tcp_output.c 82.6 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 37 38 39
 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Corey Minyard <wf-rch!minyard@relay.EU.net>
 *		Florian La Roche, <flla@stud.uni-sb.de>
 *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
 *		Linus Torvalds, <torvalds@cs.helsinki.fi>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 *		Matthew Dillon, <dillon@apollo.west.oic.com>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 */

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

#include <net/tcp.h>

#include <linux/compiler.h>
40
#include <linux/gfp.h>
L
Linus Torvalds 已提交
41 42 43
#include <linux/module.h>

/* People can turn this off for buggy TCP's found in printers etc. */
44
int sysctl_tcp_retrans_collapse __read_mostly = 1;
L
Linus Torvalds 已提交
45

46
/* People can turn this on to work with those rare, broken TCPs that
47 48
 * interpret the window field as a signed quantity.
 */
49
int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
50

L
Linus Torvalds 已提交
51 52 53 54
/* 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.
 */
55
int sysctl_tcp_tso_win_divisor __read_mostly = 3;
L
Linus Torvalds 已提交
56

57
int sysctl_tcp_mtu_probing __read_mostly = 0;
58
int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
J
John Heffner 已提交
59

60
/* By default, RFC2861 behavior.  */
61
int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
62

63
int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
64
EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
65 66


67
/* Account for new data that has been sent to the network. */
68
static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
L
Linus Torvalds 已提交
69
{
70
	struct tcp_sock *tp = tcp_sk(sk);
71
	unsigned int prior_packets = tp->packets_out;
72

73
	tcp_advance_send_head(sk, skb);
L
Linus Torvalds 已提交
74
	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
75

L
Lucas De Marchi 已提交
76
	/* Don't override Nagle indefinitely with F-RTO */
77 78
	if (tp->frto_counter == 2)
		tp->frto_counter = 3;
79 80 81 82 83

	tp->packets_out += tcp_skb_pcount(skb);
	if (!prior_packets)
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
					  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
84 85 86 87 88 89 90 91
}

/* 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:
 */
92
static inline __u32 tcp_acceptable_seq(const struct sock *sk)
L
Linus Torvalds 已提交
93
{
94
	const struct tcp_sock *tp = tcp_sk(sk);
95

96
	if (!before(tcp_wnd_end(tp), tp->snd_nxt))
L
Linus Torvalds 已提交
97 98
		return tp->snd_nxt;
	else
99
		return tcp_wnd_end(tp);
L
Linus Torvalds 已提交
100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
}

/* 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);
119
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
120 121
	int mss = tp->advmss;

122 123 124 125 126 127 128
	if (dst) {
		unsigned int metric = dst_metric_advmss(dst);

		if (metric < mss) {
			mss = metric;
			tp->advmss = mss;
		}
L
Linus Torvalds 已提交
129 130 131 132 133 134 135
	}

	return (__u16)mss;
}

/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
 * This is the first part of cwnd validation mechanism. */
136
static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
L
Linus Torvalds 已提交
137
{
138
	struct tcp_sock *tp = tcp_sk(sk);
L
Linus Torvalds 已提交
139 140 141 142
	s32 delta = tcp_time_stamp - tp->lsndtime;
	u32 restart_cwnd = tcp_init_cwnd(tp, dst);
	u32 cwnd = tp->snd_cwnd;

143
	tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
L
Linus Torvalds 已提交
144

145
	tp->snd_ssthresh = tcp_current_ssthresh(sk);
L
Linus Torvalds 已提交
146 147
	restart_cwnd = min(restart_cwnd, cwnd);

148
	while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
L
Linus Torvalds 已提交
149 150 151 152 153 154
		cwnd >>= 1;
	tp->snd_cwnd = max(cwnd, restart_cwnd);
	tp->snd_cwnd_stamp = tcp_time_stamp;
	tp->snd_cwnd_used = 0;
}

155
/* Congestion state accounting after a packet has been sent. */
S
Stephen Hemminger 已提交
156
static void tcp_event_data_sent(struct tcp_sock *tp,
157
				struct sock *sk)
L
Linus Torvalds 已提交
158
{
159 160
	struct inet_connection_sock *icsk = inet_csk(sk);
	const u32 now = tcp_time_stamp;
L
Linus Torvalds 已提交
161

162 163
	if (sysctl_tcp_slow_start_after_idle &&
	    (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
164
		tcp_cwnd_restart(sk, __sk_dst_get(sk));
L
Linus Torvalds 已提交
165 166 167 168 169 170

	tp->lsndtime = now;

	/* If it is a reply for ato after last received
	 * packet, enter pingpong mode.
	 */
171 172
	if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
		icsk->icsk_ack.pingpong = 1;
L
Linus Torvalds 已提交
173 174
}

175
/* Account for an ACK we sent. */
S
Stephen Hemminger 已提交
176
static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
L
Linus Torvalds 已提交
177
{
178 179
	tcp_dec_quickack_mode(sk, pkts);
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
L
Linus Torvalds 已提交
180 181 182 183 184 185 186 187 188 189 190
}

/* 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,
191 192
			       int wscale_ok, __u8 *rcv_wscale,
			       __u32 init_rcv_wnd)
L
Linus Torvalds 已提交
193 194 195 196 197 198 199 200 201 202 203 204 205
{
	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
206 207 208 209 210 211
	 * 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
212
	 */
213 214 215 216 217
	if (sysctl_tcp_workaround_signed_windows)
		(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
	else
		(*rcv_wnd) = space;

L
Linus Torvalds 已提交
218 219 220
	(*rcv_wscale) = 0;
	if (wscale_ok) {
		/* Set window scaling on max possible window
221
		 * See RFC1323 for an explanation of the limit to 14
L
Linus Torvalds 已提交
222 223
		 */
		space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
224
		space = min_t(u32, space, *window_clamp);
L
Linus Torvalds 已提交
225 226 227 228 229 230
		while (space > 65535 && (*rcv_wscale) < 14) {
			space >>= 1;
			(*rcv_wscale)++;
		}
	}

231 232 233 234
	/* Set initial window to a value enough for senders starting with
	 * initial congestion window of TCP_DEFAULT_INIT_RCVWND. Place
	 * a limit on the initial window when mss is larger than 1460.
	 */
235
	if (mss > (1 << *rcv_wscale)) {
236 237 238 239
		int init_cwnd = TCP_DEFAULT_INIT_RCVWND;
		if (mss > 1460)
			init_cwnd =
			max_t(u32, (1460 * TCP_DEFAULT_INIT_RCVWND) / mss, 2);
240 241 242
		/* when initializing use the value from init_rcv_wnd
		 * rather than the default from above
		 */
243 244 245 246
		if (init_rcv_wnd)
			*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
		else
			*rcv_wnd = min(*rcv_wnd, init_cwnd * mss);
L
Linus Torvalds 已提交
247 248 249 250 251
	}

	/* Set the clamp no higher than max representable value */
	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
}
E
Eric Dumazet 已提交
252
EXPORT_SYMBOL(tcp_select_initial_window);
L
Linus Torvalds 已提交
253 254 255 256 257 258

/* 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
259
static u16 tcp_select_window(struct sock *sk)
L
Linus Torvalds 已提交
260 261 262 263 264 265
{
	struct tcp_sock *tp = tcp_sk(sk);
	u32 cur_win = tcp_receive_window(tp);
	u32 new_win = __tcp_select_window(sk);

	/* Never shrink the offered window */
S
Stephen Hemminger 已提交
266
	if (new_win < cur_win) {
L
Linus Torvalds 已提交
267 268 269 270 271 272 273
		/* 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.
		 */
274
		new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
L
Linus Torvalds 已提交
275 276 277 278 279 280 281
	}
	tp->rcv_wnd = new_win;
	tp->rcv_wup = tp->rcv_nxt;

	/* Make sure we do not exceed the maximum possible
	 * scaled window.
	 */
282
	if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
L
Linus Torvalds 已提交
283 284 285 286 287 288 289 290 291 292 293 294 295 296
		new_win = min(new_win, MAX_TCP_WINDOW);
	else
		new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));

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

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

	return new_win;
}

297
/* Packet ECN state for a SYN-ACK */
298
static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
299
{
E
Eric Dumazet 已提交
300
	TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
301
	if (!(tp->ecn_flags & TCP_ECN_OK))
E
Eric Dumazet 已提交
302
		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
303 304
}

305
/* Packet ECN state for a SYN.  */
306 307 308 309 310
static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);

	tp->ecn_flags = 0;
311
	if (sysctl_tcp_ecn == 1) {
E
Eric Dumazet 已提交
312
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
313 314 315 316 317
		tp->ecn_flags = TCP_ECN_OK;
	}
}

static __inline__ void
318
TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
319 320 321 322 323
{
	if (inet_rsk(req)->ecn_ok)
		th->ece = 1;
}

324 325 326
/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
 * be sent.
 */
327 328 329 330 331 332 333 334 335 336
static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
				int tcp_header_len)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (tp->ecn_flags & TCP_ECN_OK) {
		/* Not-retransmitted data segment: set ECT and inject CWR. */
		if (skb->len != tcp_header_len &&
		    !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
			INET_ECN_xmit(sk);
337
			if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
338 339 340 341 342 343 344 345 346 347 348 349 350
				tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
				tcp_hdr(skb)->cwr = 1;
				skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
			}
		} else {
			/* ACK or retransmitted segment: clear ECT|CE */
			INET_ECN_dontxmit(sk);
		}
		if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
			tcp_hdr(skb)->ece = 1;
	}
}

351 352 353 354 355
/* 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)
{
356
	skb->ip_summed = CHECKSUM_PARTIAL;
357 358
	skb->csum = 0;

E
Eric Dumazet 已提交
359
	TCP_SKB_CB(skb)->tcp_flags = flags;
360 361 362 363 364 365 366
	TCP_SKB_CB(skb)->sacked = 0;

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

	TCP_SKB_CB(skb)->seq = seq;
C
Changli Gao 已提交
367
	if (flags & (TCPHDR_SYN | TCPHDR_FIN))
368 369 370 371
		seq++;
	TCP_SKB_CB(skb)->end_seq = seq;
}

I
Ilpo Järvinen 已提交
372 373 374 375 376
static inline int tcp_urg_mode(const struct tcp_sock *tp)
{
	return tp->snd_una != tp->snd_up;
}

A
Adam Langley 已提交
377 378 379
#define OPTION_SACK_ADVERTISE	(1 << 0)
#define OPTION_TS		(1 << 1)
#define OPTION_MD5		(1 << 2)
380
#define OPTION_WSCALE		(1 << 3)
381
#define OPTION_COOKIE_EXTENSION	(1 << 4)
A
Adam Langley 已提交
382 383 384 385 386

struct tcp_out_options {
	u8 options;		/* bit field of OPTION_* */
	u8 ws;			/* window scale, 0 to disable */
	u8 num_sack_blocks;	/* number of SACK blocks to include */
387
	u8 hash_size;		/* bytes in hash_location */
A
Adam Langley 已提交
388 389
	u16 mss;		/* 0 to disable */
	__u32 tsval, tsecr;	/* need to include OPTION_TS */
390
	__u8 *hash_location;	/* temporary pointer, overloaded */
A
Adam Langley 已提交
391 392
};

