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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> |
5ffc02a1 | 71 | #include <net/dst.h> |
1da177e4 LT |
72 | #include <net/tcp.h> |
73 | #include <net/inet_common.h> | |
74 | #include <linux/ipsec.h> | |
75 | #include <asm/unaligned.h> | |
1a2449a8 | 76 | #include <net/netdma.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; | |
82 | int sysctl_tcp_fack __read_mostly = 1; | |
83 | int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; | |
4bc2f18b | 84 | EXPORT_SYMBOL(sysctl_tcp_reordering); |
ab32ea5d BH |
85 | int sysctl_tcp_dsack __read_mostly = 1; |
86 | int sysctl_tcp_app_win __read_mostly = 31; | |
b49960a0 | 87 | int sysctl_tcp_adv_win_scale __read_mostly = 1; |
4bc2f18b | 88 | EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); |
1da177e4 | 89 | |
282f23c6 ED |
90 | /* rfc5961 challenge ack rate limiting */ |
91 | int sysctl_tcp_challenge_ack_limit = 100; | |
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; |
1da177e4 | 97 | |
7e380175 AP |
98 | int sysctl_tcp_thin_dupack __read_mostly; |
99 | ||
ab32ea5d | 100 | int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; |
6ba8a3b1 | 101 | int sysctl_tcp_early_retrans __read_mostly = 3; |
1da177e4 | 102 | |
1da177e4 LT |
103 | #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
104 | #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ | |
105 | #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ | |
106 | #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ | |
107 | #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ | |
108 | #define FLAG_DATA_SACKED 0x20 /* New SACK. */ | |
109 | #define FLAG_ECE 0x40 /* ECE in this ACK */ | |
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 | |
e905a9ed | 125 | /* Adapt the MSS value used to make delayed ack decision to the |
1da177e4 | 126 | * real world. |
e905a9ed | 127 | */ |
056834d9 | 128 | static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 129 | { |
463c84b9 | 130 | struct inet_connection_sock *icsk = inet_csk(sk); |
e905a9ed | 131 | const unsigned int lss = icsk->icsk_ack.last_seg_size; |
463c84b9 | 132 | unsigned int len; |
1da177e4 | 133 | |
e905a9ed | 134 | icsk->icsk_ack.last_seg_size = 0; |
1da177e4 LT |
135 | |
136 | /* skb->len may jitter because of SACKs, even if peer | |
137 | * sends good full-sized frames. | |
138 | */ | |
056834d9 | 139 | len = skb_shinfo(skb)->gso_size ? : skb->len; |
463c84b9 ACM |
140 | if (len >= icsk->icsk_ack.rcv_mss) { |
141 | icsk->icsk_ack.rcv_mss = len; | |
1da177e4 LT |
142 | } else { |
143 | /* Otherwise, we make more careful check taking into account, | |
144 | * that SACKs block is variable. | |
145 | * | |
146 | * "len" is invariant segment length, including TCP header. | |
147 | */ | |
9c70220b | 148 | len += skb->data - skb_transport_header(skb); |
bee7ca9e | 149 | if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || |
1da177e4 LT |
150 | /* If PSH is not set, packet should be |
151 | * full sized, provided peer TCP is not badly broken. | |
152 | * This observation (if it is correct 8)) allows | |
153 | * to handle super-low mtu links fairly. | |
154 | */ | |
155 | (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && | |
aa8223c7 | 156 | !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
1da177e4 LT |
157 | /* Subtract also invariant (if peer is RFC compliant), |
158 | * tcp header plus fixed timestamp option length. | |
159 | * Resulting "len" is MSS free of SACK jitter. | |
160 | */ | |
463c84b9 ACM |
161 | len -= tcp_sk(sk)->tcp_header_len; |
162 | icsk->icsk_ack.last_seg_size = len; | |
1da177e4 | 163 | if (len == lss) { |
463c84b9 | 164 | icsk->icsk_ack.rcv_mss = len; |
1da177e4 LT |
165 | return; |
166 | } | |
167 | } | |
1ef9696c AK |
168 | if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
169 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; | |
463c84b9 | 170 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
1da177e4 LT |
171 | } |
172 | } | |
173 | ||
463c84b9 | 174 | static void tcp_incr_quickack(struct sock *sk) |
1da177e4 | 175 | { |
463c84b9 | 176 | struct inet_connection_sock *icsk = inet_csk(sk); |
95c96174 | 177 | unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); |
1da177e4 | 178 | |
056834d9 IJ |
179 | if (quickacks == 0) |
180 | quickacks = 2; | |
463c84b9 ACM |
181 | if (quickacks > icsk->icsk_ack.quick) |
182 | icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); | |
1da177e4 LT |
183 | } |
184 | ||
1b9f4092 | 185 | static void tcp_enter_quickack_mode(struct sock *sk) |
1da177e4 | 186 | { |
463c84b9 ACM |
187 | struct inet_connection_sock *icsk = inet_csk(sk); |
188 | tcp_incr_quickack(sk); | |
189 | icsk->icsk_ack.pingpong = 0; | |
190 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
1da177e4 LT |
191 | } |
192 | ||
193 | /* Send ACKs quickly, if "quick" count is not exhausted | |
194 | * and the session is not interactive. | |
195 | */ | |
196 | ||
a2a385d6 | 197 | static inline bool tcp_in_quickack_mode(const struct sock *sk) |
1da177e4 | 198 | { |
463c84b9 | 199 | const struct inet_connection_sock *icsk = inet_csk(sk); |
a2a385d6 | 200 | |
463c84b9 | 201 | return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; |
1da177e4 LT |
202 | } |
203 | ||
bdf1ee5d IJ |
204 | static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) |
205 | { | |
056834d9 | 206 | if (tp->ecn_flags & TCP_ECN_OK) |
bdf1ee5d IJ |
207 | tp->ecn_flags |= TCP_ECN_QUEUE_CWR; |
208 | } | |
209 | ||
cf533ea5 | 210 | static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) |
bdf1ee5d IJ |
211 | { |
212 | if (tcp_hdr(skb)->cwr) | |
213 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; | |
214 | } | |
215 | ||
216 | static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) | |
217 | { | |
218 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; | |
219 | } | |
220 | ||
7a269ffa | 221 | static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) |
bdf1ee5d | 222 | { |
7a269ffa ED |
223 | if (!(tp->ecn_flags & TCP_ECN_OK)) |
224 | return; | |
225 | ||
b82d1bb4 | 226 | switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { |
7a269ffa | 227 | case INET_ECN_NOT_ECT: |
bdf1ee5d | 228 | /* Funny extension: if ECT is not set on a segment, |
7a269ffa ED |
229 | * and we already seen ECT on a previous segment, |
230 | * it is probably a retransmit. | |
231 | */ | |
232 | if (tp->ecn_flags & TCP_ECN_SEEN) | |
bdf1ee5d | 233 | tcp_enter_quickack_mode((struct sock *)tp); |
7a269ffa ED |
234 | break; |
235 | case INET_ECN_CE: | |
aae06bf5 ED |
236 | if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { |
237 | /* Better not delay acks, sender can have a very low cwnd */ | |
238 | tcp_enter_quickack_mode((struct sock *)tp); | |
239 | tp->ecn_flags |= TCP_ECN_DEMAND_CWR; | |
240 | } | |
7a269ffa ED |
241 | /* fallinto */ |
242 | default: | |
243 | tp->ecn_flags |= TCP_ECN_SEEN; | |
bdf1ee5d IJ |
244 | } |
245 | } | |
246 | ||
cf533ea5 | 247 | static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) |
bdf1ee5d | 248 | { |
056834d9 | 249 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) |
bdf1ee5d IJ |
250 | tp->ecn_flags &= ~TCP_ECN_OK; |
251 | } | |
252 | ||
cf533ea5 | 253 | static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) |
bdf1ee5d | 254 | { |
056834d9 | 255 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) |
bdf1ee5d IJ |
256 | tp->ecn_flags &= ~TCP_ECN_OK; |
257 | } | |
258 | ||
a2a385d6 | 259 | static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) |
bdf1ee5d | 260 | { |
056834d9 | 261 | if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) |
a2a385d6 ED |
262 | return true; |
263 | return false; | |
bdf1ee5d IJ |
264 | } |
265 | ||
1da177e4 LT |
266 | /* Buffer size and advertised window tuning. |
267 | * | |
268 | * 1. Tuning sk->sk_sndbuf, when connection enters established state. | |
269 | */ | |
270 | ||
6ae70532 | 271 | static void tcp_sndbuf_expand(struct sock *sk) |
1da177e4 | 272 | { |
6ae70532 ED |
273 | const struct tcp_sock *tp = tcp_sk(sk); |
274 | int sndmem, per_mss; | |
275 | u32 nr_segs; | |
276 | ||
277 | /* Worst case is non GSO/TSO : each frame consumes one skb | |
278 | * and skb->head is kmalloced using power of two area of memory | |
279 | */ | |
280 | per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + | |
281 | MAX_TCP_HEADER + | |
282 | SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); | |
283 | ||
284 | per_mss = roundup_pow_of_two(per_mss) + | |
