1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2020 Facebook */
3
4 #include <stddef.h>
5 #include <errno.h>
6 #include <stdbool.h>
7 #include <sys/types.h>
8 #include <sys/socket.h>
9 #include <linux/tcp.h>
10 #include <linux/socket.h>
11 #include <linux/bpf.h>
12 #include <linux/types.h>
13 #include <bpf/bpf_helpers.h>
14 #include <bpf/bpf_endian.h>
15 #define BPF_PROG_TEST_TCP_HDR_OPTIONS
16 #include "test_tcp_hdr_options.h"
17
18 #ifndef sizeof_field
19 #define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
20 #endif
21
22 __u8 test_kind = TCPOPT_EXP;
23 __u16 test_magic = 0xeB9F;
24 __u32 inherit_cb_flags = 0;
25
26 struct bpf_test_option passive_synack_out = {};
27 struct bpf_test_option passive_fin_out = {};
28
29 struct bpf_test_option passive_estab_in = {};
30 struct bpf_test_option passive_fin_in = {};
31
32 struct bpf_test_option active_syn_out = {};
33 struct bpf_test_option active_fin_out = {};
34
35 struct bpf_test_option active_estab_in = {};
36 struct bpf_test_option active_fin_in = {};
37
38 struct {
39 __uint(type, BPF_MAP_TYPE_SK_STORAGE);
40 __uint(map_flags, BPF_F_NO_PREALLOC);
41 __type(key, int);
42 __type(value, struct hdr_stg);
43 } hdr_stg_map SEC(".maps");
44
45 static bool skops_want_cookie(const struct bpf_sock_ops *skops)
46 {
47 return skops->args[0] == BPF_WRITE_HDR_TCP_SYNACK_COOKIE;
48 }
49
50 static bool skops_current_mss(const struct bpf_sock_ops *skops)
51 {
52 return skops->args[0] == BPF_WRITE_HDR_TCP_CURRENT_MSS;
53 }
54
55 static __u8 option_total_len(__u8 flags)
56 {
57 __u8 i, len = 1; /* +1 for flags */
58
59 if (!flags)
60 return 0;
61
62 /* RESEND bit does not use a byte */
63 for (i = OPTION_RESEND + 1; i < __NR_OPTION_FLAGS; i++)
64 len += !!TEST_OPTION_FLAGS(flags, i);
65
66 if (test_kind == TCPOPT_EXP)
67 return len + TCP_BPF_EXPOPT_BASE_LEN;
68 else
69 return len + 2; /* +1 kind, +1 kind-len */
70 }
71
72 static void write_test_option(const struct bpf_test_option *test_opt,
73 __u8 *data)
74 {
75 __u8 offset = 0;
76
77 data[offset++] = test_opt->flags;
78 if (TEST_OPTION_FLAGS(test_opt->flags, OPTION_MAX_DELACK_MS))
79 data[offset++] = test_opt->max_delack_ms;
80
81 if (TEST_OPTION_FLAGS(test_opt->flags, OPTION_RAND))
82 data[offset++] = test_opt->rand;
83 }
84
85 static int store_option(struct bpf_sock_ops *skops,
86 const struct bpf_test_option *test_opt)
87 {
88 union {
89 struct tcp_exprm_opt exprm;
90 struct tcp_opt regular;
91 } write_opt;
92 int err;
93
94 if (test_kind == TCPOPT_EXP) {
95 write_opt.exprm.kind = TCPOPT_EXP;
96 write_opt.exprm.len = option_total_len(test_opt->flags);
97 write_opt.exprm.magic = __bpf_htons(test_magic);
