1 // SPDX-License-Identifier: GPL-2.0
2 /* Multipath TCP
3 *
4 * Copyright (c) 2017 - 2019, Intel Corporation.
5 */
6
7 #define pr_fmt(fmt) "MPTCP: " fmt
8
9 #include <linux/kernel.h>
10 #include <crypto/sha2.h>
11 #include <net/tcp.h>
12 #include <net/mptcp.h>
13 #include "protocol.h"
14 #include "mib.h"
15
16 #include <trace/events/mptcp.h>
17
mptcp_cap_flag_sha256(u8 flags)18 static bool mptcp_cap_flag_sha256(u8 flags)
19 {
20 return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
21 }
22
mptcp_parse_option(const struct sk_buff * skb,const unsigned char * ptr,int opsize,struct mptcp_options_received * mp_opt)23 static void mptcp_parse_option(const struct sk_buff *skb,
24 const unsigned char *ptr, int opsize,
25 struct mptcp_options_received *mp_opt)
26 {
27 u8 subtype = *ptr >> 4;
28 int expected_opsize;
29 u16 subopt;
30 u8 version;
31 u8 flags;
32 u8 i;
33
34 switch (subtype) {
35 case MPTCPOPT_MP_CAPABLE:
36 /* strict size checking */
37 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
38 if (skb->len > tcp_hdr(skb)->doff << 2)
39 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
40 else
41 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
42 subopt = OPTION_MPTCP_MPC_ACK;
43 } else {
44 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) {
45 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
46 subopt = OPTION_MPTCP_MPC_SYNACK;
47 } else {
48 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
49 subopt = OPTION_MPTCP_MPC_SYN;
50 }
51 }
52
53 /* Cfr RFC 8684 Section 3.3.0:
54 * If a checksum is present but its use had
55 * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
56 * close the subflow with a RST, as it is not behaving as negotiated.
57 * If a checksum is not present when its use has been negotiated, the
58 * receiver MUST close the subflow with a RST, as it is considered
59 * broken
60 * We parse even option with mismatching csum presence, so that
61 * later in subflow_data_ready we can trigger the reset.
62 */
63 if (opsize != expected_opsize &&
64 (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
65 opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
66 break;
67
68 /* try to be gentle vs future versions on the initial syn */
69 version = *ptr++ & MPTCP_VERSION_MASK;
70 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
71 if (version != MPTCP_SUPPORTED_VERSION)
72 break;
73 } else if (version < MPTCP_SUPPORTED_VERSION) {
74 break;
75 }
76
77 flags = *ptr++;
78 if (!mptcp_cap_flag_sha256(flags) ||
79 (flags & MPTCP_CAP_EXTENSIBILITY))
80 break;
81
82 /* RFC 6824, Section 3.1:
83 * "For the Checksum Required bit (labeled "A"), if either
84 * host requires the use of checksums, checksums MUST be used.
85 * In other words, the only way for checksums not to be used
86 * is if both hosts in their SYNs set A=0."
87 */
88 if (flags & MPTCP_CAP_CHECKSUM_REQD)
89 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
90
91 mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
92
93 mp_opt->suboptions |= subopt;
94 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
95 mp_opt->sndr_key = get_unaligned_be64(ptr);
96 ptr += 8;
97 }
98 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
99 mp_opt->rcvr_key = get_unaligned_be64(ptr);
100 ptr += 8;
101 }
102 if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
103 /* Section 3.1.:
104 * "the data parameters in a MP_CAPABLE are semantically
105 * equivalent to those in a DSS option and can be used
106 * interchangeably."
107 */
108 mp_opt->suboptions |= OPTION_MPTCP_DSS;
109 mp_opt->use_map = 1;
110 mp_opt->mpc_map = 1;
111 mp_opt->data_len = get_unaligned_be16(ptr);
112 ptr += 2;
113 }
114 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
115 mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
116 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
117 ptr += 2;
118 }
119 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u\n",
120 version, flags, opsize, mp_opt->sndr_key,
121 mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
122 break;
123
124 case MPTCPOPT_MP_JOIN:
125 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
126 mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
127 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
128 mp_opt->join_id = *ptr++;
129 mp_opt->token = get_unaligned_be32(ptr);
130 ptr += 4;
131 mp_opt->nonce = get_unaligned_be32(ptr);
132 ptr += 4;
133 pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u\n",
134 mp_opt->backup, mp_opt->join_id,
135 mp_opt->token, mp_opt->nonce);
136 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
137 mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK;
138 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
139 mp_opt->join_id = *ptr++;
140 mp_opt->thmac = get_unaligned_be64(ptr);
141 ptr += 8;
142 mp_opt->nonce = get_unaligned_be32(ptr);
143 ptr += 4;
144 pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
145 mp_opt->backup, mp_opt->join_id,
146 mp_opt->thmac, mp_opt->nonce);
147 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
148 mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK;
149 ptr += 2;
150 memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
151 pr_debug("MP_JOIN hmac\n");
152 }
153 break;
154
155 case MPTCPOPT_DSS:
156 pr_debug("DSS\n");
157 ptr++;
158
159 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
160 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
161 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
162 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
163 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
164 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
165
166 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d\n",
167 mp_opt->data_fin, mp_opt->dsn64,
168 mp_opt->use_map, mp_opt->ack64,
169 mp_opt->use_ack);
170
171 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
172
173 if (mp_opt->use_ack) {
174 if (mp_opt->ack64)
175 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
176 else
177 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
178 }
179
180 if (mp_opt->use_map) {
181 if (mp_opt->dsn64)
182 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
183 else
184 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
185 }
186
187 /* Always parse any csum presence combination, we will enforce
188 * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
189 */
190 if (opsize != expected_opsize &&
191 opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
192 break;
193
194 mp_opt->suboptions |= OPTION_MPTCP_DSS;
195 if (mp_opt->use_ack) {
196 if (mp_opt->ack64) {
197 mp_opt->data_ack = get_unaligned_be64(ptr);
198 ptr += 8;
199 } else {
200 mp_opt->data_ack = get_unaligned_be32(ptr);
201 ptr += 4;
202 }
203
204 pr_debug("data_ack=%llu\n", mp_opt->data_ack);
205 }
206
207 if (mp_opt->use_map) {
208 if (mp_opt->dsn64) {
209 mp_opt->data_seq = get_unaligned_be64(ptr);
210 ptr += 8;
211 } else {
212 mp_opt->data_seq = get_unaligned_be32(ptr);
213 ptr += 4;
214 }
215
216 mp_opt->subflow_seq = get_unaligned_be32(ptr);
217 ptr += 4;
218
219 mp_opt->data_len = get_unaligned_be16(ptr);
220 ptr += 2;
221
222 if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
223 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
224 mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
225 ptr += 2;
226 }
227
228 pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
