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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * INET An implementation of the TCP/IP protocol suite for the LINUX | |
3 | * operating system. INET is implemented using the BSD Socket | |
4 | * interface as the means of communication with the user level. | |
5 | * | |
6 | * Implementation of the Transmission Control Protocol(TCP). | |
7 | * | |
02c30a84 | 8 | * Authors: Ross Biro |
1da177e4 LT |
9 | * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> |
10 | * Mark Evans, <evansmp@uhura.aston.ac.uk> | |
11 | * Corey Minyard <wf-rch!minyard@relay.EU.net> | |
12 | * Florian La Roche, <flla@stud.uni-sb.de> | |
13 | * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> | |
14 | * Linus Torvalds, <torvalds@cs.helsinki.fi> | |
15 | * Alan Cox, <gw4pts@gw4pts.ampr.org> | |
16 | * Matthew Dillon, <dillon@apollo.west.oic.com> | |
17 | * Arnt Gulbrandsen, <agulbra@nvg.unit.no> | |
18 | * Jorge Cwik, <jorge@laser.satlink.net> | |
19 | */ | |
20 | ||
21 | /* | |
22 | * Changes: | |
23 | * Pedro Roque : Fast Retransmit/Recovery. | |
24 | * Two receive queues. | |
25 | * Retransmit queue handled by TCP. | |
26 | * Better retransmit timer handling. | |
27 | * New congestion avoidance. | |
28 | * Header prediction. | |
29 | * Variable renaming. | |
30 | * | |
31 | * Eric : Fast Retransmit. | |
32 | * Randy Scott : MSS option defines. | |
33 | * Eric Schenk : Fixes to slow start algorithm. | |
34 | * Eric Schenk : Yet another double ACK bug. | |
35 | * Eric Schenk : Delayed ACK bug fixes. | |
36 | * Eric Schenk : Floyd style fast retrans war avoidance. | |
37 | * David S. Miller : Don't allow zero congestion window. | |
38 | * Eric Schenk : Fix retransmitter so that it sends | |
39 | * next packet on ack of previous packet. | |
40 | * Andi Kleen : Moved open_request checking here | |
41 | * and process RSTs for open_requests. | |
42 | * Andi Kleen : Better prune_queue, and other fixes. | |
caa20d9a | 43 | * Andrey Savochkin: Fix RTT measurements in the presence of |
1da177e4 LT |
44 | * timestamps. |
45 | * Andrey Savochkin: Check sequence numbers correctly when | |
46 | * removing SACKs due to in sequence incoming | |
47 | * data segments. | |
48 | * Andi Kleen: Make sure we never ack data there is not | |
49 | * enough room for. Also make this condition | |
50 | * a fatal error if it might still happen. | |
e905a9ed | 51 | * Andi Kleen: Add tcp_measure_rcv_mss to make |
1da177e4 | 52 | * connections with MSS<min(MTU,ann. MSS) |
e905a9ed | 53 | * work without delayed acks. |
1da177e4 LT |
54 | * Andi Kleen: Process packets with PSH set in the |
55 | * fast path. | |
56 | * J Hadi Salim: ECN support | |
57 | * Andrei Gurtov, | |
58 | * Pasi Sarolahti, | |
59 | * Panu Kuhlberg: Experimental audit of TCP (re)transmission | |
60 | * engine. Lots of bugs are found. | |
61 | * Pasi Sarolahti: F-RTO for dealing with spurious RTOs | |
1da177e4 LT |
62 | */ |
63 | ||
afd46503 JP |
64 | #define pr_fmt(fmt) "TCP: " fmt |
65 | ||
1da177e4 | 66 | #include <linux/mm.h> |
5a0e3ad6 | 67 | #include <linux/slab.h> |
1da177e4 LT |
68 | #include <linux/module.h> |
69 | #include <linux/sysctl.h> | |
a0bffffc | 70 | #include <linux/kernel.h> |
ad971f61 | 71 | #include <linux/prefetch.h> |
5ffc02a1 | 72 | #include <net/dst.h> |
1da177e4 LT |
73 | #include <net/tcp.h> |
74 | #include <net/inet_common.h> | |
75 | #include <linux/ipsec.h> | |
76 | #include <asm/unaligned.h> | |
e1c8a607 | 77 | #include <linux/errqueue.h> |
1da177e4 | 78 | |
ab32ea5d BH |
79 | int sysctl_tcp_timestamps __read_mostly = 1; |
80 | int sysctl_tcp_window_scaling __read_mostly = 1; | |
81 | int sysctl_tcp_sack __read_mostly = 1; | |
94bdc978 | 82 | int sysctl_tcp_fack __read_mostly; |
dca145ff | 83 | int sysctl_tcp_max_reordering __read_mostly = 300; |
ab32ea5d BH |
84 | int sysctl_tcp_dsack __read_mostly = 1; |
85 | int sysctl_tcp_app_win __read_mostly = 31; | |
b49960a0 | 86 | int sysctl_tcp_adv_win_scale __read_mostly = 1; |
4bc2f18b | 87 | EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); |
25429d7b | 88 | EXPORT_SYMBOL(sysctl_tcp_timestamps); |
1da177e4 | 89 | |
282f23c6 | 90 | /* rfc5961 challenge ack rate limiting */ |
75ff39cc | 91 | int sysctl_tcp_challenge_ack_limit = 1000; |
282f23c6 | 92 | |
ab32ea5d BH |
93 | int sysctl_tcp_stdurg __read_mostly; |
94 | int sysctl_tcp_rfc1337 __read_mostly; | |
95 | int sysctl_tcp_max_orphans __read_mostly = NR_FILE; | |
c96fd3d4 | 96 | int sysctl_tcp_frto __read_mostly = 2; |
f6722583 | 97 | int sysctl_tcp_min_rtt_wlen __read_mostly = 300; |
ab32ea5d | 98 | int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; |
6ba8a3b1 | 99 | int sysctl_tcp_early_retrans __read_mostly = 3; |
032ee423 | 100 | int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2; |
1da177e4 | 101 | |
1da177e4 LT |
102 | #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
103 | #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ | |
104 | #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ | |
105 | #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ | |
106 | #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ | |
107 | #define FLAG_DATA_SACKED 0x20 /* New SACK. */ | |
108 | #define FLAG_ECE 0x40 /* ECE in this ACK */ | |
291a00d1 | 109 | #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */ |
1da177e4 | 110 | #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ |
e33099f9 | 111 | #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */ |
2e605294 | 112 | #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ |
564262c1 | 113 | #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ |
cadbd031 | 114 | #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ |
12fb3dd9 | 115 | #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */ |
1da177e4 LT |
116 | |
117 | #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) | |
118 | #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) | |
119 | #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) | |
120 | #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) | |
121 | ||
1da177e4 | 122 | #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) |
bdf1ee5d | 123 | #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) |
1da177e4 | 124 | |
e662ca40 YC |
125 | #define REXMIT_NONE 0 /* no loss recovery to do */ |
126 | #define REXMIT_LOST 1 /* retransmit packets marked lost */ | |
127 | #define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */ | |
128 | ||
0b9aefea MRL |
129 | static void tcp_gro_dev_warn(struct sock *sk, const struct sk_buff *skb, |
130 | unsigned int len) | |
dcb17d22 MRL |
131 | { |
132 | static bool __once __read_mostly; | |
133 | ||
134 | if (!__once) { | |
135 | struct net_device *dev; | |
136 | ||
137 | __once = true; | |
138 | ||
139 | rcu_read_lock(); | |
140 | dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif); | |
0b9aefea MRL |
141 | if (!dev || len >= dev->mtu) |
142 | pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n", | |
143 | dev ? dev->name : "Unknown driver"); | |
dcb17d22 MRL |
144 | rcu_read_unlock(); |
145 | } | |
146 | } | |
147 | ||
e905a9ed | 148 | /* Adapt the MSS value used to make delayed ack decision to the |
1da177e4 | 149 | * real world. |
e905a9ed | 150 | */ |
056834d9 | 151 | static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 152 | { |
463c84b9 | 153 | struct inet_connection_sock *icsk = inet_csk(sk); |
e905a9ed | 154 | const unsigned int lss = icsk->icsk_ack.last_seg_size; |
463c84b9 | 155 | unsigned int len; |
1da177e4 | 156 | |
e905a9ed | 157 | icsk->icsk_ack.last_seg_size = 0; |
1da177e4 LT |
158 | |
159 | /* skb->len may jitter because of SACKs, even if peer | |
160 | * sends good full-sized frames. | |
161 | */ | |
056834d9 | 162 | len = skb_shinfo(skb)->gso_size ? : skb->len; |
463c84b9 | 163 | if (len >= icsk->icsk_ack.rcv_mss) { |
dcb17d22 MRL |
164 | icsk->icsk_ack.rcv_mss = min_t(unsigned int, len, |
165 | tcp_sk(sk)->advmss); | |
0b9aefea MRL |
166 | /* Account for possibly-removed options */ |
167 | if (unlikely(len > icsk->icsk_ack.rcv_mss + | |
168 | MAX_TCP_OPTION_SPACE)) | |
169 | tcp_gro_dev_warn(sk, skb, len); | |
1da177e4 LT |
170 | } else { |
171 | /* Otherwise, we make more careful check taking into account, | |
172 | * that SACKs block is variable. | |
173 | * | |
174 | * "len" is invariant segment length, including TCP header. | |
175 | */ | |
9c70220b | 176 | len += skb->data - skb_transport_header(skb); |
bee7ca9e | 177 | if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || |
1da177e4 LT |
178 | /* If PSH is not set, packet should be |
179 | * full sized, provided peer TCP is not badly broken. | |
180 | * This observation (if it is correct 8)) allows | |
181 | * to handle super-low mtu links fairly. | |
182 | */ | |
183 | (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && | |
aa8223c7 | 184 | !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
1da177e4 LT |
185 | /* Subtract also invariant (if peer is RFC compliant), |
186 | * tcp header plus fixed timestamp option length. | |
187 | * Resulting "len" is MSS free of SACK jitter. | |
188 | */ | |
463c84b9 ACM |
189 | len -= tcp_sk(sk)->tcp_header_len; |