393 394 395 396
/* The sysctl int routines are generic, so check consistency here.
 */
static u8 tcp_cookie_size_check(u8 desired)
{
397 398 399
	int cookie_size;

	if (desired > 0)
400 401
		/* previously specified */
		return desired;
402 403 404

	cookie_size = ACCESS_ONCE(sysctl_tcp_cookie_size);
	if (cookie_size <= 0)
405 406
		/* no default specified */
		return 0;
407 408

	if (cookie_size <= TCP_COOKIE_MIN)
409 410
		/* value too small, specify minimum */
		return TCP_COOKIE_MIN;
411 412

	if (cookie_size >= TCP_COOKIE_MAX)
413 414
		/* value too large, specify maximum */
		return TCP_COOKIE_MAX;
415 416

	if (cookie_size & 1)
417
		/* 8-bit multiple, illegal, fix it */
418 419 420
		cookie_size++;

	return (u8)cookie_size;
421 422
}

423 424 425
/* Write previously computed TCP options to the packet.
 *
 * Beware: Something in the Internet is very sensitive to the ordering of
426 427 428 429 430 431 432 433 434 435
 * 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
 * inter-operatibility perspective it seems that we're somewhat stuck with
 * the ordering which we have been using if we want to keep working with
 * those broken things (not that it currently hurts anybody as there isn't
 * particular reason why the ordering would need to be changed).
 *
 * At least SACK_PERM as the first option is known to lead to a disaster
 * (but it may well be that other scenarios fail similarly).
 */
A
Adam Langley 已提交
436
static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463
			      struct tcp_out_options *opts)
{
	u8 options = opts->options;	/* mungable copy */

	/* Having both authentication and cookies for security is redundant,
	 * and there's certainly not enough room.  Instead, the cookie-less
	 * extension variant is proposed.
	 *
	 * Consider the pessimal case with authentication.  The options
	 * could look like:
	 *   COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
	 */
	if (unlikely(OPTION_MD5 & options)) {
		if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
			*ptr++ = htonl((TCPOPT_COOKIE << 24) |
				       (TCPOLEN_COOKIE_BASE << 16) |
				       (TCPOPT_MD5SIG << 8) |
				       TCPOLEN_MD5SIG);
		} else {
			*ptr++ = htonl((TCPOPT_NOP << 24) |
				       (TCPOPT_NOP << 16) |
				       (TCPOPT_MD5SIG << 8) |
				       TCPOLEN_MD5SIG);
		}
		options &= ~OPTION_COOKIE_EXTENSION;
		/* overload cookie hash location */
		opts->hash_location = (__u8 *)ptr;
A
Adam Langley 已提交
464
		ptr += 4;
S
Stephen Hemminger 已提交
465
	}
A
Adam Langley 已提交
466

467 468 469 470 471 472
	if (unlikely(opts->mss)) {
		*ptr++ = htonl((TCPOPT_MSS << 24) |
			       (TCPOLEN_MSS << 16) |
			       opts->mss);
	}

473 474
	if (likely(OPTION_TS & options)) {
		if (unlikely(OPTION_SACK_ADVERTISE & options)) {
A
Adam Langley 已提交
475 476 477 478
			*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
				       (TCPOLEN_SACK_PERM << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
479
			options &= ~OPTION_SACK_ADVERTISE;
A
Adam Langley 已提交
480 481 482 483 484 485 486 487 488 489
		} else {
			*ptr++ = htonl((TCPOPT_NOP << 24) |
				       (TCPOPT_NOP << 16) |
				       (TCPOPT_TIMESTAMP << 8) |
				       TCPOLEN_TIMESTAMP);
		}
		*ptr++ = htonl(opts->tsval);
		*ptr++ = htonl(opts->tsecr);
	}

490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528
	/* Specification requires after timestamp, so do it now.
	 *
	 * Consider the pessimal case without authentication.  The options
	 * could look like:
	 *   MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
	 */
	if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
		__u8 *cookie_copy = opts->hash_location;
		u8 cookie_size = opts->hash_size;

		/* 8-bit multiple handled in tcp_cookie_size_check() above,
		 * and elsewhere.
		 */
		if (0x2 & cookie_size) {
			__u8 *p = (__u8 *)ptr;

			/* 16-bit multiple */
			*p++ = TCPOPT_COOKIE;
			*p++ = TCPOLEN_COOKIE_BASE + cookie_size;
			*p++ = *cookie_copy++;
			*p++ = *cookie_copy++;
			ptr++;
			cookie_size -= 2;
		} else {
			/* 32-bit multiple */
			*ptr++ = htonl(((TCPOPT_NOP << 24) |
					(TCPOPT_NOP << 16) |
					(TCPOPT_COOKIE << 8) |
					TCPOLEN_COOKIE_BASE) +
				       cookie_size);
		}

		if (cookie_size > 0) {
			memcpy(ptr, cookie_copy, cookie_size);
			ptr += (cookie_size / 4);
		}
	}

	if (unlikely(OPTION_SACK_ADVERTISE & options)) {
A
Adam Langley 已提交
529 530 531 532 533 534
		*ptr++ = htonl((TCPOPT_NOP << 24) |
			       (TCPOPT_NOP << 16) |
			       (TCPOPT_SACK_PERM << 8) |
			       TCPOLEN_SACK_PERM);
	}

535
	if (unlikely(OPTION_WSCALE & options)) {
A
Adam Langley 已提交
536 537 538 539 540 541 542 543 544
		*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
545 546 547 548 549
		int this_sack;

		*ptr++ = htonl((TCPOPT_NOP  << 24) |
			       (TCPOPT_NOP  << 16) |
			       (TCPOPT_SACK <<  8) |
A
Adam Langley 已提交
550
			       (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
S
Stephen Hemminger 已提交
551
						     TCPOLEN_SACK_PERBLOCK)));
S
Stephen Hemminger 已提交
552

A
Adam Langley 已提交
553 554
		for (this_sack = 0; this_sack < opts->num_sack_blocks;
		     ++this_sack) {
S
Stephen Hemminger 已提交
555 556 557
			*ptr++ = htonl(sp[this_sack].start_seq);
			*ptr++ = htonl(sp[this_sack].end_seq);
		}
S
Stephen Hemminger 已提交
558

559
		tp->rx_opt.dsack = 0;
S
Stephen Hemminger 已提交
560
	}
A
Adam Langley 已提交
561 562
}

563 564 565
/* Compute TCP options for SYN packets. This is not the final
 * network wire format yet.
 */
A
Adam Langley 已提交
566 567
static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
				struct tcp_out_options *opts,
568 569
				struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
570
	struct tcp_sock *tp = tcp_sk(sk);
571 572 573 574 575
	struct tcp_cookie_values *cvp = tp->cookie_values;
	unsigned remaining = MAX_TCP_OPTION_SPACE;
	u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ?
			 tcp_cookie_size_check(cvp->cookie_desired) :
			 0;
A
Adam Langley 已提交
576

577
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
578 579 580
	*md5 = tp->af_specific->md5_lookup(sk, sk);
	if (*md5) {
		opts->options |= OPTION_MD5;
581
		remaining -= TCPOLEN_MD5SIG_ALIGNED;
582
	}
A
Adam Langley 已提交
583 584
#else
	*md5 = NULL;
585
#endif
A
Adam Langley 已提交
586 587 588 589 590 591 592 593 594 595 596

	/* 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);
597
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
598

599
	if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
A
Adam Langley 已提交
600 601 602
		opts->options |= OPTION_TS;
		opts->tsval = TCP_SKB_CB(skb)->when;
		opts->tsecr = tp->rx_opt.ts_recent;
603
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
604
	}
605
	if (likely(sysctl_tcp_window_scaling)) {
A
Adam Langley 已提交
606
		opts->ws = tp->rx_opt.rcv_wscale;
607
		opts->options |= OPTION_WSCALE;
608
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
609
	}
610
	if (likely(sysctl_tcp_sack)) {
A
Adam Langley 已提交
611
		opts->options |= OPTION_SACK_ADVERTISE;
612
		if (unlikely(!(OPTION_TS & opts->options)))
613
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
614 615
	}

616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662
	/* Note that timestamps are required by the specification.
	 *
	 * Odd numbers of bytes are prohibited by the specification, ensuring
	 * that the cookie is 16-bit aligned, and the resulting cookie pair is
	 * 32-bit aligned.
	 */
	if (*md5 == NULL &&
	    (OPTION_TS & opts->options) &&
	    cookie_size > 0) {
		int need = TCPOLEN_COOKIE_BASE + cookie_size;

		if (0x2 & need) {
			/* 32-bit multiple */
			need += 2; /* NOPs */

			if (need > remaining) {
				/* try shrinking cookie to fit */
				cookie_size -= 2;
				need -= 4;
			}
		}
		while (need > remaining && TCP_COOKIE_MIN <= cookie_size) {
			cookie_size -= 4;
			need -= 4;
		}
		if (TCP_COOKIE_MIN <= cookie_size) {
			opts->options |= OPTION_COOKIE_EXTENSION;
			opts->hash_location = (__u8 *)&cvp->cookie_pair[0];
			opts->hash_size = cookie_size;

			/* Remember for future incarnations. */
			cvp->cookie_desired = cookie_size;

			if (cvp->cookie_desired != cvp->cookie_pair_size) {
				/* Currently use random bytes as a nonce,
				 * assuming these are completely unpredictable
				 * by hostile users of the same system.
				 */
				get_random_bytes(&cvp->cookie_pair[0],
						 cookie_size);
				cvp->cookie_pair_size = cookie_size;
			}

			remaining -= need;
		}
	}
	return MAX_TCP_OPTION_SPACE - remaining;
S
Stephen Hemminger 已提交
663 664
}

665
/* Set up TCP options for SYN-ACKs. */
A
Adam Langley 已提交
666 667 668 669
static unsigned tcp_synack_options(struct sock *sk,
				   struct request_sock *req,
				   unsigned mss, struct sk_buff *skb,
				   struct tcp_out_options *opts,
670 671 672
				   struct tcp_md5sig_key **md5,
				   struct tcp_extend_values *xvp)
{
A
Adam Langley 已提交
673
	struct inet_request_sock *ireq = inet_rsk(req);
674 675 676 677
	unsigned remaining = MAX_TCP_OPTION_SPACE;
	u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
			 xvp->cookie_plus :
			 0;
A
Adam Langley 已提交
678

679
#ifdef CONFIG_TCP_MD5SIG
A
Adam Langley 已提交
680 681 682
	*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
	if (*md5) {
		opts->options |= OPTION_MD5;
683 684 685 686 687 688 689
		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
690
		ireq->tstamp_ok &= !ireq->sack_ok;
691
	}
A
Adam Langley 已提交
692 693
#else
	*md5 = NULL;
694
#endif
A
Adam Langley 已提交
695

696
	/* We always send an MSS option. */
A
Adam Langley 已提交
697
	opts->mss = mss;
698
	remaining -= TCPOLEN_MSS_ALIGNED;
A
Adam Langley 已提交
699 700 701

	if (likely(ireq->wscale_ok)) {
		opts->ws = ireq->rcv_wscale;
702
		opts->options |= OPTION_WSCALE;
703
		remaining -= TCPOLEN_WSCALE_ALIGNED;
A
Adam Langley 已提交
704
	}
E
Eric Dumazet 已提交
705
	if (likely(ireq->tstamp_ok)) {
A
Adam Langley 已提交
706 707 708
		opts->options |= OPTION_TS;
		opts->tsval = TCP_SKB_CB(skb)->when;
		opts->tsecr = req->ts_recent;
709
		remaining -= TCPOLEN_TSTAMP_ALIGNED;
A
Adam Langley 已提交
710 711 712
	}
	if (likely(ireq->sack_ok)) {
		opts->options |= OPTION_SACK_ADVERTISE;
E
Eric Dumazet 已提交
713
		if (unlikely(!ireq->tstamp_ok))
714
			remaining -= TCPOLEN_SACKPERM_ALIGNED;
A
Adam Langley 已提交
715 716
	}