229 mp_opt->data_seq, mp_opt->subflow_seq,
230 mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
231 mp_opt->csum);
232 }
233
234 break;
235
236 case MPTCPOPT_ADD_ADDR:
237 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
238 if (!mp_opt->echo) {
239 if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
240 opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
241 mp_opt->addr.family = AF_INET;
242 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
243 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
244 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
245 mp_opt->addr.family = AF_INET6;
246 #endif
247 else
248 break;
249 } else {
250 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
251 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
252 mp_opt->addr.family = AF_INET;
253 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
254 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
255 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
256 mp_opt->addr.family = AF_INET6;
257 #endif
258 else
259 break;
260 }
261
262 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
263 mp_opt->addr.id = *ptr++;
264 mp_opt->addr.port = 0;
265 mp_opt->ahmac = 0;
266 if (mp_opt->addr.family == AF_INET) {
267 memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
268 ptr += 4;
269 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
270 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
271 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
272 ptr += 2;
273 }
274 }
275 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
276 else {
277 memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
278 ptr += 16;
279 if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
280 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
281 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
282 ptr += 2;
283 }
284 }
285 #endif
286 if (!mp_opt->echo) {
287 mp_opt->ahmac = get_unaligned_be64(ptr);
288 ptr += 8;
289 }
290 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d\n",
291 (mp_opt->addr.family == AF_INET6) ? "6" : "",
292 mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
293 break;
294
295 case MPTCPOPT_RM_ADDR:
296 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
297 opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
298 break;
299
300 ptr++;
301
302 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
303 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
304 for (i = 0; i < mp_opt->rm_list.nr; i++)
305 mp_opt->rm_list.ids[i] = *ptr++;
306 pr_debug("RM_ADDR: rm_list_nr=%d\n", mp_opt->rm_list.nr);
307 break;
308
309 case MPTCPOPT_MP_PRIO:
310 if (opsize != TCPOLEN_MPTCP_PRIO)
311 break;
312
313 mp_opt->suboptions |= OPTION_MPTCP_PRIO;
314 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
315 pr_debug("MP_PRIO: prio=%d\n", mp_opt->backup);
316 break;
317
318 case MPTCPOPT_MP_FASTCLOSE:
319 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
320 break;
321
322 ptr += 2;
323 mp_opt->rcvr_key = get_unaligned_be64(ptr);
324 ptr += 8;
325 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
326 pr_debug("MP_FASTCLOSE: recv_key=%llu\n", mp_opt->rcvr_key);
327 break;
328
329 case MPTCPOPT_RST:
330 if (opsize != TCPOLEN_MPTCP_RST)
331 break;
332
333 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
334 break;
335
336 mp_opt->suboptions |= OPTION_MPTCP_RST;
337 flags = *ptr++;
338 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
339 mp_opt->reset_reason = *ptr;
340 pr_debug("MP_RST: transient=%u reason=%u\n",
341 mp_opt->reset_transient, mp_opt->reset_reason);
342 break;
343
344 case MPTCPOPT_MP_FAIL:
345 if (opsize != TCPOLEN_MPTCP_FAIL)
346 break;
347
348 ptr += 2;
349 mp_opt->suboptions |= OPTION_MPTCP_FAIL;
350 mp_opt->fail_seq = get_unaligned_be64(ptr);
351 pr_debug("MP_FAIL: data_seq=%llu\n", mp_opt->fail_seq);
352 break;
353
354 default:
355 break;
356 }
357 }
358
mptcp_get_options(const struct sk_buff * skb,struct mptcp_options_received * mp_opt)359 void mptcp_get_options(const struct sk_buff *skb,
360 struct mptcp_options_received *mp_opt)
361 {
362 const struct tcphdr *th = tcp_hdr(skb);
363 const unsigned char *ptr;
364 int length;
365
366 /* Ensure that casting the whole status to u32 is efficient and safe */
367 BUILD_BUG_ON(sizeof_field(struct mptcp_options_received, status) != sizeof(u32));
368 BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct mptcp_options_received, status),
369 sizeof(u32)));
370 *(u32 *)&mp_opt->status = 0;
371
372 length = (th->doff * 4) - sizeof(struct tcphdr);
373 ptr = (const unsigned char *)(th + 1);
374
375 while (length > 0) {
376 int opcode = *ptr++;
377 int opsize;
378
379 switch (opcode) {
380 case TCPOPT_EOL:
381 return;
382 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
383 length--;
384 continue;
385 default:
386 if (length < 2)
387 return;
388 opsize = *ptr++;
389 if (opsize < 2) /* "silly options" */
390 return;
391 if (opsize > length)
392 return; /* don't parse partial options */
393 if (opcode == TCPOPT_MPTCP)
394 mptcp_parse_option(skb, ptr, opsize, mp_opt);
395 ptr += opsize - 2;
396 length -= opsize;
397 }
398 }
399 }
400
mptcp_syn_options(struct sock * sk,const struct sk_buff * skb,unsigned int * size,struct mptcp_out_options * opts)401 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
402 unsigned int *size, struct mptcp_out_options *opts)
403 {
404 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
405
406 /* we will use snd_isn to detect first pkt [re]transmission
407 * in mptcp_established_options_mp()
408 */
409 subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
410 if (subflow->request_mptcp) {
411 opts->suboptions = OPTION_MPTCP_MPC_SYN;
412 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
413 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
414 *size = TCPOLEN_MPTCP_MPC_SYN;
415 return true;
416 } else if (subflow->request_join) {
417 pr_debug("remote_token=%u, nonce=%u\n", subflow->remote_token,
418 subflow->local_nonce);
419 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
420 opts->join_id = subflow->local_id;
421 opts->token = subflow->remote_token;
422 opts->nonce = subflow->local_nonce;
423 opts->backup = subflow->request_bkup;
424 *size = TCPOLEN_MPTCP_MPJ_SYN;
425 return true;
426 }
427 return false;
428 }
429
clear_3rdack_retransmission(struct sock * sk)430 static void clear_3rdack_retransmission(struct sock *sk)
431 {
432 struct inet_connection_sock *icsk = inet_csk(sk);
433
434 sk_stop_timer(sk, &icsk->icsk_delack_timer);
435 icsk->icsk_ack.ato = 0;
436 icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
437 }
438
mptcp_established_options_mp(struct sock * sk,struct sk_buff * skb,bool snd_data_fin_enable,unsigned int * size,struct mptcp_out_options * opts)439 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
440 bool snd_data_fin_enable,
441 unsigned int *size,
442 struct mptcp_out_options *opts)
443 {
444 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
445 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
446 struct mptcp_ext *mpext;
447 unsigned int data_len;
448 u8 len;
449
450 /* When skb is not available, we better over-estimate the emitted
451 * options len. A full DSS option (28 bytes) is longer than
452 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
453 * tell the caller to defer the estimate to
454 * mptcp_established_options_dss(), which will reserve enough space.