190 | icsk->icsk_ack.last_seg_size = len; | |
1da177e4 | 191 | if (len == lss) { |
463c84b9 | 192 | icsk->icsk_ack.rcv_mss = len; |
1da177e4 LT |
193 | return; |
194 | } | |
195 | } | |
1ef9696c AK |
196 | if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
197 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; | |
463c84b9 | 198 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
1da177e4 LT |
199 | } |
200 | } | |
201 | ||
463c84b9 | 202 | static void tcp_incr_quickack(struct sock *sk) |
1da177e4 | 203 | { |
463c84b9 | 204 | struct inet_connection_sock *icsk = inet_csk(sk); |
95c96174 | 205 | unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); |
1da177e4 | 206 | |
056834d9 IJ |
207 | if (quickacks == 0) |
208 | quickacks = 2; | |
463c84b9 ACM |
209 | if (quickacks > icsk->icsk_ack.quick) |
210 | icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); | |
1da177e4 LT |
211 | } |
212 | ||
1b9f4092 | 213 | static void tcp_enter_quickack_mode(struct sock *sk) |
1da177e4 | 214 | { |
463c84b9 ACM |
215 | struct inet_connection_sock *icsk = inet_csk(sk); |
216 | tcp_incr_quickack(sk); | |
217 | icsk->icsk_ack.pingpong = 0; | |
218 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
1da177e4 LT |
219 | } |
220 | ||
221 | /* Send ACKs quickly, if "quick" count is not exhausted | |
222 | * and the session is not interactive. | |
223 | */ | |
224 | ||
2251ae46 | 225 | static bool tcp_in_quickack_mode(struct sock *sk) |
1da177e4 | 226 | { |
463c84b9 | 227 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2251ae46 | 228 | const struct dst_entry *dst = __sk_dst_get(sk); |
a2a385d6 | 229 | |
2251ae46 JM |
230 | return (dst && dst_metric(dst, RTAX_QUICKACK)) || |
231 | (icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong); | |
1da177e4 LT |
232 | } |
233 | ||
735d3831 | 234 | static void tcp_ecn_queue_cwr(struct tcp_sock *tp) |
bdf1ee5d | 235 | { |
056834d9 | 236 | if (tp->ecn_flags & TCP_ECN_OK) |
bdf1ee5d IJ |
237 | tp->ecn_flags |= TCP_ECN_QUEUE_CWR; |
238 | } | |
239 | ||
735d3831 | 240 | static void tcp_ecn_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) |
bdf1ee5d IJ |
241 | { |
242 | if (tcp_hdr(skb)->cwr) | |
243 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; | |
244 | } | |
245 | ||
735d3831 | 246 | static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp) |
bdf1ee5d IJ |
247 | { |
248 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; | |
249 | } | |
250 | ||
735d3831 | 251 | static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) |
bdf1ee5d | 252 | { |
b82d1bb4 | 253 | switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { |
7a269ffa | 254 | case INET_ECN_NOT_ECT: |
bdf1ee5d | 255 | /* Funny extension: if ECT is not set on a segment, |
7a269ffa ED |
256 | * and we already seen ECT on a previous segment, |
257 | * it is probably a retransmit. | |
258 | */ | |
259 | if (tp->ecn_flags & TCP_ECN_SEEN) | |
bdf1ee5d | 260 | tcp_enter_quickack_mode((struct sock *)tp); |
7a269ffa ED |
261 | break; |
262 | case INET_ECN_CE: | |
9890092e FW |
263 | if (tcp_ca_needs_ecn((struct sock *)tp)) |
264 | tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_IS_CE); | |
265 | ||
aae06bf5 ED |
266 | if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { |
267 | /* Better not delay acks, sender can have a very low cwnd */ | |
268 | tcp_enter_quickack_mode((struct sock *)tp); | |
269 | tp->ecn_flags |= TCP_ECN_DEMAND_CWR; | |
270 | } | |
9890092e FW |
271 | tp->ecn_flags |= TCP_ECN_SEEN; |
272 | break; | |
7a269ffa | 273 | default: |
9890092e FW |
274 | if (tcp_ca_needs_ecn((struct sock *)tp)) |
275 | tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_NO_CE); | |
7a269ffa | 276 | tp->ecn_flags |= TCP_ECN_SEEN; |
9890092e | 277 | break; |
bdf1ee5d IJ |
278 | } |
279 | } | |
280 | ||
735d3831 FW |
281 | static void tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) |
282 | { | |
283 | if (tp->ecn_flags & TCP_ECN_OK) | |
284 | __tcp_ecn_check_ce(tp, skb); | |
285 | } | |
286 | ||
287 | static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) | |
bdf1ee5d | 288 | { |
056834d9 | 289 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) |
bdf1ee5d IJ |
290 | tp->ecn_flags &= ~TCP_ECN_OK; |
291 | } | |
292 | ||
735d3831 | 293 | static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) |
bdf1ee5d | 294 | { |
056834d9 | 295 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) |
bdf1ee5d IJ |
296 | tp->ecn_flags &= ~TCP_ECN_OK; |
297 | } | |
298 | ||
735d3831 | 299 | static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) |
bdf1ee5d | 300 | { |
056834d9 | 301 | if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) |
a2a385d6 ED |
302 | return true; |
303 | return false; | |
bdf1ee5d IJ |
304 | } |
305 | ||
1da177e4 LT |
306 | /* Buffer size and advertised window tuning. |
307 | * | |
308 | * 1. Tuning sk->sk_sndbuf, when connection enters established state. | |
309 | */ | |
310 | ||
6ae70532 | 311 | static void tcp_sndbuf_expand(struct sock *sk) |
1da177e4 | 312 | { |
6ae70532 | 313 | const struct tcp_sock *tp = tcp_sk(sk); |
77bfc174 | 314 | const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; |
6ae70532 ED |
315 | int sndmem, per_mss; |
316 | u32 nr_segs; | |
317 | ||
318 | /* Worst case is non GSO/TSO : each frame consumes one skb | |
319 | * and skb->head is kmalloced using power of two area of memory | |
320 | */ | |
321 | per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + | |
322 | MAX_TCP_HEADER + | |
323 | SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); | |
324 | ||
325 | per_mss = roundup_pow_of_two(per_mss) + | |
326 | SKB_DATA_ALIGN(sizeof(struct sk_buff)); | |
327 | ||
328 | nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd); | |
329 | nr_segs = max_t(u32, nr_segs, tp->reordering + 1); | |
330 | ||
331 | /* Fast Recovery (RFC 5681 3.2) : | |
332 | * Cubic needs 1.7 factor, rounded to 2 to include | |
333 | * extra cushion (application might react slowly to POLLOUT) | |
334 | */ | |
77bfc174 YC |
335 | sndmem = ca_ops->sndbuf_expand ? ca_ops->sndbuf_expand(sk) : 2; |
336 | sndmem *= nr_segs * per_mss; | |
1da177e4 | 337 | |
06a59ecb ED |
338 | if (sk->sk_sndbuf < sndmem) |
339 | sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); | |
1da177e4 LT |
340 | } |
341 | ||
342 | /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) | |
343 | * | |
344 | * All tcp_full_space() is split to two parts: "network" buffer, allocated | |
345 | * forward and advertised in receiver window (tp->rcv_wnd) and | |
346 | * "application buffer", required to isolate scheduling/application | |
347 | * latencies from network. | |
348 | * window_clamp is maximal advertised window. It can be less than | |
349 | * tcp_full_space(), in this case tcp_full_space() - window_clamp | |
350 | * is reserved for "application" buffer. The less window_clamp is | |
351 | * the smoother our behaviour from viewpoint of network, but the lower | |
352 | * throughput and the higher sensitivity of the connection to losses. 8) | |
353 | * | |
354 | * rcv_ssthresh is more strict window_clamp used at "slow start" | |
355 | * phase to predict further behaviour of this connection. | |
356 | * It is used for two goals: | |
357 | * - to enforce header prediction at sender, even when application | |
358 | * requires some significant "application buffer". It is check #1. | |
359 | * - to prevent pruning of receive queue because of misprediction | |
360 | * of receiver window. Check #2. | |
361 | * | |
362 | * The scheme does not work when sender sends good segments opening | |
caa20d9a | 363 | * window and then starts to feed us spaghetti. But it should work |
1da177e4 LT |
364 | * in common situations. Otherwise, we have to rely on queue collapsing. |
365 | */ | |
366 | ||
367 | /* Slow part of check#2. */ | |
9e412ba7 | 368 | static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 369 | { |
9e412ba7 | 370 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 371 | /* Optimize this! */ |
dfd4f0ae ED |
372 | int truesize = tcp_win_from_space(skb->truesize) >> 1; |
373 | int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; | |
1da177e4 LT |
374 | |
375 | while (tp->rcv_ssthresh <= window) { | |
376 | if (truesize <= skb->len) | |
463c84b9 | 377 | return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
1da177e4 LT |
378 | |
379 | truesize >>= 1; | |
380 | window >>= 1; | |
381 | } | |
382 | return 0; | |
383 | } | |
384 | ||
cf533ea5 | 385 | static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 386 | { |
9e412ba7 IJ |
387 | struct tcp_sock *tp = tcp_sk(sk); |
388 | ||
1da177e4 LT |
389 | /* Check #1 */ |
390 | if (tp->rcv_ssthresh < tp->window_clamp && | |
391 | (int)tp->rcv_ssthresh < tcp_space(sk) && | |
b8da51eb | 392 | !tcp_under_memory_pressure(sk)) { |
1da177e4 LT |
393 | int incr; |
394 | ||
395 | /* Check #2. Increase window, if skb with such overhead | |
396 | * will fit to rcvbuf in future. | |
397 | */ | |
398 | if (tcp_win_from_space(skb->truesize) <= skb->len) | |
056834d9 | 399 | incr = 2 * tp->advmss; |
1da177e4 | 400 | else |
9e412ba7 | 401 | incr = __tcp_grow_window(sk, skb); |
1da177e4 LT |
402 | |
403 | if (incr) { | |