717 718 719 720
	/* Similar rationale to tcp_syn_options() applies here, too.
	 * If the <SYN> options fit, the same options should fit now!
	 */
	if (*md5 == NULL &&
E
Eric Dumazet 已提交
721
	    ireq->tstamp_ok &&
722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739
	    cookie_plus > TCPOLEN_COOKIE_BASE) {
		int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */

		if (0x2 & need) {
			/* 32-bit multiple */
			need += 2; /* NOPs */
		}
		if (need <= remaining) {
			opts->options |= OPTION_COOKIE_EXTENSION;
			opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE;
			remaining -= need;
		} else {
			/* There's no error return, so flag it. */
			xvp->cookie_out_never = 1; /* true */
			opts->hash_size = 0;
		}
	}
	return MAX_TCP_OPTION_SPACE - remaining;
A
Adam Langley 已提交
740 741
}

742 743 744
/* Compute TCP options for ESTABLISHED sockets. This is not the
 * final wire format yet.
 */
A
Adam Langley 已提交
745 746
static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb,
					struct tcp_out_options *opts,
747 748
					struct tcp_md5sig_key **md5)
{
A
Adam Langley 已提交
749 750 751
	struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
	struct tcp_sock *tp = tcp_sk(sk);
	unsigned size = 0;
752
	unsigned int eff_sacks;
A
Adam Langley 已提交
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770

#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;
		opts->tsval = tcb ? tcb->when : 0;
		opts->tsecr = tp->rx_opt.ts_recent;
		size += TCPOLEN_TSTAMP_ALIGNED;
	}

771 772
	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
	if (unlikely(eff_sacks)) {
A
Adam Langley 已提交
773 774
		const unsigned remaining = MAX_TCP_OPTION_SPACE - size;
		opts->num_sack_blocks =
775
			min_t(unsigned, eff_sacks,
A
Adam Langley 已提交
776 777 778 779 780 781 782
			      (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
783
}
L
Linus Torvalds 已提交
784 785 786 787 788 789 790 791 792 793 794 795

/* 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.
 */
796 797
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
798
{
799 800 801 802
	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
803 804
	struct tcp_out_options opts;
	unsigned tcp_options_size, tcp_header_size;
805
	struct tcp_md5sig_key *md5;
806 807 808 809 810 811 812 813
	struct tcphdr *th;
	int err;

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

	/* If congestion control is doing timestamping, we must
	 * take such a timestamp before we potentially clone/copy.
	 */
814
	if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP)
815 816 817 818 819 820 821 822 823 824
		__net_timestamp(skb);

	if (likely(clone_it)) {
		if (unlikely(skb_cloned(skb)))
			skb = pskb_copy(skb, gfp_mask);
		else
			skb = skb_clone(skb, gfp_mask);
		if (unlikely(!skb))
			return -ENOBUFS;
	}
L
Linus Torvalds 已提交
825

826 827 828
	inet = inet_sk(sk);
	tp = tcp_sk(sk);
	tcb = TCP_SKB_CB(skb);
A
Adam Langley 已提交
829
	memset(&opts, 0, sizeof(opts));
L
Linus Torvalds 已提交
830

E
Eric Dumazet 已提交
831
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
A
Adam Langley 已提交
832 833 834 835 836
		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);
837

838
	if (tcp_packets_in_flight(tp) == 0) {
839
		tcp_ca_event(sk, CA_EVENT_TX_START);
840 841 842
		skb->ooo_okay = 1;
	} else
		skb->ooo_okay = 0;
843

844 845
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
846
	skb_set_owner_w(skb, sk);
847 848

	/* Build TCP header and checksum it. */
849
	th = tcp_hdr(skb);
E
Eric Dumazet 已提交
850 851
	th->source		= inet->inet_sport;
	th->dest		= inet->inet_dport;
852 853
	th->seq			= htonl(tcb->seq);
	th->ack_seq		= htonl(tp->rcv_nxt);
854
	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
E
Eric Dumazet 已提交
855
					tcb->tcp_flags);
856

E
Eric Dumazet 已提交
857
	if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
858 859 860
		/* RFC1323: The window in SYN & SYN/ACK segments
		 * is never scaled.
		 */
861
		th->window	= htons(min(tp->rcv_wnd, 65535U));
862 863 864 865 866
	} else {
		th->window	= htons(tcp_select_window(sk));
	}
	th->check		= 0;
	th->urg_ptr		= 0;
L
Linus Torvalds 已提交
867

I
Ilpo Järvinen 已提交
868
	/* The urg_mode check is necessary during a below snd_una win probe */
869 870 871 872 873
	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)) {
874
			th->urg_ptr = htons(0xFFFF);
875 876
			th->urg = 1;
		}
877
	}
L
Linus Torvalds 已提交
878

879
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
E
Eric Dumazet 已提交
880
	if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
881
		TCP_ECN_send(sk, skb, tcp_header_size);
L
Linus Torvalds 已提交
882

883 884 885
#ifdef CONFIG_TCP_MD5SIG
	/* Calculate the MD5 hash, as we have all we need now */
	if (md5) {
E
Eric Dumazet 已提交
886
		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
887
		tp->af_specific->calc_md5_hash(opts.hash_location,
888
					       md5, sk, NULL, skb);
889 890 891
	}
#endif

892
	icsk->icsk_af_ops->send_check(sk, skb);
L
Linus Torvalds 已提交
893

E
Eric Dumazet 已提交
894
	if (likely(tcb->tcp_flags & TCPHDR_ACK))
895
		tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
896

897
	if (skb->len != tcp_header_size)
898
		tcp_event_data_sent(tp, sk);
L
Linus Torvalds 已提交
899

900
	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
901 902
		TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
			      tcp_skb_pcount(skb));
L
Linus Torvalds 已提交
903

904
	err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl);
905
	if (likely(err <= 0))
906 907
		return err;

908
	tcp_enter_cwr(sk, 1);
909

910
	return net_xmit_eval(err);
L
Linus Torvalds 已提交
911 912
}

913
/* This routine just queues the buffer for sending.
L
Linus Torvalds 已提交
914 915 916 917 918 919 920 921 922 923 924
 *
 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
 * otherwise socket can stall.
 */
static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);

	/* Advance write_seq and place onto the write_queue. */
	tp->write_seq = TCP_SKB_CB(skb)->end_seq;
	skb_header_release(skb);
925
	tcp_add_write_queue_tail(sk, skb);
926 927
	sk->sk_wmem_queued += skb->truesize;
	sk_mem_charge(sk, skb->truesize);
L
Linus Torvalds 已提交
928 929
}

930
/* Initialize TSO segments for a packet. */
931
static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
932
				 unsigned int mss_now)
933
{
934 935
	if (skb->len <= mss_now || !sk_can_gso(sk) ||
	    skb->ip_summed == CHECKSUM_NONE) {
936 937 938
		/* Avoid the costly divide in the normal
		 * non-TSO case.
		 */
939 940 941
		skb_shinfo(skb)->gso_segs = 1;
		skb_shinfo(skb)->gso_size = 0;
		skb_shinfo(skb)->gso_type = 0;
942
	} else {
I
Ilpo Järvinen 已提交
943
		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
944
		skb_shinfo(skb)->gso_size = mss_now;
945
		skb_shinfo(skb)->gso_type = sk->sk_gso_type;
L
Linus Torvalds 已提交
946 947 948
	}
}

I
Ilpo Järvinen 已提交
949
/* When a modification to fackets out becomes necessary, we need to check
950
 * skb is counted to fackets_out or not.
I
Ilpo Järvinen 已提交
951
 */
952
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
I
Ilpo Järvinen 已提交
953 954
				   int decr)
{
955 956
	struct tcp_sock *tp = tcp_sk(sk);

957
	if (!tp->sacked_out || tcp_is_reno(tp))
I
Ilpo Järvinen 已提交
958 959
		return;

960
	if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
I
Ilpo Järvinen 已提交
961 962 963
		tp->fackets_out -= decr;
}

964 965 966
/* Pcount in the middle of the write queue got changed, we need to do various
 * tweaks to fix counters
 */
967
static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987
{
	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) &&
988
	    (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
989 990 991 992 993
		tp->lost_cnt_hint -= decr;

	tcp_verify_left_out(tp);
}

L
Linus Torvalds 已提交
994 995
/* 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
996
 * packet to the list.  This won't be called frequently, I hope.
L
Linus Torvalds 已提交
997 998
 * Remember, these are still headerless SKBs at this point.
 */
999 1000
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
		 unsigned int mss_now)
L
Linus Torvalds 已提交
1001 1002 1003
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
1004
	int nsize, old_factor;
1005
	int nlen;
1006
	u8 flags;
L
Linus Torvalds 已提交
1007

1008 1009
	if (WARN_ON(len > skb->len))
		return -EINVAL;
1010

L
Linus Torvalds 已提交
1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023
	nsize = skb_headlen(skb) - len;
	if (nsize < 0)
		nsize = 0;

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

	/* Get a new skb... force flag on. */
	buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
	if (buff == NULL)
		return -ENOMEM; /* We'll just try again later. */
H
Herbert Xu 已提交
1024

1025 1026
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1027 1028 1029
	nlen = skb->len - len - nsize;
	buff->truesize += nlen;
	skb->truesize -= nlen;
L
Linus Torvalds 已提交
1030 1031 1032 1033 1034 1035 1036

	/* 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
1037 1038 1039
	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;
1040
	TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
1041

1042
	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
L
Linus Torvalds 已提交
1043
		/* Copy and checksum data tail into the new buffer. */
1044 1045
		buff->csum = csum_partial_copy_nocheck(skb->data + len,
						       skb_put(buff, nsize),
L
Linus Torvalds 已提交
1046 1047 1048 1049 1050 1051
						       nsize, 0);

		skb_trim(skb, len);

		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
	} else {
1052
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1053 1054 1055 1056 1057 1058 1059 1060 1061
		skb_split(skb, buff, len);
	}

	buff->ip_summed = skb->ip_summed;

	/* Looks stupid, but our code really uses when of
	 * skbs, which it never sent before. --ANK
	 */
	TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1062
	buff->tstamp = skb->tstamp;
L
Linus Torvalds 已提交
1063

1064 1065
	old_factor = tcp_skb_pcount(skb);

L
Linus Torvalds 已提交
1066
	/* Fix up tso_factor for both original and new SKB.  */
1067 1068
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
L
Linus Torvalds 已提交
1069

1070 1071 1072
	/* If this packet has been sent out already, we must
	 * adjust the various packet counters.
	 */
1073
	if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1074 1075
		int diff = old_factor - tcp_skb_pcount(skb) -
			tcp_skb_pcount(buff);
L
Linus Torvalds 已提交
1076

1077 1078
		if (diff)
			tcp_adjust_pcount(sk, skb, diff);
L
Linus Torvalds 已提交
1079 1080 1081
	}

	/* Link BUFF into the send queue. */
1082
	skb_header_release(buff);
1083
	tcp_insert_write_queue_after(skb, buff, sk);
L
Linus Torvalds 已提交
1084 1085 1086 1087 1088 1089 1090 1091