455 */
456 if (!skb)
457 return false;
458
459 /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
460 if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable ||
461 subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
462 sk->sk_state != TCP_ESTABLISHED)
463 return false;
464
465 if (subflow->mp_capable) {
466 mpext = mptcp_get_ext(skb);
467 data_len = mpext ? mpext->data_len : 0;
468
469 /* we will check ops->data_len in mptcp_write_options() to
470 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
471 * TCPOLEN_MPTCP_MPC_ACK
472 */
473 opts->data_len = data_len;
474 opts->suboptions = OPTION_MPTCP_MPC_ACK;
475 opts->sndr_key = subflow->local_key;
476 opts->rcvr_key = subflow->remote_key;
477 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
478 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
479
480 /* Section 3.1.
481 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
482 * packets that start the first subflow of an MPTCP connection,
483 * as well as the first packet that carries data
484 */
485 if (data_len > 0) {
486 len = TCPOLEN_MPTCP_MPC_ACK_DATA;
487 if (opts->csum_reqd) {
488 /* we need to propagate more info to csum the pseudo hdr */
489 opts->data_seq = mpext->data_seq;
490 opts->subflow_seq = mpext->subflow_seq;
491 opts->csum = mpext->csum;
492 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
493 }
494 *size = ALIGN(len, 4);
495 } else {
496 *size = TCPOLEN_MPTCP_MPC_ACK;
497 }
498
499 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d\n",
500 subflow, subflow->local_key, subflow->remote_key,
501 data_len);
502
503 return true;
504 } else if (subflow->mp_join) {
505 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
506 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
507 *size = TCPOLEN_MPTCP_MPJ_ACK;
508 pr_debug("subflow=%p\n", subflow);
509
510 /* we can use the full delegate action helper only from BH context
511 * If we are in process context - sk is flushing the backlog at
512 * socket lock release time - just set the appropriate flag, will
513 * be handled by the release callback
514 */
515 if (sock_owned_by_user(sk))
516 set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
517 else
518 mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
519 return true;
520 }
521 return false;
522 }
523
mptcp_write_data_fin(struct mptcp_subflow_context * subflow,struct sk_buff * skb,struct mptcp_ext * ext)524 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
525 struct sk_buff *skb, struct mptcp_ext *ext)
526 {
527 /* The write_seq value has already been incremented, so the actual
528 * sequence number for the DATA_FIN is one less.
529 */
530 u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
531
532 if (!ext->use_map || !skb->len) {
533 /* RFC6824 requires a DSS mapping with specific values
534 * if DATA_FIN is set but no data payload is mapped
535 */
536 ext->data_fin = 1;
537 ext->use_map = 1;
538 ext->dsn64 = 1;
539 ext->data_seq = data_fin_tx_seq;
540 ext->subflow_seq = 0;
541 ext->data_len = 1;
542 } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
543 /* If there's an existing DSS mapping and it is the
544 * final mapping, DATA_FIN consumes 1 additional byte of
545 * mapping space.
546 */
547 ext->data_fin = 1;
548 ext->data_len++;
549 }
550 }
551
mptcp_established_options_dss(struct sock * sk,struct sk_buff * skb,bool snd_data_fin_enable,unsigned int * size,struct mptcp_out_options * opts)552 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
553 bool snd_data_fin_enable,
554 unsigned int *size,
555 struct mptcp_out_options *opts)
556 {
557 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
558 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
559 unsigned int dss_size = 0;
560 struct mptcp_ext *mpext;
561 unsigned int ack_size;
562 bool ret = false;
563 u64 ack_seq;
564
565 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
566 mpext = skb ? mptcp_get_ext(skb) : NULL;
567
568 if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
569 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
570
571 if (mpext) {
572 if (opts->csum_reqd)
573 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
574
575 opts->ext_copy = *mpext;
576 }
577
578 dss_size = map_size;
579 if (skb && snd_data_fin_enable)
580 mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
581 opts->suboptions = OPTION_MPTCP_DSS;
582 ret = true;
583 }
584
585 /* passive sockets msk will set the 'can_ack' after accept(), even
586 * if the first subflow may have the already the remote key handy
587 */
588 opts->ext_copy.use_ack = 0;
589 if (!READ_ONCE(msk->can_ack)) {
590 *size = ALIGN(dss_size, 4);
591 return ret;
592 }
593
594 ack_seq = READ_ONCE(msk->ack_seq);
595 if (READ_ONCE(msk->use_64bit_ack)) {
596 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
597 opts->ext_copy.data_ack = ack_seq;
598 opts->ext_copy.ack64 = 1;
599 } else {
600 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
601 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
602 opts->ext_copy.ack64 = 0;
603 }
604 opts->ext_copy.use_ack = 1;
605 opts->suboptions = OPTION_MPTCP_DSS;
606
607 /* Add kind/length/subtype/flag overhead if mapping is not populated */
608 if (dss_size == 0)
609 ack_size += TCPOLEN_MPTCP_DSS_BASE;
610
611 dss_size += ack_size;
612
613 *size = ALIGN(dss_size, 4);
614 return true;
615 }
616
add_addr_generate_hmac(u64 key1,u64 key2,struct mptcp_addr_info * addr)617 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
618 struct mptcp_addr_info *addr)
619 {
620 u16 port = ntohs(addr->port);
621 u8 hmac[SHA256_DIGEST_SIZE];
622 u8 msg[19];
623 int i = 0;
624
625 msg[i++] = addr->id;
626 if (addr->family == AF_INET) {
627 memcpy(&msg[i], &addr->addr.s_addr, 4);
628 i += 4;
629 }
630 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
631 else if (addr->family == AF_INET6) {
632 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
633 i += 16;
634 }
635 #endif
636 msg[i++] = port >> 8;
637 msg[i++] = port & 0xFF;
638
639 mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
640
641 return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
642 }
643
mptcp_established_options_add_addr(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)644 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
645 unsigned int *size,
646 unsigned int remaining,
647 struct mptcp_out_options *opts)
648 {
649 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
650 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
651 bool drop_other_suboptions = false;
652 unsigned int opt_size = *size;
653 struct mptcp_addr_info addr;
654 bool echo;
655 int len;
656
657 /* add addr will strip the existing options, be sure to avoid breaking
658 * MPC/MPJ handshakes
659 */
660 if (!mptcp_pm_should_add_signal(msk) ||
661 (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
662 !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &addr,
663 &echo, &drop_other_suboptions))
664 return false;
665
666 /*
667 * Later on, mptcp_write_options() will enforce mutually exclusion with
668 * DSS, bail out if such option is set and we can't drop it.