4d846f02 | 404 | incr = max_t(int, incr, 2 * skb->len); |
056834d9 IJ |
405 | tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, |
406 | tp->window_clamp); | |
463c84b9 | 407 | inet_csk(sk)->icsk_ack.quick |= 1; |
1da177e4 LT |
408 | } |
409 | } | |
410 | } | |
411 | ||
412 | /* 3. Tuning rcvbuf, when connection enters established state. */ | |
1da177e4 LT |
413 | static void tcp_fixup_rcvbuf(struct sock *sk) |
414 | { | |
e9266a02 | 415 | u32 mss = tcp_sk(sk)->advmss; |
e9266a02 | 416 | int rcvmem; |
1da177e4 | 417 | |
85f16525 YC |
418 | rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) * |
419 | tcp_default_init_rwnd(mss); | |
e9266a02 | 420 | |
b0983d3c ED |
421 | /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency |
422 | * Allow enough cushion so that sender is not limited by our window | |
423 | */ | |
424 | if (sysctl_tcp_moderate_rcvbuf) | |
425 | rcvmem <<= 2; | |
426 | ||
e9266a02 ED |
427 | if (sk->sk_rcvbuf < rcvmem) |
428 | sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]); | |
1da177e4 LT |
429 | } |
430 | ||
caa20d9a | 431 | /* 4. Try to fixup all. It is made immediately after connection enters |
1da177e4 LT |
432 | * established state. |
433 | */ | |
10467163 | 434 | void tcp_init_buffer_space(struct sock *sk) |
1da177e4 LT |
435 | { |
436 | struct tcp_sock *tp = tcp_sk(sk); | |
437 | int maxwin; | |
438 | ||
439 | if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) | |
440 | tcp_fixup_rcvbuf(sk); | |
441 | if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) | |
6ae70532 | 442 | tcp_sndbuf_expand(sk); |
1da177e4 LT |
443 | |
444 | tp->rcvq_space.space = tp->rcv_wnd; | |
b0983d3c ED |
445 | tp->rcvq_space.time = tcp_time_stamp; |
446 | tp->rcvq_space.seq = tp->copied_seq; | |
1da177e4 LT |
447 | |
448 | maxwin = tcp_full_space(sk); | |
449 | ||
450 | if (tp->window_clamp >= maxwin) { | |
451 | tp->window_clamp = maxwin; | |
452 | ||
453 | if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) | |
454 | tp->window_clamp = max(maxwin - | |
455 | (maxwin >> sysctl_tcp_app_win), | |
456 | 4 * tp->advmss); | |
457 | } | |
458 | ||
459 | /* Force reservation of one segment. */ | |
460 | if (sysctl_tcp_app_win && | |
461 | tp->window_clamp > 2 * tp->advmss && | |
462 | tp->window_clamp + tp->advmss > maxwin) | |
463 | tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); | |
464 | ||
465 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); | |
466 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
467 | } | |
468 | ||
1da177e4 | 469 | /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
9e412ba7 | 470 | static void tcp_clamp_window(struct sock *sk) |
1da177e4 | 471 | { |
9e412ba7 | 472 | struct tcp_sock *tp = tcp_sk(sk); |
6687e988 | 473 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 | 474 | |
6687e988 | 475 | icsk->icsk_ack.quick = 0; |
1da177e4 | 476 | |
326f36e9 JH |
477 | if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && |
478 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && | |
b8da51eb | 479 | !tcp_under_memory_pressure(sk) && |
180d8cd9 | 480 | sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { |
326f36e9 JH |
481 | sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), |
482 | sysctl_tcp_rmem[2]); | |
1da177e4 | 483 | } |
326f36e9 | 484 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
056834d9 | 485 | tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); |
1da177e4 LT |
486 | } |
487 | ||
40efc6fa SH |
488 | /* Initialize RCV_MSS value. |
489 | * RCV_MSS is an our guess about MSS used by the peer. | |
490 | * We haven't any direct information about the MSS. | |
491 | * It's better to underestimate the RCV_MSS rather than overestimate. | |
492 | * Overestimations make us ACKing less frequently than needed. | |
493 | * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). | |
494 | */ | |
495 | void tcp_initialize_rcv_mss(struct sock *sk) | |
496 | { | |
cf533ea5 | 497 | const struct tcp_sock *tp = tcp_sk(sk); |
40efc6fa SH |
498 | unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); |
499 | ||
056834d9 | 500 | hint = min(hint, tp->rcv_wnd / 2); |
bee7ca9e | 501 | hint = min(hint, TCP_MSS_DEFAULT); |
40efc6fa SH |
502 | hint = max(hint, TCP_MIN_MSS); |
503 | ||
504 | inet_csk(sk)->icsk_ack.rcv_mss = hint; | |
505 | } | |
4bc2f18b | 506 | EXPORT_SYMBOL(tcp_initialize_rcv_mss); |
40efc6fa | 507 | |
1da177e4 LT |
508 | /* Receiver "autotuning" code. |
509 | * | |
510 | * The algorithm for RTT estimation w/o timestamps is based on | |
511 | * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. | |
631dd1a8 | 512 | * <http://public.lanl.gov/radiant/pubs.html#DRS> |
1da177e4 LT |
513 | * |
514 | * More detail on this code can be found at | |
631dd1a8 | 515 | * <http://staff.psc.edu/jheffner/>, |
1da177e4 LT |
516 | * though this reference is out of date. A new paper |
517 | * is pending. | |
518 | */ | |
519 | static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) | |
520 | { | |
521 | u32 new_sample = tp->rcv_rtt_est.rtt; | |
522 | long m = sample; | |
523 | ||
524 | if (m == 0) | |
525 | m = 1; | |
526 | ||
527 | if (new_sample != 0) { | |
528 | /* If we sample in larger samples in the non-timestamp | |
529 | * case, we could grossly overestimate the RTT especially | |
530 | * with chatty applications or bulk transfer apps which | |
531 | * are stalled on filesystem I/O. | |
532 | * | |
533 | * Also, since we are only going for a minimum in the | |
31f34269 | 534 | * non-timestamp case, we do not smooth things out |
caa20d9a | 535 | * else with timestamps disabled convergence takes too |
1da177e4 LT |
536 | * long. |
537 | */ | |
538 | if (!win_dep) { | |
539 | m -= (new_sample >> 3); | |
540 | new_sample += m; | |
18a223e0 NC |
541 | } else { |
542 | m <<= 3; | |
543 | if (m < new_sample) | |
544 | new_sample = m; | |
545 | } | |
1da177e4 | 546 | } else { |
caa20d9a | 547 | /* No previous measure. */ |
1da177e4 LT |
548 | new_sample = m << 3; |
549 | } | |
550 | ||
551 | if (tp->rcv_rtt_est.rtt != new_sample) | |
552 | tp->rcv_rtt_est.rtt = new_sample; | |
553 | } | |
554 | ||
555 | static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) | |
556 | { | |
557 | if (tp->rcv_rtt_est.time == 0) | |
558 | goto new_measure; | |
559 | if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) | |
560 | return; | |
651913ce | 561 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1); |
1da177e4 LT |
562 | |
563 | new_measure: | |
564 | tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; | |
565 | tp->rcv_rtt_est.time = tcp_time_stamp; | |
566 | } | |
567 | ||
056834d9 IJ |
568 | static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, |
569 | const struct sk_buff *skb) | |
1da177e4 | 570 | { |
463c84b9 | 571 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
572 | if (tp->rx_opt.rcv_tsecr && |
573 | (TCP_SKB_CB(skb)->end_seq - | |
463c84b9 | 574 | TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) |
1da177e4 LT |
575 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); |
576 | } | |
577 | ||
578 | /* | |
579 | * This function should be called every time data is copied to user space. | |
580 | * It calculates the appropriate TCP receive buffer space. | |
581 | */ | |
582 | void tcp_rcv_space_adjust(struct sock *sk) | |
583 | { | |
584 | struct tcp_sock *tp = tcp_sk(sk); | |
585 | int time; | |
b0983d3c | 586 | int copied; |
e905a9ed | 587 | |
1da177e4 | 588 | time = tcp_time_stamp - tp->rcvq_space.time; |
056834d9 | 589 | if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) |
1da177e4 | 590 | return; |
e905a9ed | 591 | |
b0983d3c ED |
592 | /* Number of bytes copied to user in last RTT */ |
593 | copied = tp->copied_seq - tp->rcvq_space.seq; | |
594 | if (copied <= tp->rcvq_space.space) | |
595 | goto new_measure; | |
596 | ||
597 | /* A bit of theory : | |
598 | * copied = bytes received in previous RTT, our base window | |
599 | * To cope with packet losses, we need a 2x factor | |
600 | * To cope with slow start, and sender growing its cwin by 100 % | |
601 | * every RTT, we need a 4x factor, because the ACK we are sending | |
602 | * now is for the next RTT, not the current one : | |
603 | * <prev RTT . ><current RTT .. ><next RTT .... > | |
604 | */ | |
605 | ||
606 | if (sysctl_tcp_moderate_rcvbuf && | |
607 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { | |
608 | int rcvwin, rcvmem, rcvbuf; | |
1da177e4 | 609 | |
b0983d3c ED |
610 | /* minimal window to cope with packet losses, assuming |
611 | * steady state. Add some cushion because of small variations. | |
612 | */ | |
613 | rcvwin = (copied << 1) + 16 * tp->advmss; | |
1da177e4 | 614 | |
b0983d3c ED |
615 | /* If rate increased by 25%, |
616 | * assume slow start, rcvwin = 3 * copied | |
617 | * If rate increased by 50%, | |
618 | * assume sender can use 2x growth, rcvwin = 4 * copied | |
619 | */ | |
620 | if (copied >= | |
621 | tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) { | |
622 | if (copied >= | |
623 | tp->rcvq_space.space + (tp->rcvq_space.space >> 1)) | |
624 | rcvwin <<= 1; | |
625 | else | |
626 | rcvwin += (rcvwin >> 1); | |
627 | } | |
1da177e4 | 628 | |
b0983d3c ED |
