimation and ACK scheduling
		 *  - faster recovery
		 *  - high rates
2099 2100 2101
		 * Alas, some drivers / subsystems require a fair amount
		 * of queued bytes to ensure line rate.
		 * One example is wifi aggregation (802.11 AMPDU)
E
Eric Dumazet 已提交
2102
		 */
E
Eric Dumazet 已提交
2103 2104
		limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
		limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
E
Eric Dumazet 已提交
2105 2106

		if (atomic_read(&sk->sk_wmem_alloc) > limit) {
E
Eric Dumazet 已提交
2107
			set_bit(TSQ_THROTTLED, &tp->tsq_flags);
J
John Ogness 已提交
2108 2109 2110 2111
			/* It is possible TX completion already happened
			 * before we set TSQ_THROTTLED, so we must
			 * test again the condition.
			 */
2112
			smp_mb__after_atomic();
J
John Ogness 已提交
2113 2114
			if (atomic_read(&sk->sk_wmem_alloc) > limit)
				break;
E
Eric Dumazet 已提交
2115
		}
E
Eric Dumazet 已提交
2116

2117
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2118
			break;
L
Linus Torvalds 已提交
2119

2120
repair:
2121 2122 2123
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
2124
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
2125

2126
		tcp_minshall_update(tp, mss_now, skb);
2127
		sent_pkts += tcp_skb_pcount(skb);
2128 2129 2130

		if (push_one)
			break;
2131
	}
L
Linus Torvalds 已提交
2132

2133
	if (likely(sent_pkts)) {
2134 2135
		if (tcp_in_cwnd_reduction(sk))
			tp->prr_out += sent_pkts;
N
Nandita Dukkipati 已提交
2136 2137 2138 2139

		/* Send one loss probe per tail loss episode. */
		if (push_one != 2)
			tcp_schedule_loss_probe(sk);
2140
		is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2141
		tcp_cwnd_validate(sk, is_cwnd_limited);
E
Eric Dumazet 已提交
2142
		return false;
L
Linus Torvalds 已提交
2143
	}
2144
	return !tp->packets_out && tcp_send_head(sk);
N
Nandita Dukkipati 已提交
2145 2146 2147 2148 2149 2150 2151
}

bool tcp_schedule_loss_probe(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_sock *tp = tcp_sk(sk);
	u32 timeout, tlp_time_stamp, rto_time_stamp;
2152
	u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
N
Nandita Dukkipati 已提交
2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163

	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
		return false;
	/* No consecutive loss probes. */
	if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
		tcp_rearm_rto(sk);
		return false;
	}
	/* Don't do any loss probe on a Fast Open connection before 3WHS
	 * finishes.
	 */
2164
	if (tp->fastopen_rsk)
N
Nandita Dukkipati 已提交
2165 2166 2167 2168 2169 2170 2171 2172 2173
		return false;

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

	/* Schedule a loss probe in 2*RTT for SACK capable connections
	 * in Open state, that are either limited by cwnd or application.
	 */
2174
	if (sysctl_tcp_early_retrans < 3 || !tp->packets_out ||
N
Nandita Dukkipati 已提交
2175 2176 2177 2178 2179 2180 2181 2182
	    !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
		return false;

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

	/* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2183 2184
	 * for delayed ack when there's one outstanding packet. If no RTT
	 * sample is available then probe after TCP_TIMEOUT_INIT.
N
Nandita Dukkipati 已提交
2185
	 */
2186
	timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
N
Nandita Dukkipati 已提交
2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205
	if (tp->packets_out == 1)
		timeout = max_t(u32, timeout,
				(rtt + (rtt >> 1) + TCP_DELACK_MAX));
	timeout = max_t(u32, timeout, msecs_to_jiffies(10));

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

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

2206 2207 2208 2209 2210 2211 2212 2213
/* Thanks to skb fast clones, we can detect if a prior transmit of
 * a packet is still in a qdisc or driver queue.
 * In this case, there is very little point doing a retransmit !
 * Note: This is called from BH context only.
 */
static bool skb_still_in_host_queue(const struct sock *sk,
				    const struct sk_buff *skb)
{
2214
	if (unlikely(skb_fclone_busy(sk, skb))) {
2215 2216 2217 2218 2219 2220 2221
		NET_INC_STATS_BH(sock_net(sk),
				 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
		return true;
	}
	return false;
}

2222
/* When probe timeout (PTO) fires, try send a new segment if possible, else
N
Nandita Dukkipati 已提交
2223 2224 2225 2226
 * retransmit the last segment.
 */
void tcp_send_loss_probe(struct sock *sk)
{
N
Nandita Dukkipati 已提交
2227
	struct tcp_sock *tp = tcp_sk(sk);
N
Nandita Dukkipati 已提交
2228 2229 2230 2231
	struct sk_buff *skb;
	int pcount;
	int mss = tcp_current_mss(sk);

2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243
	skb = tcp_send_head(sk);
	if (skb) {
		if (tcp_snd_wnd_test(tp, skb, mss)) {
			pcount = tp->packets_out;
			tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
			if (tp->packets_out > pcount)
				goto probe_sent;
			goto rearm_timer;
		}
		skb = tcp_write_queue_prev(sk, skb);
	} else {
		skb = tcp_write_queue_tail(sk);
N
Nandita Dukkipati 已提交
2244 2245
	}