669 */
670 if (drop_other_suboptions)
671 remaining += opt_size;
672 else if (opts->suboptions & OPTION_MPTCP_DSS)
673 return false;
674
675 len = mptcp_add_addr_len(addr.family, echo, !!addr.port);
676 if (remaining < len)
677 return false;
678
679 *size = len;
680 if (drop_other_suboptions) {
681 pr_debug("drop other suboptions\n");
682 opts->suboptions = 0;
683
684 /* note that e.g. DSS could have written into the memory
685 * aliased by ahmac, we must reset the field here
686 * to avoid appending the hmac even for ADD_ADDR echo
687 * options
688 */
689 opts->ahmac = 0;
690 *size -= opt_size;
691 }
692 opts->addr = addr;
693 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
694 if (!echo) {
695 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
696 opts->ahmac = add_addr_generate_hmac(READ_ONCE(msk->local_key),
697 READ_ONCE(msk->remote_key),
698 &opts->addr);
699 } else {
700 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
701 }
702 pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d\n",
703 opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
704
705 return true;
706 }
707
mptcp_established_options_rm_addr(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)708 static bool mptcp_established_options_rm_addr(struct sock *sk,
709 unsigned int *size,
710 unsigned int remaining,
711 struct mptcp_out_options *opts)
712 {
713 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
714 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
715 struct mptcp_rm_list rm_list;
716 int i, len;
717
718 if (!mptcp_pm_should_rm_signal(msk) ||
719 !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
720 return false;
721
722 len = mptcp_rm_addr_len(&rm_list);
723 if (len < 0)
724 return false;
725 if (remaining < len)
726 return false;
727
728 *size = len;
729 opts->suboptions |= OPTION_MPTCP_RM_ADDR;
730 opts->rm_list = rm_list;
731
732 for (i = 0; i < opts->rm_list.nr; i++)
733 pr_debug("rm_list_ids[%d]=%d\n", i, opts->rm_list.ids[i]);
734 MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr);
735 return true;
736 }
737
mptcp_established_options_mp_prio(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)738 static bool mptcp_established_options_mp_prio(struct sock *sk,
739 unsigned int *size,
740 unsigned int remaining,
741 struct mptcp_out_options *opts)
742 {
743 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
744
745 /* can't send MP_PRIO with MPC, as they share the same option space:
746 * 'backup'. Also it makes no sense at all
747 */
748 if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
749 return false;
750
751 /* account for the trailing 'nop' option */
752 if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
753 return false;
754
755 *size = TCPOLEN_MPTCP_PRIO_ALIGN;
756 opts->suboptions |= OPTION_MPTCP_PRIO;
757 opts->backup = subflow->request_bkup;
758
759 pr_debug("prio=%d\n", opts->backup);
760
761 return true;
762 }
763
mptcp_established_options_rst(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)764 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
765 unsigned int *size,
766 unsigned int remaining,
767 struct mptcp_out_options *opts)
768 {
769 const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
770
771 if (remaining < TCPOLEN_MPTCP_RST)
772 return false;
773
774 *size = TCPOLEN_MPTCP_RST;
775 opts->suboptions |= OPTION_MPTCP_RST;
776 opts->reset_transient = subflow->reset_transient;
777 opts->reset_reason = subflow->reset_reason;
778 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
779
780 return true;
781 }
782
mptcp_established_options_fastclose(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)783 static bool mptcp_established_options_fastclose(struct sock *sk,
784 unsigned int *size,
785 unsigned int remaining,
786 struct mptcp_out_options *opts)
787 {
788 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
789 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
790
791 if (likely(!subflow->send_fastclose))
792 return false;
793
794 if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
795 return false;
796
797 *size = TCPOLEN_MPTCP_FASTCLOSE;
798 opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
799 opts->rcvr_key = READ_ONCE(msk->remote_key);
800
801 pr_debug("FASTCLOSE key=%llu\n", opts->rcvr_key);
802 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
803 return true;
804 }
805
mptcp_established_options_mp_fail(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)806 static bool mptcp_established_options_mp_fail(struct sock *sk,
807 unsigned int *size,
808 unsigned int remaining,
809 struct mptcp_out_options *opts)
810 {
811 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
812
813 if (likely(!subflow->send_mp_fail))
814 return false;
815
816 if (remaining < TCPOLEN_MPTCP_FAIL)
817 return false;
818
819 *size = TCPOLEN_MPTCP_FAIL;
820 opts->suboptions |= OPTION_MPTCP_FAIL;
821 opts->fail_seq = subflow->map_seq;
822
823 pr_debug("MP_FAIL fail_seq=%llu\n", opts->fail_seq);
824 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
825
826 return true;
827 }
828
mptcp_established_options(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)829 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
830 unsigned int *size, unsigned int remaining,
831 struct mptcp_out_options *opts)
832 {
833 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
834 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
835 unsigned int opt_size = 0;
836 bool snd_data_fin;
837 bool ret = false;
838
839 opts->suboptions = 0;
840
841 if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
842 return false;
843
844 if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
845 if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
846 mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
847 *size += opt_size;
848 remaining -= opt_size;
849 }
850 /* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
851 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
852 *size += opt_size;
853 remaining -= opt_size;
854 }
855 return true;
856 }
857
858 snd_data_fin = mptcp_data_fin_enabled(msk);
859 if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts))
860 ret = true;
861 else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) {
862 unsigned int mp_fail_size;
863
864 ret = true;
865 if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
866 remaining - opt_size, opts)) {
867 *size += opt_size + mp_fail_size;
868 remaining -= opt_size - mp_fail_size;
869 return true;
870 }
871 }
872
873 /* we reserved enough space for the above options, and exceeding the
874 * TCP option space would be fatal
875 */
876 if (WARN_ON_ONCE(opt_size > remaining))
877 return false;
878
879 *size += opt_size;
880 remaining -= opt_size;
881 if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
882 *size += opt_size;
883 remaining -= opt_size;
884 ret = true;
885 } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
886 *size += opt_size;
887 remaining -= opt_size;
888 ret = true;
889 }
890
891 if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
