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/sha.h>
11 #include <net/tcp.h>
12 #include <net/mptcp.h>
13 #include "protocol.h"
14 #include "mib.h"
15
mptcp_cap_flag_sha256(u8 flags)16 static bool mptcp_cap_flag_sha256(u8 flags)
17 {
18 return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
19 }
20
mptcp_parse_option(const struct sk_buff * skb,const unsigned char * ptr,int opsize,struct mptcp_options_received * mp_opt)21 static void mptcp_parse_option(const struct sk_buff *skb,
22 const unsigned char *ptr, int opsize,
23 struct mptcp_options_received *mp_opt)
24 {
25 u8 subtype = *ptr >> 4;
26 int expected_opsize;
27 u8 version;
28 u8 flags;
29
30 switch (subtype) {
31 case MPTCPOPT_MP_CAPABLE:
32 /* strict size checking */
33 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
34 if (skb->len > tcp_hdr(skb)->doff << 2)
35 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
36 else
37 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
38 } else {
39 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
40 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
41 else
42 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
43 }
44 if (opsize != expected_opsize)
45 break;
46
47 /* try to be gentle vs future versions on the initial syn */
48 version = *ptr++ & MPTCP_VERSION_MASK;
49 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
50 if (version != MPTCP_SUPPORTED_VERSION)
51 break;
52 } else if (version < MPTCP_SUPPORTED_VERSION) {
53 break;
54 }
55
56 flags = *ptr++;
57 if (!mptcp_cap_flag_sha256(flags) ||
58 (flags & MPTCP_CAP_EXTENSIBILITY))
59 break;
60
61 /* RFC 6824, Section 3.1:
62 * "For the Checksum Required bit (labeled "A"), if either
63 * host requires the use of checksums, checksums MUST be used.
64 * In other words, the only way for checksums not to be used
65 * is if both hosts in their SYNs set A=0."
66 *
67 * Section 3.3.0:
68 * "If a checksum is not present when its use has been
69 * negotiated, the receiver MUST close the subflow with a RST as
70 * it is considered broken."
71 *
72 * We don't implement DSS checksum - fall back to TCP.
73 */
74 if (flags & MPTCP_CAP_CHECKSUM_REQD)
75 break;
76
77 mp_opt->mp_capable = 1;
78 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
79 mp_opt->sndr_key = get_unaligned_be64(ptr);
80 ptr += 8;
81 }
82 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
83 mp_opt->rcvr_key = get_unaligned_be64(ptr);
84 ptr += 8;
85 }
86 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
87 /* Section 3.1.:
88 * "the data parameters in a MP_CAPABLE are semantically
89 * equivalent to those in a DSS option and can be used
90 * interchangeably."
91 */
92 mp_opt->dss = 1;
93 mp_opt->use_map = 1;
94 mp_opt->mpc_map = 1;
95 mp_opt->use_ack = 0;
96 mp_opt->data_len = get_unaligned_be16(ptr);
97 ptr += 2;
98 }
99 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
100 version, flags, opsize, mp_opt->sndr_key,
101 mp_opt->rcvr_key, mp_opt->data_len);
102 break;
103
104 case MPTCPOPT_MP_JOIN:
105 mp_opt->mp_join = 1;
106 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
107 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
108 mp_opt->join_id = *ptr++;
109 mp_opt->token = get_unaligned_be32(ptr);
110 ptr += 4;
111 mp_opt->nonce = get_unaligned_be32(ptr);
112 ptr += 4;
113 pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
114 mp_opt->backup, mp_opt->join_id,
115 mp_opt->token, mp_opt->nonce);
116 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
117 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
118 mp_opt->join_id = *ptr++;
119 mp_opt->thmac = get_unaligned_be64(ptr);
120 ptr += 8;
121 mp_opt->nonce = get_unaligned_be32(ptr);
122 ptr += 4;
123 pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
124 mp_opt->backup, mp_opt->join_id,
125 mp_opt->thmac, mp_opt->nonce);
126 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
127 ptr += 2;
128 memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
129 pr_debug("MP_JOIN hmac");
130 } else {
131 mp_opt->mp_join = 0;
132 }
133 break;
134
135 case MPTCPOPT_DSS:
136 pr_debug("DSS");
137 ptr++;
138
139 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
140 * map vs DSS map in mptcp_incoming_options(), and reconstruct
141 * map info accordingly
142 */
143 mp_opt->mpc_map = 0;
144 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
145 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
146 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
147 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
148 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
149 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
150
151 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
152 mp_opt->data_fin, mp_opt->dsn64,
153 mp_opt->use_map, mp_opt->ack64,
154 mp_opt->use_ack);
155
156 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
157
158 if (mp_opt->use_ack) {
159 if (mp_opt->ack64)
160 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
161 else
162 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
163 }
164
165 if (mp_opt->use_map) {
166 if (mp_opt->dsn64)
167 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
168 else
169 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
170 }
171
172 /* RFC 6824, Section 3.3:
173 * If a checksum is present, but its use had
174 * not been negotiated in the MP_CAPABLE handshake,
175 * the checksum field MUST be ignored.