98 write_opt.exprm.data32 = 0;
99 write_test_option(test_opt, write_opt.exprm.data);
100 err = bpf_store_hdr_opt(skops, &write_opt.exprm,
101 sizeof(write_opt.exprm), 0);
102 } else {
103 write_opt.regular.kind = test_kind;
104 write_opt.regular.len = option_total_len(test_opt->flags);
105 write_opt.regular.data32 = 0;
106 write_test_option(test_opt, write_opt.regular.data);
107 err = bpf_store_hdr_opt(skops, &write_opt.regular,
108 sizeof(write_opt.regular), 0);
109 }
110
111 if (err)
112 RET_CG_ERR(err);
113
114 return CG_OK;
115 }
116
117 static int parse_test_option(struct bpf_test_option *opt, const __u8 *start)
118 {
119 opt->flags = *start++;
120
121 if (TEST_OPTION_FLAGS(opt->flags, OPTION_MAX_DELACK_MS))
122 opt->max_delack_ms = *start++;
123
124 if (TEST_OPTION_FLAGS(opt->flags, OPTION_RAND))
125 opt->rand = *start++;
126
127 return 0;
128 }
129
130 static int load_option(struct bpf_sock_ops *skops,
131 struct bpf_test_option *test_opt, bool from_syn)
132 {
133 union {
134 struct tcp_exprm_opt exprm;
135 struct tcp_opt regular;
136 } search_opt;
137 int ret, load_flags = from_syn ? BPF_LOAD_HDR_OPT_TCP_SYN : 0;
138
139 if (test_kind == TCPOPT_EXP) {
140 search_opt.exprm.kind = TCPOPT_EXP;
141 search_opt.exprm.len = 4;
142 search_opt.exprm.magic = __bpf_htons(test_magic);
143 search_opt.exprm.data32 = 0;
144 ret = bpf_load_hdr_opt(skops, &search_opt.exprm,
145 sizeof(search_opt.exprm), load_flags);
146 if (ret < 0)
147 return ret;
148 return parse_test_option(test_opt, search_opt.exprm.data);
149 } else {
150 search_opt.regular.kind = test_kind;
151 search_opt.regular.len = 0;
152 search_opt.regular.data32 = 0;
153 ret = bpf_load_hdr_opt(skops, &search_opt.regular,
154 sizeof(search_opt.regular), load_flags);
155 if (ret < 0)
156 return ret;
157 return parse_test_option(test_opt, search_opt.regular.data);
158 }
159 }
160
161 static int synack_opt_len(struct bpf_sock_ops *skops)
162 {
163 struct bpf_test_option test_opt = {};
164 __u8 optlen;
165 int err;
166
167 if (!passive_synack_out.flags)
168 return CG_OK;
169
170 err = load_option(skops, &test_opt, true);
171
172 /* bpf_test_option is not found */
173 if (err == -ENOMSG)
174 return CG_OK;
175
176 if (err)
177 RET_CG_ERR(err);
178
179 optlen = option_total_len(passive_synack_out.flags);
180 if (optlen) {
181 err = bpf_reserve_hdr_opt(skops, optlen, 0);
182 if (err)
183 RET_CG_ERR(err);
184 }
185
186 return CG_OK;
187 }
188
189 static int write_synack_opt(struct bpf_sock_ops *skops)
190 {
191 struct bpf_test_option opt;
192
193 if (!passive_synack_out.flags)
194 /* We should not even be called since no header
195 * space has been reserved.