892 *size += opt_size;
893 remaining -= opt_size;
894 ret = true;
895 }
896
897 return ret;
898 }
899
mptcp_synack_options(const struct request_sock * req,unsigned int * size,struct mptcp_out_options * opts)900 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
901 struct mptcp_out_options *opts)
902 {
903 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
904
905 if (subflow_req->mp_capable) {
906 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
907 opts->sndr_key = subflow_req->local_key;
908 opts->csum_reqd = subflow_req->csum_reqd;
909 opts->allow_join_id0 = subflow_req->allow_join_id0;
910 *size = TCPOLEN_MPTCP_MPC_SYNACK;
911 pr_debug("subflow_req=%p, local_key=%llu\n",
912 subflow_req, subflow_req->local_key);
913 return true;
914 } else if (subflow_req->mp_join) {
915 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
916 opts->backup = subflow_req->request_bkup;
917 opts->join_id = subflow_req->local_id;
918 opts->thmac = subflow_req->thmac;
919 opts->nonce = subflow_req->local_nonce;
920 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
921 subflow_req, opts->backup, opts->join_id,
922 opts->thmac, opts->nonce);
923 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
924 return true;
925 }
926 return false;
927 }
928
check_fully_established(struct mptcp_sock * msk,struct sock * ssk,struct mptcp_subflow_context * subflow,struct sk_buff * skb,struct mptcp_options_received * mp_opt)929 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
930 struct mptcp_subflow_context *subflow,
931 struct sk_buff *skb,
932 struct mptcp_options_received *mp_opt)
933 {
934 /* here we can process OoO, in-window pkts, only in-sequence 4th ack
935 * will make the subflow fully established
936 */
937 if (likely(READ_ONCE(subflow->fully_established))) {
938 /* on passive sockets, check for 3rd ack retransmission
939 * note that msk is always set by subflow_syn_recv_sock()
940 * for mp_join subflows
941 */
942 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
943 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
944 subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
945 !subflow->request_join)
946 tcp_send_ack(ssk);
947 goto check_notify;
948 }
949
950 /* we must process OoO packets before the first subflow is fully
951 * established. OoO packets are instead a protocol violation
952 * for MP_JOIN subflows as the peer must not send any data
953 * before receiving the forth ack - cfr. RFC 8684 section 3.2.
954 */
955 if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
956 if (subflow->mp_join)
957 goto reset;
958 if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
959 goto set_fully_established;
960 return subflow->mp_capable;
961 }
962
963 if (subflow->remote_key_valid &&
964 (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
965 ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) &&
966 (!mp_opt->echo || subflow->mp_join)))) {
967 /* subflows are fully established as soon as we get any
968 * additional ack, including ADD_ADDR.
969 */
970 goto set_fully_established;
971 }
972
973 /* If the first established packet does not contain MP_CAPABLE + data
974 * then fallback to TCP. Fallback scenarios requires a reset for
975 * MP_JOIN subflows.
976 */
977 if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
978 if (subflow->mp_join)
979 goto reset;
980 subflow->mp_capable = 0;
981 if (!mptcp_try_fallback(ssk, MPTCP_MIB_MPCAPABLEDATAFALLBACK)) {
982 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_FALLBACKFAILED);
983 goto reset;
984 }
985 return false;
986 }
987
988 if (mp_opt->deny_join_id0)
989 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
990
991 if (unlikely(!READ_ONCE(msk->pm.server_side)))
992 pr_warn_once("bogus mpc option on established client sk");
993
994 set_fully_established:
995 mptcp_data_lock((struct sock *)msk);
996 __mptcp_subflow_fully_established(msk, subflow, mp_opt);
997 mptcp_data_unlock((struct sock *)msk);
998
999 check_notify:
1000 /* if the subflow is not already linked into the conn_list, we can't
1001 * notify the PM: this subflow is still on the listener queue
1002 * and the PM possibly acquiring the subflow lock could race with
1003 * the listener close
1004 */
1005 if (likely(subflow->pm_notified) || list_empty(&subflow->node))
1006 return true;
1007
1008 subflow->pm_notified = 1;
1009 if (subflow->mp_join) {
1010 clear_3rdack_retransmission(ssk);
1011 mptcp_pm_subflow_established(msk);
1012 } else {
1013 mptcp_pm_fully_established(msk, ssk);
1014 }
1015 return true;
1016
1017 reset:
1018 mptcp_subflow_reset(ssk);
1019 return false;
1020 }
1021
__mptcp_expand_seq(u64 old_seq,u64 cur_seq)1022 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
1023 {
1024 u32 old_seq32, cur_seq32;
1025
1026 old_seq32 = (u32)old_seq;
1027 cur_seq32 = (u32)cur_seq;
1028 cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
1029 if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
1030 return cur_seq + (1LL << 32);
1031
1032 /* reverse wrap could happen, too */
1033 if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1034 return cur_seq - (1LL << 32);
1035 return cur_seq;
1036 }
1037
__mptcp_snd_una_update(struct mptcp_sock * msk,u64 new_snd_una)1038 static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
1039 {
1040 msk->bytes_acked += new_snd_una - msk->snd_una;
1041 WRITE_ONCE(msk->snd_una, new_snd_una);
1042 }
1043
ack_update_msk(struct mptcp_sock * msk,struct sock * ssk,struct mptcp_options_received * mp_opt)1044 static void ack_update_msk(struct mptcp_sock *msk,
1045 struct sock *ssk,
1046 struct mptcp_options_received *mp_opt)
1047 {
1048 u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1049 struct sock *sk = (struct sock *)msk;
1050 u64 old_snd_una;
1051
1052 mptcp_data_lock(sk);
1053
1054 /* avoid ack expansion on update conflict, to reduce the risk of
1055 * wrongly expanding to a future ack sequence number, which is way
1056 * more dangerous than missing an ack
1057 */
1058 old_snd_una = msk->snd_una;
1059 new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1060
1061 /* ACK for data not even sent yet? Ignore.*/
1062 if (unlikely(after64(new_snd_una, snd_nxt)))
1063 new_snd_una = old_snd_una;
1064
1065 new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1066
1067 if (after64(new_wnd_end, msk->wnd_end))
1068 WRITE_ONCE(msk->wnd_end, new_wnd_end);
1069
1070 /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1071 if (after64(msk->wnd_end, snd_nxt))
1072 __mptcp_check_push(sk, ssk);
1073
1074 if (after64(new_snd_una, old_snd_una)) {
1075 __mptcp_snd_una_update(msk, new_snd_una);
1076 __mptcp_data_acked(sk);
1077 }
1078 msk->last_ack_recv = tcp_jiffies32;
1079 mptcp_data_unlock(sk);
1080
1081 trace_ack_update_msk(mp_opt->data_ack,
1082 old_snd_una, new_snd_una,
1083 new_wnd_end, READ_ONCE(msk->wnd_end));
1084 }
1085
mptcp_update_rcv_data_fin(struct mptcp_sock * msk,u64 data_fin_seq,bool use_64bit)1086 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1087 {
1088 /* Skip if DATA_FIN was already received.