176 */
177 if (opsize != expected_opsize &&
178 opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
179 break;
180
181 mp_opt->dss = 1;
182
183 if (mp_opt->use_ack) {
184 if (mp_opt->ack64) {
185 mp_opt->data_ack = get_unaligned_be64(ptr);
186 ptr += 8;
187 } else {
188 mp_opt->data_ack = get_unaligned_be32(ptr);
189 ptr += 4;
190 }
191
192 pr_debug("data_ack=%llu", mp_opt->data_ack);
193 }
194
195 if (mp_opt->use_map) {
196 if (mp_opt->dsn64) {
197 mp_opt->data_seq = get_unaligned_be64(ptr);
198 ptr += 8;
199 } else {
200 mp_opt->data_seq = get_unaligned_be32(ptr);
201 ptr += 4;
202 }
203
204 mp_opt->subflow_seq = get_unaligned_be32(ptr);
205 ptr += 4;
206
207 mp_opt->data_len = get_unaligned_be16(ptr);
208 ptr += 2;
209
210 pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
211 mp_opt->data_seq, mp_opt->subflow_seq,
212 mp_opt->data_len);
213 }
214
215 break;
216
217 case MPTCPOPT_ADD_ADDR:
218 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
219 if (!mp_opt->echo) {
220 if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
221 opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
222 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
223 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
224 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
225 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
226 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
227 #endif
228 else
229 break;
230 } else {
231 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
232 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
233 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
234 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
235 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
236 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
237 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
238 #endif
239 else
240 break;
241 }
242
243 mp_opt->add_addr = 1;
244 mp_opt->addr_id = *ptr++;
245 pr_debug("ADD_ADDR: id=%d, echo=%d", mp_opt->addr_id, mp_opt->echo);
246 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
247 memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
248 ptr += 4;
249 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
250 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
251 mp_opt->port = get_unaligned_be16(ptr);
252 ptr += 2;
253 }
254 }
255 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
256 else {
257 memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
258 ptr += 16;
259 if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
260 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
261 mp_opt->port = get_unaligned_be16(ptr);
262 ptr += 2;
263 }
264 }
265 #endif
266 if (!mp_opt->echo) {
267 mp_opt->ahmac = get_unaligned_be64(ptr);
268 ptr += 8;
269 }
270 break;
271
272 case MPTCPOPT_RM_ADDR:
273 if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
274 break;
275
276 ptr++;
277
278 mp_opt->rm_addr = 1;
279 mp_opt->rm_id = *ptr++;
280 pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
281 break;
282
283 default:
284 break;
285 }
286 }
287
mptcp_get_options(const struct sk_buff * skb,struct mptcp_options_received * mp_opt)288 void mptcp_get_options(const struct sk_buff *skb,
289 struct mptcp_options_received *mp_opt)
290 {
291 const struct tcphdr *th = tcp_hdr(skb);
292 const unsigned char *ptr;
293 int length;
294
295 /* initialize option status */
296 mp_opt->mp_capable = 0;
297 mp_opt->mp_join = 0;
298 mp_opt->add_addr = 0;
299 mp_opt->ahmac = 0;
300 mp_opt->port = 0;
301 mp_opt->rm_addr = 0;
302 mp_opt->dss = 0;
303
304 length = (th->doff * 4) - sizeof(struct tcphdr);
305 ptr = (const unsigned char *)(th + 1);
306
307 while (length > 0) {
308 int opcode = *ptr++;
309 int opsize;
310
311 switch (opcode) {
312 case TCPOPT_EOL:
313 return;
314 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
315 length--;
316 continue;
317 default:
318 if (length < 2)