196 */
197 RET_CG_ERR(0);
198
199 opt = passive_synack_out;
200 if (skops_want_cookie(skops))
201 SET_OPTION_FLAGS(opt.flags, OPTION_RESEND);
202
203 return store_option(skops, &opt);
204 }
205
206 static int syn_opt_len(struct bpf_sock_ops *skops)
207 {
208 __u8 optlen;
209 int err;
210
211 if (!active_syn_out.flags)
212 return CG_OK;
213
214 optlen = option_total_len(active_syn_out.flags);
215 if (optlen) {
216 err = bpf_reserve_hdr_opt(skops, optlen, 0);
217 if (err)
218 RET_CG_ERR(err);
219 }
220
221 return CG_OK;
222 }
223
224 static int write_syn_opt(struct bpf_sock_ops *skops)
225 {
226 if (!active_syn_out.flags)
227 RET_CG_ERR(0);
228
229 return store_option(skops, &active_syn_out);
230 }
231
232 static int fin_opt_len(struct bpf_sock_ops *skops)
233 {
234 struct bpf_test_option *opt;
235 struct hdr_stg *hdr_stg;
236 __u8 optlen;
237 int err;
238
239 if (!skops->sk)
240 RET_CG_ERR(0);
241
242 hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
243 if (!hdr_stg)
244 RET_CG_ERR(0);
245
246 if (hdr_stg->active)
247 opt = &active_fin_out;
248 else
249 opt = &passive_fin_out;
250
251 optlen = option_total_len(opt->flags);
252 if (optlen) {
253 err = bpf_reserve_hdr_opt(skops, optlen, 0);
254 if (err)
255 RET_CG_ERR(err);
256 }
257
258 return CG_OK;
259 }
260
261 static int write_fin_opt(struct bpf_sock_ops *skops)
262 {
263 struct bpf_test_option *opt;
264 struct hdr_stg *hdr_stg;
265
266 if (!skops->sk)
267 RET_CG_ERR(0);
268
269 hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
270 if (!hdr_stg)
271 RET_CG_ERR(0);
272
273 if (hdr_stg->active)
274 opt = &active_fin_out;
275 else
276 opt = &passive_fin_out;
277
278 if (!opt->flags)
279 RET_CG_ERR(0);
280
281 return store_option(skops, opt);
282 }
283
284 static int resend_in_ack(struct bpf_sock_ops *skops)
285 {
286 struct hdr_stg *hdr_stg;
287
288 if (!skops->sk)
289 return -1;
290
291 hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
292 if (!hdr_stg)
293 return -1;
294
295 return !!hdr_stg->resend_syn;
296 }
297
298 static int nodata_opt_len(struct bpf_sock_ops *skops)
299 {
300 int resend;
301
302 resend = resend_in_ack(skops);
303 if (resend < 0)
304 RET_CG_ERR(0);
305
306 if (resend)
307 return syn_opt_len(skops);
308
309 return CG_OK;
310 }
311
312 static int write_nodata_opt(struct bpf_sock_ops *skops)
313 {
314 int resend;
315
316 resend = resend_in_ack(skops);
317 if (resend < 0)
318 RET_CG_ERR(0);
319
320 if (resend)
321 return write_syn_opt(skops);
322
323 return CG_OK;
324 }
325
326 static int data_opt_len(struct bpf_sock_ops *skops)
327 {
328 /* Same as the nodata version. Mostly to show
329 * an example usage on skops->skb_len.
330 */
331 return nodata_opt_len(skops);
332 }
333
334 static int write_data_opt(struct bpf_sock_ops *skops)
335 {
336 return write_nodata_opt(skops);
337 }
338
339 static int current_mss_opt_len(struct bpf_sock_ops *skops)
340 {
341 /* Reserve maximum that may be needed */
342 int err;
343
344 err = bpf_reserve_hdr_opt(skops, option_total_len(OPTION_MASK), 0);
345 if (err)
346 RET_CG_ERR(err);
347
348 return CG_OK;
349 }
350
351 static int handle_hdr_opt_len(struct bpf_sock_ops *skops)
352 {
353 __u8 tcp_flags = skops_tcp_flags(skops);
354
355 if ((tcp_flags & TCPHDR_SYNACK) == TCPHDR_SYNACK)
356 return synack_opt_len(skops);
357
358 if (tcp_flags & TCPHDR_SYN)
359 return syn_opt_len(skops);
360
361 if (tcp_flags & TCPHDR_FIN)
362 return fin_opt_len(skops);
363
364 if (skops_current_mss(skops))
365 /* The kernel is calculating the MSS */
366 return current_mss_opt_len(skops);
367
368 if (skops->skb_len)
369 return data_opt_len(skops);
370
371 return nodata_opt_len(skops);