1089 * If updating simultaneously with the recvmsg loop, values
1090 * should match. If they mismatch, the peer is misbehaving and
1091 * we will prefer the most recent information.
1092 */
1093 if (READ_ONCE(msk->rcv_data_fin))
1094 return false;
1095
1096 WRITE_ONCE(msk->rcv_data_fin_seq,
1097 mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1098 WRITE_ONCE(msk->rcv_data_fin, 1);
1099
1100 return true;
1101 }
1102
add_addr_hmac_valid(struct mptcp_sock * msk,struct mptcp_options_received * mp_opt)1103 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1104 struct mptcp_options_received *mp_opt)
1105 {
1106 u64 hmac = 0;
1107
1108 if (mp_opt->echo)
1109 return true;
1110
1111 hmac = add_addr_generate_hmac(READ_ONCE(msk->remote_key),
1112 READ_ONCE(msk->local_key),
1113 &mp_opt->addr);
1114
1115 pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1116 msk, hmac, mp_opt->ahmac);
1117
1118 return hmac == mp_opt->ahmac;
1119 }
1120
1121 /* Return false in case of error (or subflow has been reset),
1122 * else return true.
1123 */
mptcp_incoming_options(struct sock * sk,struct sk_buff * skb)1124 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1125 {
1126 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1127 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1128 struct mptcp_options_received mp_opt;
1129 struct mptcp_ext *mpext;
1130
1131 if (__mptcp_check_fallback(msk)) {
1132 /* Keep it simple and unconditionally trigger send data cleanup and
1133 * pending queue spooling. We will need to acquire the data lock
1134 * for more accurate checks, and once the lock is acquired, such
1135 * helpers are cheap.
1136 */
1137 mptcp_data_lock(subflow->conn);
1138 if (sk_stream_memory_free(sk))
1139 __mptcp_check_push(subflow->conn, sk);
1140
1141 /* on fallback we just need to ignore the msk-level snd_una, as
1142 * this is really plain TCP
1143 */
1144 __mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
1145
1146 __mptcp_data_acked(subflow->conn);
1147 mptcp_data_unlock(subflow->conn);
1148 return true;
1149 }
1150
1151 mptcp_get_options(skb, &mp_opt);
1152
1153 /* The subflow can be in close state only if check_fully_established()
1154 * just sent a reset. If so, tell the caller to ignore the current packet.
1155 */
1156 if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1157 return sk->sk_state != TCP_CLOSE;
1158
1159 if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1160 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1161 READ_ONCE(msk->local_key) == mp_opt.rcvr_key) {
1162 WRITE_ONCE(msk->rcv_fastclose, true);
1163 mptcp_schedule_work((struct sock *)msk);
1164 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1165 }
1166
1167 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1168 add_addr_hmac_valid(msk, &mp_opt)) {
1169 if (!mp_opt.echo) {
1170 mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1171 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1172 } else {
1173 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1174 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1175 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1176 }
1177
1178 if (mp_opt.addr.port)
1179 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1180 }
1181
1182 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1183 mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1184
1185 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1186 mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1187 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1188 }
1189
1190 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1191 mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1192 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1193 }
1194
1195 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1196 subflow->reset_seen = 1;
1197 subflow->reset_reason = mp_opt.reset_reason;
1198 subflow->reset_transient = mp_opt.reset_transient;
1199 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1200 }
1201
1202 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1203 return true;
1204 }
1205
1206 /* we can't wait for recvmsg() to update the ack_seq, otherwise
1207 * monodirectional flows will stuck
1208 */
1209 if (mp_opt.use_ack)
1210 ack_update_msk(msk, sk, &mp_opt);
1211
1212 /* Zero-data-length packets are dropped by the caller and not
1213 * propagated to the MPTCP layer, so the skb extension does not
1214 * need to be allocated or populated. DATA_FIN information, if
1215 * present, needs to be updated here before the skb is freed.
1216 */
1217 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1218 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1219 mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
1220 mptcp_schedule_work((struct sock *)msk);
1221
1222 return true;
1223 }
1224
1225 mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1226 if (!mpext)
1227 return false;
1228
1229 memset(mpext, 0, sizeof(*mpext));
1230
1231 if (likely(mp_opt.use_map)) {
1232 if (mp_opt.mpc_map) {
1233 /* this is an MP_CAPABLE carrying MPTCP data
1234 * we know this map the first chunk of data
1235 */
1236 mptcp_crypto_key_sha(subflow->remote_key, NULL,
1237 &mpext->data_seq);
1238 mpext->data_seq++;
1239 mpext->subflow_seq = 1;
1240 mpext->dsn64 = 1;
1241 mpext->mpc_map = 1;
1242 mpext->data_fin = 0;
1243 } else {
1244 mpext->data_seq = mp_opt.data_seq;
1245 mpext->subflow_seq = mp_opt.subflow_seq;
1246 mpext->dsn64 = mp_opt.dsn64;
1247 mpext->data_fin = mp_opt.data_fin;
1248 }
1249 mpext->data_len = mp_opt.data_len;
1250 mpext->use_map = 1;
1251 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1252
1253 if (mpext->csum_reqd)
1254 mpext->csum = mp_opt.csum;
1255 }
1256
1257 return true;
1258 }
1259
mptcp_set_rwin(struct tcp_sock * tp,struct tcphdr * th)1260 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1261 {
1262 const struct sock *ssk = (const struct sock *)tp;
1263 struct mptcp_subflow_context *subflow;
1264 u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1265 struct mptcp_sock *msk;
1266 u32 new_win;
1267 u64 win;
1268
1269 subflow = mptcp_subflow_ctx(ssk);
1270 msk = mptcp_sk(subflow->conn);
1271
1272 ack_seq = READ_ONCE(msk->ack_seq);
1273 rcv_wnd_new = ack_seq + tp->rcv_wnd;
1274
1275 rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1276 if (after64(rcv_wnd_new, rcv_wnd_old)) {
1277 u64 rcv_wnd;
1278
1279 for (;;) {
1280 rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1281
1282 if (rcv_wnd == rcv_wnd_old)
1283 break;
1284
1285 rcv_wnd_old = rcv_wnd;
1286 if (before64(rcv_wnd_new, rcv_wnd_old)) {
1287 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1288 goto raise_win;
1289 }
1290 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1291 }
1292 goto update_wspace;
1293 }
1294
1295 if (rcv_wnd_new != rcv_wnd_old) {
1296 raise_win:
1297 win = rcv_wnd_old - ack_seq;
1298 tp->rcv_wnd = min_t(u64, win, U32_MAX);
1299 new_win = tp->rcv_wnd;
1300
1301 /* Make sure we do not exceed the maximum possible
1302 * scaled window.