N
Nandita Dukkipati 已提交
2246 2247 2248 2249
	/* At most one outstanding TLP retransmission. */
	if (tp->tlp_high_seq)
		goto rearm_timer;

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

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

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

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

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

2271 2272
	if (__tcp_retransmit_skb(sk, skb))
		goto rearm_timer;
N
Nandita Dukkipati 已提交
2273

N
Nandita Dukkipati 已提交
2274
	/* Record snd_nxt for loss detection. */
2275
	tp->tlp_high_seq = tp->snd_nxt;
N
Nandita Dukkipati 已提交
2276

2277 2278 2279 2280
probe_sent:
	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
	/* Reset s.t. tcp_rearm_rto will restart timer from now */
	inet_csk(sk)->icsk_pending = 0;
N
Nandita Dukkipati 已提交
2281
rearm_timer:
2282
	tcp_rearm_rto(sk);
L
Linus Torvalds 已提交
2283 2284
}

2285 2286 2287 2288
/* 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.
 */
2289 2290
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
2291
{
2292 2293 2294 2295 2296 2297 2298
	/* If we are closed, the bytes will have to remain here.
	 * In time closedown will finish, we empty the write queue and
	 * all will be happy.
	 */
	if (unlikely(sk->sk_state == TCP_CLOSE))
		return;

2299
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2300
			   sk_gfp_mask(sk, GFP_ATOMIC)))
2301
		tcp_check_probe_timer(sk);
2302 2303
}

2304 2305 2306 2307 2308
/* 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)
{
2309
	struct sk_buff *skb = tcp_send_head(sk);
2310 2311 2312

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

2313
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2314 2315
}

L
Linus Torvalds 已提交
2316 2317
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
2318
 *
L
Linus Torvalds 已提交
2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336
 * 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.
2337
 *
L
Linus Torvalds 已提交
2338 2339
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
2340
 *
L
Linus Torvalds 已提交
2341
 * BSD seems to make the following compromise:
2342
 *
L
Linus Torvalds 已提交
2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369
 *	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)
{
2370
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2371
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
2372
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
2373 2374 2375 2376 2377
	 * 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
	 */
2378
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
2379
	int free_space = tcp_space(sk);
2380 2381
	int allowed_space = tcp_full_space(sk);
	int full_space = min_t(int, tp->window_clamp, allowed_space);
L
Linus Torvalds 已提交
2382 2383 2384
	int window;

	if (mss > full_space)
2385
		mss = full_space;
L
Linus Torvalds 已提交
2386

2387
	if (free_space < (full_space >> 1)) {
2388
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
2389

2390
		if (tcp_under_memory_pressure(sk))
2391 2392
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
2393

2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406
		/* free_space might become our new window, make sure we don't
		 * increase it due to wscale.
		 */
		free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);

		/* if free space is less than mss estimate, or is below 1/16th
		 * of the maximum allowed, try to move to zero-window, else
		 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
		 * new incoming data is dropped due to memory limits.
		 * With large window, mss test triggers way too late in order
		 * to announce zero window in time before rmem limit kicks in.
		 */
		if (free_space < (allowed_space >> 4) || free_space < mss)
L
Linus Torvalds 已提交
2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436
			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)
2437
			window = (free_space / mss) * mss;
2438
		else if (mss == full_space &&
2439
			 free_space > window + (full_space >> 1))
2440
			window = free_space;
L
Linus Torvalds 已提交
2441 2442 2443 2444 2445
	}

	return window;
}

2446 2447
void tcp_skb_collapse_tstamp(struct sk_buff *skb,
			     const struct sk_buff *next_skb)
2448 2449 2450 2451 2452 2453 2454 2455 2456
{
	const struct skb_shared_info *next_shinfo = skb_shinfo(next_skb);
	u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;

	if (unlikely(tsflags)) {
		struct skb_shared_info *shinfo = skb_shinfo(skb);

		shinfo->tx_flags |= tsflags;
		shinfo->tskey = next_shinfo->tskey;
2457 2458
		TCP_SKB_CB(skb)->txstamp_ack |=
			TCP_SKB_CB(next_skb)->txstamp_ack;
2459 2460 2461
	}
}

2462 2463
/* Collapses two adjacent SKB's during retransmission. */
static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2464 2465
{
	struct tcp_sock *tp = tcp_sk(sk);
2466
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2467
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
2468

2469 2470
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
2471

2472
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2473

2474
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
2475

2476
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
2477

2478 2479
	skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
				  next_skb_size);
L
Linus Torvalds 已提交
2480

2481 2482
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
2483

2484 2485
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
2486

2487 2488
	/* 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
2489

2490
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
2491
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2492 2493 2494 2495 2496 2497 2498

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

	/* changed transmit queue under us so clear hints */
2499 2500 2501
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2502

2503 2504
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2505 2506
	tcp_skb_collapse_tstamp(skb, next_skb);