285 | SKB_DATA_ALIGN(sizeof(struct sk_buff)); | |
286 | ||
287 | nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd); | |
288 | nr_segs = max_t(u32, nr_segs, tp->reordering + 1); | |
289 | ||
290 | /* Fast Recovery (RFC 5681 3.2) : | |
291 | * Cubic needs 1.7 factor, rounded to 2 to include | |
292 | * extra cushion (application might react slowly to POLLOUT) | |
293 | */ | |
294 | sndmem = 2 * nr_segs * per_mss; | |
1da177e4 | 295 | |
06a59ecb ED |
296 | if (sk->sk_sndbuf < sndmem) |
297 | sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); | |
1da177e4 LT |
298 | } |
299 | ||
300 | /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) | |
301 | * | |
302 | * All tcp_full_space() is split to two parts: "network" buffer, allocated | |
303 | * forward and advertised in receiver window (tp->rcv_wnd) and | |
304 | * "application buffer", required to isolate scheduling/application | |
305 | * latencies from network. | |
306 | * window_clamp is maximal advertised window. It can be less than | |
307 | * tcp_full_space(), in this case tcp_full_space() - window_clamp | |
308 | * is reserved for "application" buffer. The less window_clamp is | |
309 | * the smoother our behaviour from viewpoint of network, but the lower | |
310 | * throughput and the higher sensitivity of the connection to losses. 8) | |
311 | * | |
312 | * rcv_ssthresh is more strict window_clamp used at "slow start" | |
313 | * phase to predict further behaviour of this connection. | |
314 | * It is used for two goals: | |
315 | * - to enforce header prediction at sender, even when application | |
316 | * requires some significant "application buffer". It is check #1. | |
317 | * - to prevent pruning of receive queue because of misprediction | |
318 | * of receiver window. Check #2. | |
319 | * | |
320 | * The scheme does not work when sender sends good segments opening | |
caa20d9a | 321 | * window and then starts to feed us spaghetti. But it should work |
1da177e4 LT |
322 | * in common situations. Otherwise, we have to rely on queue collapsing. |
323 | */ | |
324 | ||
325 | /* Slow part of check#2. */ | |
9e412ba7 | 326 | static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 327 | { |
9e412ba7 | 328 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 329 | /* Optimize this! */ |
dfd4f0ae ED |
330 | int truesize = tcp_win_from_space(skb->truesize) >> 1; |
331 | int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; | |
1da177e4 LT |
332 | |
333 | while (tp->rcv_ssthresh <= window) { | |
334 | if (truesize <= skb->len) | |
463c84b9 | 335 | return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
1da177e4 LT |
336 | |
337 | truesize >>= 1; | |
338 | window >>= 1; | |
339 | } | |
340 | return 0; | |
341 | } | |
342 | ||
cf533ea5 | 343 | static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) |
1da177e4 | 344 | { |
9e412ba7 IJ |
345 | struct tcp_sock *tp = tcp_sk(sk); |
346 | ||
1da177e4 LT |
347 | /* Check #1 */ |
348 | if (tp->rcv_ssthresh < tp->window_clamp && | |
349 | (int)tp->rcv_ssthresh < tcp_space(sk) && | |
180d8cd9 | 350 | !sk_under_memory_pressure(sk)) { |
1da177e4 LT |
351 | int incr; |
352 | ||
353 | /* Check #2. Increase window, if skb with such overhead | |
354 | * will fit to rcvbuf in future. | |
355 | */ | |
356 | if (tcp_win_from_space(skb->truesize) <= skb->len) | |
056834d9 | 357 | incr = 2 * tp->advmss; |
1da177e4 | 358 | else |
9e412ba7 | 359 | incr = __tcp_grow_window(sk, skb); |
1da177e4 LT |
360 | |
361 | if (incr) { | |
4d846f02 | 362 | incr = max_t(int, incr, 2 * skb->len); |
056834d9 IJ |
363 | tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, |
364 | tp->window_clamp); | |
463c84b9 | 365 | inet_csk(sk)->icsk_ack.quick |= 1; |
1da177e4 LT |
366 | } |
367 | } | |
368 | } | |
369 | ||
370 | /* 3. Tuning rcvbuf, when connection enters established state. */ | |
1da177e4 LT |
371 | static void tcp_fixup_rcvbuf(struct sock *sk) |
372 | { | |
e9266a02 | 373 | u32 mss = tcp_sk(sk)->advmss; |
e9266a02 | 374 | int rcvmem; |
1da177e4 | 375 | |
85f16525 YC |
376 | rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) * |
377 | tcp_default_init_rwnd(mss); | |
e9266a02 | 378 | |
b0983d3c ED |
379 | /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency |
380 | * Allow enough cushion so that sender is not limited by our window | |
381 | */ | |
382 | if (sysctl_tcp_moderate_rcvbuf) | |
383 | rcvmem <<= 2; | |
384 | ||
e9266a02 ED |
385 | if (sk->sk_rcvbuf < rcvmem) |
386 | sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]); | |
1da177e4 LT |
387 | } |
388 | ||
caa20d9a | 389 | /* 4. Try to fixup all. It is made immediately after connection enters |
1da177e4 LT |
390 | * established state. |
391 | */ | |
10467163 | 392 | void tcp_init_buffer_space(struct sock *sk) |
1da177e4 LT |
393 | { |
394 | struct tcp_sock *tp = tcp_sk(sk); | |
395 | int maxwin; | |
396 | ||
397 | if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) | |
398 | tcp_fixup_rcvbuf(sk); | |
399 | if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) | |
6ae70532 | 400 | tcp_sndbuf_expand(sk); |
1da177e4 LT |
401 | |
402 | tp->rcvq_space.space = tp->rcv_wnd; | |
b0983d3c ED |
403 | tp->rcvq_space.time = tcp_time_stamp; |
404 | tp->rcvq_space.seq = tp->copied_seq; | |
1da177e4 LT |
405 | |
406 | maxwin = tcp_full_space(sk); | |
407 | ||
408 | if (tp->window_clamp >= maxwin) { | |
409 | tp->window_clamp = maxwin; | |
410 | ||
411 | if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) | |
412 | tp->window_clamp = max(maxwin - | |
413 | (maxwin >> sysctl_tcp_app_win), | |
414 | 4 * tp->advmss); | |
415 | } | |
416 | ||
417 | /* Force reservation of one segment. */ | |
418 | if (sysctl_tcp_app_win && | |
419 | tp->window_clamp > 2 * tp->advmss && | |
420 | tp->window_clamp + tp->advmss > maxwin) | |
421 | tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); | |
422 | ||
423 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); | |
424 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
425 | } | |
426 | ||
1da177e4 | 427 | /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
9e412ba7 | 428 | static void tcp_clamp_window(struct sock *sk) |
1da177e4 | 429 | { |
9e412ba7 | 430 | struct tcp_sock *tp = tcp_sk(sk); |
6687e988 | 431 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 | 432 | |
6687e988 | 433 | icsk->icsk_ack.quick = 0; |
1da177e4 | 434 | |
326f36e9 JH |
435 | if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && |
436 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && | |
180d8cd9 GC |
437 | !sk_under_memory_pressure(sk) && |
438 | sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { | |
326f36e9 JH |
439 | sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), |
440 | sysctl_tcp_rmem[2]); | |
1da177e4 | 441 | } |
326f36e9 | 442 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
056834d9 | 443 | tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); |
1da177e4 LT |
444 | } |
445 | ||
40efc6fa SH |
446 | /* Initialize RCV_MSS value. |
447 | * RCV_MSS is an our guess about MSS used by the peer. | |
448 | * We haven't any direct information about the MSS. | |
449 | * It's better to underestimate the RCV_MSS rather than overestimate. | |
450 | * Overestimations make us ACKing less frequently than needed. | |
451 | * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). | |
452 | */ | |
453 | void tcp_initialize_rcv_mss(struct sock *sk) | |
454 | { | |
cf533ea5 | 455 | const struct tcp_sock *tp = tcp_sk(sk); |
40efc6fa SH |
456 | unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); |
457 | ||
056834d9 | 458 | hint = min(hint, tp->rcv_wnd / 2); |
bee7ca9e | 459 | hint = min(hint, TCP_MSS_DEFAULT); |
40efc6fa SH |
460 | hint = max(hint, TCP_MIN_MSS); |
461 | ||
462 | inet_csk(sk)->icsk_ack.rcv_mss = hint; | |
463 | } | |
4bc2f18b | 464 | EXPORT_SYMBOL(tcp_initialize_rcv_mss); |
40efc6fa | 465 | |
1da177e4 LT |
466 | /* Receiver "autotuning" code. |
467 | * | |
468 | * The algorithm for RTT estimation w/o timestamps is based on | |
469 | * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. | |
631dd1a8 | 470 | * <http://public.lanl.gov/radiant/pubs.html#DRS> |
1da177e4 LT |
471 | * |
472 | * More detail on this code can be found at | |
631dd1a8 | 473 | * <http://staff.psc.edu/jheffner/>, |
1da177e4 LT |
474 | * though this reference is out of date. A new paper |
475 | * is pending. | |
476 | */ | |
477 | static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) | |