319 return;
320 opsize = *ptr++;
321 if (opsize < 2) /* "silly options" */
322 return;
323 if (opsize > length)
324 return; /* don't parse partial options */
325 if (opcode == TCPOPT_MPTCP)
326 mptcp_parse_option(skb, ptr, opsize, mp_opt);
327 ptr += opsize - 2;
328 length -= opsize;
329 }
330 }
331 }
332
mptcp_syn_options(struct sock * sk,const struct sk_buff * skb,unsigned int * size,struct mptcp_out_options * opts)333 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
334 unsigned int *size, struct mptcp_out_options *opts)
335 {
336 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
337
338 /* we will use snd_isn to detect first pkt [re]transmission
339 * in mptcp_established_options_mp()
340 */
341 subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
342 if (subflow->request_mptcp) {
343 opts->suboptions = OPTION_MPTCP_MPC_SYN;
344 *size = TCPOLEN_MPTCP_MPC_SYN;
345 return true;
346 } else if (subflow->request_join) {
347 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
348 subflow->local_nonce);
349 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
350 opts->join_id = subflow->local_id;
351 opts->token = subflow->remote_token;
352 opts->nonce = subflow->local_nonce;
353 opts->backup = subflow->request_bkup;
354 *size = TCPOLEN_MPTCP_MPJ_SYN;
355 return true;
356 }
357 return false;
358 }
359
360 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
361 * TCP can't schedule delack timer before the subflow is fully established.
362 * MPTCP uses the delack timer to do 3rd ack retransmissions
363 */
schedule_3rdack_retransmission(struct sock * sk)364 static void schedule_3rdack_retransmission(struct sock *sk)
365 {
366 struct inet_connection_sock *icsk = inet_csk(sk);
367 struct tcp_sock *tp = tcp_sk(sk);
368 unsigned long timeout;
369
370 /* reschedule with a timeout above RTT, as we must look only for drop */
371 if (tp->srtt_us)
372 timeout = usecs_to_jiffies(tp->srtt_us >> (3 - 1));
373 else
374 timeout = TCP_TIMEOUT_INIT;
375 timeout += jiffies;
376
377 WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
378 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
379 icsk->icsk_ack.timeout = timeout;
380 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
381 }
382
clear_3rdack_retransmission(struct sock * sk)383 static void clear_3rdack_retransmission(struct sock *sk)
384 {
385 struct inet_connection_sock *icsk = inet_csk(sk);
386
387 sk_stop_timer(sk, &icsk->icsk_delack_timer);
388 icsk->icsk_ack.timeout = 0;
389 icsk->icsk_ack.ato = 0;
390 icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
391 }
392
mptcp_established_options_mp(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)393 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
394 unsigned int *size,
395 unsigned int remaining,
396 struct mptcp_out_options *opts)
397 {
398 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
399 struct mptcp_ext *mpext;
400 unsigned int data_len;
401
402 /* When skb is not available, we better over-estimate the emitted
403 * options len. A full DSS option (28 bytes) is longer than
404 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
405 * tell the caller to defer the estimate to
406 * mptcp_established_options_dss(), which will reserve enough space.
407 */
408 if (!skb)
409 return false;
410
411 /* MPC/MPJ needed only on 3rd ack packet */
412 if (subflow->fully_established ||
413 subflow->snd_isn != TCP_SKB_CB(skb)->seq)
414 return false;
415
416 if (subflow->mp_capable) {
417 mpext = mptcp_get_ext(skb);
418 data_len = mpext ? mpext->data_len : 0;
419
420 /* we will check ext_copy.data_len in mptcp_write_options() to
421 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
422 * TCPOLEN_MPTCP_MPC_ACK
423 */
424 opts->ext_copy.data_len = data_len;
425 opts->suboptions = OPTION_MPTCP_MPC_ACK;
426 opts->sndr_key = subflow->local_key;
427 opts->rcvr_key = subflow->remote_key;
428
429 /* Section 3.1.