2507
	sk_wmem_free_skb(sk, next_skb);
L
Linus Torvalds 已提交
2508 2509
}

2510
/* Check if coalescing SKBs is legal. */
E
Eric Dumazet 已提交
2511
static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2512 2513
{
	if (tcp_skb_pcount(skb) > 1)
E
Eric Dumazet 已提交
2514
		return false;
2515 2516
	/* TODO: SACK collapsing could be used to remove this condition */
	if (skb_shinfo(skb)->nr_frags != 0)
E
Eric Dumazet 已提交
2517
		return false;
2518
	if (skb_cloned(skb))
E
Eric Dumazet 已提交
2519
		return false;
2520
	if (skb == tcp_send_head(sk))
E
Eric Dumazet 已提交
2521
		return false;
2522 2523
	/* Some heurestics for collapsing over SACK'd could be invented */
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
E
Eric Dumazet 已提交
2524
		return false;
2525

E
Eric Dumazet 已提交
2526
	return true;
2527 2528
}

2529 2530 2531
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2532 2533 2534 2535 2536
static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
				     int space)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb = to, *tmp;
E
Eric Dumazet 已提交
2537
	bool first = true;
2538 2539 2540

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2541
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2542 2543 2544 2545 2546 2547 2548 2549 2550
		return;

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

		space -= skb->len;

		if (first) {
E
Eric Dumazet 已提交
2551
			first = false;
2552 2553 2554 2555 2556 2557 2558 2559
			continue;
		}

		if (space < 0)
			break;
		/* Punt if not enough space exists in the first SKB for
		 * the data in the second
		 */
2560
		if (skb->len > skb_availroom(to))
2561 2562 2563 2564 2565 2566 2567 2568 2569
			break;

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

		tcp_collapse_retrans(sk, to);
	}
}

L
Linus Torvalds 已提交
2570 2571 2572 2573
/* 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.
 */
2574
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
L
Linus Torvalds 已提交
2575 2576
{
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2577
	struct inet_connection_sock *icsk = inet_csk(sk);
2578
	unsigned int cur_mss;
2579
	int err;
L
Linus Torvalds 已提交
2580

J
John Heffner 已提交
2581 2582 2583 2584 2585
	/* Inconslusive MTU probe */
	if (icsk->icsk_mtup.probe_size) {
		icsk->icsk_mtup.probe_size = 0;
	}

L
Linus Torvalds 已提交
2586
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2587
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2588 2589 2590 2591 2592
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
	    min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
		return -EAGAIN;

2593 2594 2595
	if (skb_still_in_host_queue(sk, skb))
		return -EBUSY;

L
Linus Torvalds 已提交
2596 2597 2598 2599 2600 2601 2602
	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;
	}

2603 2604 2605
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2606
	cur_mss = tcp_current_mss(sk);
2607

L
Linus Torvalds 已提交
2608 2609 2610 2611 2612
	/* 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.
	 */
2613 2614
	if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
	    TCP_SKB_CB(skb)->seq != tp->snd_una)
L
Linus Torvalds 已提交
2615 2616 2617
		return -EAGAIN;

	if (skb->len > cur_mss) {
2618
		if (tcp_fragment(sk, skb, cur_mss, cur_mss, GFP_ATOMIC))
L
Linus Torvalds 已提交
2619
			return -ENOMEM; /* We'll try again later. */
2620
	} else {
2621 2622 2623
		int oldpcount = tcp_skb_pcount(skb);

		if (unlikely(oldpcount > 1)) {
2624 2625
			if (skb_unclone(skb, GFP_ATOMIC))
				return -ENOMEM;
2626
			tcp_init_tso_segs(skb, cur_mss);
2627 2628
			tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
		}
L
Linus Torvalds 已提交
2629 2630
	}

2631 2632 2633 2634
	/* RFC3168, section 6.1.1.1. ECN fallback */
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
		tcp_ecn_clear_syn(sk, skb);

2635
	tcp_retrans_try_collapse(sk, skb, cur_mss);
L
Linus Torvalds 已提交
2636 2637 2638 2639 2640

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

2641 2642 2643 2644 2645 2646
	/* make sure skb->data is aligned on arches that require it
	 * and check if ack-trimming & collapsing extended the headroom
	 * beyond what csum_start can cover.
	 */
	if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
		     skb_headroom(skb) >= 0xFFFF)) {
E
Eric Dumazet 已提交
2647 2648
		struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
						   GFP_ATOMIC);
2649 2650
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
E
Eric Dumazet 已提交
2651
	} else {
2652
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
E
Eric Dumazet 已提交
2653
	}
2654

2655
	if (likely(!err)) {
2656
		TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2657 2658 2659 2660 2661 2662
		/* Update global TCP statistics. */
		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
		tp->total_retrans++;
	}
2663
	return err;
2664 2665 2666 2667 2668 2669
}

int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
	int err = __tcp_retransmit_skb(sk, skb);
L
Linus Torvalds 已提交
2670 2671 2672

	if (err == 0) {
#if FASTRETRANS_DEBUG > 0
2673
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2674
			net_dbg_ratelimited("retrans_out leaked\n");
L
Linus Torvalds 已提交
2675 2676 2677 2678 2679 2680 2681
		}
#endif
		TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
		tp->retrans_out += tcp_skb_pcount(skb);