478 | { | |
479 | u32 new_sample = tp->rcv_rtt_est.rtt; | |
480 | long m = sample; | |
481 | ||
482 | if (m == 0) | |
483 | m = 1; | |
484 | ||
485 | if (new_sample != 0) { | |
486 | /* If we sample in larger samples in the non-timestamp | |
487 | * case, we could grossly overestimate the RTT especially | |
488 | * with chatty applications or bulk transfer apps which | |
489 | * are stalled on filesystem I/O. | |
490 | * | |
491 | * Also, since we are only going for a minimum in the | |
31f34269 | 492 | * non-timestamp case, we do not smooth things out |
caa20d9a | 493 | * else with timestamps disabled convergence takes too |
1da177e4 LT |
494 | * long. |
495 | */ | |
496 | if (!win_dep) { | |
497 | m -= (new_sample >> 3); | |
498 | new_sample += m; | |
18a223e0 NC |
499 | } else { |
500 | m <<= 3; | |
501 | if (m < new_sample) | |
502 | new_sample = m; | |
503 | } | |
1da177e4 | 504 | } else { |
caa20d9a | 505 | /* No previous measure. */ |
1da177e4 LT |
506 | new_sample = m << 3; |
507 | } | |
508 | ||
509 | if (tp->rcv_rtt_est.rtt != new_sample) | |
510 | tp->rcv_rtt_est.rtt = new_sample; | |
511 | } | |
512 | ||
513 | static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) | |
514 | { | |
515 | if (tp->rcv_rtt_est.time == 0) | |
516 | goto new_measure; | |
517 | if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) | |
518 | return; | |
651913ce | 519 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1); |
1da177e4 LT |
520 | |
521 | new_measure: | |
522 | tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; | |
523 | tp->rcv_rtt_est.time = tcp_time_stamp; | |
524 | } | |
525 | ||
056834d9 IJ |
526 | static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, |
527 | const struct sk_buff *skb) | |
1da177e4 | 528 | { |
463c84b9 | 529 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
530 | if (tp->rx_opt.rcv_tsecr && |
531 | (TCP_SKB_CB(skb)->end_seq - | |
463c84b9 | 532 | TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) |
1da177e4 LT |
533 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); |
534 | } | |
535 | ||
536 | /* | |
537 | * This function should be called every time data is copied to user space. | |
538 | * It calculates the appropriate TCP receive buffer space. | |
539 | */ | |
540 | void tcp_rcv_space_adjust(struct sock *sk) | |
541 | { | |
542 | struct tcp_sock *tp = tcp_sk(sk); | |
543 | int time; | |
b0983d3c | 544 | int copied; |
e905a9ed | 545 | |
1da177e4 | 546 | time = tcp_time_stamp - tp->rcvq_space.time; |
056834d9 | 547 | if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) |
1da177e4 | 548 | return; |
e905a9ed | 549 | |
b0983d3c ED |
550 | /* Number of bytes copied to user in last RTT */ |
551 | copied = tp->copied_seq - tp->rcvq_space.seq; | |
552 | if (copied <= tp->rcvq_space.space) | |
553 | goto new_measure; | |
554 | ||
555 | /* A bit of theory : | |
556 | * copied = bytes received in previous RTT, our base window | |
557 | * To cope with packet losses, we need a 2x factor | |
558 | * To cope with slow start, and sender growing its cwin by 100 % | |
559 | * every RTT, we need a 4x factor, because the ACK we are sending | |
560 | * now is for the next RTT, not the current one : | |
561 | * <prev RTT . ><current RTT .. ><next RTT .... > | |
562 | */ | |
563 | ||
564 | if (sysctl_tcp_moderate_rcvbuf && | |
565 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { | |
566 | int rcvwin, rcvmem, rcvbuf; | |
1da177e4 | 567 | |
b0983d3c ED |
568 | /* minimal window to cope with packet losses, assuming |
569 | * steady state. Add some cushion because of small variations. | |
570 | */ | |
571 | rcvwin = (copied << 1) + 16 * tp->advmss; | |
1da177e4 | 572 | |
b0983d3c ED |
573 | /* If rate increased by 25%, |
574 | * assume slow start, rcvwin = 3 * copied | |
575 | * If rate increased by 50%, | |
576 | * assume sender can use 2x growth, rcvwin = 4 * copied | |
577 | */ | |
578 | if (copied >= | |
579 | tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) { | |
580 | if (copied >= | |
581 | tp->rcvq_space.space + (tp->rcvq_space.space >> 1)) | |
582 | rcvwin <<= 1; | |
583 | else | |
584 | rcvwin += (rcvwin >> 1); | |
585 | } | |
1da177e4 | 586 | |
b0983d3c ED |
587 | rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); |
588 | while (tcp_win_from_space(rcvmem) < tp->advmss) | |
589 | rcvmem += 128; | |
1da177e4 | 590 | |
b0983d3c ED |
591 | rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]); |
592 | if (rcvbuf > sk->sk_rcvbuf) { | |
593 | sk->sk_rcvbuf = rcvbuf; | |
1da177e4 | 594 | |
b0983d3c ED |
595 | /* Make the window clamp follow along. */ |
596 | tp->window_clamp = rcvwin; | |
1da177e4 LT |
597 | } |
598 | } | |
b0983d3c | 599 | tp->rcvq_space.space = copied; |
e905a9ed | 600 | |
1da177e4 LT |
601 | new_measure: |
602 | tp->rcvq_space.seq = tp->copied_seq; | |
603 | tp->rcvq_space.time = tcp_time_stamp; | |
604 | } | |
605 | ||
606 | /* There is something which you must keep in mind when you analyze the | |
607 | * behavior of the tp->ato delayed ack timeout interval. When a | |
608 | * connection starts up, we want to ack as quickly as possible. The | |
609 | * problem is that "good" TCP's do slow start at the beginning of data | |
610 | * transmission. The means that until we send the first few ACK's the | |
611 | * sender will sit on his end and only queue most of his data, because | |
612 | * he can only send snd_cwnd unacked packets at any given time. For | |
613 | * each ACK we send, he increments snd_cwnd and transmits more of his | |
614 | * queue. -DaveM | |
615 | */ | |
9e412ba7 | 616 | static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) |
1da177e4 | 617 | { |
9e412ba7 | 618 | struct tcp_sock *tp = tcp_sk(sk); |
463c84b9 | 619 | struct inet_connection_sock *icsk = inet_csk(sk); |
1da177e4 LT |
620 | u32 now; |
621 | ||
463c84b9 | 622 | inet_csk_schedule_ack(sk); |
1da177e4 | 623 | |
463c84b9 | 624 | tcp_measure_rcv_mss(sk, skb); |
1da177e4 LT |
625 | |
626 | tcp_rcv_rtt_measure(tp); | |
e905a9ed | 627 | |
1da177e4 LT |
628 | now = tcp_time_stamp; |
629 | ||
463c84b9 | 630 | if (!icsk->icsk_ack.ato) { |
1da177e4 LT |
631 | /* The _first_ data packet received, initialize |
632 | * delayed ACK engine. | |
633 | */ | |
463c84b9 ACM |
634 | tcp_incr_quickack(sk); |
635 | icsk->icsk_ack.ato = TCP_ATO_MIN; | |
1da177e4 | 636 | } else { |
463c84b9 | 637 | int m = now - icsk->icsk_ack.lrcvtime; |
1da177e4 | 638 | |
056834d9 | 639 | if (m <= TCP_ATO_MIN / 2) { |
1da177e4 | 640 | /* The fastest case is the first. */ |
463c84b9 ACM |
641 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
642 | } else if (m < icsk->icsk_ack.ato) { | |
643 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; | |
644 | if (icsk->icsk_ack.ato > icsk->icsk_rto) | |
645 | icsk->icsk_ack.ato = icsk->icsk_rto; | |
646 | } else if (m > icsk->icsk_rto) { | |
caa20d9a | 647 | /* Too long gap. Apparently sender failed to |
1da177e4 LT |
648 | * restart window, so that we send ACKs quickly. |
649 | */ | |
463c84b9 | 650 | tcp_incr_quickack(sk); |
3ab224be | 651 | sk_mem_reclaim(sk); |
1da177e4 LT |
652 | } |
653 | } | |
463c84b9 | 654 | icsk->icsk_ack.lrcvtime = now; |
1da177e4 LT |
655 | |
656 | TCP_ECN_check_ce(tp, skb); | |
657 | ||
658 | if (skb->len >= 128) | |
9e412ba7 | 659 | tcp_grow_window(sk, skb); |
1da177e4 LT |
660 | } |
661 | ||
1da177e4 LT |
662 | /* Called to compute a smoothed rtt estimate. The data fed to this |
663 | * routine either comes from timestamps, or from segments that were | |
664 | * known _not_ to have been retransmitted [see Karn/Partridge | |
665 | * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 | |
666 | * piece by Van Jacobson. | |
667 | * NOTE: the next three routines used to be one big routine. | |
668 | * To save cycles in the RFC 1323 implementation it was better to break | |
669 | * it up into three procedures. -- erics | |
670 | */ | |
740b0f18 | 671 | static void tcp_rtt_estimator(struct sock *sk, long mrtt_us) |
1da177e4 | 672 | { |
6687e988 | 673 | struct tcp_sock *tp = tcp_sk(sk); |
740b0f18 ED |
674 | long m = mrtt_us; /* RTT */ |
675 | u32 srtt = tp->srtt_us; | |
1da177e4 | 676 | |
1da177e4 LT |
677 | /* The following amusing code comes from Jacobson's |
678 | * article in SIGCOMM '88. Note that rtt and mdev | |
679 | * are scaled versions of rtt and mean deviation. | |
e905a9ed | 680 | * This is designed to be as fast as possible |
1da177e4 LT |
681 | * m stands for "measurement". |