	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.
 */
1092
static void __pskb_trim_head(struct sk_buff *skb, int len)
L
Linus Torvalds 已提交
1093 1094 1095
{
	int i, k, eat;

E
Eric Dumazet 已提交
1096 1097 1098 1099 1100 1101 1102
	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
1103 1104
	eat = len;
	k = 0;
1105
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
E
Eric Dumazet 已提交
1106 1107 1108
		int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

		if (size <= eat) {
1109
			skb_frag_unref(skb, i);
E
Eric Dumazet 已提交
1110
			eat -= size;
L
Linus Torvalds 已提交
1111 1112 1113 1114
		} else {
			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
			if (eat) {
				skb_shinfo(skb)->frags[k].page_offset += eat;
E
Eric Dumazet 已提交
1115
				skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
L
Linus Torvalds 已提交
1116 1117 1118 1119 1120 1121 1122
				eat = 0;
			}
			k++;
		}
	}
	skb_shinfo(skb)->nr_frags = k;

1123
	skb_reset_tail_pointer(skb);
L
Linus Torvalds 已提交
1124 1125 1126 1127
	skb->data_len -= len;
	skb->len = skb->data_len;
}

1128
/* Remove acked data from a packet in the transmit queue. */
L
Linus Torvalds 已提交
1129 1130
int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
{
1131
	if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
L
Linus Torvalds 已提交
1132 1133
		return -ENOMEM;

E
Eric Dumazet 已提交
1134
	__pskb_trim_head(skb, len);
L
Linus Torvalds 已提交
1135 1136

	TCP_SKB_CB(skb)->seq += len;
1137
	skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1138 1139 1140

	skb->truesize	     -= len;
	sk->sk_wmem_queued   -= len;
1141
	sk_mem_uncharge(sk, len);
L
Linus Torvalds 已提交
1142 1143
	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);

1144
	/* Any change of skb->len requires recalculation of tso factor. */
L
Linus Torvalds 已提交
1145
	if (tcp_skb_pcount(skb) > 1)
1146
		tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
L
Linus Torvalds 已提交
1147 1148 1149 1150

	return 0;
}

1151
/* Calculate MSS. Not accounting for SACKs here.  */
1152
int tcp_mtu_to_mss(const struct sock *sk, int pmtu)
J
John Heffner 已提交
1153
{
1154 1155
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180
	int mss_now;

	/* Calculate base mss without TCP options:
	   It is MMS_S - sizeof(tcphdr) of rfc1122
	 */
	mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);

	/* Clamp it (mss_clamp does not include tcp options) */
	if (mss_now > tp->rx_opt.mss_clamp)
		mss_now = tp->rx_opt.mss_clamp;

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

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

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

	return mss_now;
}

/* Inverse of above */
1181
int tcp_mss_to_mtu(const struct sock *sk, int mss)
J
John Heffner 已提交
1182
{
1183 1184
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1185 1186 1187 1188 1189 1190 1191 1192 1193 1194
	int mtu;

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

	return mtu;
}

1195
/* MTU probing init per socket */
J
John Heffner 已提交
1196 1197 1198 1199 1200 1201 1202
void tcp_mtup_init(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);

	icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1203
			       icsk->icsk_af_ops->net_header_len;
J
John Heffner 已提交
1204 1205 1206
	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
	icsk->icsk_mtup.probe_size = 0;
}
E
Eric Dumazet 已提交
1207
EXPORT_SYMBOL(tcp_mtup_init);
J
John Heffner 已提交
1208

L
Linus Torvalds 已提交
1209 1210 1211 1212 1213 1214
/* 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
1215
   It is minimum of user_mss and mss received with SYN.
L
Linus Torvalds 已提交
1216 1217
   It also does not include TCP options.

1218
   inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
L
Linus Torvalds 已提交
1219 1220 1221 1222 1223 1224 1225 1226 1227

   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.

1228 1229
   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
1230 1231 1232 1233
 */
unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
{
	struct tcp_sock *tp = tcp_sk(sk);
1234
	struct inet_connection_sock *icsk = inet_csk(sk);
J
John Heffner 已提交
1235
	int mss_now;
L
Linus Torvalds 已提交
1236

J
John Heffner 已提交
1237 1238
	if (icsk->icsk_mtup.search_high > pmtu)
		icsk->icsk_mtup.search_high = pmtu;
L
Linus Torvalds 已提交
1239

J
John Heffner 已提交
1240
	mss_now = tcp_mtu_to_mss(sk, pmtu);
1241
	mss_now = tcp_bound_to_half_wnd(tp, mss_now);
L
Linus Torvalds 已提交
1242 1243

	/* And store cached results */
1244
	icsk->icsk_pmtu_cookie = pmtu;
J
John Heffner 已提交
1245 1246
	if (icsk->icsk_mtup.enabled)
		mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1247
	tp->mss_cache = mss_now;
L
Linus Torvalds 已提交
1248 1249 1250

	return mss_now;
}
E
Eric Dumazet 已提交
1251
EXPORT_SYMBOL(tcp_sync_mss);
L
Linus Torvalds 已提交
1252 1253 1254 1255

/* Compute the current effective MSS, taking SACKs and IP options,
 * and even PMTU discovery events into account.
 */
I
Ilpo Järvinen 已提交
1256
unsigned int tcp_current_mss(struct sock *sk)
L
Linus Torvalds 已提交
1257
{
1258 1259
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct dst_entry *dst = __sk_dst_get(sk);
1260
	u32 mss_now;
A
Adam Langley 已提交
1261 1262 1263
	unsigned header_len;
	struct tcp_out_options opts;
	struct tcp_md5sig_key *md5;
1264 1265 1266

	mss_now = tp->mss_cache;

L
Linus Torvalds 已提交
1267 1268
	if (dst) {
		u32 mtu = dst_mtu(dst);
1269
		if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
L
Linus Torvalds 已提交
1270 1271 1272
			mss_now = tcp_sync_mss(sk, mtu);
	}

A
Adam Langley 已提交
1273 1274 1275 1276 1277 1278 1279 1280 1281 1282
	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;
	}
1283

L
Linus Torvalds 已提交
1284 1285 1286
	return mss_now;
}

1287
/* Congestion window validation. (RFC2861) */
1288
static void tcp_cwnd_validate(struct sock *sk)
1289
{
1290
	struct tcp_sock *tp = tcp_sk(sk);
1291

1292
	if (tp->packets_out >= tp->snd_cwnd) {
1293 1294 1295 1296 1297 1298 1299 1300
		/* 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;

1301 1302
		if (sysctl_tcp_slow_start_after_idle &&
		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1303 1304 1305 1306
			tcp_cwnd_application_limited(sk);
	}
}

1307 1308 1309 1310
/* Returns the portion of skb which can be sent right away without
 * introducing MSS oddities to segment boundaries. In rare cases where
 * mss_now != mss_cache, we will request caller to create a small skb
 * per input skb which could be mostly avoided here (if desired).
1311 1312 1313 1314 1315 1316 1317
 *
 * We explicitly want to create a request for splitting write queue tail
 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
 * thus all the complexity (cwnd_len is always MSS multiple which we
 * return whenever allowed by the other factors). Basically we need the
 * modulo only when the receiver window alone is the limiting factor or
 * when we would be allowed to send the split-due-to-Nagle skb fully.
1318
 */
1319
static unsigned int tcp_mss_split_point(const struct sock *sk, const struct sk_buff *skb,
1320
					unsigned int mss_now, unsigned int cwnd)
1321
{
1322
	const struct tcp_sock *tp = tcp_sk(sk);
1323
	u32 needed, window, cwnd_len;
1324

1325
	window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1326
	cwnd_len = mss_now * cwnd;
1327 1328 1329 1330

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

1331 1332
	needed = min(skb->len, window);

1333
	if (cwnd_len <= needed)
1334 1335 1336
		return cwnd_len;

	return needed - needed % mss_now;
1337 1338 1339 1340 1341
}

/* 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.
 */
1342 1343
static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
					 const struct sk_buff *skb)
1344 1345 1346 1347
{
	u32 in_flight, cwnd;

	/* Don't be strict about the congestion window for the final FIN.  */
E
Eric Dumazet 已提交
1348 1349
	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
	    tcp_skb_pcount(skb) == 1)
1350 1351 1352 1353 1354 1355 1356 1357 1358 1359
		return 1;

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

	return 0;
}

1360
/* Initialize TSO state of a skb.
1361
 * This must be invoked the first time we consider transmitting
1362 1363
 * SKB onto the wire.
 */
1364
static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
1365
			     unsigned int mss_now)
1366 1367 1368
{
	int tso_segs = tcp_skb_pcount(skb);

1369
	if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1370
		tcp_set_skb_tso_segs(sk, skb, mss_now);
1371 1372 1373 1374 1375
		tso_segs = tcp_skb_pcount(skb);
	}
	return tso_segs;
}

1376
/* Minshall's variant of the Nagle send check. */
1377 1378
static inline int tcp_minshall_check(const struct tcp_sock *tp)
{
1379
	return after(tp->snd_sml, tp->snd_una) &&
1380 1381 1382 1383 1384 1385
		!after(tp->snd_sml, tp->snd_nxt);
}

/* Return 0, if packet can be sent now without violation Nagle's rules:
 * 1. It is full sized.
 * 2. Or it contains FIN. (already checked by caller)
F
Feng King 已提交
1386
 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1387 1388 1389 1390
 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
 *    With Minshall's modification: all sent small packets are ACKed.
 */
static inline int tcp_nagle_check(const struct tcp_sock *tp,
1391
				  const struct sk_buff *skb,
1392 1393
				  unsigned mss_now, int nonagle)
{
E
Eric Dumazet 已提交
1394
	return skb->len < mss_now &&
1395
		((nonagle & TCP_NAGLE_CORK) ||
E
Eric Dumazet 已提交
1396
		 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1397 1398 1399 1400 1401
}

/* Return non-zero if the Nagle test allows this packet to be
 * sent now.
 */
1402
static inline int tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413
				 unsigned int cur_mss, int nonagle)
{
	/* Nagle rule does not apply to frames, which sit in the middle of the
	 * write_queue (they have no chances to get new data).
	 *
	 * This is implemented in the callers, where they modify the 'nonagle'
	 * argument based upon the location of SKB in the send queue.
	 */
	if (nonagle & TCP_NAGLE_PUSH)
		return 1;

1414 1415 1416
	/* Don't use the nagle rule for urgent data (or for the final FIN).
	 * Nagle can be ignored during F-RTO too (see RFC4138).
	 */
I
Ilpo Järvinen 已提交
1417
	if (tcp_urg_mode(tp) || (tp->frto_counter == 2) ||
E
Eric Dumazet 已提交
1418
	    (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1419 1420 1421 1422 1423 1424 1425 1426 1427
		return 1;

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

	return 0;
}

/* Does at least the first segment of SKB fit into the send window? */
1428
static inline int tcp_snd_wnd_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1429
				   unsigned int cur_mss)
1430 1431 1432 1433 1434 1435
{
	u32 end_seq = TCP_SKB_CB(skb)->end_seq;

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

1436
	return !after(end_seq, tcp_wnd_end(tp));
1437 1438
}

1439
/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1440 1441 1442
 * should be put on the wire right now.  If so, it returns the number of
 * packets allowed by the congestion window.
 */
1443
static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1444 1445
				 unsigned int cur_mss, int nonagle)
{
1446
	const struct tcp_sock *tp = tcp_sk(sk);
1447 1448
	unsigned int cwnd_quota;