		/* Save stamp of the first retransmit. */
		if (!tp->retrans_stamp)
E
Eric Dumazet 已提交
2682
			tp->retrans_stamp = tcp_skb_timestamp(skb);
L
Linus Torvalds 已提交
2683

2684
	} else if (err != -EBUSY) {
2685
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
L
Linus Torvalds 已提交
2686
	}
Y
Yuchung Cheng 已提交
2687 2688 2689 2690

	if (tp->undo_retrans < 0)
		tp->undo_retrans = 0;
	tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2691 2692 2693
	return err;
}

2694 2695 2696
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
E
Eric Dumazet 已提交
2697
static bool tcp_can_forward_retransmit(struct sock *sk)
2698 2699
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2700
	const struct tcp_sock *tp = tcp_sk(sk);
2701 2702 2703

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
E
Eric Dumazet 已提交
2704
		return false;
2705 2706 2707

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
E
Eric Dumazet 已提交
2708
		return false;
2709 2710 2711 2712 2713 2714 2715 2716 2717 2718

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

	if (tcp_may_send_now(sk))
E
Eric Dumazet 已提交
2719
		return false;
2720

E
Eric Dumazet 已提交
2721
	return true;
2722 2723
}

L
Linus Torvalds 已提交
2724 2725 2726 2727 2728 2729 2730 2731 2732 2733
/* 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)
{
2734
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2735 2736
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2737
	struct sk_buff *hole = NULL;
2738
	u32 last_lost;
2739
	int mib_idx;
2740
	int fwd_rexmitting = 0;
2741

2742 2743 2744
	if (!tp->packets_out)
		return;

2745 2746 2747
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2748
	if (tp->retransmit_skb_hint) {
2749
		skb = tp->retransmit_skb_hint;
2750 2751 2752 2753
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2754
		skb = tcp_write_queue_head(sk);
2755 2756
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2757

2758 2759
	tcp_for_write_queue_from(skb, sk) {
		__u8 sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
2760

2761 2762 2763
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2764
		if (!hole)
2765
			tp->retransmit_skb_hint = skb;
2766 2767 2768 2769 2770 2771 2772 2773 2774 2775

		/* Assume this retransmit will generate
		 * only one packet for congestion window
		 * calculation purposes.  This works because
		 * tcp_retransmit_skb() will chop up the
		 * packet to be MSS sized and all the
		 * packet counting works out.
		 */
		if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
			return;
L
Linus Torvalds 已提交
2776

2777 2778 2779 2780 2781
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2782

2783
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2784
			tp->retransmit_high = last_lost;
2785 2786 2787
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
2788
			if (hole) {
2789 2790 2791 2792 2793
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2794

2795
		} else if (!(sacked & TCPCB_LOST)) {
2796
			if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2797 2798
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2799

2800
		} else {
2801
			last_lost = TCP_SKB_CB(skb)->end_seq;
2802 2803 2804 2805 2806
			if (icsk->icsk_ca_state != TCP_CA_Loss)
				mib_idx = LINUX_MIB_TCPFASTRETRANS;
			else
				mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
		}
L
Linus Torvalds 已提交
2807

2808
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2809 2810
			continue;

2811
		if (tcp_retransmit_skb(sk, skb))
2812
			return;
2813

2814
		NET_INC_STATS_BH(sock_net(sk), mib_idx);
L
Linus Torvalds 已提交
2815

2816
		if (tcp_in_cwnd_reduction(sk))
2817 2818
			tp->prr_out += tcp_skb_pcount(skb);

2819
		if (skb == tcp_write_queue_head(sk))
2820 2821 2822
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2823 2824 2825
	}
}

2826 2827
/* We allow to exceed memory limits for FIN packets to expedite
 * connection tear down and (memory) recovery.
2828 2829
 * Otherwise tcp_send_fin() could be tempted to either delay FIN
 * or even be forced to close flow without any FIN.
2830 2831
 * In general, we want to allow one skb per socket to avoid hangs
 * with edge trigger epoll()
2832
 */
2833
void sk_forced_mem_schedule(struct sock *sk, int size)
2834
{
2835
	int amt;
2836 2837 2838 2839 2840

	if (size <= sk->sk_forward_alloc)
		return;
	amt = sk_mem_pages(size);
	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2841 2842
	sk_memory_allocated_add(sk, amt);

2843 2844
	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
		mem_cgroup_charge_skmem(sk->sk_memcg, amt);
2845 2846
}

2847 2848
/* Send a FIN. The caller locks the socket for us.
 * We should try to send a FIN packet really hard, but eventually give up.
L
Linus Torvalds 已提交
2849 2850 2851
 */
void tcp_send_fin(struct sock *sk)
{
2852
	struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2853 2854
	struct tcp_sock *tp = tcp_sk(sk);