629 | rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); |
630 | while (tcp_win_from_space(rcvmem) < tp->advmss) | |
631 | rcvmem += 128; | |
1da177e4 | 632 | |
b0983d3c ED |
633 | rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]); |
634 | if (rcvbuf > sk->sk_rcvbuf) { | |
635 | sk->sk_rcvbuf = rcvbuf; | |
1da177e4 | 636 | |
b0983d3c ED |
637 | /* Make the window clamp follow along. */ |
638 | tp->window_clamp = rcvwin; | |
1da177e4 LT |
639 | } |
640 | } | |
b0983d3c | 641 | tp->rcvq_space.space = copied; |
e905a9ed | 642 | |
1da177e4 LT |
643 | new_measure: |
644 | tp->rcvq_space.seq = tp->copied_seq; | |
645 | tp->rcvq_space.time = tcp_time_stamp; | |
646 | } | |
647 | ||
648 | /* There is something which you must keep in mind when you analyze the | |
649 | * behavior of the tp->ato delayed ack timeout interval. When a | |
650 | * connection starts up, we want to ack as quickly as possible. The | |
651 | * problem is that "good" TCP's do slow start at the beginning of data | |
652 | * transmission. The means that until we send the first few ACK's the | |
653 | * sender will sit on his end and only queue most of his data, because | |
654 | * he can only send snd_cwnd unacked packets at any given time. For | |
655 | * each ACK we send, he increments snd_cwnd and transmits more of his | |
656 | * queue. -DaveM | |
657 | */ | |
9e412ba7 | 658 | static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) |
1da177e4 | 659 | { |
9e412ba7 | 660 | struct tcp_sock *tp = tcp_sk(sk); |
463c84b9 | 661 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
662 | u32 now; |
663 | ||
463c84b9 | 664 | inet_csk_schedule_ack(sk); |
1da177e4 | 665 | |
463c84b9 | 666 | tcp_measure_rcv_mss(sk, skb); |
1da177e4 LT |
667 | |
668 | tcp_rcv_rtt_measure(tp); | |
e905a9ed | 669 | |
1da177e4 LT |
670 | now = tcp_time_stamp; |
671 | ||
463c84b9 | 672 | if (!icsk->icsk_ack.ato) { |
1da177e4 LT |
673 | /* The _first_ data packet received, initialize |
674 | * delayed ACK engine. | |
675 | */ | |
463c84b9 ACM |
676 | tcp_incr_quickack(sk); |
677 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
1da177e4 | 678 | } else { |
463c84b9 | 679 | int m = now - icsk->icsk_ack.lrcvtime; |
1da177e4 | 680 | |
056834d9 | 681 | if (m <= TCP_ATO_MIN / 2) { |
1da177e4 | 682 | /* The fastest case is the first. */ |
463c84b9 ACM |
683 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
684 | } else if (m < icsk->icsk_ack.ato) { | |
685 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; | |
686 | if (icsk->icsk_ack.ato > icsk->icsk_rto) | |
687 | icsk->icsk_ack.ato = icsk->icsk_rto; | |
688 | } else if (m > icsk->icsk_rto) { | |
caa20d9a | 689 | /* Too long gap. Apparently sender failed to |
1da177e4 LT |
690 | * restart window, so that we send ACKs quickly. |
691 | */ | |
463c84b9 | 692 | tcp_incr_quickack(sk); |
3ab224be | 693 | sk_mem_reclaim(sk); |
1da177e4 LT |
694 | } |
695 | } | |
463c84b9 | 696 | icsk->icsk_ack.lrcvtime = now; |
1da177e4 | 697 | |
735d3831 | 698 | tcp_ecn_check_ce(tp, skb); |
1da177e4 LT |
699 | |
700 | if (skb->len >= 128) | |
9e412ba7 | 701 | tcp_grow_window(sk, skb); |
1da177e4 LT |
702 | } |
703 | ||
1da177e4 LT |
704 | /* Called to compute a smoothed rtt estimate. The data fed to this |
705 | * routine either comes from timestamps, or from segments that were | |
706 | * known _not_ to have been retransmitted [see Karn/Partridge | |
707 | * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 | |
708 | * piece by Van Jacobson. | |
709 | * NOTE: the next three routines used to be one big routine. | |
710 | * To save cycles in the RFC 1323 implementation it was better to break | |
711 | * it up into three procedures. -- erics | |
712 | */ | |
740b0f18 | 713 | static void tcp_rtt_estimator(struct sock *sk, long mrtt_us) |
1da177e4 | 714 | { |
6687e988 | 715 | struct tcp_sock *tp = tcp_sk(sk); |
740b0f18 ED |
716 | long m = mrtt_us; /* RTT */ |
717 | u32 srtt = tp->srtt_us; | |
1da177e4 | 718 | |
1da177e4 LT |
719 | /* The following amusing code comes from Jacobson's |
720 | * article in SIGCOMM '88. Note that rtt and mdev | |
721 | * are scaled versions of rtt and mean deviation. | |
e905a9ed | 722 | * This is designed to be as fast as possible |
1da177e4 LT |
723 | * m stands for "measurement". |
724 | * | |
725 | * On a 1990 paper the rto value is changed to: | |
726 | * RTO = rtt + 4 * mdev | |
727 | * | |
728 | * Funny. This algorithm seems to be very broken. | |
729 | * These formulae increase RTO, when it should be decreased, increase | |
31f34269 | 730 | * too slowly, when it should be increased quickly, decrease too quickly |
1da177e4 LT |
731 | * etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
732 | * does not matter how to _calculate_ it. Seems, it was trap | |
733 | * that VJ failed to avoid. 8) | |
734 | */ | |
4a5ab4e2 ED |
735 | if (srtt != 0) { |
736 | m -= (srtt >> 3); /* m is now error in rtt est */ | |
737 | srtt += m; /* rtt = 7/8 rtt + 1/8 new */ | |
1da177e4 LT |
738 | if (m < 0) { |
739 | m = -m; /* m is now abs(error) */ | |
740b0f18 | 740 | m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
1da177e4 LT |
741 | /* This is similar to one of Eifel findings. |
742 | * Eifel blocks mdev updates when rtt decreases. | |
743 | * This solution is a bit different: we use finer gain | |
744 | * for mdev in this case (alpha*beta). | |
745 | * Like Eifel it also prevents growth of rto, | |
746 | * but also it limits too fast rto decreases, | |
747 | * happening in pure Eifel. | |
748 | */ | |
749 | if (m > 0) | |
750 | m >>= 3; | |
751 | } else { | |
740b0f18 | 752 | m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
1da177e4 | 753 | } |
740b0f18 ED |
754 | tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */ |
755 | if (tp->mdev_us > tp->mdev_max_us) { | |
756 | tp->mdev_max_us = tp->mdev_us; | |
757 | if (tp->mdev_max_us > tp->rttvar_us) | |
758 | tp->rttvar_us = tp->mdev_max_us; | |
1da177e4 LT |
759 | } |
760 | if (after(tp->snd_una, tp->rtt_seq)) { | |
740b0f18 ED |
761 | if (tp->mdev_max_us < tp->rttvar_us) |
762 | tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2; | |
1da177e4 | 763 | tp->rtt_seq = tp->snd_nxt; |
740b0f18 | 764 | tp->mdev_max_us = tcp_rto_min_us(sk); |
1da177e4 LT |
765 | } |
766 | } else { | |
767 | /* no previous measure. */ | |
4a5ab4e2 | 768 | srtt = m << 3; /* take the measured time to be rtt */ |
740b0f18 ED |
769 | tp->mdev_us = m << 1; /* make sure rto = 3*rtt */ |
770 | tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk)); | |
771 | tp->mdev_max_us = tp->rttvar_us; | |
1da177e4 LT |
772 | tp->rtt_seq = tp->snd_nxt; |
773 | } | |
740b0f18 | 774 | tp->srtt_us = max(1U, srtt); |
1da177e4 LT |
775 | } |
776 | ||
95bd09eb ED |
777 | /* Set the sk_pacing_rate to allow proper sizing of TSO packets. |
778 | * Note: TCP stack does not yet implement pacing. | |
779 | * FQ packet scheduler can be used to implement cheap but effective | |
780 | * TCP pacing, to smooth the burst on large writes when packets | |
781 | * in flight is significantly lower than cwnd (or rwin) | |
782 | */ | |
43e122b0 ED |
783 | int sysctl_tcp_pacing_ss_ratio __read_mostly = 200; |
784 | int sysctl_tcp_pacing_ca_ratio __read_mostly = 120; | |
785 | ||
95bd09eb ED |
786 | static void tcp_update_pacing_rate(struct sock *sk) |
787 | { | |
788 | const struct tcp_sock *tp = tcp_sk(sk); | |
789 | u64 rate; | |
790 | ||
791 | /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */ | |
43e122b0 ED |
792 | rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3); |
793 | ||
794 | /* current rate is (cwnd * mss) / srtt | |
795 | * In Slow Start [1], set sk_pacing_rate to 200 % the current rate. | |
796 | * In Congestion Avoidance phase, set it to 120 % the current rate. | |
797 | * | |
798 | * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh) | |
799 | * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching | |
800 | * end of slow start and should slow down. | |
801 | */ | |
802 | if (tp->snd_cwnd < tp->snd_ssthresh / 2) | |
803 | rate *= sysctl_tcp_pacing_ss_ratio; | |
804 | else | |
805 | rate *= sysctl_tcp_pacing_ca_ratio; | |
95bd09eb ED |
806 | |
807 | rate *= max(tp->snd_cwnd, tp->packets_out); | |
808 | ||
740b0f18 ED |
809 | if (likely(tp->srtt_us)) |
810 | do_div(rate, tp->srtt_us); | |
95bd09eb | 811 | |
ba537427 ED |
812 | /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate |
813 | * without any lock. We want to make sure compiler wont store | |
814 | * intermediate values in this location. | |
815 | */ | |
816 | ACCESS_ONCE(sk->sk_pacing_rate) = min_t(u64, rate, | |
817 | sk->sk_max_pacing_rate); | |
95bd09eb ED |
818 | } |
819 | ||
1da177e4 LT |
820 | /* Calculate rto without backoff. This is the second half of Van Jacobson's |
821 | * routine referred to above. | |
822 | */ | |
f7e56a76 | 823 | static void tcp_set_rto(struct sock *sk) |
1da177e4 | 824 | { |
463c84b9 | 825 | const struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
826 | /* Old crap is replaced with new one. 8) |
827 | * | |
828 | * More seriously: | |
829 | * 1. If rtt variance happened to be less 50msec, it is hallucination. | |
830 | * It cannot be less due to utterly erratic ACK generation made | |