1449
	tcp_init_tso_segs(sk, skb, cur_mss);
1450 1451 1452 1453 1454

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

	cwnd_quota = tcp_cwnd_test(tp, skb);
1455
	if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1456 1457 1458 1459 1460
		cwnd_quota = 0;

	return cwnd_quota;
}

1461
/* Test if sending is allowed right now. */
1462
int tcp_may_send_now(struct sock *sk)
1463
{
1464
	const struct tcp_sock *tp = tcp_sk(sk);
1465
	struct sk_buff *skb = tcp_send_head(sk);
1466

E
Eric Dumazet 已提交
1467
	return skb &&
I
Ilpo Järvinen 已提交
1468
		tcp_snd_test(sk, skb, tcp_current_mss(sk),
1469
			     (tcp_skb_is_last(sk, skb) ?
E
Eric Dumazet 已提交
1470
			      tp->nonagle : TCP_NAGLE_PUSH));
1471 1472 1473 1474 1475 1476 1477 1478 1479
}

/* 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).
 */
1480
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1481
			unsigned int mss_now, gfp_t gfp)
1482 1483 1484
{
	struct sk_buff *buff;
	int nlen = skb->len - len;
1485
	u8 flags;
1486 1487

	/* All of a TSO frame must be composed of paged data.  */
1488 1489
	if (skb->len != skb->data_len)
		return tcp_fragment(sk, skb, len, mss_now);
1490

1491
	buff = sk_stream_alloc_skb(sk, 0, gfp);
1492 1493 1494
	if (unlikely(buff == NULL))
		return -ENOMEM;

1495 1496
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
1497
	buff->truesize += nlen;
1498 1499 1500 1501 1502 1503 1504 1505
	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
1506 1507 1508
	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;
1509 1510 1511 1512

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

1513
	buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1514 1515 1516
	skb_split(skb, buff, len);

	/* Fix up tso_factor for both original and new SKB.  */
1517 1518
	tcp_set_skb_tso_segs(sk, skb, mss_now);
	tcp_set_skb_tso_segs(sk, buff, mss_now);
1519 1520 1521

	/* Link BUFF into the send queue. */
	skb_header_release(buff);
1522
	tcp_insert_write_queue_after(skb, buff, sk);
1523 1524 1525 1526 1527 1528 1529 1530 1531

	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.
 */
1532
static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1533
{
1534
	struct tcp_sock *tp = tcp_sk(sk);
1535
	const struct inet_connection_sock *icsk = inet_csk(sk);
1536
	u32 send_win, cong_win, limit, in_flight;
1537
	int win_divisor;
1538

E
Eric Dumazet 已提交
1539
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
J
John Heffner 已提交
1540
		goto send_now;
1541

1542
	if (icsk->icsk_ca_state != TCP_CA_Open)
J
John Heffner 已提交
1543 1544 1545
		goto send_now;

	/* Defer for less than two clock ticks. */
I
Ilpo Järvinen 已提交
1546
	if (tp->tso_deferred &&
1547
	    (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
J
John Heffner 已提交
1548
		goto send_now;
1549

1550 1551
	in_flight = tcp_packets_in_flight(tp);

1552
	BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1553

1554
	send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1555 1556 1557 1558 1559 1560

	/* 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);

1561
	/* If a full-sized TSO skb can be sent, do it. */
1562
	if (limit >= sk->sk_gso_max_size)
J
John Heffner 已提交
1563
		goto send_now;
1564

1565 1566 1567 1568
	/* 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;

1569 1570
	win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
	if (win_divisor) {
1571 1572 1573 1574 1575
		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.
		 */
1576
		chunk /= win_divisor;
1577
		if (limit >= chunk)
J
John Heffner 已提交
1578
			goto send_now;
1579 1580 1581 1582 1583 1584
	} 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.
		 */
1585
		if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
J
John Heffner 已提交
1586
			goto send_now;
1587 1588 1589
	}

	/* Ok, it looks like it is advisable to defer.  */
1590
	tp->tso_deferred = 1 | (jiffies << 1);
J
John Heffner 已提交
1591

1592
	return 1;
J
John Heffner 已提交
1593 1594 1595 1596

send_now:
	tp->tso_deferred = 0;
	return 0;
1597 1598
}

J
John Heffner 已提交
1599
/* Create a new MTU probe if we are ready.
1600 1601 1602 1603
 * 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
1604 1605
 * Returns 0 if we should wait to probe (no cwnd available),
 *         1 if a probe was sent,
1606 1607
 *         -1 otherwise
 */
J
John Heffner 已提交
1608 1609 1610 1611 1612 1613 1614
static int tcp_mtu_probe(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct sk_buff *skb, *nskb, *next;
	int len;
	int probe_size;
1615
	int size_needed;
J
John Heffner 已提交
1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626
	int copy;
	int mss_now;

	/* Not currently probing/verifying,
	 * not in recovery,
	 * have enough cwnd, and
	 * not SACKing (the variable headers throw things off) */
	if (!icsk->icsk_mtup.enabled ||
	    icsk->icsk_mtup.probe_size ||
	    inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
	    tp->snd_cwnd < 11 ||
1627
	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
J
John Heffner 已提交
1628 1629 1630
		return -1;

	/* Very simple search strategy: just double the MSS. */
I
Ilpo Järvinen 已提交
1631
	mss_now = tcp_current_mss(sk);
1632
	probe_size = 2 * tp->mss_cache;
1633
	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
J
John Heffner 已提交
1634 1635 1636 1637 1638 1639
	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
		/* TODO: set timer for probe_converge_event */
		return -1;
	}

	/* Have enough data in the send queue to probe? */
1640
	if (tp->write_seq - tp->snd_nxt < size_needed)
J
John Heffner 已提交
1641 1642
		return -1;

1643 1644
	if (tp->snd_wnd < size_needed)
		return -1;
1645
	if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1646
		return 0;
J
John Heffner 已提交
1647

1648 1649 1650
	/* 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
1651 1652 1653 1654 1655 1656 1657 1658
			return -1;
		else
			return 0;
	}

	/* We're allowed to probe.  Build it now. */
	if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
		return -1;
1659 1660
	sk->sk_wmem_queued += nskb->truesize;
	sk_mem_charge(sk, nskb->truesize);
J
John Heffner 已提交
1661

1662
	skb = tcp_send_head(sk);
J
John Heffner 已提交
1663 1664 1665

	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
1666
	TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
J
John Heffner 已提交
1667 1668
	TCP_SKB_CB(nskb)->sacked = 0;
	nskb->csum = 0;
1669
	nskb->ip_summed = skb->ip_summed;
J
John Heffner 已提交
1670

1671 1672
	tcp_insert_write_queue_before(nskb, skb, sk);

J
John Heffner 已提交
1673
	len = 0;
1674
	tcp_for_write_queue_from_safe(skb, next, sk) {
J
John Heffner 已提交
1675 1676 1677 1678 1679
		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,
1680 1681
							    skb_put(nskb, copy),
							    copy, nskb->csum);
J
John Heffner 已提交
1682 1683 1684 1685

		if (skb->len <= copy) {
			/* We've eaten all the data from this skb.
			 * Throw it away. */
E
Eric Dumazet 已提交
1686
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1687
			tcp_unlink_write_queue(skb, sk);
1688
			sk_wmem_free_skb(sk, skb);
J
John Heffner 已提交
1689
		} else {
E
Eric Dumazet 已提交
1690
			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
C
Changli Gao 已提交
1691
						   ~(TCPHDR_FIN|TCPHDR_PSH);
J
John Heffner 已提交
1692 1693
			if (!skb_shinfo(skb)->nr_frags) {
				skb_pull(skb, copy);
1694
				if (skb->ip_summed != CHECKSUM_PARTIAL)
1695 1696
					skb->csum = csum_partial(skb->data,
								 skb->len, 0);
J
John Heffner 已提交
1697 1698 1699 1700 1701 1702 1703 1704
			} else {
				__pskb_trim_head(skb, copy);
				tcp_set_skb_tso_segs(sk, skb, mss_now);
			}
			TCP_SKB_CB(skb)->seq += copy;
		}

		len += copy;
1705 1706 1707

		if (len >= probe_size)
			break;
J
John Heffner 已提交
1708 1709 1710 1711 1712 1713 1714 1715
	}
	tcp_init_tso_segs(sk, nskb, nskb->len);

	/* We're ready to send.  If this fails, the probe will
	 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
	TCP_SKB_CB(nskb)->when = tcp_time_stamp;
	if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
		/* Decrement cwnd here because we are sending
1716
		 * effectively two packets. */
J
John Heffner 已提交
1717
		tp->snd_cwnd--;
1718
		tcp_event_new_data_sent(sk, nskb);
J
John Heffner 已提交
1719 1720

		icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1721 1722
		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
1723 1724 1725 1726 1727 1728 1729

		return 1;
	}

	return -1;
}

L
Linus Torvalds 已提交
1730 1731 1732 1733
/* This routine writes packets to the network.  It advances the
 * send_head.  This happens as incoming acks open up the remote
 * window for us.
 *
1734 1735 1736 1737
 * 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.
 *
L
Linus Torvalds 已提交
1738 1739 1740
 * Returns 1, if no segments are in flight and we have queued segments, but
 * cannot send anything now because of SWS or another problem.
 */
1741 1742
static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
			  int push_one, gfp_t gfp)
L
Linus Torvalds 已提交
1743 1744
{
	struct tcp_sock *tp = tcp_sk(sk);
1745
	struct sk_buff *skb;
1746 1747
	unsigned int tso_segs, sent_pkts;
	int cwnd_quota;
J
John Heffner 已提交
1748
	int result;
L
Linus Torvalds 已提交
1749

1750
	sent_pkts = 0;
J
John Heffner 已提交
1751

1752 1753 1754 1755 1756 1757 1758 1759
	if (!push_one) {
		/* Do MTU probing. */
		result = tcp_mtu_probe(sk);
		if (!result) {
			return 0;
		} else if (result > 0) {
			sent_pkts = 1;
		}
J
John Heffner 已提交
1760 1761
	}

1762
	while ((skb = tcp_send_head(sk))) {
1763 1764
		unsigned int limit;

1765
		tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1766
		BUG_ON(!tso_segs);
1767

1768 1769 1770 1771 1772 1773 1774
		cwnd_quota = tcp_cwnd_test(tp, skb);
		if (!cwnd_quota)
			break;

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

1775 1776 1777 1778 1779 1780
		if (tso_segs == 1) {
			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
						     (tcp_skb_is_last(sk, skb) ?
						      nonagle : TCP_NAGLE_PUSH))))
				break;
		} else {
1781
			if (!push_one && tcp_tso_should_defer(sk, skb))
1782 1783
				break;
		}
1784

1785
		limit = mss_now;
1786
		if (tso_segs > 1 && !tcp_urg_mode(tp))
1787 1788
			limit = tcp_mss_split_point(sk, skb, mss_now,
						    cwnd_quota);
L
Linus Torvalds 已提交
1789

1790
		if (skb->len > limit &&
1791
		    unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
1792 1793
			break;

1794
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
1795

1796
		if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1797
			break;
L
Linus Torvalds 已提交
1798

1799 1800 1801
		/* Advance the send_head.  This one is sent out.
		 * This call will increment packets_out.
		 */
1802
		tcp_event_new_data_sent(sk, skb);
L
Linus Torvalds 已提交
1803