2855 2856 2857 2858
	/* Optimization, tack on the FIN if we have one skb in write queue and
	 * this skb was not yet sent, or we are under memory pressure.
	 * Note: in the latter case, FIN packet will be sent after a timeout,
	 * as TCP stack thinks it has already been transmitted.
L
Linus Torvalds 已提交
2859
	 */
2860
	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
2861 2862 2863
coalesce:
		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
		TCP_SKB_CB(tskb)->end_seq++;
L
Linus Torvalds 已提交
2864
		tp->write_seq++;
2865 2866 2867 2868 2869 2870 2871 2872 2873 2874
		if (!tcp_send_head(sk)) {
			/* This means tskb was already sent.
			 * Pretend we included the FIN on previous transmit.
			 * We need to set tp->snd_nxt to the value it would have
			 * if FIN had been sent. This is because retransmit path
			 * does not change tp->snd_nxt.
			 */
			tp->snd_nxt++;
			return;
		}
L
Linus Torvalds 已提交
2875
	} else {
2876 2877 2878 2879 2880
		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
		if (unlikely(!skb)) {
			if (tskb)
				goto coalesce;
			return;
L
Linus Torvalds 已提交
2881
		}
2882
		skb_reserve(skb, MAX_TCP_HEADER);
2883
		sk_forced_mem_schedule(sk, skb->truesize);
L
Linus Torvalds 已提交
2884
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2885
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
2886
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
2887 2888
		tcp_queue_skb(sk, skb);
	}
2889
	__tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
2890 2891 2892 2893 2894
}

/* 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
2895
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2896
 */
A
Al Viro 已提交
2897
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
2898 2899 2900 2901 2902 2903
{
	struct sk_buff *skb;

	/* NOTE: No TCP options attached and we never retransmit this. */
	skb = alloc_skb(MAX_TCP_HEADER, priority);
	if (!skb) {
P
Pavel Emelyanov 已提交
2904
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
2905 2906 2907 2908 2909
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
2910
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
2911
			     TCPHDR_ACK | TCPHDR_RST);
2912
	skb_mstamp_get(&skb->skb_mstamp);
L
Linus Torvalds 已提交
2913
	/* Send it off. */
2914
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
2915
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2916

P
Pavel Emelyanov 已提交
2917
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
2918 2919
}

2920 2921
/* Send a crossed SYN-ACK during socket establishment.
 * WARNING: This routine must only be called when we have already sent
L
Linus Torvalds 已提交
2922 2923 2924 2925 2926 2927
 * 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)
{
2928
	struct sk_buff *skb;
L
Linus Torvalds 已提交
2929

2930
	skb = tcp_write_queue_head(sk);
2931
	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2932
		pr_debug("%s: wrong queue state\n", __func__);
L
Linus Torvalds 已提交
2933 2934
		return -EFAULT;
	}
E
Eric Dumazet 已提交
2935
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
2936 2937
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2938
			if (!nskb)
L
Linus Torvalds 已提交
2939
				return -ENOMEM;
2940
			tcp_unlink_write_queue(skb, sk);
2941
			__skb_header_release(nskb);
2942
			__tcp_add_write_queue_head(sk, nskb);
2943 2944 2945
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
2946 2947 2948
			skb = nskb;
		}

E
Eric Dumazet 已提交
2949
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2950
		tcp_ecn_send_synack(sk, skb);
L
Linus Torvalds 已提交
2951
	}
2952
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
2953 2954
}

2955 2956 2957 2958 2959 2960 2961 2962 2963
/**
 * tcp_make_synack - Prepare a SYN-ACK.
 * sk: listener socket
 * dst: dst entry attached to the SYNACK
 * req: request_sock pointer
 *
 * Allocate one skb and build a SYNACK packet.
 * @dst is consumed : Caller should not use it again.
 */
2964
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
2965
				struct request_sock *req,
2966
				struct tcp_fastopen_cookie *foc,
2967
				enum tcp_synack_type synack_type)
L
Linus Torvalds 已提交
2968
{
2969
	struct inet_request_sock *ireq = inet_rsk(req);
2970
	const struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
2971
	struct tcp_md5sig_key *md5 = NULL;
2972 2973
	struct tcp_out_options opts;
	struct sk_buff *skb;
2974
	int tcp_header_size;
2975 2976
	struct tcphdr *th;
	u16 user_mss;
2977
	int mss;
L
Linus Torvalds 已提交
2978

2979
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2980 2981
	if (unlikely(!skb)) {
		dst_release(dst);
L
Linus Torvalds 已提交
2982
		return NULL;
2983
	}
L
Linus Torvalds 已提交
2984 2985 2986
	/* Reserve space for headers. */
	skb_reserve(skb, MAX_TCP_HEADER);

2987 2988
	switch (synack_type) {
	case TCP_SYNACK_NORMAL:
2989
		skb_set_owner_w(skb, req_to_sk(req));
2990 2991 2992 2993 2994 2995 2996
		break;
	case TCP_SYNACK_COOKIE:
		/* Under synflood, we do not attach skb to a socket,
		 * to avoid false sharing.
		 */
		break;
	case TCP_SYNACK_FASTOPEN:
2997 2998 2999 3000 3001
		/* sk is a const pointer, because we want to express multiple
		 * cpu might call us concurrently.
		 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
		 */
		skb_set_owner_w(skb, (struct sock *)sk);
3002
		break;
3003
	}
3004
	skb_dst_set(skb, dst);
L
Linus Torvalds 已提交
3005