682 | * | |
683 | * On a 1990 paper the rto value is changed to: | |
684 | * RTO = rtt + 4 * mdev | |
685 | * | |
686 | * Funny. This algorithm seems to be very broken. | |
687 | * These formulae increase RTO, when it should be decreased, increase | |
31f34269 | 688 | * too slowly, when it should be increased quickly, decrease too quickly |
1da177e4 LT |
689 | * etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
690 | * does not matter how to _calculate_ it. Seems, it was trap | |
691 | * that VJ failed to avoid. 8) | |
692 | */ | |
4a5ab4e2 ED |
693 | if (srtt != 0) { |
694 | m -= (srtt >> 3); /* m is now error in rtt est */ | |
695 | srtt += m; /* rtt = 7/8 rtt + 1/8 new */ | |
1da177e4 LT |
696 | if (m < 0) { |
697 | m = -m; /* m is now abs(error) */ | |
740b0f18 | 698 | m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
1da177e4 LT |
699 | /* This is similar to one of Eifel findings. |
700 | * Eifel blocks mdev updates when rtt decreases. | |
701 | * This solution is a bit different: we use finer gain | |
702 | * for mdev in this case (alpha*beta). | |
703 | * Like Eifel it also prevents growth of rto, | |
704 | * but also it limits too fast rto decreases, | |
705 | * happening in pure Eifel. | |
706 | */ | |
707 | if (m > 0) | |
708 | m >>= 3; | |
709 | } else { | |
740b0f18 | 710 | m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
1da177e4 | 711 | } |
740b0f18 ED |
712 | tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */ |
713 | if (tp->mdev_us > tp->mdev_max_us) { | |
714 | tp->mdev_max_us = tp->mdev_us; | |
715 | if (tp->mdev_max_us > tp->rttvar_us) | |
716 | tp->rttvar_us = tp->mdev_max_us; | |
1da177e4 LT |
717 | } |
718 | if (after(tp->snd_una, tp->rtt_seq)) { | |
740b0f18 ED |
719 | if (tp->mdev_max_us < tp->rttvar_us) |
720 | tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2; | |
1da177e4 | 721 | tp->rtt_seq = tp->snd_nxt; |
740b0f18 | 722 | tp->mdev_max_us = tcp_rto_min_us(sk); |
1da177e4 LT |
723 | } |
724 | } else { | |
725 | /* no previous measure. */ | |
4a5ab4e2 | 726 | srtt = m << 3; /* take the measured time to be rtt */ |
740b0f18 ED |
727 | tp->mdev_us = m << 1; /* make sure rto = 3*rtt */ |
728 | tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk)); | |
729 | tp->mdev_max_us = tp->rttvar_us; | |
1da177e4 LT |
730 | tp->rtt_seq = tp->snd_nxt; |
731 | } | |
740b0f18 | 732 | tp->srtt_us = max(1U, srtt); |
1da177e4 LT |
733 | } |
734 | ||
95bd09eb ED |
735 | /* Set the sk_pacing_rate to allow proper sizing of TSO packets. |
736 | * Note: TCP stack does not yet implement pacing. | |
737 | * FQ packet scheduler can be used to implement cheap but effective | |
738 | * TCP pacing, to smooth the burst on large writes when packets | |
739 | * in flight is significantly lower than cwnd (or rwin) | |
740 | */ | |
741 | static void tcp_update_pacing_rate(struct sock *sk) | |
742 | { | |
743 | const struct tcp_sock *tp = tcp_sk(sk); | |
744 | u64 rate; | |
745 | ||
746 | /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */ | |
740b0f18 | 747 | rate = (u64)tp->mss_cache * 2 * (USEC_PER_SEC << 3); |
95bd09eb ED |
748 | |
749 | rate *= max(tp->snd_cwnd, tp->packets_out); | |
750 | ||
740b0f18 ED |
751 | if (likely(tp->srtt_us)) |
752 | do_div(rate, tp->srtt_us); | |
95bd09eb | 753 | |
ba537427 ED |
754 | /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate |
755 | * without any lock. We want to make sure compiler wont store | |
756 | * intermediate values in this location. | |
757 | */ | |
758 | ACCESS_ONCE(sk->sk_pacing_rate) = min_t(u64, rate, | |
759 | sk->sk_max_pacing_rate); | |
95bd09eb ED |
760 | } |
761 | ||
1da177e4 LT |
762 | /* Calculate rto without backoff. This is the second half of Van Jacobson's |
763 | * routine referred to above. | |
764 | */ | |
f7e56a76 | 765 | static void tcp_set_rto(struct sock *sk) |
1da177e4 | 766 | { |
463c84b9 | 767 | const struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 LT |
768 | /* Old crap is replaced with new one. 8) |
769 | * | |
770 | * More seriously: | |
771 | * 1. If rtt variance happened to be less 50msec, it is hallucination. | |
772 | * It cannot be less due to utterly erratic ACK generation made | |
773 | * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ | |
774 | * to do with delayed acks, because at cwnd>2 true delack timeout | |
775 | * is invisible. Actually, Linux-2.4 also generates erratic | |
caa20d9a | 776 | * ACKs in some circumstances. |
1da177e4 | 777 | */ |
f1ecd5d9 | 778 | inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); |
1da177e4 LT |
779 | |
780 | /* 2. Fixups made earlier cannot be right. | |
781 | * If we do not estimate RTO correctly without them, | |
782 | * all the algo is pure shit and should be replaced | |
caa20d9a | 783 | * with correct one. It is exactly, which we pretend to do. |
1da177e4 | 784 | */ |
1da177e4 | 785 | |
ee6aac59 IJ |
786 | /* NOTE: clamping at TCP_RTO_MIN is not required, current algo |
787 | * guarantees that rto is higher. | |
788 | */ | |
f1ecd5d9 | 789 | tcp_bound_rto(sk); |
1da177e4 LT |
790 | } |
791 | ||
cf533ea5 | 792 | __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) |
1da177e4 LT |
793 | { |
794 | __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); | |
795 | ||
22b71c8f | 796 | if (!cwnd) |
442b9635 | 797 | cwnd = TCP_INIT_CWND; |
1da177e4 LT |
798 | return min_t(__u32, cwnd, tp->snd_cwnd_clamp); |
799 | } | |
800 | ||
e60402d0 IJ |
801 | /* |
802 | * Packet counting of FACK is based on in-order assumptions, therefore TCP | |
803 | * disables it when reordering is detected | |
804 | */ | |
4aabd8ef | 805 | void tcp_disable_fack(struct tcp_sock *tp) |
e60402d0 | 806 | { |
85cc391c IJ |
807 | /* RFC3517 uses different metric in lost marker => reset on change */ |
808 | if (tcp_is_fack(tp)) | |
809 | tp->lost_skb_hint = NULL; | |
ab56222a | 810 | tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED; |
e60402d0 IJ |
811 | } |
812 | ||
564262c1 | 813 | /* Take a notice that peer is sending D-SACKs */ |
e60402d0 IJ |
814 | static void tcp_dsack_seen(struct tcp_sock *tp) |
815 | { | |
ab56222a | 816 | tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; |
e60402d0 IJ |
817 | } |
818 | ||
6687e988 ACM |
819 | static void tcp_update_reordering(struct sock *sk, const int metric, |
820 | const int ts) | |
1da177e4 | 821 | { |
6687e988 | 822 | struct tcp_sock *tp = tcp_sk(sk); |
1da177e4 | 823 | if (metric > tp->reordering) { |
40b215e5 PE |
824 | int mib_idx; |
825 | ||
1da177e4 LT |
826 | tp->reordering = min(TCP_MAX_REORDERING, metric); |
827 | ||
828 | /* This exciting event is worth to be remembered. 8) */ | |
829 | if (ts) | |
40b215e5 | 830 | mib_idx = LINUX_MIB_TCPTSREORDER; |
e60402d0 | 831 | else if (tcp_is_reno(tp)) |
40b215e5 | 832 | mib_idx = LINUX_MIB_TCPRENOREORDER; |
e60402d0 | 833 | else if (tcp_is_fack(tp)) |
40b215e5 | 834 | mib_idx = LINUX_MIB_TCPFACKREORDER; |
1da177e4 | 835 | else |
40b215e5 PE |
836 | mib_idx = LINUX_MIB_TCPSACKREORDER; |
837 | ||
de0744af | 838 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
1da177e4 | 839 | #if FASTRETRANS_DEBUG > 1 |
91df42be JP |
840 | pr_debug("Disorder%d %d %u f%u s%u rr%d\n", |
841 | tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, | |
842 | tp->reordering, | |
843 | tp->fackets_out, | |
844 | tp->sacked_out, | |
845 | tp->undo_marker ? tp->undo_retrans : 0); | |
1da177e4 | 846 | #endif |
e60402d0 | 847 | tcp_disable_fack(tp); |
1da177e4 | 848 | } |
eed530b6 YC |
849 | |
850 | if (metric > 0) | |
851 | tcp_disable_early_retrans(tp); | |
1da177e4 LT |
852 | } |
853 | ||
006f582c | 854 | /* This must be called before lost_out is incremented */ |
c8c213f2 IJ |
855 | static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) |
856 | { | |
006f582c | 857 | if ((tp->retransmit_skb_hint == NULL) || |
c8c213f2 IJ |
858 | before(TCP_SKB_CB(skb)->seq, |
859 | TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) | |
006f582c IJ |
860 | tp->retransmit_skb_hint = skb; |
861 | ||
862 | if (!tp->lost_out || | |
863 | after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) | |
864 | tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; | |
c8c213f2 IJ |
865 | } |
866 | ||
41ea36e3 IJ |
867 | static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) |
868 | { | |
869 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { | |
870 | tcp_verify_retransmit_hint(tp, skb); | |
871 | ||
872 | tp->lost_out += tcp_skb_pcount(skb); | |