1804
		tcp_minshall_update(tp, mss_now, skb);
1805
		sent_pkts += tcp_skb_pcount(skb);
1806 1807 1808

		if (push_one)
			break;
1809
	}
1810 1811
	if (inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery)
		tp->prr_out += sent_pkts;
L
Linus Torvalds 已提交
1812

1813
	if (likely(sent_pkts)) {
1814
		tcp_cwnd_validate(sk);
1815
		return 0;
L
Linus Torvalds 已提交
1816
	}
1817
	return !tp->packets_out && tcp_send_head(sk);
L
Linus Torvalds 已提交
1818 1819
}

1820 1821 1822 1823
/* 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.
 */
1824 1825
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
			       int nonagle)
1826
{
1827 1828 1829 1830 1831 1832 1833
	/* 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;

1834
	if (tcp_write_xmit(sk, cur_mss, nonagle, 0, GFP_ATOMIC))
1835
		tcp_check_probe_timer(sk);
1836 1837
}

1838 1839 1840 1841 1842
/* 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)
{
1843
	struct sk_buff *skb = tcp_send_head(sk);
1844 1845 1846

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

1847
	tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
1848 1849
}

L
Linus Torvalds 已提交
1850 1851
/* This function returns the amount that we can raise the
 * usable window based on the following constraints
1852
 *
L
Linus Torvalds 已提交
1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870
 * 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.
1871
 *
L
Linus Torvalds 已提交
1872 1873
 * Of course, if the sender implements sender side SWS prevention
 * then this will not be a problem.
1874
 *
L
Linus Torvalds 已提交
1875
 * BSD seems to make the following compromise:
1876
 *
L
Linus Torvalds 已提交
1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903
 *	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)
{
1904
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
1905
	struct tcp_sock *tp = tcp_sk(sk);
S
Stephen Hemminger 已提交
1906
	/* MSS for the peer's data.  Previous versions used mss_clamp
L
Linus Torvalds 已提交
1907 1908 1909 1910 1911
	 * 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
	 */
1912
	int mss = icsk->icsk_ack.rcv_mss;
L
Linus Torvalds 已提交
1913 1914 1915 1916 1917
	int free_space = tcp_space(sk);
	int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
	int window;

	if (mss > full_space)
1918
		mss = full_space;
L
Linus Torvalds 已提交
1919

1920
	if (free_space < (full_space >> 1)) {
1921
		icsk->icsk_ack.quick = 0;
L
Linus Torvalds 已提交
1922

1923
		if (sk_under_memory_pressure(sk))
1924 1925
			tp->rcv_ssthresh = min(tp->rcv_ssthresh,
					       4U * tp->advmss);
L
Linus Torvalds 已提交
1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957

		if (free_space < mss)
			return 0;
	}

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

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

		/* Advertise enough space so that it won't get scaled away.
		 * Import case: prevent zero window announcement if
		 * 1<<rcv_wscale > mss.
		 */
		if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
			window = (((window >> tp->rx_opt.rcv_wscale) + 1)
				  << tp->rx_opt.rcv_wscale);
	} else {
		/* Get the largest window that is a nice multiple of mss.
		 * Window clamp already applied above.
		 * If our current window offering is within 1 mss of the
		 * free space we just keep it. This prevents the divide
		 * and multiply from happening most of the time.
		 * We also don't do any window rounding when the free space
		 * is too small.
		 */
		if (window <= free_space - mss || window > free_space)
1958
			window = (free_space / mss) * mss;
1959
		else if (mss == full_space &&
1960
			 free_space > window + (full_space >> 1))
1961
			window = free_space;
L
Linus Torvalds 已提交
1962 1963 1964 1965 1966
	}

	return window;
}

1967 1968
/* 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
1969 1970
{
	struct tcp_sock *tp = tcp_sk(sk);
1971
	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
1972
	int skb_size, next_skb_size;
L
Linus Torvalds 已提交
1973

1974 1975
	skb_size = skb->len;
	next_skb_size = next_skb->len;
L
Linus Torvalds 已提交
1976

1977
	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
1978

1979
	tcp_highest_sack_combine(sk, next_skb, skb);
L
Linus Torvalds 已提交
1980

1981
	tcp_unlink_write_queue(next_skb, sk);
L
Linus Torvalds 已提交
1982

1983 1984
	skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
				  next_skb_size);
L
Linus Torvalds 已提交
1985

1986 1987
	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
		skb->ip_summed = CHECKSUM_PARTIAL;
L
Linus Torvalds 已提交
1988

1989 1990
	if (skb->ip_summed != CHECKSUM_PARTIAL)
		skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
L
Linus Torvalds 已提交
1991

1992 1993
	/* 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
1994

1995
	/* Merge over control information. This moves PSH/FIN etc. over */
E
Eric Dumazet 已提交
1996
	TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
1997 1998 1999 2000 2001 2002 2003

	/* 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 */
2004 2005 2006
	tcp_clear_retrans_hints_partial(tp);
	if (next_skb == tp->retransmit_skb_hint)
		tp->retransmit_skb_hint = skb;
2007

2008 2009
	tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));

2010
	sk_wmem_free_skb(sk, next_skb);
L
Linus Torvalds 已提交
2011 2012
}

2013
/* Check if coalescing SKBs is legal. */
2014
static int tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031
{
	if (tcp_skb_pcount(skb) > 1)
		return 0;
	/* TODO: SACK collapsing could be used to remove this condition */
	if (skb_shinfo(skb)->nr_frags != 0)
		return 0;
	if (skb_cloned(skb))
		return 0;
	if (skb == tcp_send_head(sk))
		return 0;
	/* Some heurestics for collapsing over SACK'd could be invented */
	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
		return 0;

	return 1;
}

2032 2033 2034
/* Collapse packets in the retransmit queue to make to create
 * less packets on the wire. This is only done on retransmission.
 */
2035 2036 2037 2038 2039 2040 2041 2042 2043
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;
	int first = 1;

	if (!sysctl_tcp_retrans_collapse)
		return;
E
Eric Dumazet 已提交
2044
	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062
		return;

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

		space -= skb->len;

		if (first) {
			first = 0;
			continue;
		}

		if (space < 0)
			break;
		/* Punt if not enough space exists in the first SKB for
		 * the data in the second
		 */
2063
		if (skb->len > skb_availroom(to))
2064 2065 2066 2067 2068 2069 2070 2071 2072
			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
2073 2074 2075 2076 2077 2078 2079
/* This retransmits one SKB.  Policy decisions and retransmit queue
 * state updates are done by the caller.  Returns non-zero if an
 * error occurred which prevented the send.
 */
int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);
J
John Heffner 已提交
2080
	struct inet_connection_sock *icsk = inet_csk(sk);
2081
	unsigned int cur_mss;
L
Linus Torvalds 已提交
2082 2083
	int err;

J
John Heffner 已提交
2084 2085 2086 2087 2088
	/* Inconslusive MTU probe */
	if (icsk->icsk_mtup.probe_size) {
		icsk->icsk_mtup.probe_size = 0;
	}

L
Linus Torvalds 已提交
2089
	/* Do not sent more than we queued. 1/4 is reserved for possible
S
Stephen Hemminger 已提交
2090
	 * copying overhead: fragmentation, tunneling, mangling etc.
L
Linus Torvalds 已提交
2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102
	 */
	if (atomic_read(&sk->sk_wmem_alloc) >
	    min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
		return -EAGAIN;

	if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
		if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
			BUG();
		if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
			return -ENOMEM;
	}

2103 2104 2105
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
		return -EHOSTUNREACH; /* Routing failure or similar. */

I
Ilpo Järvinen 已提交
2106
	cur_mss = tcp_current_mss(sk);
2107

L
Linus Torvalds 已提交
2108 2109 2110 2111 2112
	/* 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.
	 */
2113 2114
	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
2115 2116 2117
		return -EAGAIN;

	if (skb->len > cur_mss) {
2118
		if (tcp_fragment(sk, skb, cur_mss, cur_mss))
L
Linus Torvalds 已提交
2119
			return -ENOMEM; /* We'll try again later. */
2120
	} else {
2121 2122 2123 2124 2125 2126
		int oldpcount = tcp_skb_pcount(skb);

		if (unlikely(oldpcount > 1)) {
			tcp_init_tso_segs(sk, skb, cur_mss);
			tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
		}
L
Linus Torvalds 已提交
2127 2128
	}

2129
	tcp_retrans_try_collapse(sk, skb, cur_mss);
L
Linus Torvalds 已提交
2130 2131 2132 2133 2134

	/* Some Solaris stacks overoptimize and ignore the FIN on a
	 * retransmit when old data is attached.  So strip it off
	 * since it is cheap to do so and saves bytes on the network.
	 */
S
Stephen Hemminger 已提交
2135
	if (skb->len > 0 &&
E
Eric Dumazet 已提交
2136
	    (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
S
Stephen Hemminger 已提交
2137
	    tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
L
Linus Torvalds 已提交
2138
		if (!pskb_trim(skb, 0)) {
2139 2140
			/* Reuse, even though it does some unnecessary work */
			tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1,
E
Eric Dumazet 已提交
2141
					     TCP_SKB_CB(skb)->tcp_flags);
L
Linus Torvalds 已提交
2142 2143 2144 2145 2146 2147 2148 2149 2150
			skb->ip_summed = CHECKSUM_NONE;
		}
	}

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

E
Eric Dumazet 已提交
2151 2152 2153 2154 2155 2156 2157 2158 2159
	/* make sure skb->data is aligned on arches that require it */
	if (unlikely(NET_IP_ALIGN && ((unsigned long)skb->data & 3))) {
		struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
						   GFP_ATOMIC);
		err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
			     -ENOBUFS;
	} else {
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
	}
L
Linus Torvalds 已提交
2160 2161 2162

	if (err == 0) {
		/* Update global TCP statistics. */
P
Pavel Emelyanov 已提交
2163
		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
L
Linus Torvalds 已提交
2164 2165 2166 2167

		tp->total_retrans++;

#if FASTRETRANS_DEBUG > 0
2168
		if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
L
Linus Torvalds 已提交
2169 2170 2171 2172
			if (net_ratelimit())
				printk(KERN_DEBUG "retrans_out leaked.\n");
		}
#endif
2173 2174
		if (!tp->retrans_out)
			tp->lost_retrans_low = tp->snd_nxt;
L
Linus Torvalds 已提交
2175 2176 2177 2178 2179 2180 2181
		TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
		tp->retrans_out += tcp_skb_pcount(skb);

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

Y
Yuchung Cheng 已提交
2182
		tp->undo_retrans += tcp_skb_pcount(skb);
L
Linus Torvalds 已提交
2183 2184 2185 2186 2187 2188 2189 2190 2191

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

2192 2193 2194
/* Check if we forward retransmits are possible in the current
 * window/congestion state.
 */
2195 2196 2197
static int tcp_can_forward_retransmit(struct sock *sk)
{
	const struct inet_connection_sock *icsk = inet_csk(sk);
2198
	const struct tcp_sock *tp = tcp_sk(sk);
2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221

	/* Forward retransmissions are possible only during Recovery. */
	if (icsk->icsk_ca_state != TCP_CA_Recovery)
		return 0;

	/* No forward retransmissions in Reno are possible. */
	if (tcp_is_reno(tp))
		return 0;