372 }
373
374 static int handle_write_hdr_opt(struct bpf_sock_ops *skops)
375 {
376 __u8 tcp_flags = skops_tcp_flags(skops);
377 struct tcphdr *th;
378
379 if ((tcp_flags & TCPHDR_SYNACK) == TCPHDR_SYNACK)
380 return write_synack_opt(skops);
381
382 if (tcp_flags & TCPHDR_SYN)
383 return write_syn_opt(skops);
384
385 if (tcp_flags & TCPHDR_FIN)
386 return write_fin_opt(skops);
387
388 th = skops->skb_data;
389 if (th + 1 > skops->skb_data_end)
390 RET_CG_ERR(0);
391
392 if (skops->skb_len > tcp_hdrlen(th))
393 return write_data_opt(skops);
394
395 return write_nodata_opt(skops);
396 }
397
398 static int set_delack_max(struct bpf_sock_ops *skops, __u8 max_delack_ms)
399 {
400 __u32 max_delack_us = max_delack_ms * 1000;
401
402 return bpf_setsockopt(skops, SOL_TCP, TCP_BPF_DELACK_MAX,
403 &max_delack_us, sizeof(max_delack_us));
404 }
405
406 static int set_rto_min(struct bpf_sock_ops *skops, __u8 peer_max_delack_ms)
407 {
408 __u32 min_rto_us = peer_max_delack_ms * 1000;
409
410 return bpf_setsockopt(skops, SOL_TCP, TCP_BPF_RTO_MIN, &min_rto_us,
411 sizeof(min_rto_us));
412 }
413
414 static int handle_active_estab(struct bpf_sock_ops *skops)
415 {
416 struct hdr_stg init_stg = {
417 .active = true,
418 };
419 int err;
420
421 err = load_option(skops, &active_estab_in, false);
422 if (err && err != -ENOMSG)
423 RET_CG_ERR(err);
424
425 init_stg.resend_syn = TEST_OPTION_FLAGS(active_estab_in.flags,
426 OPTION_RESEND);
427 if (!skops->sk || !bpf_sk_storage_get(&hdr_stg_map, skops->sk,
428 &init_stg,
429 BPF_SK_STORAGE_GET_F_CREATE))
430 RET_CG_ERR(0);
431
432 if (init_stg.resend_syn)
433 /* Don't clear the write_hdr cb now because
434 * the ACK may get lost and retransmit may
435 * be needed.
436 *
437 * PARSE_ALL_HDR cb flag is set to learn if this
438 * resend_syn option has received by the peer.
439 *
440 * The header option will be resent until a valid
441 * packet is received at handle_parse_hdr()
442 * and all hdr cb flags will be cleared in
443 * handle_parse_hdr().
444 */
445 set_parse_all_hdr_cb_flags(skops);
446 else if (!active_fin_out.flags)
447 /* No options will be written from now */
448 clear_hdr_cb_flags(skops);
449
450 if (active_syn_out.max_delack_ms) {
451 err = set_delack_max(skops, active_syn_out.max_delack_ms);
452 if (err)
453 RET_CG_ERR(err);
454 }
455
456 if (active_estab_in.max_delack_ms) {
457 err = set_rto_min(skops, active_estab_in.max_delack_ms);
458 if (err)
459 RET_CG_ERR(err);
460 }
461
462 return CG_OK;
463 }
464
465 static int handle_passive_estab(struct bpf_sock_ops *skops)
466 {
467 struct hdr_stg init_stg = {};
468 struct tcphdr *th;
469 int err;
470
471 inherit_cb_flags = skops->bpf_sock_ops_cb_flags;
472
473 err = load_option(skops, &passive_estab_in, true);
474 if (err == -ENOENT) {
475 /* saved_syn is not found. It was in syncookie mode.
476 * We have asked the active side to resend the options
477 * in ACK, so try to find the bpf_test_option from ACK now.
478 */
479 err = load_option(skops, &passive_estab_in, false);
480 init_stg.syncookie = true;
481 }
482
483 /* ENOMSG: The bpf_test_option is not found which is fine.
484 * Bail out now for all other errors.
485 */
486 if (err && err != -ENOMSG)
487 RET_CG_ERR(err);
488
489 th = skops->skb_data;
490 if (th + 1 > skops->skb_data_end)
491 RET_CG_ERR(0);
492
493 if (th->syn) {
494 /* Fastopen */
495
496 /* Cannot clear cb_flags to stop write_hdr cb.
497 * synack is not sent yet for fast open.
498 * Even it was, the synack may need to be retransmitted.
499 *
500 * PARSE_ALL_HDR cb flag is set to learn
501 * if synack has reached the peer.
502 * All cb_flags will be cleared in handle_parse_hdr().