430 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
431 * packets that start the first subflow of an MPTCP connection,
432 * as well as the first packet that carries data
433 */
434 if (data_len > 0)
435 *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
436 else
437 *size = TCPOLEN_MPTCP_MPC_ACK;
438
439 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
440 subflow, subflow->local_key, subflow->remote_key,
441 data_len);
442
443 return true;
444 } else if (subflow->mp_join) {
445 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
446 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
447 *size = TCPOLEN_MPTCP_MPJ_ACK;
448 pr_debug("subflow=%p", subflow);
449
450 schedule_3rdack_retransmission(sk);
451 return true;
452 }
453 return false;
454 }
455
mptcp_write_data_fin(struct mptcp_subflow_context * subflow,struct sk_buff * skb,struct mptcp_ext * ext)456 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
457 struct sk_buff *skb, struct mptcp_ext *ext)
458 {
459 /* The write_seq value has already been incremented, so the actual
460 * sequence number for the DATA_FIN is one less.
461 */
462 u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
463
464 if (!ext->use_map || !skb->len) {
465 /* RFC6824 requires a DSS mapping with specific values
466 * if DATA_FIN is set but no data payload is mapped
467 */
468 ext->data_fin = 1;
469 ext->use_map = 1;
470 ext->dsn64 = 1;
471 ext->data_seq = data_fin_tx_seq;
472 ext->subflow_seq = 0;
473 ext->data_len = 1;
474 } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
475 /* If there's an existing DSS mapping and it is the
476 * final mapping, DATA_FIN consumes 1 additional byte of
477 * mapping space.
478 */
479 ext->data_fin = 1;
480 ext->data_len++;
481 }
482 }
483
mptcp_established_options_dss(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)484 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
485 unsigned int *size,
486 unsigned int remaining,
487 struct mptcp_out_options *opts)
488 {
489 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
490 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
491 unsigned int dss_size = 0;
492 u64 snd_data_fin_enable;
493 struct mptcp_ext *mpext;
494 unsigned int ack_size;
495 bool ret = false;
496
497 mpext = skb ? mptcp_get_ext(skb) : NULL;
498 snd_data_fin_enable = READ_ONCE(msk->snd_data_fin_enable);
499
500 if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
501 unsigned int map_size;
502
503 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
504
505 remaining -= map_size;
506 dss_size = map_size;
507 if (mpext)
508 opts->ext_copy = *mpext;
509
510 if (skb && snd_data_fin_enable)
511 mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
512 ret = true;
513 }
514
515 /* passive sockets msk will set the 'can_ack' after accept(), even
516 * if the first subflow may have the already the remote key handy
517 */
518 opts->ext_copy.use_ack = 0;
519 if (!READ_ONCE(msk->can_ack)) {
520 *size = ALIGN(dss_size, 4);
521 return ret;
522 }
523
524 if (READ_ONCE(msk->use_64bit_ack)) {
525 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
526 opts->ext_copy.data_ack = READ_ONCE(msk->ack_seq);
527 opts->ext_copy.ack64 = 1;
528 } else {
529 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
530 opts->ext_copy.data_ack32 = (uint32_t)READ_ONCE(msk->ack_seq);
531 opts->ext_copy.ack64 = 0;
532 }
533 opts->ext_copy.use_ack = 1;
534
535 /* Add kind/length/subtype/flag overhead if mapping is not populated */
536 if (dss_size == 0)
537 ack_size += TCPOLEN_MPTCP_DSS_BASE;
538
539 dss_size += ack_size;
540
541 *size = ALIGN(dss_size, 4);
542 return true;
543 }
544
add_addr_generate_hmac(u64 key1,u64 key2,u8 addr_id,struct in_addr * addr)545 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
546 struct in_addr *addr)
547 {
548 u8 hmac[SHA256_DIGEST_SIZE];
549 u8 msg[7];
550
551 msg[0] = addr_id;
552 memcpy(&msg[1], &addr->s_addr, 4);
553 msg[5] = 0;
554 msg[6] = 0;
555
556 mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
557
558 return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
559 }
560
561 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
add_addr6_generate_hmac(u64 key1,u64 key2,u8 addr_id,struct in6_addr * addr)562 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
563 struct in6_addr *addr)
564 {
565 u8 hmac[SHA256_DIGEST_SIZE];
566 u8 msg[19];
567
568 msg[0] = addr_id;
569 memcpy(&msg[1], &addr->s6_addr, 16);
570 msg[17] = 0;
571 msg[18] = 0;
572
573 mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
574
575 return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
576 }
577 #endif
578
mptcp_established_options_add_addr(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)579 static bool mptcp_established_options_add_addr(struct sock *sk,
580 unsigned int *size,
581 unsigned int remaining,
582 struct mptcp_out_options *opts)
583 {
584 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
585 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
586 struct mptcp_addr_info saddr;
587 bool echo;
588 int len;
589
590 if (!mptcp_pm_should_add_signal(msk) ||
591 !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo)))