831 | * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ | |
832 | * to do with delayed acks, because at cwnd>2 true delack timeout | |
833 | * is invisible. Actually, Linux-2.4 also generates erratic | |
caa20d9a | 834 | * ACKs in some circumstances. |
1da177e4 | 835 | */ |
f1ecd5d9 | 836 | inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); |
1da177e4 LT |
837 | |
838 | /* 2. Fixups made earlier cannot be right. | |
839 | * If we do not estimate RTO correctly without them, | |
840 | * all the algo is pure shit and should be replaced | |
caa20d9a | 841 | * with correct one. It is exactly, which we pretend to do. |
1da177e4 | 842 | */ |
1da177e4 | 843 | |
ee6aac59 IJ |
844 | /* NOTE: clamping at TCP_RTO_MIN is not required, current algo |
845 | * guarantees that rto is higher. | |
846 | */ | |
f1ecd5d9 | 847 | tcp_bound_rto(sk); |
1da177e4 LT |
848 | } |
849 | ||
cf533ea5 | 850 | __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) |
1da177e4 LT |
851 | { |
852 | __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); | |
853 | ||
22b71c8f | 854 | if (!cwnd) |
442b9635 | 855 | cwnd = TCP_INIT_CWND; |
1da177e4 LT |
856 | return min_t(__u32, cwnd, tp->snd_cwnd_clamp); |
857 | } | |
858 | ||
e60402d0 IJ |
859 | /* |
860 | * Packet counting of FACK is based on in-order assumptions, therefore TCP | |
861 | * disables it when reordering is detected | |
862 | */ | |
4aabd8ef | 863 | void tcp_disable_fack(struct tcp_sock *tp) |
e60402d0 | 864 | { |
85cc391c IJ |
865 | /* RFC3517 uses different metric in lost marker => reset on change */ |
866 | if (tcp_is_fack(tp)) | |
867 | tp->lost_skb_hint = NULL; | |
ab56222a | 868 | tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED; |
e60402d0 IJ |
869 | } |
870 | ||
564262c1 | 871 | /* Take a notice that peer is sending D-SACKs */ |
e60402d0 IJ |
872 | static void tcp_dsack_seen(struct tcp_sock *tp) |
873 | { | |
ab56222a | 874 | tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; |
e60402d0 IJ |
875 | } |
876 | ||
6687e988 ACM |
877 | static void tcp_update_reordering(struct sock *sk, const int metric, |
878 | const int ts) | |
1da177e4 | 879 | { |
6687e988 | 880 | struct tcp_sock *tp = tcp_sk(sk); |
2d2517ee | 881 | int mib_idx; |
40b215e5 | 882 | |
2d2517ee | 883 | if (metric > tp->reordering) { |
dca145ff | 884 | tp->reordering = min(sysctl_tcp_max_reordering, metric); |
1da177e4 | 885 | |
1da177e4 | 886 | #if FASTRETRANS_DEBUG > 1 |
91df42be JP |
887 | pr_debug("Disorder%d %d %u f%u s%u rr%d\n", |
888 | tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, | |
889 | tp->reordering, | |
890 | tp->fackets_out, | |
891 | tp->sacked_out, | |
892 | tp->undo_marker ? tp->undo_retrans : 0); | |
1da177e4 | 893 | #endif |
e60402d0 | 894 | tcp_disable_fack(tp); |
1da177e4 | 895 | } |
eed530b6 | 896 | |
4f41b1c5 | 897 | tp->rack.reord = 1; |
2d2517ee YC |
898 | |
899 | /* This exciting event is worth to be remembered. 8) */ | |
900 | if (ts) | |
901 | mib_idx = LINUX_MIB_TCPTSREORDER; | |
902 | else if (tcp_is_reno(tp)) | |
903 | mib_idx = LINUX_MIB_TCPRENOREORDER; | |
904 | else if (tcp_is_fack(tp)) | |
905 | mib_idx = LINUX_MIB_TCPFACKREORDER; | |
906 | else | |
907 | mib_idx = LINUX_MIB_TCPSACKREORDER; | |
908 | ||
909 | NET_INC_STATS(sock_net(sk), mib_idx); | |
1da177e4 LT |
910 | } |
911 | ||
006f582c | 912 | /* This must be called before lost_out is incremented */ |
c8c213f2 IJ |
913 | static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) |
914 | { | |
51456b29 | 915 | if (!tp->retransmit_skb_hint || |
c8c213f2 IJ |
916 | before(TCP_SKB_CB(skb)->seq, |
917 | TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) | |
006f582c | 918 | tp->retransmit_skb_hint = skb; |
c8c213f2 IJ |
919 | } |
920 | ||
0682e690 NC |
921 | /* Sum the number of packets on the wire we have marked as lost. |
922 | * There are two cases we care about here: | |
923 | * a) Packet hasn't been marked lost (nor retransmitted), | |
924 | * and this is the first loss. | |
925 | * b) Packet has been marked both lost and retransmitted, | |
926 | * and this means we think it was lost again. | |
927 | */ | |
928 | static void tcp_sum_lost(struct tcp_sock *tp, struct sk_buff *skb) | |
929 | { | |
930 | __u8 sacked = TCP_SKB_CB(skb)->sacked; | |
931 | ||
932 | if (!(sacked & TCPCB_LOST) || | |
933 | ((sacked & TCPCB_LOST) && (sacked & TCPCB_SACKED_RETRANS))) | |
934 | tp->lost += tcp_skb_pcount(skb); | |
935 | } | |
936 | ||
41ea36e3 IJ |
937 | static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) |
938 | { | |
939 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { | |
940 | tcp_verify_retransmit_hint(tp, skb); | |
941 | ||
942 | tp->lost_out += tcp_skb_pcount(skb); | |
0682e690 | 943 | tcp_sum_lost(tp, skb); |
41ea36e3 IJ |
944 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
945 | } | |
946 | } | |
947 | ||
4f41b1c5 | 948 | void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb) |
006f582c IJ |
949 | { |
950 | tcp_verify_retransmit_hint(tp, skb); | |
951 | ||
0682e690 | 952 | tcp_sum_lost(tp, skb); |
006f582c IJ |
953 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
954 | tp->lost_out += tcp_skb_pcount(skb); | |
955 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
956 | } | |
957 | } | |
958 | ||
1da177e4 LT |
959 | /* This procedure tags the retransmission queue when SACKs arrive. |
960 | * | |
961 | * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). | |
962 | * Packets in queue with these bits set are counted in variables | |
963 | * sacked_out, retrans_out and lost_out, correspondingly. | |
964 | * | |
965 | * Valid combinations are: | |
966 | * Tag InFlight Description | |
967 | * 0 1 - orig segment is in flight. | |
968 | * S 0 - nothing flies, orig reached receiver. | |
969 | * L 0 - nothing flies, orig lost by net. | |
970 | * R 2 - both orig and retransmit are in flight. | |
971 | * L|R 1 - orig is lost, retransmit is in flight. | |
972 | * S|R 1 - orig reached receiver, retrans is still in flight. | |
973 | * (L|S|R is logically valid, it could occur when L|R is sacked, | |
974 | * but it is equivalent to plain S and code short-curcuits it to S. | |
975 | * L|S is logically invalid, it would mean -1 packet in flight 8)) | |
976 | * | |
977 | * These 6 states form finite state machine, controlled by the following events: | |
978 | * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) | |
979 | * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) | |
974c1236 | 980 | * 3. Loss detection event of two flavors: |
1da177e4 LT |
981 | * A. Scoreboard estimator decided the packet is lost. |
982 | * A'. Reno "three dupacks" marks head of queue lost. | |
974c1236 YC |
983 | * A''. Its FACK modification, head until snd.fack is lost. |
984 | * B. SACK arrives sacking SND.NXT at the moment, when the | |
1da177e4 LT |
985 | * segment was retransmitted. |
986 | * 4. D-SACK added new rule: D-SACK changes any tag to S. | |
987 | * | |
988 | * It is pleasant to note, that state diagram turns out to be commutative, | |
989 | * so that we are allowed not to be bothered by order of our actions, | |
990 | * when multiple events arrive simultaneously. (see the function below). | |
991 | * | |
992 | * Reordering detection. | |
993 | * -------------------- | |
994 | * Reordering metric is maximal distance, which a packet can be displaced | |
995 | * in packet stream. With SACKs we can estimate it: | |
996 | * | |
997 | * 1. SACK fills old hole and the corresponding segment was not | |
998 | * ever retransmitted -> reordering. Alas, we cannot use it | |
999 | * when segment was retransmitted. | |
1000 | * 2. The last flaw is solved with D-SACK. D-SACK arrives | |
1001 | * for retransmitted and already SACKed segment -> reordering.. | |
1002 | * Both of these heuristics are not used in Loss state, when we cannot | |
1003 | * account for retransmits accurately. | |
5b3c9882 IJ |
1004 | * |
1005 | * SACK block validation. | |
1006 | * ---------------------- | |
1007 | * | |
1008 | * SACK block range validation checks that the received SACK block fits to | |
1009 | * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. | |
1010 | * Note that SND.UNA is not included to the range though being valid because | |
0e835331 IJ |
1011 | * it means that the receiver is rather inconsistent with itself reporting |
1012 | * SACK reneging when it should advance SND.UNA. Such SACK block this is | |
1013 | * perfectly valid, however, in light of RFC2018 which explicitly states | |
1014 | * that "SACK block MUST reflect the newest segment. Even if the newest | |
1015 | * segment is going to be discarded ...", not that it looks very clever | |
1016 | * in case of head skb. Due to potentional receiver driven attacks, we | |
1017 | * choose to avoid immediate execution of a walk in write queue due to | |
1018 | * reneging and defer head skb's loss recovery to standard loss recovery | |
1019 | * procedure that will eventually trigger (nothing forbids us doing this). | |
5b3c9882 IJ |
1020 | * |
1021 | * Implements also blockage to start_seq wrap-around. Problem lies in the | |
1022 | * fact that though start_seq (s) is before end_seq (i.e., not reversed), | |