873 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
874 | } | |
875 | } | |
876 | ||
e1aa680f IJ |
877 | static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, |
878 | struct sk_buff *skb) | |
006f582c IJ |
879 | { |
880 | tcp_verify_retransmit_hint(tp, skb); | |
881 | ||
882 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { | |
883 | tp->lost_out += tcp_skb_pcount(skb); | |
884 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
885 | } | |
886 | } | |
887 | ||
1da177e4 LT |
888 | /* This procedure tags the retransmission queue when SACKs arrive. |
889 | * | |
890 | * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). | |
891 | * Packets in queue with these bits set are counted in variables | |
892 | * sacked_out, retrans_out and lost_out, correspondingly. | |
893 | * | |
894 | * Valid combinations are: | |
895 | * Tag InFlight Description | |
896 | * 0 1 - orig segment is in flight. | |
897 | * S 0 - nothing flies, orig reached receiver. | |
898 | * L 0 - nothing flies, orig lost by net. | |
899 | * R 2 - both orig and retransmit are in flight. | |
900 | * L|R 1 - orig is lost, retransmit is in flight. | |
901 | * S|R 1 - orig reached receiver, retrans is still in flight. | |
902 | * (L|S|R is logically valid, it could occur when L|R is sacked, | |
903 | * but it is equivalent to plain S and code short-curcuits it to S. | |
904 | * L|S is logically invalid, it would mean -1 packet in flight 8)) | |
905 | * | |
906 | * These 6 states form finite state machine, controlled by the following events: | |
907 | * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) | |
908 | * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) | |
974c1236 | 909 | * 3. Loss detection event of two flavors: |
1da177e4 LT |
910 | * A. Scoreboard estimator decided the packet is lost. |
911 | * A'. Reno "three dupacks" marks head of queue lost. | |
974c1236 YC |
912 | * A''. Its FACK modification, head until snd.fack is lost. |
913 | * B. SACK arrives sacking SND.NXT at the moment, when the | |
1da177e4 LT |
914 | * segment was retransmitted. |
915 | * 4. D-SACK added new rule: D-SACK changes any tag to S. | |
916 | * | |
917 | * It is pleasant to note, that state diagram turns out to be commutative, | |
918 | * so that we are allowed not to be bothered by order of our actions, | |
919 | * when multiple events arrive simultaneously. (see the function below). | |
920 | * | |
921 | * Reordering detection. | |
922 | * -------------------- | |
923 | * Reordering metric is maximal distance, which a packet can be displaced | |
924 | * in packet stream. With SACKs we can estimate it: | |
925 | * | |
926 | * 1. SACK fills old hole and the corresponding segment was not | |
927 | * ever retransmitted -> reordering. Alas, we cannot use it | |
928 | * when segment was retransmitted. | |
929 | * 2. The last flaw is solved with D-SACK. D-SACK arrives | |
930 | * for retransmitted and already SACKed segment -> reordering.. | |
931 | * Both of these heuristics are not used in Loss state, when we cannot | |
932 | * account for retransmits accurately. | |
5b3c9882 IJ |
933 | * |
934 | * SACK block validation. | |
935 | * ---------------------- | |
936 | * | |
937 | * SACK block range validation checks that the received SACK block fits to | |
938 | * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. | |
939 | * Note that SND.UNA is not included to the range though being valid because | |
0e835331 IJ |
940 | * it means that the receiver is rather inconsistent with itself reporting |
941 | * SACK reneging when it should advance SND.UNA. Such SACK block this is | |
942 | * perfectly valid, however, in light of RFC2018 which explicitly states | |
943 | * that "SACK block MUST reflect the newest segment. Even if the newest | |
944 | * segment is going to be discarded ...", not that it looks very clever | |
945 | * in case of head skb. Due to potentional receiver driven attacks, we | |
946 | * choose to avoid immediate execution of a walk in write queue due to | |
947 | * reneging and defer head skb's loss recovery to standard loss recovery | |
948 | * procedure that will eventually trigger (nothing forbids us doing this). | |
5b3c9882 IJ |
949 | * |
950 | * Implements also blockage to start_seq wrap-around. Problem lies in the | |
951 | * fact that though start_seq (s) is before end_seq (i.e., not reversed), | |
952 | * there's no guarantee that it will be before snd_nxt (n). The problem | |
953 | * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt | |
954 | * wrap (s_w): | |
955 | * | |
956 | * <- outs wnd -> <- wrapzone -> | |
957 | * u e n u_w e_w s n_w | |
958 | * | | | | | | | | |
959 | * |<------------+------+----- TCP seqno space --------------+---------->| | |
960 | * ...-- <2^31 ->| |<--------... | |
961 | * ...---- >2^31 ------>| |<--------... | |
962 | * | |
963 | * Current code wouldn't be vulnerable but it's better still to discard such | |
964 | * crazy SACK blocks. Doing this check for start_seq alone closes somewhat | |
965 | * similar case (end_seq after snd_nxt wrap) as earlier reversed check in | |
966 | * snd_nxt wrap -> snd_una region will then become "well defined", i.e., | |
967 | * equal to the ideal case (infinite seqno space without wrap caused issues). | |
968 | * | |
969 | * With D-SACK the lower bound is extended to cover sequence space below | |
970 | * SND.UNA down to undo_marker, which is the last point of interest. Yet | |
564262c1 | 971 | * again, D-SACK block must not to go across snd_una (for the same reason as |
5b3c9882 IJ |
972 | * for the normal SACK blocks, explained above). But there all simplicity |
973 | * ends, TCP might receive valid D-SACKs below that. As long as they reside | |
974 | * fully below undo_marker they do not affect behavior in anyway and can | |
975 | * therefore be safely ignored. In rare cases (which are more or less | |
976 | * theoretical ones), the D-SACK will nicely cross that boundary due to skb | |
977 | * fragmentation and packet reordering past skb's retransmission. To consider | |
978 | * them correctly, the acceptable range must be extended even more though | |
979 | * the exact amount is rather hard to quantify. However, tp->max_window can | |
980 | * be used as an exaggerated estimate. | |
1da177e4 | 981 | */ |
a2a385d6 ED |
982 | static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack, |
983 | u32 start_seq, u32 end_seq) | |
5b3c9882 IJ |
984 | { |
985 | /* Too far in future, or reversed (interpretation is ambiguous) */ | |
986 | if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) | |
a2a385d6 | 987 | return false; |
5b3c9882 IJ |
988 | |
989 | /* Nasty start_seq wrap-around check (see comments above) */ | |
990 | if (!before(start_seq, tp->snd_nxt)) | |
a2a385d6 | 991 | return false; |
5b3c9882 | 992 | |
564262c1 | 993 | /* In outstanding window? ...This is valid exit for D-SACKs too. |
5b3c9882 IJ |
994 | * start_seq == snd_una is non-sensical (see comments above) |
995 | */ | |
996 | if (after(start_seq, tp->snd_una)) | |
a2a385d6 | 997 | return true; |
5b3c9882 IJ |
998 | |
999 | if (!is_dsack || !tp->undo_marker) | |
a2a385d6 | 1000 | return false; |
5b3c9882 IJ |
1001 | |
1002 | /* ...Then it's D-SACK, and must reside below snd_una completely */ | |
f779b2d6 | 1003 | if (after(end_seq, tp->snd_una)) |
a2a385d6 | 1004 | return false; |
5b3c9882 IJ |
1005 | |
1006 | if (!before(start_seq, tp->undo_marker)) | |
a2a385d6 | 1007 | return true; |
5b3c9882 IJ |
1008 | |
1009 | /* Too old */ | |
1010 | if (!after(end_seq, tp->undo_marker)) | |
a2a385d6 | 1011 | return false; |
5b3c9882 IJ |
1012 | |
1013 | /* Undo_marker boundary crossing (overestimates a lot). Known already: | |
1014 | * start_seq < undo_marker and end_seq >= undo_marker. | |
1015 | */ | |
1016 | return !before(start_seq, end_seq - tp->max_window); | |
1017 | } | |
1018 | ||
1c1e87ed | 1019 | /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". |
974c1236 | 1020 | * Event "B". Later note: FACK people cheated me again 8), we have to account |
1c1e87ed | 1021 | * for reordering! Ugly, but should help. |
f785a8e2 IJ |
1022 | * |
1023 | * Search retransmitted skbs from write_queue that were sent when snd_nxt was | |
1024 | * less than what is now known to be received by the other end (derived from | |
9f58f3b7 IJ |
1025 | * highest SACK block). Also calculate the lowest snd_nxt among the remaining |
1026 | * retransmitted skbs to avoid some costly processing per ACKs. | |