1303 */
1304 if (unlikely(th->syn))
1305 new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1306 if (!tp->rx_opt.rcv_wscale &&
1307 READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1308 new_win = min(new_win, MAX_TCP_WINDOW);
1309 else
1310 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1311
1312 /* RFC1323 scaling applied */
1313 new_win >>= tp->rx_opt.rcv_wscale;
1314 th->window = htons(new_win);
1315 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1316 }
1317
1318 update_wspace:
1319 WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
1320 }
1321
__mptcp_make_csum(u64 data_seq,u32 subflow_seq,u16 data_len,__wsum sum)1322 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1323 {
1324 struct csum_pseudo_header header;
1325 __wsum csum;
1326
1327 /* cfr RFC 8684 3.3.1.:
1328 * the data sequence number used in the pseudo-header is
1329 * always the 64-bit value, irrespective of what length is used in the
1330 * DSS option itself.
1331 */
1332 header.data_seq = cpu_to_be64(data_seq);
1333 header.subflow_seq = htonl(subflow_seq);
1334 header.data_len = htons(data_len);
1335 header.csum = 0;
1336
1337 csum = csum_partial(&header, sizeof(header), sum);
1338 return csum_fold(csum);
1339 }
1340
mptcp_make_csum(const struct mptcp_ext * mpext)1341 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1342 {
1343 return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1344 ~csum_unfold(mpext->csum));
1345 }
1346
put_len_csum(u16 len,__sum16 csum,void * data)1347 static void put_len_csum(u16 len, __sum16 csum, void *data)
1348 {
1349 __sum16 *sumptr = data + 2;
1350 __be16 *ptr = data;
1351
1352 put_unaligned_be16(len, ptr);
1353
1354 put_unaligned(csum, sumptr);
1355 }
1356
mptcp_write_options(struct tcphdr * th,__be32 * ptr,struct tcp_sock * tp,struct mptcp_out_options * opts)1357 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1358 struct mptcp_out_options *opts)
1359 {
1360 const struct sock *ssk = (const struct sock *)tp;
1361 struct mptcp_subflow_context *subflow;
1362
1363 /* Which options can be used together?
1364 *
1365 * X: mutually exclusive
1366 * O: often used together
1367 * C: can be used together in some cases
1368 * P: could be used together but we prefer not to (optimisations)
1369 *
1370 * Opt: | MPC | MPJ | DSS | ADD | RM | PRIO | FAIL | FC |
1371 * ------|------|------|------|------|------|------|------|------|
1372 * MPC |------|------|------|------|------|------|------|------|
1373 * MPJ | X |------|------|------|------|------|------|------|
1374 * DSS | X | X |------|------|------|------|------|------|
1375 * ADD | X | X | P |------|------|------|------|------|
1376 * RM | C | C | C | P |------|------|------|------|
1377 * PRIO | X | C | C | C | C |------|------|------|
1378 * FAIL | X | X | C | X | X | X |------|------|
1379 * FC | X | X | X | X | X | X | X |------|
1380 * RST | X | X | X | X | X | X | O | O |
1381 * ------|------|------|------|------|------|------|------|------|
1382 *
1383 * The same applies in mptcp_established_options() function.
1384 */
1385 if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1386 struct mptcp_ext *mpext = &opts->ext_copy;
1387 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1388 u8 flags = 0;
1389
1390 if (mpext->use_ack) {
1391 flags = MPTCP_DSS_HAS_ACK;
1392 if (mpext->ack64) {
1393 len += TCPOLEN_MPTCP_DSS_ACK64;
1394 flags |= MPTCP_DSS_ACK64;
1395 } else {
1396 len += TCPOLEN_MPTCP_DSS_ACK32;
1397 }
1398 }
1399
1400 if (mpext->use_map) {
1401 len += TCPOLEN_MPTCP_DSS_MAP64;
1402
1403 /* Use only 64-bit mapping flags for now, add
1404 * support for optional 32-bit mappings later.
1405 */
1406 flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1407 if (mpext->data_fin)
1408 flags |= MPTCP_DSS_DATA_FIN;
1409
1410 if (opts->csum_reqd)
1411 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1412 }
1413
1414 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1415
1416 if (mpext->use_ack) {
1417 if (mpext->ack64) {
1418 put_unaligned_be64(mpext->data_ack, ptr);
1419 ptr += 2;
1420 } else {
1421 put_unaligned_be32(mpext->data_ack32, ptr);
1422 ptr += 1;
1423 }
1424 }
1425
1426 if (mpext->use_map) {
1427 put_unaligned_be64(mpext->data_seq, ptr);
1428 ptr += 2;
1429 put_unaligned_be32(mpext->subflow_seq, ptr);
1430 ptr += 1;
1431 if (opts->csum_reqd) {
1432 /* data_len == 0 is reserved for the infinite mapping,
1433 * the checksum will also be set to 0.