592 return false;
593
594 len = mptcp_add_addr_len(saddr.family, echo);
595 if (remaining < len)
596 return false;
597
598 *size = len;
599 opts->addr_id = saddr.id;
600 if (saddr.family == AF_INET) {
601 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
602 opts->addr = saddr.addr;
603 if (!echo) {
604 opts->ahmac = add_addr_generate_hmac(msk->local_key,
605 msk->remote_key,
606 opts->addr_id,
607 &opts->addr);
608 }
609 }
610 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
611 else if (saddr.family == AF_INET6) {
612 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
613 opts->addr6 = saddr.addr6;
614 if (!echo) {
615 opts->ahmac = add_addr6_generate_hmac(msk->local_key,
616 msk->remote_key,
617 opts->addr_id,
618 &opts->addr6);
619 }
620 }
621 #endif
622 pr_debug("addr_id=%d, ahmac=%llu, echo=%d", opts->addr_id, opts->ahmac, echo);
623
624 return true;
625 }
626
mptcp_established_options_rm_addr(struct sock * sk,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)627 static bool mptcp_established_options_rm_addr(struct sock *sk,
628 unsigned int *size,
629 unsigned int remaining,
630 struct mptcp_out_options *opts)
631 {
632 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
633 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
634 u8 rm_id;
635
636 if (!mptcp_pm_should_rm_signal(msk) ||
637 !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id)))
638 return false;
639
640 if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
641 return false;
642
643 *size = TCPOLEN_MPTCP_RM_ADDR_BASE;
644 opts->suboptions |= OPTION_MPTCP_RM_ADDR;
645 opts->rm_id = rm_id;
646
647 pr_debug("rm_id=%d", opts->rm_id);
648
649 return true;
650 }
651
mptcp_established_options(struct sock * sk,struct sk_buff * skb,unsigned int * size,unsigned int remaining,struct mptcp_out_options * opts)652 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
653 unsigned int *size, unsigned int remaining,
654 struct mptcp_out_options *opts)
655 {
656 unsigned int opt_size = 0;
657 bool ret = false;
658
659 opts->suboptions = 0;
660
661 if (unlikely(mptcp_check_fallback(sk)))
662 return false;
663
664 /* prevent adding of any MPTCP related options on reset packet
665 * until we support MP_TCPRST/MP_FASTCLOSE
666 */
667 if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
668 return false;
669
670 if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
671 ret = true;
672 else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
673 opts))
674 ret = true;
675
676 /* we reserved enough space for the above options, and exceeding the
677 * TCP option space would be fatal
678 */
679 if (WARN_ON_ONCE(opt_size > remaining))
680 return false;
681
682 *size += opt_size;
683 remaining -= opt_size;
684 if (mptcp_established_options_add_addr(sk, &opt_size, remaining, opts)) {
685 *size += opt_size;
686 remaining -= opt_size;
687 ret = true;
688 } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
689 *size += opt_size;
690 remaining -= opt_size;
691 ret = true;
692 }
693
694 return ret;
695 }
696
mptcp_synack_options(const struct request_sock * req,unsigned int * size,struct mptcp_out_options * opts)697 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
698 struct mptcp_out_options *opts)
699 {
700 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
701
702 if (subflow_req->mp_capable) {
703 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
704 opts->sndr_key = subflow_req->local_key;
705 *size = TCPOLEN_MPTCP_MPC_SYNACK;
706 pr_debug("subflow_req=%p, local_key=%llu",
707 subflow_req, subflow_req->local_key);
708 return true;
709 } else if (subflow_req->mp_join) {
710 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
711 opts->backup = subflow_req->backup;
712 opts->join_id = subflow_req->local_id;
713 opts->thmac = subflow_req->thmac;
714 opts->nonce = subflow_req->local_nonce;
715 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
716 subflow_req, opts->backup, opts->join_id,
717 opts->thmac, opts->nonce);
718 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
719 return true;
720 }
721 return false;
722 }
723
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)724 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
725 struct mptcp_subflow_context *subflow,
726 struct sk_buff *skb,
727 struct mptcp_options_received *mp_opt)
728 {
729 /* here we can process OoO, in-window pkts, only in-sequence 4th ack
730 * will make the subflow fully established
731 */
732 if (likely(subflow->fully_established)) {
733 /* on passive sockets, check for 3rd ack retransmission
734 * note that msk is always set by subflow_syn_recv_sock()
735 * for mp_join subflows
736 */
737 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
738 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
739 subflow->mp_join && mp_opt->mp_join &&
740 READ_ONCE(msk->pm.server_side))
741 tcp_send_ack(ssk);
742 goto fully_established;
743 }
744
745 /* we must process OoO packets before the first subflow is fully
746 * established. OoO packets are instead a protocol violation
747 * for MP_JOIN subflows as the peer must not send any data
748 * before receiving the forth ack - cfr. RFC 8684 section 3.2.