1c1e87ed | 1027 | */ |
407ef1de | 1028 | static void tcp_mark_lost_retrans(struct sock *sk) |
1c1e87ed | 1029 | { |
9f58f3b7 | 1030 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1c1e87ed IJ |
1031 | struct tcp_sock *tp = tcp_sk(sk); |
1032 | struct sk_buff *skb; | |
f785a8e2 | 1033 | int cnt = 0; |
df2e014b | 1034 | u32 new_low_seq = tp->snd_nxt; |
6859d494 | 1035 | u32 received_upto = tcp_highest_sack_seq(tp); |
9f58f3b7 IJ |
1036 | |
1037 | if (!tcp_is_fack(tp) || !tp->retrans_out || | |
1038 | !after(received_upto, tp->lost_retrans_low) || | |
1039 | icsk->icsk_ca_state != TCP_CA_Recovery) | |
407ef1de | 1040 | return; |
1c1e87ed IJ |
1041 | |
1042 | tcp_for_write_queue(skb, sk) { | |
1043 | u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; | |
1044 | ||
1045 | if (skb == tcp_send_head(sk)) | |
1046 | break; | |
f785a8e2 | 1047 | if (cnt == tp->retrans_out) |
1c1e87ed IJ |
1048 | break; |
1049 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) | |
1050 | continue; | |
1051 | ||
f785a8e2 IJ |
1052 | if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) |
1053 | continue; | |
1054 | ||
d0af4160 IJ |
1055 | /* TODO: We would like to get rid of tcp_is_fack(tp) only |
1056 | * constraint here (see above) but figuring out that at | |
1057 | * least tp->reordering SACK blocks reside between ack_seq | |
1058 | * and received_upto is not easy task to do cheaply with | |
1059 | * the available datastructures. | |
1060 | * | |
1061 | * Whether FACK should check here for tp->reordering segs | |
1062 | * in-between one could argue for either way (it would be | |
1063 | * rather simple to implement as we could count fack_count | |
1064 | * during the walk and do tp->fackets_out - fack_count). | |
1065 | */ | |
1066 | if (after(received_upto, ack_seq)) { | |
1c1e87ed IJ |
1067 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
1068 | tp->retrans_out -= tcp_skb_pcount(skb); | |
1069 | ||
006f582c | 1070 | tcp_skb_mark_lost_uncond_verify(tp, skb); |
de0744af | 1071 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); |
f785a8e2 | 1072 | } else { |
df2e014b | 1073 | if (before(ack_seq, new_low_seq)) |
b08d6cb2 | 1074 | new_low_seq = ack_seq; |
f785a8e2 | 1075 | cnt += tcp_skb_pcount(skb); |
1c1e87ed IJ |
1076 | } |
1077 | } | |
b08d6cb2 IJ |
1078 | |
1079 | if (tp->retrans_out) | |
1080 | tp->lost_retrans_low = new_low_seq; | |
1c1e87ed | 1081 | } |
5b3c9882 | 1082 | |
a2a385d6 ED |
1083 | static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, |
1084 | struct tcp_sack_block_wire *sp, int num_sacks, | |
1085 | u32 prior_snd_una) | |
d06e021d | 1086 | { |
1ed83465 | 1087 | struct tcp_sock *tp = tcp_sk(sk); |
d3e2ce3b HH |
1088 | u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); |
1089 | u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); | |
a2a385d6 | 1090 | bool dup_sack = false; |
d06e021d DM |
1091 | |
1092 | if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { | |
a2a385d6 | 1093 | dup_sack = true; |
e60402d0 | 1094 | tcp_dsack_seen(tp); |
de0744af | 1095 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); |
d06e021d | 1096 | } else if (num_sacks > 1) { |
d3e2ce3b HH |
1097 | u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); |
1098 | u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); | |
d06e021d DM |
1099 | |
1100 | if (!after(end_seq_0, end_seq_1) && | |
1101 | !before(start_seq_0, start_seq_1)) { | |
a2a385d6 | 1102 | dup_sack = true; |
e60402d0 | 1103 | tcp_dsack_seen(tp); |
de0744af PE |
1104 | NET_INC_STATS_BH(sock_net(sk), |
1105 | LINUX_MIB_TCPDSACKOFORECV); | |
d06e021d DM |
1106 | } |
1107 | } | |
1108 | ||
1109 | /* D-SACK for already forgotten data... Do dumb counting. */ | |
6e08d5e3 | 1110 | if (dup_sack && tp->undo_marker && tp->undo_retrans > 0 && |
d06e021d DM |
1111 | !after(end_seq_0, prior_snd_una) && |
1112 | after(end_seq_0, tp->undo_marker)) | |
1113 | tp->undo_retrans--; | |
1114 | ||
1115 | return dup_sack; | |
1116 | } | |
1117 | ||
a1197f5a | 1118 | struct tcp_sacktag_state { |
740b0f18 ED |
1119 | int reord; |
1120 | int fack_count; | |
1121 | long rtt_us; /* RTT measured by SACKing never-retransmitted data */ | |
1122 | int flag; | |
a1197f5a IJ |
1123 | }; |
1124 | ||
d1935942 IJ |
1125 | /* Check if skb is fully within the SACK block. In presence of GSO skbs, |
1126 | * the incoming SACK may not exactly match but we can find smaller MSS | |
1127 | * aligned portion of it that matches. Therefore we might need to fragment | |
1128 | * which may fail and creates some hassle (caller must handle error case | |
1129 | * returns). | |
832d11c5 IJ |
1130 | * |
1131 | * FIXME: this could be merged to shift decision code | |
d1935942 | 1132 | */ |
0f79efdc | 1133 | static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, |
a2a385d6 | 1134 | u32 start_seq, u32 end_seq) |
d1935942 | 1135 | { |
a2a385d6 ED |
1136 | int err; |
1137 | bool in_sack; | |
d1935942 | 1138 | unsigned int pkt_len; |
adb92db8 | 1139 | unsigned int mss; |
d1935942 IJ |
1140 | |
1141 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && | |
1142 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); | |
1143 | ||
1144 | if (tcp_skb_pcount(skb) > 1 && !in_sack && | |
1145 | after(TCP_SKB_CB(skb)->end_seq, start_seq)) { | |
adb92db8 | 1146 | mss = tcp_skb_mss(skb); |
d1935942 IJ |
1147 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
1148 | ||
adb92db8 | 1149 | if (!in_sack) { |
d1935942 | 1150 | pkt_len = start_seq - TCP_SKB_CB(skb)->seq; |
adb92db8 IJ |
1151 | if (pkt_len < mss) |
1152 | pkt_len = mss; | |
1153 | } else { | |
d1935942 | 1154 | pkt_len = end_seq - TCP_SKB_CB(skb)->seq; |
adb92db8 IJ |
1155 | if (pkt_len < mss) |
1156 | return -EINVAL; | |
1157 | } | |
1158 | ||
1159 | /* Round if necessary so that SACKs cover only full MSSes | |
1160 | * and/or the remaining small portion (if present) | |
1161 | */ | |
1162 | if (pkt_len > mss) { | |
1163 | unsigned int new_len = (pkt_len / mss) * mss; | |
1164 | if (!in_sack && new_len < pkt_len) { | |
1165 | new_len += mss; | |
2cd0d743 | 1166 | if (new_len >= skb->len) |
adb92db8 IJ |
1167 | return 0; |
1168 | } | |
1169 | pkt_len = new_len; | |
1170 | } | |
6cc55e09 | 1171 | err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC); |
d1935942 IJ |
1172 | if (err < 0) |
1173 | return err; | |
1174 | } | |
1175 | ||
1176 | return in_sack; | |
1177 | } | |
1178 | ||
cc9a672e NC |
1179 | /* Mark the given newly-SACKed range as such, adjusting counters and hints. */ |
1180 | static u8 tcp_sacktag_one(struct sock *sk, | |
1181 | struct tcp_sacktag_state *state, u8 sacked, | |
1182 | u32 start_seq, u32 end_seq, | |
740b0f18 ED |
1183 | int dup_sack, int pcount, |
1184 | const struct skb_mstamp *xmit_time) | |
9e10c47c | 1185 | { |
6859d494 | 1186 | struct tcp_sock *tp = tcp_sk(sk); |
a1197f5a | 1187 | int fack_count = state->fack_count; |
9e10c47c IJ |
1188 | |
1189 | /* Account D-SACK for retransmitted packet. */ | |
1190 | if (dup_sack && (sacked & TCPCB_RETRANS)) { | |
6e08d5e3 | 1191 | if (tp->undo_marker && tp->undo_retrans > 0 && |
cc9a672e | 1192 | after(end_seq, tp->undo_marker)) |
9e10c47c | 1193 | tp->undo_retrans--; |
ede9f3b1 | 1194 | if (sacked & TCPCB_SACKED_ACKED) |
a1197f5a | 1195 | state->reord = min(fack_count, state->reord); |
9e10c47c IJ |
1196 | } |
1197 | ||
1198 | /* Nothing to do; acked frame is about to be dropped (was ACKed). */ | |
cc9a672e | 1199 | if (!after(end_seq, tp->snd_una)) |
a1197f5a | 1200 | return sacked; |
9e10c47c IJ |
1201 | |
1202 | if (!(sacked & TCPCB_SACKED_ACKED)) { | |
1203 | if (sacked & TCPCB_SACKED_RETRANS) { | |
1204 | /* If the segment is not tagged as lost, | |
1205 | * we do not clear RETRANS, believing | |
1206 | * that retransmission is still in flight. | |
1207 | */ | |
1208 | if (sacked & TCPCB_LOST) { | |
a1197f5a | 1209 | sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); |
f58b22fd IJ |
1210 | tp->lost_out -= pcount; |
1211 | tp->retrans_out -= pcount; | |
9e10c47c IJ |
1212 | } |
1213 | } else { | |
1214 | if (!(sacked & TCPCB_RETRANS)) { | |
1215 | /* New sack for not retransmitted frame, | |
1216 | * which was in hole. It is reordering. | |
1217 | */ | |
cc9a672e | 1218 | if (before(start_seq, |
9e10c47c | 1219 | tcp_highest_sack_seq(tp))) |
a1197f5a IJ |
1220 | state->reord = min(fack_count, |
1221 | state->reord); | |
e33099f9 YC |
1222 | if (!after(end_seq, tp->high_seq)) |
1223 | state->flag |= FLAG_ORIG_SACK_ACKED; | |