3006
	mss = dst_metric_advmss(dst);
3007 3008 3009
	user_mss = READ_ONCE(tp->rx_opt.user_mss);
	if (user_mss && user_mss < mss)
		mss = user_mss;
3010

A
Adam Langley 已提交
3011
	memset(&opts, 0, sizeof(opts));
3012 3013
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
E
Eric Dumazet 已提交
3014
		skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3015 3016
	else
#endif
E
Eric Dumazet 已提交
3017
	skb_mstamp_get(&skb->skb_mstamp);
E
Eric Dumazet 已提交
3018 3019 3020

#ifdef CONFIG_TCP_MD5SIG
	rcu_read_lock();
3021
	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
E
Eric Dumazet 已提交
3022
#endif
3023
	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3024 3025
	tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
			  sizeof(*th);
3026

3027 3028
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
3029

3030
	th = tcp_hdr(skb);
L
Linus Torvalds 已提交
3031 3032 3033
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
3034
	tcp_ecn_make_synack(req, th);
E
Eric Dumazet 已提交
3035
	th->source = htons(ireq->ir_num);
3036
	th->dest = ireq->ir_rmt_port;
3037 3038 3039 3040
	/* Setting of flags are superfluous here for callers (and ECE is
	 * not even correctly set)
	 */
	tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
C
Changli Gao 已提交
3041
			     TCPHDR_SYN | TCPHDR_ACK);
3042

L
Linus Torvalds 已提交
3043
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
3044 3045
	/* XXX data is queued and acked as is. No buffer/window check */
	th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
L
Linus Torvalds 已提交
3046 3047

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3048
	th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3049
	tcp_options_write((__be32 *)(th + 1), NULL, &opts);
L
Linus Torvalds 已提交
3050
	th->doff = (tcp_header_size >> 2);
3051
	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
3052 3053 3054

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
E
Eric Dumazet 已提交
3055
	if (md5)
3056
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3057
					       md5, req_to_sk(req), skb);
E
Eric Dumazet 已提交
3058
	rcu_read_unlock();
3059 3060
#endif

3061 3062
	/* Do not fool tcpdump (if any), clean our debris */
	skb->tstamp.tv64 = 0;
L
Linus Torvalds 已提交
3063 3064
	return skb;
}
E
Eric Dumazet 已提交
3065
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
3066

3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085
static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	const struct tcp_congestion_ops *ca;
	u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);

	if (ca_key == TCP_CA_UNSPEC)
		return;

	rcu_read_lock();
	ca = tcp_ca_find_key(ca_key);
	if (likely(ca && try_module_get(ca->owner))) {
		module_put(icsk->icsk_ca_ops->owner);
		icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
		icsk->icsk_ca_ops = ca;
	}
	rcu_read_unlock();
}

3086
/* Do all connect socket setups that can be done AF independent. */
3087
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
3088
{
3089
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
3090 3091 3092 3093 3094 3095 3096
	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) +
3097
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
3098

3099
#ifdef CONFIG_TCP_MD5SIG
3100
	if (tp->af_specific->md5_lookup(sk, sk))
3101 3102 3103
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
3104 3105 3106 3107
	/* 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
3108
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
3109 3110
	tcp_sync_mss(sk, dst_mtu(dst));

3111 3112
	tcp_ca_dst_init(sk, dst);

L
Linus Torvalds 已提交
3113 3114
	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3115
	tp->advmss = dst_metric_advmss(dst);
3116 3117 3118
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
		tp->advmss = tp->rx_opt.user_mss;

L
Linus Torvalds 已提交
3119 3120
	tcp_initialize_rcv_mss(sk);

3121 3122 3123 3124 3125
	/* limit the window selection if the user enforce a smaller rx buffer */
	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
	    (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
		tp->window_clamp = tcp_full_space(sk);

L
Linus Torvalds 已提交
3126 3127 3128 3129
	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,
3130
				  sysctl_tcp_window_scaling,
3131 3132
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
3133 3134 3135 3136 3137 3138 3139

	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;
3140
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
3141 3142
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
3143
	tp->snd_up = tp->write_seq;
P
Pavel Emelyanov 已提交
3144
	tp->snd_nxt = tp->write_seq;
P
Pavel Emelyanov 已提交
3145 3146 3147

	if (likely(!tp->repair))
		tp->rcv_nxt = 0;
3148 3149
	else
		tp->rcv_tstamp = tcp_time_stamp;
P
Pavel Emelyanov 已提交
3150 3151
	tp->rcv_wup = tp->rcv_nxt;
	tp->copied_seq = tp->rcv_nxt;
L
Linus Torvalds 已提交
3152

3153 3154
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
3155 3156 3157
	tcp_clear_retrans(tp);
}

3158 3159 3160 3161 3162 3163
static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);

	tcb->end_seq += skb->len;
3164
	__skb_header_release(skb);
3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182
	__tcp_add_write_queue_tail(sk, skb);
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
	tp->write_seq = tcb->end_seq;
	tp->packets_out += tcp_skb_pcount(skb);
}