503 */
504 set_parse_all_hdr_cb_flags(skops);
505 init_stg.fastopen = true;
506 } else if (!passive_fin_out.flags) {
507 /* No options will be written from now */
508 clear_hdr_cb_flags(skops);
509 }
510
511 if (!skops->sk ||
512 !bpf_sk_storage_get(&hdr_stg_map, skops->sk, &init_stg,
513 BPF_SK_STORAGE_GET_F_CREATE))
514 RET_CG_ERR(0);
515
516 if (passive_synack_out.max_delack_ms) {
517 err = set_delack_max(skops, passive_synack_out.max_delack_ms);
518 if (err)
519 RET_CG_ERR(err);
520 }
521
522 if (passive_estab_in.max_delack_ms) {
523 err = set_rto_min(skops, passive_estab_in.max_delack_ms);
524 if (err)
525 RET_CG_ERR(err);
526 }
527
528 return CG_OK;
529 }
530
531 static int handle_parse_hdr(struct bpf_sock_ops *skops)
532 {
533 struct hdr_stg *hdr_stg;
534 struct tcphdr *th;
535
536 if (!skops->sk)
537 RET_CG_ERR(0);
538
539 th = skops->skb_data;
540 if (th + 1 > skops->skb_data_end)
541 RET_CG_ERR(0);
542
543 hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
544 if (!hdr_stg)
545 RET_CG_ERR(0);
546
547 if (hdr_stg->resend_syn || hdr_stg->fastopen)
548 /* The PARSE_ALL_HDR cb flag was turned on
549 * to ensure that the previously written
550 * options have reached the peer.
551 * Those previously written option includes:
552 * - Active side: resend_syn in ACK during syncookie
553 * or
554 * - Passive side: SYNACK during fastopen
555 *
556 * A valid packet has been received here after
557 * the 3WHS, so the PARSE_ALL_HDR cb flag
558 * can be cleared now.
559 */
560 clear_parse_all_hdr_cb_flags(skops);
561
562 if (hdr_stg->resend_syn && !active_fin_out.flags)
563 /* Active side resent the syn option in ACK
564 * because the server was in syncookie mode.
565 * A valid packet has been received, so
566 * clear header cb flags if there is no
567 * more option to send.
568 */
569 clear_hdr_cb_flags(skops);
570
571 if (hdr_stg->fastopen && !passive_fin_out.flags)
572 /* Passive side was in fastopen.
573 * A valid packet has been received, so
574 * the SYNACK has reached the peer.
575 * Clear header cb flags if there is no more
576 * option to send.
577 */
578 clear_hdr_cb_flags(skops);
579
580 if (th->fin) {
581 struct bpf_test_option *fin_opt;
582 int err;
583
584 if (hdr_stg->active)
585 fin_opt = &active_fin_in;
586 else
587 fin_opt = &passive_fin_in;
588
589 err = load_option(skops, fin_opt, false);
590 if (err && err != -ENOMSG)
591 RET_CG_ERR(err);
592 }
593
594 return CG_OK;
595 }
596
597 SEC("sockops")
598 int estab(struct bpf_sock_ops *skops)
599 {
600 int true_val = 1;
601
602 switch (skops->op) {
603 case BPF_SOCK_OPS_TCP_LISTEN_CB:
604 bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
605 &true_val, sizeof(true_val));
606 set_hdr_cb_flags(skops, BPF_SOCK_OPS_STATE_CB_FLAG);
607 break;
608 case BPF_SOCK_OPS_TCP_CONNECT_CB:
609 set_hdr_cb_flags(skops, 0);
610 break;
611 case BPF_SOCK_OPS_PARSE_HDR_OPT_CB:
612 return handle_parse_hdr(skops);
613 case BPF_SOCK_OPS_HDR_OPT_LEN_CB:
614 return handle_hdr_opt_len(skops);
615 case BPF_SOCK_OPS_WRITE_HDR_OPT_CB:
616 return handle_write_hdr_opt(skops);
617 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
618 return handle_passive_estab(skops);
619 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
620 return handle_active_estab(skops);
621 }
622
623 return CG_OK;
624 }
625
626 char _license[] SEC("license") = "GPL";
627
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