1023 | * there's no guarantee that it will be before snd_nxt (n). The problem | |
1024 | * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt | |
1025 | * wrap (s_w): | |
1026 | * | |
1027 | * <- outs wnd -> <- wrapzone -> | |
1028 | * u e n u_w e_w s n_w | |
1029 | * | | | | | | | | |
1030 | * |<------------+------+----- TCP seqno space --------------+---------->| | |
1031 | * ...-- <2^31 ->| |<--------... | |
1032 | * ...---- >2^31 ------>| |<--------... | |
1033 | * | |
1034 | * Current code wouldn't be vulnerable but it's better still to discard such | |
1035 | * crazy SACK blocks. Doing this check for start_seq alone closes somewhat | |
1036 | * similar case (end_seq after snd_nxt wrap) as earlier reversed check in | |
1037 | * snd_nxt wrap -> snd_una region will then become "well defined", i.e., | |
1038 | * equal to the ideal case (infinite seqno space without wrap caused issues). | |
1039 | * | |
1040 | * With D-SACK the lower bound is extended to cover sequence space below | |
1041 | * SND.UNA down to undo_marker, which is the last point of interest. Yet | |
564262c1 | 1042 | * again, D-SACK block must not to go across snd_una (for the same reason as |
5b3c9882 IJ |
1043 | * for the normal SACK blocks, explained above). But there all simplicity |
1044 | * ends, TCP might receive valid D-SACKs below that. As long as they reside | |
1045 | * fully below undo_marker they do not affect behavior in anyway and can | |
1046 | * therefore be safely ignored. In rare cases (which are more or less | |
1047 | * theoretical ones), the D-SACK will nicely cross that boundary due to skb | |
1048 | * fragmentation and packet reordering past skb's retransmission. To consider | |
1049 | * them correctly, the acceptable range must be extended even more though | |
1050 | * the exact amount is rather hard to quantify. However, tp->max_window can | |
1051 | * be used as an exaggerated estimate. | |
1da177e4 | 1052 | */ |
a2a385d6 ED |
1053 | static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack, |
1054 | u32 start_seq, u32 end_seq) | |
5b3c9882 IJ |
1055 | { |
1056 | /* Too far in future, or reversed (interpretation is ambiguous) */ | |
1057 | if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) | |
a2a385d6 | 1058 | return false; |
5b3c9882 IJ |
1059 | |
1060 | /* Nasty start_seq wrap-around check (see comments above) */ | |
1061 | if (!before(start_seq, tp->snd_nxt)) | |
a2a385d6 | 1062 | return false; |
5b3c9882 | 1063 | |
564262c1 | 1064 | /* In outstanding window? ...This is valid exit for D-SACKs too. |
5b3c9882 IJ |
1065 | * start_seq == snd_una is non-sensical (see comments above) |
1066 | */ | |
1067 | if (after(start_seq, tp->snd_una)) | |
a2a385d6 | 1068 | return true; |
5b3c9882 IJ |
1069 | |
1070 | if (!is_dsack || !tp->undo_marker) | |
a2a385d6 | 1071 | return false; |
5b3c9882 IJ |
1072 | |
1073 | /* ...Then it's D-SACK, and must reside below snd_una completely */ | |
f779b2d6 | 1074 | if (after(end_seq, tp->snd_una)) |
a2a385d6 | 1075 | return false; |
5b3c9882 IJ |
1076 | |
1077 | if (!before(start_seq, tp->undo_marker)) | |
a2a385d6 | 1078 | return true; |
5b3c9882 IJ |
1079 | |
1080 | /* Too old */ | |
1081 | if (!after(end_seq, tp->undo_marker)) | |
a2a385d6 | 1082 | return false; |
5b3c9882 IJ |
1083 | |
1084 | /* Undo_marker boundary crossing (overestimates a lot). Known already: | |
1085 | * start_seq < undo_marker and end_seq >= undo_marker. | |
1086 | */ | |
1087 | return !before(start_seq, end_seq - tp->max_window); | |
1088 | } | |
1089 | ||
a2a385d6 ED |
1090 | static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, |
1091 | struct tcp_sack_block_wire *sp, int num_sacks, | |
1092 | u32 prior_snd_una) | |
d06e021d | 1093 | { |
1ed83465 | 1094 | struct tcp_sock *tp = tcp_sk(sk); |
d3e2ce3b HH |
1095 | u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); |
1096 | u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); | |
a2a385d6 | 1097 | bool dup_sack = false; |
d06e021d DM |
1098 | |
1099 | if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { | |
a2a385d6 | 1100 | dup_sack = true; |
e60402d0 | 1101 | tcp_dsack_seen(tp); |
c10d9310 | 1102 | NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECV); |
d06e021d | 1103 | } else if (num_sacks > 1) { |
d3e2ce3b HH |
1104 | u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); |
1105 | u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); | |
d06e021d DM |
1106 | |
1107 | if (!after(end_seq_0, end_seq_1) && | |
1108 | !before(start_seq_0, start_seq_1)) { | |
a2a385d6 | 1109 | dup_sack = true; |
e60402d0 | 1110 | tcp_dsack_seen(tp); |
c10d9310 | 1111 | NET_INC_STATS(sock_net(sk), |
de0744af | 1112 | LINUX_MIB_TCPDSACKOFORECV); |
d06e021d DM |
1113 | } |
1114 | } | |
1115 | ||
1116 | /* D-SACK for already forgotten data... Do dumb counting. */ | |
6e08d5e3 | 1117 | if (dup_sack && tp->undo_marker && tp->undo_retrans > 0 && |
d06e021d DM |
1118 | !after(end_seq_0, prior_snd_una) && |
1119 | after(end_seq_0, tp->undo_marker)) | |
1120 | tp->undo_retrans--; | |
1121 | ||
1122 | return dup_sack; | |
1123 | } | |
1124 | ||
a1197f5a | 1125 | struct tcp_sacktag_state { |
740b0f18 ED |
1126 | int reord; |
1127 | int fack_count; | |
31231a8a KKJ |
1128 | /* Timestamps for earliest and latest never-retransmitted segment |
1129 | * that was SACKed. RTO needs the earliest RTT to stay conservative, | |
1130 | * but congestion control should still get an accurate delay signal. | |
1131 | */ | |
1132 | struct skb_mstamp first_sackt; | |
1133 | struct skb_mstamp last_sackt; | |
deed7be7 | 1134 | struct skb_mstamp ack_time; /* Timestamp when the S/ACK was received */ |
b9f64820 | 1135 | struct rate_sample *rate; |
740b0f18 | 1136 | int flag; |
a1197f5a IJ |
1137 | }; |
1138 | ||
d1935942 IJ |
1139 | /* Check if skb is fully within the SACK block. In presence of GSO skbs, |
1140 | * the incoming SACK may not exactly match but we can find smaller MSS | |
1141 | * aligned portion of it that matches. Therefore we might need to fragment | |
1142 | * which may fail and creates some hassle (caller must handle error case | |
1143 | * returns). | |
832d11c5 IJ |
1144 | * |
1145 | * FIXME: this could be merged to shift decision code | |
d1935942 | 1146 | */ |
0f79efdc | 1147 | static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, |
a2a385d6 | 1148 | u32 start_seq, u32 end_seq) |
d1935942 | 1149 | { |
a2a385d6 ED |
1150 | int err; |
1151 | bool in_sack; | |
d1935942 | 1152 | unsigned int pkt_len; |
adb92db8 | 1153 | unsigned int mss; |
d1935942 IJ |
1154 | |
1155 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && | |
1156 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); | |
1157 | ||
1158 | if (tcp_skb_pcount(skb) > 1 && !in_sack && | |
1159 | after(TCP_SKB_CB(skb)->end_seq, start_seq)) { | |
adb92db8 | 1160 | mss = tcp_skb_mss(skb); |
d1935942 IJ |
1161 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
1162 | ||
adb92db8 | 1163 | if (!in_sack) { |
d1935942 | 1164 | pkt_len = start_seq - TCP_SKB_CB(skb)->seq; |
adb92db8 IJ |
1165 | if (pkt_len < mss) |
1166 | pkt_len = mss; | |
1167 | } else { | |
d1935942 | 1168 | pkt_len = end_seq - TCP_SKB_CB(skb)->seq; |
adb92db8 IJ |
1169 | if (pkt_len < mss) |
1170 | return -EINVAL; | |
1171 | } | |
1172 | ||
1173 | /* Round if necessary so that SACKs cover only full MSSes | |
1174 | * and/or the remaining small portion (if present) | |
1175 | */ | |
1176 | if (pkt_len > mss) { | |
1177 | unsigned int new_len = (pkt_len / mss) * mss; | |
1178 | if (!in_sack && new_len < pkt_len) { | |
1179 | new_len += mss; | |
2cd0d743 | 1180 | if (new_len >= skb->len) |
adb92db8 IJ |
1181 | return 0; |
1182 | } | |
1183 | pkt_len = new_len; | |
1184 | } | |
6cc55e09 | 1185 | err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC); |
d1935942 IJ |
1186 | if (err < 0) |
1187 | return err; | |
1188 | } | |
1189 | ||
1190 | return in_sack; | |
1191 | } | |
1192 | ||
cc9a672e NC |
1193 | /* Mark the given newly-SACKed range as such, adjusting counters and hints. */ |
1194 | static u8 tcp_sacktag_one(struct sock *sk, | |
1195 | struct tcp_sacktag_state *state, u8 sacked, | |
1196 | u32 start_seq, u32 end_seq, | |
740b0f18 ED |
1197 | int dup_sack, int pcount, |
1198 | const struct skb_mstamp *xmit_time) | |
9e10c47c | 1199 | { |
6859d494 | 1200 | struct tcp_sock *tp = tcp_sk(sk); |
a1197f5a | 1201 | int fack_count = state->fack_count; |
9e10c47c IJ |
1202 | |
1203 | /* Account D-SACK for retransmitted packet. */ | |
1204 | if (dup_sack && (sacked & TCPCB_RETRANS)) { | |
6e08d5e3 | 1205 | if (tp->undo_marker && tp->undo_retrans > 0 && |
cc9a672e | 1206 | after(end_seq, tp->undo_marker)) |
9e10c47c | 1207 | tp->undo_retrans--; |
ede9f3b1 | 1208 | if (sacked & TCPCB_SACKED_ACKED) |
a1197f5a | 1209 | state->reord = min(fack_count, state->reord); |
9e10c47c IJ |
1210 | } |
1211 | ||
1212 | /* Nothing to do; acked frame is about to be dropped (was ACKed). */ | |
cc9a672e | 1213 | if (!after(end_seq, tp->snd_una)) |
a1197f5a | 1214 | return sacked; |
9e10c47c IJ |
1215 | |
1216 | if (!(sacked & TCPCB_SACKED_ACKED)) { | |
1d0833df YC |
1217 | tcp_rack_advance(tp, sacked, end_seq, |