/* Build and send a SYN with data and (cached) Fast Open cookie. However,
 * queue a data-only packet after the regular SYN, such that regular SYNs
 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
 * only the SYN sequence, the data are retransmitted in the first ACK.
 * If cookie is not cached or other error occurs, falls back to send a
 * regular SYN with Fast Open cookie request option.
 */
static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct tcp_fastopen_request *fo = tp->fastopen_req;
3183
	int syn_loss = 0, space, err = 0;
3184
	unsigned long last_syn_loss = 0;
3185
	struct sk_buff *syn_data;
3186

3187
	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */
3188 3189 3190 3191 3192 3193 3194 3195
	tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
			       &syn_loss, &last_syn_loss);
	/* Recurring FO SYN losses: revert to regular handshake temporarily */
	if (syn_loss > 1 &&
	    time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
		fo->cookie.len = -1;
		goto fallback;
	}
3196

3197 3198 3199
	if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
		fo->cookie.len = -1;
	else if (fo->cookie.len <= 0)
3200 3201 3202 3203 3204 3205 3206 3207
		goto fallback;

	/* MSS for SYN-data is based on cached MSS and bounded by PMTU and
	 * user-MSS. Reserve maximum option space for middleboxes that add
	 * private TCP options. The cost is reduced data space in SYN :(
	 */
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3208
	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3209 3210
		MAX_TCP_OPTION_SPACE;

3211 3212 3213 3214 3215
	space = min_t(size_t, space, fo->size);

	/* limit to order-0 allocations */
	space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));

3216
	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3217
	if (!syn_data)
3218
		goto fallback;
3219 3220
	syn_data->ip_summed = CHECKSUM_PARTIAL;
	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231
	if (space) {
		int copied = copy_from_iter(skb_put(syn_data, space), space,
					    &fo->data->msg_iter);
		if (unlikely(!copied)) {
			kfree_skb(syn_data);
			goto fallback;
		}
		if (copied != space) {
			skb_trim(syn_data, copied);
			space = copied;
		}
3232
	}
3233 3234 3235 3236
	/* No more data pending in inet_wait_for_connect() */
	if (space == fo->size)
		fo->data = NULL;
	fo->copied = space;
3237

3238
	tcp_connect_queue_skb(sk, syn_data);
3239

3240
	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3241

3242
	syn->skb_mstamp = syn_data->skb_mstamp;
E
Eric Dumazet 已提交
3243

3244 3245 3246 3247 3248 3249 3250 3251
	/* Now full SYN+DATA was cloned and sent (or not),
	 * remove the SYN from the original skb (syn_data)
	 * we keep in write queue in case of a retransmit, as we
	 * also have the SYN packet (with no data) in the same queue.
	 */
	TCP_SKB_CB(syn_data)->seq++;
	TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
	if (!err) {
3252
		tp->syn_data = (fo->copied > 0);
3253
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268
		goto done;
	}

fallback:
	/* Send a regular SYN with Fast Open cookie request option */
	if (fo->cookie.len > 0)
		fo->cookie.len = 0;
	err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
	if (err)
		tp->syn_fastopen = 0;
done:
	fo->cookie.len = -1;  /* Exclude Fast Open option for SYN retries */
	return err;
}

3269
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
3270 3271 3272 3273
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
3274
	int err;
L
Linus Torvalds 已提交
3275 3276 3277

	tcp_connect_init(sk);

A
Andrey Vagin 已提交
3278 3279 3280 3281 3282
	if (unlikely(tp->repair)) {
		tcp_finish_connect(sk, NULL);
		return 0;
	}

3283
	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3284
	if (unlikely(!buff))
L
Linus Torvalds 已提交
3285 3286
		return -ENOBUFS;

C
Changli Gao 已提交
3287
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
E
Eric Dumazet 已提交
3288
	tp->retrans_stamp = tcp_time_stamp;
3289
	tcp_connect_queue_skb(sk, buff);
3290
	tcp_ecn_send_syn(sk, buff);
L
Linus Torvalds 已提交
3291

3292 3293 3294
	/* Send off SYN; include data in Fast Open. */
	err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
	      tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3295 3296
	if (err == -ECONNREFUSED)
		return err;
3297 3298 3299 3300 3301 3302

	/* 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
3303
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
3304 3305

	/* Timer for repeating the SYN until an answer. */
3306 3307
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
3308 3309
	return 0;
}
E
Eric Dumazet 已提交
3310
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
3311 3312 3313 3314 3315 3316 3317

/* 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)
{
3318 3319
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
3320 3321
	unsigned long timeout;

3322 3323
	tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);

L
Linus Torvalds 已提交
3324
	if (ato > TCP_DELACK_MIN) {
3325
		const struct tcp_sock *tp = tcp_sk(sk);
3326
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
3327

3328 3329
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
3330 3331 3332 3333 3334
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
3335
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
3336 3337
		 * directly.
		 */
3338 3339 3340
		if (tp->srtt_us) {
			int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
					TCP_DELACK_MIN);
L
Linus Torvalds 已提交
3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352

			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. */
3353
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
3354 3355 3356
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
3357 3358
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
3359 3360 3361 3362
			tcp_send_ack(sk);
			return;
		}