	/* 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))
		return 0;

	return 1;
}

L
Linus Torvalds 已提交
2222 2223 2224 2225 2226 2227 2228 2229 2230 2231
/* 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)
{
2232
	const struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2233 2234
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
2235
	struct sk_buff *hole = NULL;
2236
	u32 last_lost;
2237
	int mib_idx;
2238
	int fwd_rexmitting = 0;
2239

2240 2241 2242
	if (!tp->packets_out)
		return;

2243 2244 2245
	if (!tp->lost_out)
		tp->retransmit_high = tp->snd_una;

2246
	if (tp->retransmit_skb_hint) {
2247
		skb = tp->retransmit_skb_hint;
2248 2249 2250 2251
		last_lost = TCP_SKB_CB(skb)->end_seq;
		if (after(last_lost, tp->retransmit_high))
			last_lost = tp->retransmit_high;
	} else {
2252
		skb = tcp_write_queue_head(sk);
2253 2254
		last_lost = tp->snd_una;
	}
L
Linus Torvalds 已提交
2255

2256 2257
	tcp_for_write_queue_from(skb, sk) {
		__u8 sacked = TCP_SKB_CB(skb)->sacked;
L
Linus Torvalds 已提交
2258

2259 2260 2261
		if (skb == tcp_send_head(sk))
			break;
		/* we could do better than to assign each time */
2262 2263
		if (hole == NULL)
			tp->retransmit_skb_hint = skb;
2264 2265 2266 2267 2268 2269 2270 2271 2272 2273

		/* 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
2274

2275 2276 2277 2278 2279
		if (fwd_rexmitting) {
begin_fwd:
			if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
				break;
			mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2280

2281
		} else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2282
			tp->retransmit_high = last_lost;
2283 2284 2285 2286 2287 2288 2289 2290 2291
			if (!tcp_can_forward_retransmit(sk))
				break;
			/* Backtrack if necessary to non-L'ed skb */
			if (hole != NULL) {
				skb = hole;
				hole = NULL;
			}
			fwd_rexmitting = 1;
			goto begin_fwd;
L
Linus Torvalds 已提交
2292

2293
		} else if (!(sacked & TCPCB_LOST)) {
2294
			if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2295 2296
				hole = skb;
			continue;
L
Linus Torvalds 已提交
2297

2298
		} else {
2299
			last_lost = TCP_SKB_CB(skb)->end_seq;
2300 2301 2302 2303 2304
			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
2305

2306
		if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
L
Linus Torvalds 已提交
2307 2308
			continue;

2309 2310
		if (tcp_retransmit_skb(sk, skb)) {
			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2311
			return;
2312
		}
2313
		NET_INC_STATS_BH(sock_net(sk), mib_idx);
L
Linus Torvalds 已提交
2314

2315 2316 2317
		if (inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery)
			tp->prr_out += tcp_skb_pcount(skb);

2318
		if (skb == tcp_write_queue_head(sk))
2319 2320 2321
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
						  inet_csk(sk)->icsk_rto,
						  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2322 2323 2324 2325 2326 2327 2328 2329
	}
}

/* Send a fin.  The caller locks the socket for us.  This cannot be
 * allowed to fail queueing a FIN frame under any circumstances.
 */
void tcp_send_fin(struct sock *sk)
{
2330
	struct tcp_sock *tp = tcp_sk(sk);
2331
	struct sk_buff *skb = tcp_write_queue_tail(sk);
L
Linus Torvalds 已提交
2332
	int mss_now;
2333

L
Linus Torvalds 已提交
2334 2335 2336 2337
	/* Optimization, tack on the FIN if we have a queue of
	 * unsent frames.  But be careful about outgoing SACKS
	 * and IP options.
	 */
I
Ilpo Järvinen 已提交
2338
	mss_now = tcp_current_mss(sk);
L
Linus Torvalds 已提交
2339

2340
	if (tcp_send_head(sk) != NULL) {
E
Eric Dumazet 已提交
2341
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
L
Linus Torvalds 已提交
2342 2343 2344 2345 2346
		TCP_SKB_CB(skb)->end_seq++;
		tp->write_seq++;
	} else {
		/* Socket is locked, keep trying until memory is available. */
		for (;;) {
2347 2348
			skb = alloc_skb_fclone(MAX_TCP_HEADER,
					       sk->sk_allocation);
L
Linus Torvalds 已提交
2349 2350 2351 2352 2353 2354 2355 2356
			if (skb)
				break;
			yield();
		}

		/* Reserve space for headers and prepare control bits. */
		skb_reserve(skb, MAX_TCP_HEADER);
		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2357
		tcp_init_nondata_skb(skb, tp->write_seq,
C
Changli Gao 已提交
2358
				     TCPHDR_ACK | TCPHDR_FIN);
L
Linus Torvalds 已提交
2359 2360
		tcp_queue_skb(sk, skb);
	}
2361
	__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
L
Linus Torvalds 已提交
2362 2363 2364 2365 2366
}

/* 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
2367
 * by RFC 2525, section 2.17.  -DaveM
L
Linus Torvalds 已提交
2368
 */
A
Al Viro 已提交
2369
void tcp_send_active_reset(struct sock *sk, gfp_t priority)
L
Linus Torvalds 已提交
2370 2371 2372 2373 2374 2375
{
	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
2376
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
L
Linus Torvalds 已提交
2377 2378 2379 2380 2381
		return;
	}

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, MAX_TCP_HEADER);
2382
	tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
C
Changli Gao 已提交
2383
			     TCPHDR_ACK | TCPHDR_RST);
L
Linus Torvalds 已提交
2384 2385
	/* Send it off. */
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2386
	if (tcp_transmit_skb(sk, skb, 0, priority))
P
Pavel Emelyanov 已提交
2387
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2388

P
Pavel Emelyanov 已提交
2389
	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
L
Linus Torvalds 已提交
2390 2391
}

2392 2393
/* 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
2394 2395 2396 2397 2398 2399
 * 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)
{
2400
	struct sk_buff *skb;
L
Linus Torvalds 已提交
2401

2402
	skb = tcp_write_queue_head(sk);
E
Eric Dumazet 已提交
2403
	if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
L
Linus Torvalds 已提交
2404 2405 2406
		printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
		return -EFAULT;
	}
E
Eric Dumazet 已提交
2407
	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
L
Linus Torvalds 已提交
2408 2409 2410 2411
		if (skb_cloned(skb)) {
			struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
			if (nskb == NULL)
				return -ENOMEM;
2412
			tcp_unlink_write_queue(skb, sk);
L
Linus Torvalds 已提交
2413
			skb_header_release(nskb);
2414
			__tcp_add_write_queue_head(sk, nskb);
2415 2416 2417
			sk_wmem_free_skb(sk, skb);
			sk->sk_wmem_queued += nskb->truesize;
			sk_mem_charge(sk, nskb->truesize);
L
Linus Torvalds 已提交
2418 2419 2420
			skb = nskb;
		}

E
Eric Dumazet 已提交
2421
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
L
Linus Torvalds 已提交
2422 2423 2424
		TCP_ECN_send_synack(tcp_sk(sk), skb);
	}
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2425
	return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
2426 2427
}

2428
/* Prepare a SYN-ACK. */
2429
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2430 2431
				struct request_sock *req,
				struct request_values *rvp)
L
Linus Torvalds 已提交
2432
{
2433
	struct tcp_out_options opts;
2434
	struct tcp_extend_values *xvp = tcp_xv(rvp);
2435
	struct inet_request_sock *ireq = inet_rsk(req);
L
Linus Torvalds 已提交
2436
	struct tcp_sock *tp = tcp_sk(sk);
E
Eric Dumazet 已提交
2437
	const struct tcp_cookie_values *cvp = tp->cookie_values;
L
Linus Torvalds 已提交
2438 2439
	struct tcphdr *th;
	struct sk_buff *skb;
2440
	struct tcp_md5sig_key *md5;
2441
	int tcp_header_size;
2442
	int mss;
E
Eric Dumazet 已提交
2443
	int s_data_desired = 0;
L
Linus Torvalds 已提交
2444

E
Eric Dumazet 已提交
2445 2446 2447
	if (cvp != NULL && cvp->s_data_constant && cvp->s_data_desired)
		s_data_desired = cvp->s_data_desired;
	skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15 + s_data_desired, 1, GFP_ATOMIC);
L
Linus Torvalds 已提交
2448 2449 2450 2451 2452 2453
	if (skb == NULL)
		return NULL;

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

E
Eric Dumazet 已提交
2454
	skb_dst_set(skb, dst_clone(dst));
L
Linus Torvalds 已提交
2455

2456
	mss = dst_metric_advmss(dst);
2457 2458 2459
	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
		mss = tp->rx_opt.user_mss;

A
Adam Langley 已提交
2460 2461 2462 2463
	if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
		__u8 rcv_wscale;
		/* Set this up on the first call only */
		req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2464 2465 2466 2467 2468 2469

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

A
Adam Langley 已提交
2470 2471
		/* tcp_full_space because it is guaranteed to be the first packet */
		tcp_select_initial_window(tcp_full_space(sk),
2472
			mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
A
Adam Langley 已提交
2473 2474 2475
			&req->rcv_wnd,
			&req->window_clamp,
			ireq->wscale_ok,
2476 2477
			&rcv_wscale,
			dst_metric(dst, RTAX_INITRWND));
A
Adam Langley 已提交
2478 2479 2480 2481
		ireq->rcv_wscale = rcv_wscale;
	}

	memset(&opts, 0, sizeof(opts));
2482 2483 2484 2485 2486
#ifdef CONFIG_SYN_COOKIES
	if (unlikely(req->cookie_ts))
		TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
	else
#endif
A
Adam Langley 已提交
2487
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2488
	tcp_header_size = tcp_synack_options(sk, req, mss,
2489 2490
					     skb, &opts, &md5, xvp)
			+ sizeof(*th);
2491

2492 2493
	skb_push(skb, tcp_header_size);
	skb_reset_transport_header(skb);
L
Linus Torvalds 已提交
2494

2495
	th = tcp_hdr(skb);
L
Linus Torvalds 已提交
2496 2497 2498 2499
	memset(th, 0, sizeof(struct tcphdr));
	th->syn = 1;
	th->ack = 1;
	TCP_ECN_make_synack(req, th);
2500
	th->source = ireq->loc_port;
2501
	th->dest = ireq->rmt_port;
2502 2503 2504 2505
	/* 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
2506
			     TCPHDR_SYN | TCPHDR_ACK);
2507 2508

	if (OPTION_COOKIE_EXTENSION & opts.options) {
E
Eric Dumazet 已提交
2509 2510
		if (s_data_desired) {
			u8 *buf = skb_put(skb, s_data_desired);
2511 2512

			/* copy data directly from the listening socket. */
E
Eric Dumazet 已提交
2513 2514
			memcpy(buf, cvp->s_data_payload, s_data_desired);
			TCP_SKB_CB(skb)->end_seq += s_data_desired;
2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530
		}

		if (opts.hash_size > 0) {
			__u32 workspace[SHA_WORKSPACE_WORDS];
			u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS];
			u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1];

			/* Secret recipe depends on the Timestamp, (future)
			 * Sequence and Acknowledgment Numbers, Initiator
			 * Cookie, and others handled by IP variant caller.
			 */
			*tail-- ^= opts.tsval;
			*tail-- ^= tcp_rsk(req)->rcv_isn + 1;
			*tail-- ^= TCP_SKB_CB(skb)->seq + 1;