749 */
750 if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
751 if (subflow->mp_join)
752 goto reset;
753 return subflow->mp_capable;
754 }
755
756 if (mp_opt->dss && mp_opt->use_ack) {
757 /* subflows are fully established as soon as we get any
758 * additional ack.
759 */
760 subflow->fully_established = 1;
761 WRITE_ONCE(msk->fully_established, true);
762 goto fully_established;
763 }
764
765 /* If the first established packet does not contain MP_CAPABLE + data
766 * then fallback to TCP. Fallback scenarios requires a reset for
767 * MP_JOIN subflows.
768 */
769 if (!mp_opt->mp_capable) {
770 if (subflow->mp_join)
771 goto reset;
772 subflow->mp_capable = 0;
773 pr_fallback(msk);
774 __mptcp_do_fallback(msk);
775 return false;
776 }
777
778 if (unlikely(!READ_ONCE(msk->pm.server_side)))
779 pr_warn_once("bogus mpc option on established client sk");
780 mptcp_subflow_fully_established(subflow, mp_opt);
781
782 fully_established:
783 if (likely(subflow->pm_notified))
784 return true;
785
786 subflow->pm_notified = 1;
787 if (subflow->mp_join) {
788 clear_3rdack_retransmission(ssk);
789 mptcp_pm_subflow_established(msk, subflow);
790 } else {
791 mptcp_pm_fully_established(msk);
792 }
793 return true;
794
795 reset:
796 mptcp_subflow_reset(ssk);
797 return false;
798 }
799
expand_ack(u64 old_ack,u64 cur_ack,bool use_64bit)800 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
801 {
802 u32 old_ack32, cur_ack32;
803
804 if (use_64bit)
805 return cur_ack;
806
807 old_ack32 = (u32)old_ack;
808 cur_ack32 = (u32)cur_ack;
809 cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
810 if (unlikely(before(cur_ack32, old_ack32)))
811 return cur_ack + (1LL << 32);
812 return cur_ack;
813 }
814
update_una(struct mptcp_sock * msk,struct mptcp_options_received * mp_opt)815 static void update_una(struct mptcp_sock *msk,
816 struct mptcp_options_received *mp_opt)
817 {
818 u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);
819 u64 write_seq = READ_ONCE(msk->write_seq);
820
821 /* avoid ack expansion on update conflict, to reduce the risk of
822 * wrongly expanding to a future ack sequence number, which is way
823 * more dangerous than missing an ack
824 */
825 new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
826
827 /* ACK for data not even sent yet? Ignore. */
828 if (after64(new_snd_una, write_seq))
829 new_snd_una = old_snd_una;
830
831 while (after64(new_snd_una, old_snd_una)) {
832 snd_una = old_snd_una;
833 old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,
834 new_snd_una);
835 if (old_snd_una == snd_una) {
836 mptcp_data_acked((struct sock *)msk);
837 break;
838 }
839 }
840 }
841
mptcp_update_rcv_data_fin(struct mptcp_sock * msk,u64 data_fin_seq,bool use_64bit)842 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
843 {
844 /* Skip if DATA_FIN was already received.
845 * If updating simultaneously with the recvmsg loop, values
846 * should match. If they mismatch, the peer is misbehaving and
847 * we will prefer the most recent information.