3363 3364
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
3365
	}
3366 3367 3368
	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
3369 3370 3371 3372 3373
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
3374
	struct sk_buff *buff;
L
Linus Torvalds 已提交
3375

3376 3377 3378
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
3379

3380 3381
	tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);

3382 3383 3384 3385
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
3386 3387 3388
	buff = alloc_skb(MAX_TCP_HEADER,
			 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
	if (unlikely(!buff)) {
3389 3390 3391 3392 3393
		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
3394
	}
3395 3396 3397

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
3398
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3399

E
Eric Dumazet 已提交
3400 3401 3402 3403 3404 3405 3406 3407
	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
	 * too much.
	 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
	 * We also avoid tcp_wfree() overhead (cache line miss accessing
	 * tp->tsq_flags) by using regular sock_wfree()
	 */
	skb_set_tcp_pure_ack(buff);

3408
	/* Send it off, this clears delayed acks for us. */
E
Eric Dumazet 已提交
3409
	skb_mstamp_get(&buff->skb_mstamp);
3410
	tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3411
}
3412
EXPORT_SYMBOL_GPL(tcp_send_ack);
L
Linus Torvalds 已提交
3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424

/* 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.
 */
3425
static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
L
Linus Torvalds 已提交
3426 3427 3428 3429 3430
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
3431 3432
	skb = alloc_skb(MAX_TCP_HEADER,
			sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3433
	if (!skb)
L
Linus Torvalds 已提交
3434 3435 3436 3437 3438 3439 3440 3441
		return -1;

	/* Reserve space for headers and set control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
	/* Use a previous sequence.  This should cause the other
	 * end to send an ack.  Don't queue or clone SKB, just
	 * send it.
	 */
C
Changli Gao 已提交
3442
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
E
Eric Dumazet 已提交
3443
	skb_mstamp_get(&skb->skb_mstamp);
3444
	NET_INC_STATS(sock_net(sk), mib);
3445
	return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
L
Linus Torvalds 已提交
3446 3447
}

P
Pavel Emelyanov 已提交
3448 3449 3450 3451
void tcp_send_window_probe(struct sock *sk)
{
	if (sk->sk_state == TCP_ESTABLISHED) {
		tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3452
		tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
P
Pavel Emelyanov 已提交
3453 3454 3455
	}
}

3456
/* Initiate keepalive or window probe from timer. */
3457
int tcp_write_wakeup(struct sock *sk, int mib)
L
Linus Torvalds 已提交
3458
{
3459 3460
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
3461

3462 3463 3464
	if (sk->sk_state == TCP_CLOSE)
		return -1;

3465 3466
	skb = tcp_send_head(sk);
	if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3467
		int err;
I
Ilpo Järvinen 已提交
3468
		unsigned int mss = tcp_current_mss(sk);
3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480
		unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;

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

		/* We are probing the opening of a window
		 * but the window size is != 0
		 * must have been a result SWS avoidance ( sender )
		 */
		if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
		    skb->len > mss) {
			seg_size = min(seg_size, mss);
E
Eric Dumazet 已提交
3481
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3482
			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3483 3484
				return -1;
		} else if (!tcp_skb_pcount(skb))
3485
			tcp_set_skb_tso_segs(skb, mss);
3486

E
Eric Dumazet 已提交
3487
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3488 3489 3490 3491 3492
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
		if (!err)
			tcp_event_new_data_sent(sk, skb);
		return err;
	} else {
I
Ilpo Järvinen 已提交
3493
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3494 3495
			tcp_xmit_probe_skb(sk, 1, mib);
		return tcp_xmit_probe_skb(sk, 0, mib);
L
Linus Torvalds 已提交
3496 3497 3498 3499 3500 3501 3502 3503
	}
}

/* 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)
{
3504
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
3505
	struct tcp_sock *tp = tcp_sk(sk);
3506
	struct net *net = sock_net(sk);
3507
	unsigned long probe_max;
L
Linus Torvalds 已提交
3508 3509
	int err;

3510
	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
L
Linus Torvalds 已提交
3511

3512
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
3513
		/* Cancel probe timer, if it is not required. */
3514
		icsk->icsk_probes_out = 0;
3515
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
3516 3517 3518 3519
		return;
	}

	if (err <= 0) {
3520
		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3521
			icsk->icsk_backoff++;
3522
		icsk->icsk_probes_out++;
3523
		probe_max = TCP_RTO_MAX;
L
Linus Torvalds 已提交
3524 3525
	} else {
		/* If packet was not sent due to local congestion,
3526
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
3527 3528 3529 3530
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
3531 3532
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
3533
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;
L
Linus Torvalds 已提交
3534
	}
3535
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3536
				  tcp_probe0_when(sk, probe_max),
3537
				  TCP_RTO_MAX);
L
Linus Torvalds 已提交
3538
}
3539

3540
int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3541 3542 3543 3544 3545
{
	const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
	struct flowi fl;
	int res;

3546
	tcp_rsk(req)->txhash = net_tx_rndhash();
3547
	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3548 3549 3550 3551 3552 3553 3554
	if (!res) {
		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
	}
	return res;
}
EXPORT_SYMBOL(tcp_rtx_synack);