1434 */
1435 put_len_csum(mpext->data_len,
1436 (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1437 ptr);
1438 } else {
1439 put_unaligned_be32(mpext->data_len << 16 |
1440 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1441 }
1442 ptr += 1;
1443 }
1444
1445 /* We might need to add MP_FAIL options in rare cases */
1446 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1447 goto mp_fail;
1448 } else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1449 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1450
1451 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1452 len = TCPOLEN_MPTCP_MPC_SYN;
1453 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1454 len = TCPOLEN_MPTCP_MPC_SYNACK;
1455 } else if (opts->data_len) {
1456 len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1457 if (opts->csum_reqd)
1458 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1459 } else {
1460 len = TCPOLEN_MPTCP_MPC_ACK;
1461 }
1462
1463 if (opts->csum_reqd)
1464 flag |= MPTCP_CAP_CHECKSUM_REQD;
1465
1466 if (!opts->allow_join_id0)
1467 flag |= MPTCP_CAP_DENY_JOIN_ID0;
1468
1469 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1470 MPTCP_SUPPORTED_VERSION,
1471 flag);
1472
1473 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1474 opts->suboptions))
1475 goto mp_capable_done;
1476
1477 put_unaligned_be64(opts->sndr_key, ptr);
1478 ptr += 2;
1479 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1480 goto mp_capable_done;
1481
1482 put_unaligned_be64(opts->rcvr_key, ptr);
1483 ptr += 2;
1484 if (!opts->data_len)
1485 goto mp_capable_done;
1486
1487 if (opts->csum_reqd) {
1488 put_len_csum(opts->data_len,
1489 __mptcp_make_csum(opts->data_seq,
1490 opts->subflow_seq,
1491 opts->data_len,
1492 ~csum_unfold(opts->csum)),
1493 ptr);
1494 } else {
1495 put_unaligned_be32(opts->data_len << 16 |
1496 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1497 }
1498 ptr += 1;
1499
1500 /* MPC is additionally mutually exclusive with MP_PRIO */
1501 goto mp_capable_done;
1502 } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1503 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1504 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1505 TCPOLEN_MPTCP_MPJ_SYN,
1506 opts->backup, opts->join_id);
1507 put_unaligned_be32(opts->token, ptr);
1508 ptr += 1;
1509 put_unaligned_be32(opts->nonce, ptr);
1510 ptr += 1;
1511 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1512 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1513 TCPOLEN_MPTCP_MPJ_SYNACK,
1514 opts->backup, opts->join_id);
1515 put_unaligned_be64(opts->thmac, ptr);
1516 ptr += 2;
1517 put_unaligned_be32(opts->nonce, ptr);
1518 ptr += 1;
1519 } else {
1520 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1521 TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1522 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1523 ptr += 5;
1524 }
1525 } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1526 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1527 u8 echo = MPTCP_ADDR_ECHO;
1528
1529 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1530 if (opts->addr.family == AF_INET6)
1531 len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1532 #endif
1533
1534 if (opts->addr.port)
1535 len += TCPOLEN_MPTCP_PORT_LEN;
1536
1537 if (opts->ahmac) {
1538 len += sizeof(opts->ahmac);
1539 echo = 0;
1540 }
1541
1542 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1543 len, echo, opts->addr.id);
1544 if (opts->addr.family == AF_INET) {
1545 memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1546 ptr += 1;
1547 }
1548 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1549 else if (opts->addr.family == AF_INET6) {
1550 memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1551 ptr += 4;
1552 }
1553 #endif
1554
1555 if (!opts->addr.port) {
1556 if (opts->ahmac) {
1557 put_unaligned_be64(opts->ahmac, ptr);
1558 ptr += 2;
1559 }
1560 } else {
1561 u16 port = ntohs(opts->addr.port);
1562
1563 if (opts->ahmac) {
1564 u8 *bptr = (u8 *)ptr;
1565
1566 put_unaligned_be16(port, bptr);
1567 bptr += 2;
1568 put_unaligned_be64(opts->ahmac, bptr);
1569 bptr += 8;
1570 put_unaligned_be16(TCPOPT_NOP << 8 |
1571 TCPOPT_NOP, bptr);
1572
1573 ptr += 3;
1574 } else {
1575 put_unaligned_be32(port << 16 |
1576 TCPOPT_NOP << 8 |
1577 TCPOPT_NOP, ptr);
1578 ptr += 1;
1579 }
1580 }
1581 } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1582 /* FASTCLOSE is mutually exclusive with others except RST */
1583 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1584 TCPOLEN_MPTCP_FASTCLOSE,
1585 0, 0);
1586 put_unaligned_be64(opts->rcvr_key, ptr);
1587 ptr += 2;
1588
1589 if (OPTION_MPTCP_RST & opts->suboptions)
1590 goto mp_rst;
1591 return;
1592 } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1593 mp_fail:
1594 /* MP_FAIL is mutually exclusive with others except RST */
1595 subflow = mptcp_subflow_ctx(ssk);
1596 subflow->send_mp_fail = 0;
1597
1598 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1599 TCPOLEN_MPTCP_FAIL,
1600 0, 0);
1601 put_unaligned_be64(opts->fail_seq, ptr);
1602 ptr += 2;
1603
1604 if (OPTION_MPTCP_RST & opts->suboptions)
1605 goto mp_rst;
1606 return;
1607 } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1608 mp_rst:
1609 *ptr++ = mptcp_option(MPTCPOPT_RST,
1610 TCPOLEN_MPTCP_RST,
1611 opts->reset_transient,
1612 opts->reset_reason);
1613 return;
1614 }
1615
1616 if (OPTION_MPTCP_PRIO & opts->suboptions) {
1617 subflow = mptcp_subflow_ctx(ssk);
1618 subflow->send_mp_prio = 0;
1619
1620 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1621 TCPOLEN_MPTCP_PRIO,
1622 opts->backup, TCPOPT_NOP);
1623
1624 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
1625 }
1626
1627 mp_capable_done:
1628 if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1629 u8 i = 1;
1630
1631 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1632 TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1633 0, opts->rm_list.ids[0]);
1634
1635 while (i < opts->rm_list.nr) {
1636 u8 id1, id2, id3, id4;
1637
1638 id1 = opts->rm_list.ids[i];
1639 id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1640 id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1641 id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1642 put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1643 ptr += 1;
1644 i += 4;
1645 }
1646 }
1647
1648 if (tp)
1649 mptcp_set_rwin(tp, th);
1650 }
1651
mptcp_get_reset_option(const struct sk_buff * skb)1652 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1653 {
1654 const struct mptcp_ext *ext = mptcp_get_ext(skb);
1655 u8 flags, reason;
1656
1657 if (ext) {
1658 flags = ext->reset_transient;
1659 reason = ext->reset_reason;
1660
1661 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1662 flags, reason);
1663 }
1664
1665 return htonl(0u);
1666 }
1667 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);
1668