1218 | xmit_time, &state->ack_time); | |
659a8ad5 | 1219 | |
9e10c47c IJ |
1220 | if (sacked & TCPCB_SACKED_RETRANS) { |
1221 | /* If the segment is not tagged as lost, | |
1222 | * we do not clear RETRANS, believing | |
1223 | * that retransmission is still in flight. | |
1224 | */ | |
1225 | if (sacked & TCPCB_LOST) { | |
a1197f5a | 1226 | sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); |
f58b22fd IJ |
1227 | tp->lost_out -= pcount; |
1228 | tp->retrans_out -= pcount; | |
9e10c47c IJ |
1229 | } |
1230 | } else { | |
1231 | if (!(sacked & TCPCB_RETRANS)) { | |
1232 | /* New sack for not retransmitted frame, | |
1233 | * which was in hole. It is reordering. | |
1234 | */ | |
cc9a672e | 1235 | if (before(start_seq, |
9e10c47c | 1236 | tcp_highest_sack_seq(tp))) |
a1197f5a IJ |
1237 | state->reord = min(fack_count, |
1238 | state->reord); | |
e33099f9 YC |
1239 | if (!after(end_seq, tp->high_seq)) |
1240 | state->flag |= FLAG_ORIG_SACK_ACKED; | |
31231a8a KKJ |
1241 | if (state->first_sackt.v64 == 0) |
1242 | state->first_sackt = *xmit_time; | |
1243 | state->last_sackt = *xmit_time; | |
9e10c47c IJ |
1244 | } |
1245 | ||
1246 | if (sacked & TCPCB_LOST) { | |
a1197f5a | 1247 | sacked &= ~TCPCB_LOST; |
f58b22fd | 1248 | tp->lost_out -= pcount; |
9e10c47c IJ |
1249 | } |
1250 | } | |
1251 | ||
a1197f5a IJ |
1252 | sacked |= TCPCB_SACKED_ACKED; |
1253 | state->flag |= FLAG_DATA_SACKED; | |
f58b22fd | 1254 | tp->sacked_out += pcount; |
ddf1af6f | 1255 | tp->delivered += pcount; /* Out-of-order packets delivered */ |
9e10c47c | 1256 | |
f58b22fd | 1257 | fack_count += pcount; |
9e10c47c IJ |
1258 | |
1259 | /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ | |
00db4124 | 1260 | if (!tcp_is_fack(tp) && tp->lost_skb_hint && |
cc9a672e | 1261 | before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq)) |
f58b22fd | 1262 | tp->lost_cnt_hint += pcount; |
9e10c47c IJ |
1263 | |
1264 | if (fack_count > tp->fackets_out) | |
1265 | tp->fackets_out = fack_count; | |
9e10c47c IJ |
1266 | } |
1267 | ||
1268 | /* D-SACK. We can detect redundant retransmission in S|R and plain R | |
1269 | * frames and clear it. undo_retrans is decreased above, L|R frames | |
1270 | * are accounted above as well. | |
1271 | */ | |
a1197f5a IJ |
1272 | if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { |
1273 | sacked &= ~TCPCB_SACKED_RETRANS; | |
f58b22fd | 1274 | tp->retrans_out -= pcount; |
9e10c47c IJ |
1275 | } |
1276 | ||
a1197f5a | 1277 | return sacked; |
9e10c47c IJ |
1278 | } |
1279 | ||
daef52ba NC |
1280 | /* Shift newly-SACKed bytes from this skb to the immediately previous |
1281 | * already-SACKed sk_buff. Mark the newly-SACKed bytes as such. | |
1282 | */ | |
a2a385d6 ED |
1283 | static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, |
1284 | struct tcp_sacktag_state *state, | |
1285 | unsigned int pcount, int shifted, int mss, | |
1286 | bool dup_sack) | |
832d11c5 IJ |
1287 | { |
1288 | struct tcp_sock *tp = tcp_sk(sk); | |
50133161 | 1289 | struct sk_buff *prev = tcp_write_queue_prev(sk, skb); |
daef52ba NC |
1290 | u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */ |
1291 | u32 end_seq = start_seq + shifted; /* end of newly-SACKed */ | |
832d11c5 IJ |
1292 | |
1293 | BUG_ON(!pcount); | |
1294 | ||
4c90d3b3 NC |
1295 | /* Adjust counters and hints for the newly sacked sequence |
1296 | * range but discard the return value since prev is already | |
1297 | * marked. We must tag the range first because the seq | |
1298 | * advancement below implicitly advances | |
1299 | * tcp_highest_sack_seq() when skb is highest_sack. | |
1300 | */ | |
1301 | tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked, | |
59c9af42 | 1302 | start_seq, end_seq, dup_sack, pcount, |
740b0f18 | 1303 | &skb->skb_mstamp); |
b9f64820 | 1304 | tcp_rate_skb_delivered(sk, skb, state->rate); |
4c90d3b3 NC |
1305 | |
1306 | if (skb == tp->lost_skb_hint) | |
0af2a0d0 NC |
1307 | tp->lost_cnt_hint += pcount; |
1308 | ||
832d11c5 IJ |
1309 | TCP_SKB_CB(prev)->end_seq += shifted; |
1310 | TCP_SKB_CB(skb)->seq += shifted; | |
1311 | ||
cd7d8498 ED |
1312 | tcp_skb_pcount_add(prev, pcount); |
1313 | BUG_ON(tcp_skb_pcount(skb) < pcount); | |
1314 | tcp_skb_pcount_add(skb, -pcount); | |
832d11c5 IJ |
1315 | |
1316 | /* When we're adding to gso_segs == 1, gso_size will be zero, | |
1317 | * in theory this shouldn't be necessary but as long as DSACK | |
1318 | * code can come after this skb later on it's better to keep | |
1319 | * setting gso_size to something. | |
1320 | */ | |
f69ad292 ED |
1321 | if (!TCP_SKB_CB(prev)->tcp_gso_size) |
1322 | TCP_SKB_CB(prev)->tcp_gso_size = mss; | |
832d11c5 IJ |
1323 | |
1324 | /* CHECKME: To clear or not to clear? Mimics normal skb currently */ | |
51466a75 | 1325 | if (tcp_skb_pcount(skb) <= 1) |
f69ad292 | 1326 | TCP_SKB_CB(skb)->tcp_gso_size = 0; |
832d11c5 | 1327 | |
832d11c5 IJ |
1328 | /* Difference in this won't matter, both ACKed by the same cumul. ACK */ |
1329 | TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); | |
1330 | ||
832d11c5 IJ |
1331 | if (skb->len > 0) { |
1332 | BUG_ON(!tcp_skb_pcount(skb)); | |
c10d9310 | 1333 | NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTED); |
a2a385d6 | 1334 | return false; |
832d11c5 IJ |
1335 | } |
1336 | ||
1337 | /* Whole SKB was eaten :-) */ | |
1338 | ||
92ee76b6 IJ |
1339 | if (skb == tp->retransmit_skb_hint) |
1340 | tp->retransmit_skb_hint = prev; | |
92ee76b6 IJ |
1341 | if (skb == tp->lost_skb_hint) { |
1342 | tp->lost_skb_hint = prev; | |
1343 | tp->lost_cnt_hint -= tcp_skb_pcount(prev); | |
1344 | } | |
1345 | ||
5e8a402f | 1346 | TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; |
a643b5d4 | 1347 | TCP_SKB_CB(prev)->eor = TCP_SKB_CB(skb)->eor; |
5e8a402f ED |
1348 | if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) |
1349 | TCP_SKB_CB(prev)->end_seq++; | |
1350 | ||
832d11c5 IJ |
1351 | if (skb == tcp_highest_sack(sk)) |
1352 | tcp_advance_highest_sack(sk, skb); | |
1353 | ||
cfea5a68 | 1354 | tcp_skb_collapse_tstamp(prev, skb); |
b9f64820 YC |
1355 | if (unlikely(TCP_SKB_CB(prev)->tx.delivered_mstamp.v64)) |
1356 | TCP_SKB_CB(prev)->tx.delivered_mstamp.v64 = 0; | |
1357 | ||
832d11c5 IJ |
1358 | tcp_unlink_write_queue(skb, sk); |
1359 | sk_wmem_free_skb(sk, skb); | |
1360 | ||
c10d9310 | 1361 | NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKMERGED); |
111cc8b9 | 1362 | |
a2a385d6 | 1363 | return true; |
832d11c5 IJ |
1364 | } |
1365 | ||
1366 | /* I wish gso_size would have a bit more sane initialization than | |
1367 | * something-or-zero which complicates things | |
1368 | */ | |
cf533ea5 | 1369 | static int tcp_skb_seglen(const struct sk_buff *skb) |
832d11c5 | 1370 | { |
775ffabf | 1371 | return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); |
832d11c5 IJ |
1372 | } |
1373 | ||
1374 | /* Shifting pages past head area doesn't work */ | |
cf533ea5 | 1375 | static int skb_can_shift(const struct sk_buff *skb) |
832d11c5 IJ |
1376 | { |
1377 | return !skb_headlen(skb) && skb_is_nonlinear(skb); | |
1378 | } | |
1379 | ||
1380 | /* Try collapsing SACK blocks spanning across multiple skbs to a single | |
1381 | * skb. | |
1382 | */ | |
1383 | static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, | |
a1197f5a | 1384 | struct tcp_sacktag_state *state, |
832d11c5 | 1385 | u32 start_seq, u32 end_seq, |
a2a385d6 | 1386 | bool dup_sack) |
832d11c5 IJ |
1387 | { |
1388 | struct tcp_sock *tp = tcp_sk(sk); | |
1389 | struct sk_buff *prev; | |
1390 | int mss; | |
1391 | int pcount = 0; | |
1392 | int len; | |
1393 | int in_sack; | |
1394 | ||
1395 | if (!sk_can_gso(sk)) | |
1396 | goto fallback; | |
1397 | ||
1398 | /* Normally R but no L won't result in plain S */ | |
1399 | if (!dup_sack && | |
9969ca5f | 1400 | (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) |
832d11c5 IJ |
1401 | goto fallback; |
1402 | if (!skb_can_shift(skb)) | |
1403 | goto fallback; | |
1404 | /* This frame is about to be dropped (was ACKed). */ | |
1405 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) | |
1406 | goto fallback; | |
1407 | ||
1408 | /* Can only happen with delayed DSACK + discard craziness */ | |
1409 | if (unlikely(skb == tcp_write_queue_head(sk))) | |
1410 | goto fallback; | |
1411 | prev = tcp_write_queue_prev(sk, skb); | |
1412 | ||
1413 | if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) | |
1414 | goto fallback; | |
1415 | ||
a643b5d4 MKL |
1416 | if (!tcp_skb_can_collapse_to(prev)) |
1417 | goto fallback; | |
1418 | ||
832d11c5 IJ |
1419 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
1420 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); | |
1421 | ||
1422 | if (in_sack) { | |
1423 | len = skb->len; | |
1424 | pcount = tcp_skb_pcount(skb); | |
775ffabf | 1425 | mss = tcp_skb_seglen(skb); |
832d11c5 IJ |
1426 | |
1427 | /* TODO: Fix DSACKs to not fragment already SACKed and we can | |
1428 | * drop this restriction as unnecessary | |
1429 | */ | |
775ffabf | 1430 | if (mss != tcp_skb_seglen(prev)) |
832d11c5 IJ |
1431 | goto fallback; |
1432 | } else { | |
1433 | if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) | |
1434 | goto noop; | |