			/* recommended */
2531
			*tail-- ^= (((__force u32)th->dest << 16) | (__force u32)th->source);
D
David S. Miller 已提交
2532
			*tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */
2533 2534 2535 2536 2537 2538 2539 2540 2541

			sha_transform((__u32 *)&xvp->cookie_bakery[0],
				      (char *)mess,
				      &workspace[0]);
			opts.hash_location =
				(__u8 *)&xvp->cookie_bakery[0];
		}
	}

L
Linus Torvalds 已提交
2542
	th->seq = htonl(TCP_SKB_CB(skb)->seq);
2543
	th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
L
Linus Torvalds 已提交
2544 2545

	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2546
	th->window = htons(min(req->rcv_wnd, 65535U));
2547
	tcp_options_write((__be32 *)(th + 1), tp, &opts);
L
Linus Torvalds 已提交
2548
	th->doff = (tcp_header_size >> 2);
2549
	TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb));
2550 2551 2552 2553

#ifdef CONFIG_TCP_MD5SIG
	/* Okay, we have all we need - do the md5 hash if needed */
	if (md5) {
2554
		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2555
					       md5, NULL, req, skb);
2556 2557 2558
	}
#endif

L
Linus Torvalds 已提交
2559 2560
	return skb;
}
E
Eric Dumazet 已提交
2561
EXPORT_SYMBOL(tcp_make_synack);
L
Linus Torvalds 已提交
2562

2563
/* Do all connect socket setups that can be done AF independent. */
S
Stephen Hemminger 已提交
2564
static void tcp_connect_init(struct sock *sk)
L
Linus Torvalds 已提交
2565
{
2566
	const struct dst_entry *dst = __sk_dst_get(sk);
L
Linus Torvalds 已提交
2567 2568 2569 2570 2571 2572 2573
	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) +
2574
		(sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
L
Linus Torvalds 已提交
2575

2576 2577 2578 2579 2580
#ifdef CONFIG_TCP_MD5SIG
	if (tp->af_specific->md5_lookup(sk, sk) != NULL)
		tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif

L
Linus Torvalds 已提交
2581 2582 2583 2584
	/* 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
2585
	tcp_mtup_init(sk);
L
Linus Torvalds 已提交
2586 2587 2588 2589
	tcp_sync_mss(sk, dst_mtu(dst));

	if (!tp->window_clamp)
		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2590
	tp->advmss = dst_metric_advmss(dst);
2591 2592 2593
	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
2594 2595
	tcp_initialize_rcv_mss(sk);

2596 2597 2598 2599 2600
	/* 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
2601 2602 2603 2604
	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,
2605
				  sysctl_tcp_window_scaling,
2606 2607
				  &rcv_wscale,
				  dst_metric(dst, RTAX_INITRWND));
L
Linus Torvalds 已提交
2608 2609 2610 2611 2612 2613 2614

	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;
2615
	tcp_init_wl(tp, 0);
L
Linus Torvalds 已提交
2616 2617
	tp->snd_una = tp->write_seq;
	tp->snd_sml = tp->write_seq;
I
Ilpo Järvinen 已提交
2618
	tp->snd_up = tp->write_seq;
L
Linus Torvalds 已提交
2619 2620 2621 2622
	tp->rcv_nxt = 0;
	tp->rcv_wup = 0;
	tp->copied_seq = 0;

2623 2624
	inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
	inet_csk(sk)->icsk_retransmits = 0;
L
Linus Torvalds 已提交
2625 2626 2627
	tcp_clear_retrans(tp);
}

2628
/* Build a SYN and send it off. */
L
Linus Torvalds 已提交
2629 2630 2631 2632
int tcp_connect(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *buff;
2633
	int err;
L
Linus Torvalds 已提交
2634 2635 2636

	tcp_connect_init(sk);

2637
	buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
L
Linus Torvalds 已提交
2638 2639 2640 2641 2642 2643
	if (unlikely(buff == NULL))
		return -ENOBUFS;

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

2644
	tp->snd_nxt = tp->write_seq;
C
Changli Gao 已提交
2645
	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
2646
	TCP_ECN_send_syn(sk, buff);
L
Linus Torvalds 已提交
2647 2648 2649 2650 2651

	/* Send it off. */
	TCP_SKB_CB(buff)->when = tcp_time_stamp;
	tp->retrans_stamp = TCP_SKB_CB(buff)->when;
	skb_header_release(buff);
2652
	__tcp_add_write_queue_tail(sk, buff);
2653 2654
	sk->sk_wmem_queued += buff->truesize;
	sk_mem_charge(sk, buff->truesize);
L
Linus Torvalds 已提交
2655
	tp->packets_out += tcp_skb_pcount(buff);
2656 2657 2658
	err = tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
	if (err == -ECONNREFUSED)
		return err;
2659 2660 2661 2662 2663 2664

	/* 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
2665
	TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
L
Linus Torvalds 已提交
2666 2667

	/* Timer for repeating the SYN until an answer. */
2668 2669
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
				  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
L
Linus Torvalds 已提交
2670 2671
	return 0;
}
E
Eric Dumazet 已提交
2672
EXPORT_SYMBOL(tcp_connect);
L
Linus Torvalds 已提交
2673 2674 2675 2676 2677 2678 2679

/* 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)
{
2680 2681
	struct inet_connection_sock *icsk = inet_csk(sk);
	int ato = icsk->icsk_ack.ato;
L
Linus Torvalds 已提交
2682 2683 2684
	unsigned long timeout;

	if (ato > TCP_DELACK_MIN) {
2685
		const struct tcp_sock *tp = tcp_sk(sk);
2686
		int max_ato = HZ / 2;
L
Linus Torvalds 已提交
2687

2688 2689
		if (icsk->icsk_ack.pingpong ||
		    (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
L
Linus Torvalds 已提交
2690 2691 2692 2693 2694
			max_ato = TCP_DELACK_MAX;

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

		/* If some rtt estimate is known, use it to bound delayed ack.
2695
		 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
L
Linus Torvalds 已提交
2696 2697 2698
		 * directly.
		 */
		if (tp->srtt) {
2699
			int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN);
L
Linus Torvalds 已提交
2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711

			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. */
2712
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
L
Linus Torvalds 已提交
2713 2714 2715
		/* If delack timer was blocked or is about to expire,
		 * send ACK now.
		 */
2716 2717
		if (icsk->icsk_ack.blocked ||
		    time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
L
Linus Torvalds 已提交
2718 2719 2720 2721
			tcp_send_ack(sk);
			return;
		}

2722 2723
		if (!time_before(timeout, icsk->icsk_ack.timeout))
			timeout = icsk->icsk_ack.timeout;
L
Linus Torvalds 已提交
2724
	}
2725 2726 2727
	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
2728 2729 2730 2731 2732
}

/* This routine sends an ack and also updates the window. */
void tcp_send_ack(struct sock *sk)
{
2733
	struct sk_buff *buff;
L
Linus Torvalds 已提交
2734

2735 2736 2737
	/* If we have been reset, we may not send again. */
	if (sk->sk_state == TCP_CLOSE)
		return;
L
Linus Torvalds 已提交
2738

2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749
	/* We are not putting this on the write queue, so
	 * tcp_transmit_skb() will set the ownership to this
	 * sock.
	 */
	buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
	if (buff == NULL) {
		inet_csk_schedule_ack(sk);
		inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
					  TCP_DELACK_MAX, TCP_RTO_MAX);
		return;
L
Linus Torvalds 已提交
2750
	}
2751 2752 2753

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(buff, MAX_TCP_HEADER);
C
Changli Gao 已提交
2754
	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
2755 2756 2757 2758

	/* Send it off, this clears delayed acks for us. */
	TCP_SKB_CB(buff)->when = tcp_time_stamp;
	tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC);
L
Linus Torvalds 已提交
2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778
}

/* This routine sends a packet with an out of date sequence
 * number. It assumes the other end will try to ack it.
 *
 * Question: what should we make while urgent mode?
 * 4.4BSD forces sending single byte of data. We cannot send
 * out of window data, because we have SND.NXT==SND.MAX...
 *
 * Current solution: to send TWO zero-length segments in urgent mode:
 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
 * out-of-date with SND.UNA-1 to probe window.
 */
static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
{
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;

	/* We don't queue it, tcp_transmit_skb() sets ownership. */
	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2779
	if (skb == NULL)
L
Linus Torvalds 已提交
2780 2781 2782 2783 2784 2785 2786 2787
		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
2788
	tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
L
Linus Torvalds 已提交
2789
	TCP_SKB_CB(skb)->when = tcp_time_stamp;
2790
	return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
L
Linus Torvalds 已提交
2791 2792
}

2793
/* Initiate keepalive or window probe from timer. */
L
Linus Torvalds 已提交
2794 2795
int tcp_write_wakeup(struct sock *sk)
{
2796 2797
	struct tcp_sock *tp = tcp_sk(sk);
	struct sk_buff *skb;
L
Linus Torvalds 已提交
2798

2799 2800 2801 2802 2803 2804
	if (sk->sk_state == TCP_CLOSE)
		return -1;

	if ((skb = tcp_send_head(sk)) != NULL &&
	    before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
		int err;
I
Ilpo Järvinen 已提交
2805
		unsigned int mss = tcp_current_mss(sk);
2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817
		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
2818
			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
2819 2820 2821 2822 2823
			if (tcp_fragment(sk, skb, seg_size, mss))
				return -1;
		} else if (!tcp_skb_pcount(skb))
			tcp_set_skb_tso_segs(sk, skb, mss);

E
Eric Dumazet 已提交
2824
		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
2825 2826 2827 2828 2829 2830
		TCP_SKB_CB(skb)->when = tcp_time_stamp;
		err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
		if (!err)
			tcp_event_new_data_sent(sk, skb);
		return err;
	} else {
I
Ilpo Järvinen 已提交
2831
		if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
2832 2833
			tcp_xmit_probe_skb(sk, 1);
		return tcp_xmit_probe_skb(sk, 0);
L
Linus Torvalds 已提交
2834 2835 2836 2837 2838 2839 2840 2841
	}
}

/* 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)
{
2842
	struct inet_connection_sock *icsk = inet_csk(sk);
L
Linus Torvalds 已提交
2843 2844 2845 2846 2847
	struct tcp_sock *tp = tcp_sk(sk);
	int err;

	err = tcp_write_wakeup(sk);

2848
	if (tp->packets_out || !tcp_send_head(sk)) {
L
Linus Torvalds 已提交
2849
		/* Cancel probe timer, if it is not required. */
2850
		icsk->icsk_probes_out = 0;
2851
		icsk->icsk_backoff = 0;
L
Linus Torvalds 已提交
2852 2853 2854 2855
		return;
	}

	if (err <= 0) {
2856 2857
		if (icsk->icsk_backoff < sysctl_tcp_retries2)
			icsk->icsk_backoff++;
2858
		icsk->icsk_probes_out++;
2859
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2860 2861
					  min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2862 2863
	} else {
		/* If packet was not sent due to local congestion,
2864
		 * do not backoff and do not remember icsk_probes_out.
L
Linus Torvalds 已提交
2865 2866 2867 2868
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
2869 2870
		if (!icsk->icsk_probes_out)
			icsk->icsk_probes_out = 1;
2871
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2872
					  min(icsk->icsk_rto << icsk->icsk_backoff,
2873 2874
					      TCP_RESOURCE_PROBE_INTERVAL),
					  TCP_RTO_MAX);
L
Linus Torvalds 已提交
2875 2876
	}
}