59c9af42 | 1224 | /* Pick the earliest sequence sacked for RTT */ |
740b0f18 ED |
1225 | if (state->rtt_us < 0) { |
1226 | struct skb_mstamp now; | |
1227 | ||
1228 | skb_mstamp_get(&now); | |
1229 | state->rtt_us = skb_mstamp_us_delta(&now, | |
1230 | xmit_time); | |
1231 | } | |
9e10c47c IJ |
1232 | } |
1233 | ||
1234 | if (sacked & TCPCB_LOST) { | |
a1197f5a | 1235 | sacked &= ~TCPCB_LOST; |
f58b22fd | 1236 | tp->lost_out -= pcount; |
9e10c47c IJ |
1237 | } |
1238 | } | |
1239 | ||
a1197f5a IJ |
1240 | sacked |= TCPCB_SACKED_ACKED; |
1241 | state->flag |= FLAG_DATA_SACKED; | |
f58b22fd | 1242 | tp->sacked_out += pcount; |
9e10c47c | 1243 | |
f58b22fd | 1244 | fack_count += pcount; |
9e10c47c IJ |
1245 | |
1246 | /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ | |
1247 | if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && | |
cc9a672e | 1248 | before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq)) |
f58b22fd | 1249 | tp->lost_cnt_hint += pcount; |
9e10c47c IJ |
1250 | |
1251 | if (fack_count > tp->fackets_out) | |
1252 | tp->fackets_out = fack_count; | |
9e10c47c IJ |
1253 | } |
1254 | ||
1255 | /* D-SACK. We can detect redundant retransmission in S|R and plain R | |
1256 | * frames and clear it. undo_retrans is decreased above, L|R frames | |
1257 | * are accounted above as well. | |
1258 | */ | |
a1197f5a IJ |
1259 | if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { |
1260 | sacked &= ~TCPCB_SACKED_RETRANS; | |
f58b22fd | 1261 | tp->retrans_out -= pcount; |
9e10c47c IJ |
1262 | } |
1263 | ||
a1197f5a | 1264 | return sacked; |
9e10c47c IJ |
1265 | } |
1266 | ||
daef52ba NC |
1267 | /* Shift newly-SACKed bytes from this skb to the immediately previous |
1268 | * already-SACKed sk_buff. Mark the newly-SACKed bytes as such. | |
1269 | */ | |
a2a385d6 ED |
1270 | static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, |
1271 | struct tcp_sacktag_state *state, | |
1272 | unsigned int pcount, int shifted, int mss, | |
1273 | bool dup_sack) | |
832d11c5 IJ |
1274 | { |
1275 | struct tcp_sock *tp = tcp_sk(sk); | |
50133161 | 1276 | struct sk_buff *prev = tcp_write_queue_prev(sk, skb); |
daef52ba NC |
1277 | u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */ |
1278 | u32 end_seq = start_seq + shifted; /* end of newly-SACKed */ | |
832d11c5 IJ |
1279 | |
1280 | BUG_ON(!pcount); | |
1281 | ||
4c90d3b3 NC |
1282 | /* Adjust counters and hints for the newly sacked sequence |
1283 | * range but discard the return value since prev is already | |
1284 | * marked. We must tag the range first because the seq | |
1285 | * advancement below implicitly advances | |
1286 | * tcp_highest_sack_seq() when skb is highest_sack. | |
1287 | */ | |
1288 | tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked, | |
59c9af42 | 1289 | start_seq, end_seq, dup_sack, pcount, |
740b0f18 | 1290 | &skb->skb_mstamp); |
4c90d3b3 NC |
1291 | |
1292 | if (skb == tp->lost_skb_hint) | |
0af2a0d0 NC |
1293 | tp->lost_cnt_hint += pcount; |
1294 | ||
832d11c5 IJ |
1295 | TCP_SKB_CB(prev)->end_seq += shifted; |
1296 | TCP_SKB_CB(skb)->seq += shifted; | |
1297 | ||
1298 | skb_shinfo(prev)->gso_segs += pcount; | |
1299 | BUG_ON(skb_shinfo(skb)->gso_segs < pcount); | |
1300 | skb_shinfo(skb)->gso_segs -= pcount; | |
1301 | ||
1302 | /* When we're adding to gso_segs == 1, gso_size will be zero, | |
1303 | * in theory this shouldn't be necessary but as long as DSACK | |
1304 | * code can come after this skb later on it's better to keep | |
1305 | * setting gso_size to something. | |
1306 | */ | |
1307 | if (!skb_shinfo(prev)->gso_size) { | |
1308 | skb_shinfo(prev)->gso_size = mss; | |
c9af6db4 | 1309 | skb_shinfo(prev)->gso_type = sk->sk_gso_type; |
832d11c5 IJ |
1310 | } |
1311 | ||
1312 | /* CHECKME: To clear or not to clear? Mimics normal skb currently */ | |
1313 | if (skb_shinfo(skb)->gso_segs <= 1) { | |
1314 | skb_shinfo(skb)->gso_size = 0; | |
c9af6db4 | 1315 | skb_shinfo(skb)->gso_type = 0; |
832d11c5 IJ |
1316 | } |
1317 | ||
832d11c5 IJ |
1318 | /* Difference in this won't matter, both ACKed by the same cumul. ACK */ |
1319 | TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); | |
1320 | ||
832d11c5 IJ |
1321 | if (skb->len > 0) { |
1322 | BUG_ON(!tcp_skb_pcount(skb)); | |
111cc8b9 | 1323 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); |
a2a385d6 | 1324 | return false; |
832d11c5 IJ |
1325 | } |
1326 | ||
1327 | /* Whole SKB was eaten :-) */ | |
1328 | ||
92ee76b6 IJ |
1329 | if (skb == tp->retransmit_skb_hint) |
1330 | tp->retransmit_skb_hint = prev; | |
92ee76b6 IJ |
1331 | if (skb == tp->lost_skb_hint) { |
1332 | tp->lost_skb_hint = prev; | |
1333 | tp->lost_cnt_hint -= tcp_skb_pcount(prev); | |
1334 | } | |
1335 | ||
5e8a402f ED |
1336 | TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; |
1337 | if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) | |
1338 | TCP_SKB_CB(prev)->end_seq++; | |
1339 | ||
832d11c5 IJ |
1340 | if (skb == tcp_highest_sack(sk)) |
1341 | tcp_advance_highest_sack(sk, skb); | |
1342 | ||
1343 | tcp_unlink_write_queue(skb, sk); | |
1344 | sk_wmem_free_skb(sk, skb); | |
1345 | ||
111cc8b9 IJ |
1346 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); |
1347 | ||
a2a385d6 | 1348 | return true; |
832d11c5 IJ |
1349 | } |
1350 | ||
1351 | /* I wish gso_size would have a bit more sane initialization than | |
1352 | * something-or-zero which complicates things | |
1353 | */ | |
cf533ea5 | 1354 | static int tcp_skb_seglen(const struct sk_buff *skb) |
832d11c5 | 1355 | { |
775ffabf | 1356 | return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); |
832d11c5 IJ |
1357 | } |
1358 | ||
1359 | /* Shifting pages past head area doesn't work */ | |
cf533ea5 | 1360 | static int skb_can_shift(const struct sk_buff *skb) |
832d11c5 IJ |
1361 | { |
1362 | return !skb_headlen(skb) && skb_is_nonlinear(skb); | |
1363 | } | |
1364 | ||
1365 | /* Try collapsing SACK blocks spanning across multiple skbs to a single | |
1366 | * skb. | |
1367 | */ | |
1368 | static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, | |
a1197f5a | 1369 | struct tcp_sacktag_state *state, |
832d11c5 | 1370 | u32 start_seq, u32 end_seq, |
a2a385d6 | 1371 | bool dup_sack) |
832d11c5 IJ |
1372 | { |
1373 | struct tcp_sock *tp = tcp_sk(sk); | |
1374 | struct sk_buff *prev; | |
1375 | int mss; | |
1376 | int pcount = 0; | |
1377 | int len; | |
1378 | int in_sack; | |
1379 | ||
1380 | if (!sk_can_gso(sk)) | |
1381 | goto fallback; | |
1382 | ||
1383 | /* Normally R but no L won't result in plain S */ | |
1384 | if (!dup_sack && | |
9969ca5f | 1385 | (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) |
832d11c5 IJ |
1386 | goto fallback; |
1387 | if (!skb_can_shift(skb)) | |
1388 | goto fallback; | |
1389 | /* This frame is about to be dropped (was ACKed). */ | |
1390 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) | |
1391 | goto fallback; | |
1392 | ||
1393 | /* Can only happen with delayed DSACK + discard craziness */ | |
1394 | if (unlikely(skb == tcp_write_queue_head(sk))) | |
1395 | goto fallback; | |
1396 | prev = tcp_write_queue_prev(sk, skb); | |
1397 | ||
1398 | if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) | |
1399 | goto fallback; | |
1400 | ||
1401 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && | |
1402 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); | |
1403 | ||
1404 | if (in_sack) { | |
1405 | len = skb->len; | |
1406 | pcount = tcp_skb_pcount(skb); | |
775ffabf | 1407 | mss = tcp_skb_seglen(skb); |
832d11c5 IJ |
1408 | |
1409 | /* TODO: Fix DSACKs to not fragment already SACKed and we can | |
1410 | * drop this restriction as unnecessary | |
1411 | */ | |
775ffabf | 1412 | if (mss != tcp_skb_seglen(prev)) |
832d11c5 IJ |
1413 | goto fallback; |
1414 | } else { | |
1415 | if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) | |
1416 | goto noop; | |
1417 | /* CHECKME: This is non-MSS split case only?, this will | |
1418 | * cause skipped skbs due to advancing loop btw, original | |
1419 | * has that feature too | |
1420 | */ | |
1421 | if (tcp_skb_pcount(skb) <= 1) | |
1422 | goto noop; | |
1423 | ||
1424 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); | |
1425 | if (!in_sack) { | |
1426 | /* TODO: head merge to next could be attempted here | |
1427 | * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), | |
1428 | * though it might not be worth of the additional hassle | |
1429 | * | |
1430 | * ...we can probably just fallback to what was done | |