1435 | /* CHECKME: This is non-MSS split case only?, this will | |
1436 | * cause skipped skbs due to advancing loop btw, original | |
1437 | * has that feature too | |
1438 | */ | |
1439 | if (tcp_skb_pcount(skb) <= 1) | |
1440 | goto noop; | |
1441 | ||
1442 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); | |
1443 | if (!in_sack) { | |
1444 | /* TODO: head merge to next could be attempted here | |
1445 | * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), | |
1446 | * though it might not be worth of the additional hassle | |
1447 | * | |
1448 | * ...we can probably just fallback to what was done | |
1449 | * previously. We could try merging non-SACKed ones | |
1450 | * as well but it probably isn't going to buy off | |
1451 | * because later SACKs might again split them, and | |
1452 | * it would make skb timestamp tracking considerably | |
1453 | * harder problem. | |
1454 | */ | |
1455 | goto fallback; | |
1456 | } | |
1457 | ||
1458 | len = end_seq - TCP_SKB_CB(skb)->seq; | |
1459 | BUG_ON(len < 0); | |
1460 | BUG_ON(len > skb->len); | |
1461 | ||
1462 | /* MSS boundaries should be honoured or else pcount will | |
1463 | * severely break even though it makes things bit trickier. | |
1464 | * Optimize common case to avoid most of the divides | |
1465 | */ | |
1466 | mss = tcp_skb_mss(skb); | |
1467 | ||
1468 | /* TODO: Fix DSACKs to not fragment already SACKed and we can | |
1469 | * drop this restriction as unnecessary | |
1470 | */ | |
775ffabf | 1471 | if (mss != tcp_skb_seglen(prev)) |
832d11c5 IJ |
1472 | goto fallback; |
1473 | ||
1474 | if (len == mss) { | |
1475 | pcount = 1; | |
1476 | } else if (len < mss) { | |
1477 | goto noop; | |
1478 | } else { | |
1479 | pcount = len / mss; | |
1480 | len = pcount * mss; | |
1481 | } | |
1482 | } | |
1483 | ||
4648dc97 NC |
1484 | /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */ |
1485 | if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una)) | |
1486 | goto fallback; | |
1487 | ||
832d11c5 IJ |
1488 | if (!skb_shift(prev, skb, len)) |
1489 | goto fallback; | |
9ec06ff5 | 1490 | if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) |
832d11c5 IJ |
1491 | goto out; |
1492 | ||
1493 | /* Hole filled allows collapsing with the next as well, this is very | |
1494 | * useful when hole on every nth skb pattern happens | |
1495 | */ | |
1496 | if (prev == tcp_write_queue_tail(sk)) | |
1497 | goto out; | |
1498 | skb = tcp_write_queue_next(sk, prev); | |
1499 | ||
f0bc52f3 IJ |
1500 | if (!skb_can_shift(skb) || |
1501 | (skb == tcp_send_head(sk)) || | |
1502 | ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || | |
775ffabf | 1503 | (mss != tcp_skb_seglen(skb))) |
832d11c5 IJ |
1504 | goto out; |
1505 | ||
1506 | len = skb->len; | |
1507 | if (skb_shift(prev, skb, len)) { | |
1508 | pcount += tcp_skb_pcount(skb); | |
9ec06ff5 | 1509 | tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); |
832d11c5 IJ |
1510 | } |
1511 | ||
1512 | out: | |
a1197f5a | 1513 | state->fack_count += pcount; |
832d11c5 IJ |
1514 | return prev; |
1515 | ||
1516 | noop: | |
1517 | return skb; | |
1518 | ||
1519 | fallback: | |
c10d9310 | 1520 | NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); |
832d11c5 IJ |
1521 | return NULL; |
1522 | } | |
1523 | ||
68f8353b IJ |
1524 | static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, |
1525 | struct tcp_sack_block *next_dup, | |
a1197f5a | 1526 | struct tcp_sacktag_state *state, |
68f8353b | 1527 | u32 start_seq, u32 end_seq, |
a2a385d6 | 1528 | bool dup_sack_in) |
68f8353b | 1529 | { |
832d11c5 IJ |
1530 | struct tcp_sock *tp = tcp_sk(sk); |
1531 | struct sk_buff *tmp; | |
1532 | ||
68f8353b IJ |
1533 | tcp_for_write_queue_from(skb, sk) { |
1534 | int in_sack = 0; | |
a2a385d6 | 1535 | bool dup_sack = dup_sack_in; |
68f8353b IJ |
1536 | |
1537 | if (skb == tcp_send_head(sk)) | |
1538 | break; | |
1539 | ||
1540 | /* queue is in-order => we can short-circuit the walk early */ | |
1541 | if (!before(TCP_SKB_CB(skb)->seq, end_seq)) | |
1542 | break; | |
1543 | ||
00db4124 | 1544 | if (next_dup && |
68f8353b IJ |
1545 | before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { |
1546 | in_sack = tcp_match_skb_to_sack(sk, skb, | |
1547 | next_dup->start_seq, | |
1548 | next_dup->end_seq); | |
1549 | if (in_sack > 0) | |
a2a385d6 | 1550 | dup_sack = true; |
68f8353b IJ |
1551 | } |
1552 | ||
832d11c5 IJ |
1553 | /* skb reference here is a bit tricky to get right, since |
1554 | * shifting can eat and free both this skb and the next, | |
1555 | * so not even _safe variant of the loop is enough. | |
1556 | */ | |
1557 | if (in_sack <= 0) { | |
a1197f5a IJ |
1558 | tmp = tcp_shift_skb_data(sk, skb, state, |
1559 | start_seq, end_seq, dup_sack); | |
00db4124 | 1560 | if (tmp) { |
832d11c5 IJ |
1561 | if (tmp != skb) { |
1562 | skb = tmp; | |
1563 | continue; | |
1564 | } | |
1565 | ||
1566 | in_sack = 0; | |
1567 | } else { | |
1568 | in_sack = tcp_match_skb_to_sack(sk, skb, | |
1569 | start_seq, | |
1570 | end_seq); | |
1571 | } | |
1572 | } | |
1573 | ||
68f8353b IJ |
1574 | if (unlikely(in_sack < 0)) |
1575 | break; | |
1576 | ||
832d11c5 | 1577 | if (in_sack) { |
cc9a672e NC |
1578 | TCP_SKB_CB(skb)->sacked = |
1579 | tcp_sacktag_one(sk, | |
1580 | state, | |
1581 | TCP_SKB_CB(skb)->sacked, | |
1582 | TCP_SKB_CB(skb)->seq, | |
1583 | TCP_SKB_CB(skb)->end_seq, | |
1584 | dup_sack, | |
59c9af42 | 1585 | tcp_skb_pcount(skb), |
740b0f18 | 1586 | &skb->skb_mstamp); |
b9f64820 | 1587 | tcp_rate_skb_delivered(sk, skb, state->rate); |
68f8353b | 1588 | |
832d11c5 IJ |
1589 | if (!before(TCP_SKB_CB(skb)->seq, |
1590 | tcp_highest_sack_seq(tp))) | |
1591 | tcp_advance_highest_sack(sk, skb); | |
1592 | } | |
1593 | ||
a1197f5a | 1594 | state->fack_count += tcp_skb_pcount(skb); |
68f8353b IJ |
1595 | } |
1596 | return skb; | |
1597 | } | |
1598 | ||
1599 | /* Avoid all extra work that is being done by sacktag while walking in | |
1600 | * a normal way | |
1601 | */ | |
1602 | static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, | |
a1197f5a IJ |
1603 | struct tcp_sacktag_state *state, |
1604 | u32 skip_to_seq) | |
68f8353b IJ |
1605 | { |
1606 | tcp_for_write_queue_from(skb, sk) { | |
1607 | if (skb == tcp_send_head(sk)) | |
1608 | break; | |
1609 | ||
e8bae275 | 1610 | if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) |
68f8353b | 1611 | break; |
d152a7d8 | 1612 | |
a1197f5a | 1613 | state->fack_count += tcp_skb_pcount(skb); |
68f8353b IJ |
1614 | } |
1615 | return skb; | |
1616 | } | |
1617 | ||
1618 | static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, | |
1619 | struct sock *sk, | |
1620 | struct tcp_sack_block *next_dup, | |
a1197f5a IJ |
1621 | struct tcp_sacktag_state *state, |
1622 | u32 skip_to_seq) | |
68f8353b | 1623 | { |
51456b29 | 1624 | if (!next_dup) |
68f8353b IJ |
1625 | return skb; |
1626 | ||
1627 | if (before(next_dup->start_seq, skip_to_seq)) { | |
a1197f5a IJ |
1628 | skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); |
1629 | skb = tcp_sacktag_walk(skb, sk, NULL, state, | |
1630 | next_dup->start_seq, next_dup->end_seq, | |
1631 | 1); | |
68f8353b IJ |
1632 | } |
1633 | ||
1634 | return skb; | |
1635 | } | |
1636 | ||
cf533ea5 | 1637 | static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) |
68f8353b IJ |
1638 | { |
1639 | return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); | |
1640 | } | |
1641 | ||
1da177e4 | 1642 | static int |
cf533ea5 | 1643 | tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, |
196da974 | 1644 | u32 prior_snd_una, struct tcp_sacktag_state *state) |
1da177e4 LT |
1645 | { |
1646 | struct tcp_sock *tp = tcp_sk(sk); | |
cf533ea5 ED |
1647 | const unsigned char *ptr = (skb_transport_header(ack_skb) + |
1648 | TCP_SKB_CB(ack_skb)->sacked); | |
fd6dad61 | 1649 | struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); |
4389dded | 1650 | struct tcp_sack_block sp[TCP_NUM_SACKS]; |
68f8353b IJ |
1651 | struct tcp_sack_block *cache; |
1652 | struct sk_buff *skb; | |
4389dded | 1653 | int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); |
fd6dad61 | 1654 | int used_sacks; |
a2a385d6 | 1655 | bool found_dup_sack = false; |
68f8353b | 1656 | int i, j; |
fda03fbb | 1657 | int first_sack_index; |
1da177e4 | 1658 | |
196da974 KKJ |
1659 | state->flag = 0; |
1660 | state->reord = tp->packets_out; | |
a1197f5a | 1661 | |
d738cd8f | 1662 | if (!tp->sacked_out) { |
de83c058 IJ |
1663 | if (WARN_ON(tp->fackets_out)) |
1664 | tp->fackets_out = 0; | |
6859d494 | 1665 | tcp_highest_sack_reset(sk); |
d738cd8f | 1666 | } |
1da177e4 | 1667 | |
1ed83465 | 1668 | found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, |
d06e021d | 1669 | num_sacks, prior_snd_una); |
b9f64820 | 1670 | if (found_dup_sack) { |
196da974 | 1671 | state->flag |= FLAG_DSACKING_ACK; |
b9f64820 YC |
1672 | tp->delivered++; /* A spurious retransmission is delivered */ |
1673 | } | |
6f74651a BE |
1674 | |
1675 | /* Eliminate too old ACKs, but take into | |
1676 | * account more or less fresh ones, they can | |
1677 | * contain valid SACK info. | |
1678 | */ | |
1679 | if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) | |
1680 | return 0; | |
1681 | ||