848 */
849 if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first))
850 return false;
851
852 WRITE_ONCE(msk->rcv_data_fin_seq,
853 expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
854 WRITE_ONCE(msk->rcv_data_fin, 1);
855
856 return true;
857 }
858
add_addr_hmac_valid(struct mptcp_sock * msk,struct mptcp_options_received * mp_opt)859 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
860 struct mptcp_options_received *mp_opt)
861 {
862 u64 hmac = 0;
863
864 if (mp_opt->echo)
865 return true;
866
867 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
868 hmac = add_addr_generate_hmac(msk->remote_key,
869 msk->local_key,
870 mp_opt->addr_id, &mp_opt->addr);
871 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
872 else
873 hmac = add_addr6_generate_hmac(msk->remote_key,
874 msk->local_key,
875 mp_opt->addr_id, &mp_opt->addr6);
876 #endif
877
878 pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
879 msk, (unsigned long long)hmac,
880 (unsigned long long)mp_opt->ahmac);
881
882 return hmac == mp_opt->ahmac;
883 }
884
mptcp_incoming_options(struct sock * sk,struct sk_buff * skb)885 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
886 {
887 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
888 struct mptcp_sock *msk = mptcp_sk(subflow->conn);
889 struct mptcp_options_received mp_opt;
890 struct mptcp_ext *mpext;
891
892 if (__mptcp_check_fallback(msk))
893 return;
894
895 mptcp_get_options(skb, &mp_opt);
896 if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
897 return;
898
899 if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
900 struct mptcp_addr_info addr;
901
902 addr.port = htons(mp_opt.port);
903 addr.id = mp_opt.addr_id;
904 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
905 addr.family = AF_INET;
906 addr.addr = mp_opt.addr;
907 }
908 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
909 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
910 addr.family = AF_INET6;
911 addr.addr6 = mp_opt.addr6;
912 }
913 #endif
914 if (!mp_opt.echo) {
915 mptcp_pm_add_addr_received(msk, &addr);
916 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
917 } else {
918 mptcp_pm_del_add_timer(msk, &addr);
919 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
920 }
921 mp_opt.add_addr = 0;
922 }
923
924 if (mp_opt.rm_addr) {
925 mptcp_pm_rm_addr_received(msk, mp_opt.rm_id);
926 mp_opt.rm_addr = 0;
927 }
928
929 if (!mp_opt.dss)
930 return;
931
932 /* we can't wait for recvmsg() to update the ack_seq, otherwise
933 * monodirectional flows will stuck
934 */
935 if (mp_opt.use_ack)
936 update_una(msk, &mp_opt);
937
938 /* Zero-data-length packets are dropped by the caller and not
939 * propagated to the MPTCP layer, so the skb extension does not
940 * need to be allocated or populated. DATA_FIN information, if
941 * present, needs to be updated here before the skb is freed.
942 */
943 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
944 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
945 mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
946 schedule_work(&msk->work))
947 sock_hold(subflow->conn);
948
949 return;
950 }
951
952 mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
953 if (!mpext)
954 return;
955
956 memset(mpext, 0, sizeof(*mpext));
957
958 if (mp_opt.use_map) {
959 if (mp_opt.mpc_map) {
960 /* this is an MP_CAPABLE carrying MPTCP data
961 * we know this map the first chunk of data
962 */
963 mptcp_crypto_key_sha(subflow->remote_key, NULL,
964 &mpext->data_seq);
965 mpext->data_seq++;
966 mpext->subflow_seq = 1;
967 mpext->dsn64 = 1;
968 mpext->mpc_map = 1;
969 mpext->data_fin = 0;
970 } else {
971 mpext->data_seq = mp_opt.data_seq;
972 mpext->subflow_seq = mp_opt.subflow_seq;
973 mpext->dsn64 = mp_opt.dsn64;
974 mpext->data_fin = mp_opt.data_fin;
975 }
976 mpext->data_len = mp_opt.data_len;
977 mpext->use_map = 1;
978 }
979 }
980
mptcp_write_options(__be32 * ptr,struct mptcp_out_options * opts)981 void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
982 {
983 if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
984 OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
985 u8 len;
986
987 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
988 len = TCPOLEN_MPTCP_MPC_SYN;
989 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