1431 | * previously. We could try merging non-SACKed ones | |
1432 | * as well but it probably isn't going to buy off | |
1433 | * because later SACKs might again split them, and | |
1434 | * it would make skb timestamp tracking considerably | |
1435 | * harder problem. | |
1436 | */ | |
1437 | goto fallback; | |
1438 | } | |
1439 | ||
1440 | len = end_seq - TCP_SKB_CB(skb)->seq; | |
1441 | BUG_ON(len < 0); | |
1442 | BUG_ON(len > skb->len); | |
1443 | ||
1444 | /* MSS boundaries should be honoured or else pcount will | |
1445 | * severely break even though it makes things bit trickier. | |
1446 | * Optimize common case to avoid most of the divides | |
1447 | */ | |
1448 | mss = tcp_skb_mss(skb); | |
1449 | ||
1450 | /* TODO: Fix DSACKs to not fragment already SACKed and we can | |
1451 | * drop this restriction as unnecessary | |
1452 | */ | |
775ffabf | 1453 | if (mss != tcp_skb_seglen(prev)) |
832d11c5 IJ |
1454 | goto fallback; |
1455 | ||
1456 | if (len == mss) { | |
1457 | pcount = 1; | |
1458 | } else if (len < mss) { | |
1459 | goto noop; | |
1460 | } else { | |
1461 | pcount = len / mss; | |
1462 | len = pcount * mss; | |
1463 | } | |
1464 | } | |
1465 | ||
4648dc97 NC |
1466 | /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */ |
1467 | if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una)) | |
1468 | goto fallback; | |
1469 | ||
832d11c5 IJ |
1470 | if (!skb_shift(prev, skb, len)) |
1471 | goto fallback; | |
9ec06ff5 | 1472 | if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) |
832d11c5 IJ |
1473 | goto out; |
1474 | ||
1475 | /* Hole filled allows collapsing with the next as well, this is very | |
1476 | * useful when hole on every nth skb pattern happens | |
1477 | */ | |
1478 | if (prev == tcp_write_queue_tail(sk)) | |
1479 | goto out; | |
1480 | skb = tcp_write_queue_next(sk, prev); | |
1481 | ||
f0bc52f3 IJ |
1482 | if (!skb_can_shift(skb) || |
1483 | (skb == tcp_send_head(sk)) || | |
1484 | ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || | |
775ffabf | 1485 | (mss != tcp_skb_seglen(skb))) |
832d11c5 IJ |
1486 | goto out; |
1487 | ||
1488 | len = skb->len; | |
1489 | if (skb_shift(prev, skb, len)) { | |
1490 | pcount += tcp_skb_pcount(skb); | |
9ec06ff5 | 1491 | tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); |
832d11c5 IJ |
1492 | } |
1493 | ||
1494 | out: | |
a1197f5a | 1495 | state->fack_count += pcount; |
832d11c5 IJ |
1496 | return prev; |
1497 | ||
1498 | noop: | |
1499 | return skb; | |
1500 | ||
1501 | fallback: | |
111cc8b9 | 1502 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); |
832d11c5 IJ |
1503 | return NULL; |
1504 | } | |
1505 | ||
68f8353b IJ |
1506 | static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, |
1507 | struct tcp_sack_block *next_dup, | |
a1197f5a | 1508 | struct tcp_sacktag_state *state, |
68f8353b | 1509 | u32 start_seq, u32 end_seq, |
a2a385d6 | 1510 | bool dup_sack_in) |
68f8353b | 1511 | { |
832d11c5 IJ |
1512 | struct tcp_sock *tp = tcp_sk(sk); |
1513 | struct sk_buff *tmp; | |
1514 | ||
68f8353b IJ |
1515 | tcp_for_write_queue_from(skb, sk) { |
1516 | int in_sack = 0; | |
a2a385d6 | 1517 | bool dup_sack = dup_sack_in; |
68f8353b IJ |
1518 | |
1519 | if (skb == tcp_send_head(sk)) | |
1520 | break; | |
1521 | ||
1522 | /* queue is in-order => we can short-circuit the walk early */ | |
1523 | if (!before(TCP_SKB_CB(skb)->seq, end_seq)) | |
1524 | break; | |
1525 | ||
1526 | if ((next_dup != NULL) && | |
1527 | before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { | |
1528 | in_sack = tcp_match_skb_to_sack(sk, skb, | |
1529 | next_dup->start_seq, | |
1530 | next_dup->end_seq); | |
1531 | if (in_sack > 0) | |
a2a385d6 | 1532 | dup_sack = true; |
68f8353b IJ |
1533 | } |
1534 | ||
832d11c5 IJ |
1535 | /* skb reference here is a bit tricky to get right, since |
1536 | * shifting can eat and free both this skb and the next, | |
1537 | * so not even _safe variant of the loop is enough. | |
1538 | */ | |
1539 | if (in_sack <= 0) { | |
a1197f5a IJ |
1540 | tmp = tcp_shift_skb_data(sk, skb, state, |
1541 | start_seq, end_seq, dup_sack); | |
832d11c5 IJ |
1542 | if (tmp != NULL) { |
1543 | if (tmp != skb) { | |
1544 | skb = tmp; | |
1545 | continue; | |
1546 | } | |
1547 | ||
1548 | in_sack = 0; | |
1549 | } else { | |
1550 | in_sack = tcp_match_skb_to_sack(sk, skb, | |
1551 | start_seq, | |
1552 | end_seq); | |
1553 | } | |
1554 | } | |
1555 | ||
68f8353b IJ |
1556 | if (unlikely(in_sack < 0)) |
1557 | break; | |
1558 | ||
832d11c5 | 1559 | if (in_sack) { |
cc9a672e NC |
1560 | TCP_SKB_CB(skb)->sacked = |
1561 | tcp_sacktag_one(sk, | |
1562 | state, | |
1563 | TCP_SKB_CB(skb)->sacked, | |
1564 | TCP_SKB_CB(skb)->seq, | |
1565 | TCP_SKB_CB(skb)->end_seq, | |
1566 | dup_sack, | |
59c9af42 | 1567 | tcp_skb_pcount(skb), |
740b0f18 | 1568 | &skb->skb_mstamp); |
68f8353b | 1569 | |
832d11c5 IJ |
1570 | if (!before(TCP_SKB_CB(skb)->seq, |
1571 | tcp_highest_sack_seq(tp))) | |
1572 | tcp_advance_highest_sack(sk, skb); | |
1573 | } | |
1574 | ||
a1197f5a | 1575 | state->fack_count += tcp_skb_pcount(skb); |
68f8353b IJ |
1576 | } |
1577 | return skb; | |
1578 | } | |
1579 | ||
1580 | /* Avoid all extra work that is being done by sacktag while walking in | |
1581 | * a normal way | |
1582 | */ | |
1583 | static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, | |
a1197f5a IJ |
1584 | struct tcp_sacktag_state *state, |
1585 | u32 skip_to_seq) | |
68f8353b IJ |
1586 | { |
1587 | tcp_for_write_queue_from(skb, sk) { | |
1588 | if (skb == tcp_send_head(sk)) | |
1589 | break; | |
1590 | ||
e8bae275 | 1591 | if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) |
68f8353b | 1592 | break; |
d152a7d8 | 1593 | |
a1197f5a | 1594 | state->fack_count += tcp_skb_pcount(skb); |
68f8353b IJ |
1595 | } |
1596 | return skb; | |
1597 | } | |
1598 | ||
1599 | static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, | |
1600 | struct sock *sk, | |
1601 | struct tcp_sack_block *next_dup, | |
a1197f5a IJ |
1602 | struct tcp_sacktag_state *state, |
1603 | u32 skip_to_seq) | |
68f8353b IJ |
1604 | { |
1605 | if (next_dup == NULL) | |
1606 | return skb; | |
1607 | ||
1608 | if (before(next_dup->start_seq, skip_to_seq)) { | |
a1197f5a IJ |
1609 | skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); |
1610 | skb = tcp_sacktag_walk(skb, sk, NULL, state, | |
1611 | next_dup->start_seq, next_dup->end_seq, | |
1612 | 1); | |
68f8353b IJ |
1613 | } |
1614 | ||
1615 | return skb; | |
1616 | } | |
1617 | ||
cf533ea5 | 1618 | static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) |
68f8353b IJ |
1619 | { |
1620 | return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); | |
1621 | } | |
1622 | ||
1da177e4 | 1623 | static int |
cf533ea5 | 1624 | tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, |
740b0f18 | 1625 | u32 prior_snd_una, long *sack_rtt_us) |
1da177e4 LT |
1626 | { |
1627 | struct tcp_sock *tp = tcp_sk(sk); | |
cf533ea5 ED |
1628 | const unsigned char *ptr = (skb_transport_header(ack_skb) + |
1629 | TCP_SKB_CB(ack_skb)->sacked); | |
fd6dad61 | 1630 | struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); |
4389dded | 1631 | struct tcp_sack_block sp[TCP_NUM_SACKS]; |
68f8353b | 1632 | struct tcp_sack_block *cache; |
a1197f5a | 1633 | struct tcp_sacktag_state state; |
68f8353b | 1634 | struct sk_buff *skb; |
4389dded | 1635 | int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); |
fd6dad61 | 1636 | int used_sacks; |
a2a385d6 | 1637 | bool found_dup_sack = false; |
68f8353b | 1638 | int i, j; |
fda03fbb | 1639 | int first_sack_index; |
1da177e4 | 1640 | |
a1197f5a IJ |
1641 | state.flag = 0; |
1642 | state.reord = tp->packets_out; | |
740b0f18 | 1643 | state.rtt_us = -1L; |
a1197f5a | 1644 | |
d738cd8f | 1645 | if (!tp->sacked_out) { |
de83c058 IJ |
1646 | if (WARN_ON(tp->fackets_out)) |
1647 | tp->fackets_out = 0; | |
6859d494 | 1648 | tcp_highest_sack_reset(sk); |
d738cd8f | 1649 | } |
1da177e4 | 1650 | |
1ed83465 | 1651 | found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, |
d06e021d DM |
1652 | num_sacks, prior_snd_una); |
1653 | if (found_dup_sack) | |
a1197f5a | 1654 | state.flag |= FLAG_DSACKING_ACK; |
6f74651a BE |
1655 | |
1656 | /* Eliminate too old ACKs, but take into | |
1657 | * account more or less fresh ones, they can | |
1658 | * contain valid SACK info. | |
1659 | */ | |
1660 | if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) | |
1661 | return 0; | |
1662 | ||