990 len = TCPOLEN_MPTCP_MPC_SYNACK;
991 else if (opts->ext_copy.data_len)
992 len = TCPOLEN_MPTCP_MPC_ACK_DATA;
993 else
994 len = TCPOLEN_MPTCP_MPC_ACK;
995
996 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
997 MPTCP_SUPPORTED_VERSION,
998 MPTCP_CAP_HMAC_SHA256);
999
1000 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1001 opts->suboptions))
1002 goto mp_capable_done;
1003
1004 put_unaligned_be64(opts->sndr_key, ptr);
1005 ptr += 2;
1006 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1007 goto mp_capable_done;
1008
1009 put_unaligned_be64(opts->rcvr_key, ptr);
1010 ptr += 2;
1011 if (!opts->ext_copy.data_len)
1012 goto mp_capable_done;
1013
1014 put_unaligned_be32(opts->ext_copy.data_len << 16 |
1015 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1016 ptr += 1;
1017 }
1018
1019 mp_capable_done:
1020 if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1021 if (opts->ahmac)
1022 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1023 TCPOLEN_MPTCP_ADD_ADDR, 0,
1024 opts->addr_id);
1025 else
1026 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1027 TCPOLEN_MPTCP_ADD_ADDR_BASE,
1028 MPTCP_ADDR_ECHO,
1029 opts->addr_id);
1030 memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
1031 ptr += 1;
1032 if (opts->ahmac) {
1033 put_unaligned_be64(opts->ahmac, ptr);
1034 ptr += 2;
1035 }
1036 }
1037
1038 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1039 if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
1040 if (opts->ahmac)
1041 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1042 TCPOLEN_MPTCP_ADD_ADDR6, 0,
1043 opts->addr_id);
1044 else
1045 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1046 TCPOLEN_MPTCP_ADD_ADDR6_BASE,
1047 MPTCP_ADDR_ECHO,
1048 opts->addr_id);
1049 memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
1050 ptr += 4;
1051 if (opts->ahmac) {
1052 put_unaligned_be64(opts->ahmac, ptr);
1053 ptr += 2;
1054 }
1055 }
1056 #endif
1057
1058 if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1059 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1060 TCPOLEN_MPTCP_RM_ADDR_BASE,
1061 0, opts->rm_id);
1062 }
1063
1064 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1065 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1066 TCPOLEN_MPTCP_MPJ_SYN,
1067 opts->backup, opts->join_id);
1068 put_unaligned_be32(opts->token, ptr);
1069 ptr += 1;
1070 put_unaligned_be32(opts->nonce, ptr);
1071 ptr += 1;
1072 }
1073
1074 if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1075 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1076 TCPOLEN_MPTCP_MPJ_SYNACK,
1077 opts->backup, opts->join_id);
1078 put_unaligned_be64(opts->thmac, ptr);
1079 ptr += 2;
1080 put_unaligned_be32(opts->nonce, ptr);
1081 ptr += 1;
1082 }
1083
1084 if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1085 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1086 TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1087 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1088 ptr += 5;
1089 }
1090
1091 if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1092 struct mptcp_ext *mpext = &opts->ext_copy;
1093 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1094 u8 flags = 0;
1095
1096 if (mpext->use_ack) {
1097 flags = MPTCP_DSS_HAS_ACK;
1098 if (mpext->ack64) {
1099 len += TCPOLEN_MPTCP_DSS_ACK64;
1100 flags |= MPTCP_DSS_ACK64;
1101 } else {
1102 len += TCPOLEN_MPTCP_DSS_ACK32;
1103 }
1104 }
1105
1106 if (mpext->use_map) {
1107 len += TCPOLEN_MPTCP_DSS_MAP64;
1108
1109 /* Use only 64-bit mapping flags for now, add
1110 * support for optional 32-bit mappings later.
1111 */
1112 flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1113 if (mpext->data_fin)
1114 flags |= MPTCP_DSS_DATA_FIN;
1115 }
1116
1117 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1118
1119 if (mpext->use_ack) {
1120 if (mpext->ack64) {
1121 put_unaligned_be64(mpext->data_ack, ptr);
1122 ptr += 2;
1123 } else {
1124 put_unaligned_be32(mpext->data_ack32, ptr);
1125 ptr += 1;
1126 }
1127 }
1128
1129 if (mpext->use_map) {
1130 put_unaligned_be64(mpext->data_seq, ptr);
1131 ptr += 2;
1132 put_unaligned_be32(mpext->subflow_seq, ptr);
1133 ptr += 1;
1134 put_unaligned_be32(mpext->data_len << 16 |
1135 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1136 }
1137 }
1138 }
1139