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4
5
6#include <linux/module.h>
7#include <linux/skbuff.h>
8#include <asm/unaligned.h>
9#include <net/tcp.h>
10#include <net/netns/generic.h>
11#include <linux/proc_fs.h>
12
13#include <linux/netfilter_ipv6.h>
14#include <linux/netfilter/nf_synproxy.h>
15
16#include <net/netfilter/nf_conntrack.h>
17#include <net/netfilter/nf_conntrack_ecache.h>
18#include <net/netfilter/nf_conntrack_extend.h>
19#include <net/netfilter/nf_conntrack_seqadj.h>
20#include <net/netfilter/nf_conntrack_synproxy.h>
21#include <net/netfilter/nf_conntrack_zones.h>
22#include <net/netfilter/nf_synproxy.h>
23
24unsigned int synproxy_net_id;
25EXPORT_SYMBOL_GPL(synproxy_net_id);
26
27bool
28synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
29 const struct tcphdr *th, struct synproxy_options *opts)
30{
31 int length = (th->doff * 4) - sizeof(*th);
32 u8 buf[40], *ptr;
33
34 ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
35 if (ptr == NULL)
36 return false;
37
38 opts->options = 0;
39 while (length > 0) {
40 int opcode = *ptr++;
41 int opsize;
42
43 switch (opcode) {
44 case TCPOPT_EOL:
45 return true;
46 case TCPOPT_NOP:
47 length--;
48 continue;
49 default:
50 opsize = *ptr++;
51 if (opsize < 2)
52 return true;
53 if (opsize > length)
54 return true;
55
56 switch (opcode) {
57 case TCPOPT_MSS:
58 if (opsize == TCPOLEN_MSS) {
59 opts->mss_option = get_unaligned_be16(ptr);
60 opts->options |= NF_SYNPROXY_OPT_MSS;
61 }
62 break;
63 case TCPOPT_WINDOW:
64 if (opsize == TCPOLEN_WINDOW) {
65 opts->wscale = *ptr;
66 if (opts->wscale > TCP_MAX_WSCALE)
67 opts->wscale = TCP_MAX_WSCALE;
68 opts->options |= NF_SYNPROXY_OPT_WSCALE;
69 }
70 break;
71 case TCPOPT_TIMESTAMP:
72 if (opsize == TCPOLEN_TIMESTAMP) {
73 opts->tsval = get_unaligned_be32(ptr);
74 opts->tsecr = get_unaligned_be32(ptr + 4);
75 opts->options |= NF_SYNPROXY_OPT_TIMESTAMP;
76 }
77 break;
78 case TCPOPT_SACK_PERM:
79 if (opsize == TCPOLEN_SACK_PERM)
80 opts->options |= NF_SYNPROXY_OPT_SACK_PERM;
81 break;
82 }
83
84 ptr += opsize - 2;
85 length -= opsize;
86 }
87 }
88 return true;
89}
90EXPORT_SYMBOL_GPL(synproxy_parse_options);
91
92static unsigned int
93synproxy_options_size(const struct synproxy_options *opts)
94{
95 unsigned int size = 0;
96
97 if (opts->options & NF_SYNPROXY_OPT_MSS)
98 size += TCPOLEN_MSS_ALIGNED;
99 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
100 size += TCPOLEN_TSTAMP_ALIGNED;
101 else if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
102 size += TCPOLEN_SACKPERM_ALIGNED;
103 if (opts->options & NF_SYNPROXY_OPT_WSCALE)
104 size += TCPOLEN_WSCALE_ALIGNED;
105
106 return size;
107}
108
109static void
110synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts)
111{
112 __be32 *ptr = (__be32 *)(th + 1);
113 u8 options = opts->options;
114
115 if (options & NF_SYNPROXY_OPT_MSS)
116 *ptr++ = htonl((TCPOPT_MSS << 24) |
117 (TCPOLEN_MSS << 16) |
118 opts->mss_option);
119
120 if (options & NF_SYNPROXY_OPT_TIMESTAMP) {
121 if (options & NF_SYNPROXY_OPT_SACK_PERM)
122 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
123 (TCPOLEN_SACK_PERM << 16) |
124 (TCPOPT_TIMESTAMP << 8) |
125 TCPOLEN_TIMESTAMP);
126 else
127 *ptr++ = htonl((TCPOPT_NOP << 24) |
128 (TCPOPT_NOP << 16) |
129 (TCPOPT_TIMESTAMP << 8) |
130 TCPOLEN_TIMESTAMP);
131
132 *ptr++ = htonl(opts->tsval);
133 *ptr++ = htonl(opts->tsecr);
134 } else if (options & NF_SYNPROXY_OPT_SACK_PERM)
135 *ptr++ = htonl((TCPOPT_NOP << 24) |
136 (TCPOPT_NOP << 16) |
137 (TCPOPT_SACK_PERM << 8) |
138 TCPOLEN_SACK_PERM);
139
140 if (options & NF_SYNPROXY_OPT_WSCALE)
141 *ptr++ = htonl((TCPOPT_NOP << 24) |
142 (TCPOPT_WINDOW << 16) |
143 (TCPOLEN_WINDOW << 8) |
144 opts->wscale);
145}
146
147void synproxy_init_timestamp_cookie(const struct nf_synproxy_info *info,
148 struct synproxy_options *opts)
149{
150 opts->tsecr = opts->tsval;
151 opts->tsval = tcp_time_stamp_raw() & ~0x3f;
152
153 if (opts->options & NF_SYNPROXY_OPT_WSCALE) {
154 opts->tsval |= opts->wscale;
155 opts->wscale = info->wscale;
156 } else
157 opts->tsval |= 0xf;
158
159 if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
160 opts->tsval |= 1 << 4;
161
162 if (opts->options & NF_SYNPROXY_OPT_ECN)
163 opts->tsval |= 1 << 5;
164}
165EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
166
167static void
168synproxy_check_timestamp_cookie(struct synproxy_options *opts)
169{
170 opts->wscale = opts->tsecr & 0xf;
171 if (opts->wscale != 0xf)
172 opts->options |= NF_SYNPROXY_OPT_WSCALE;
173
174 opts->options |= opts->tsecr & (1 << 4) ? NF_SYNPROXY_OPT_SACK_PERM : 0;
175
176 opts->options |= opts->tsecr & (1 << 5) ? NF_SYNPROXY_OPT_ECN : 0;
177}
178
179static unsigned int
180synproxy_tstamp_adjust(struct sk_buff *skb, unsigned int protoff,
181 struct tcphdr *th, struct nf_conn *ct,
182 enum ip_conntrack_info ctinfo,
183 const struct nf_conn_synproxy *synproxy)
184{
185 unsigned int optoff, optend;
186 __be32 *ptr, old;
187
188 if (synproxy->tsoff == 0)
189 return 1;
190
191 optoff = protoff + sizeof(struct tcphdr);
192 optend = protoff + th->doff * 4;
193
194 if (skb_ensure_writable(skb, optend))
195 return 0;
196
197 while (optoff < optend) {
198 unsigned char *op = skb->data + optoff;
199
200 switch (op[0]) {
201 case TCPOPT_EOL:
202 return 1;
203 case TCPOPT_NOP:
204 optoff++;
205 continue;
206 default:
207 if (optoff + 1 == optend ||
208 optoff + op[1] > optend ||
209 op[1] < 2)
210 return 0;
211 if (op[0] == TCPOPT_TIMESTAMP &&
212 op[1] == TCPOLEN_TIMESTAMP) {
213 if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
214 ptr = (__be32 *)&op[2];
215 old = *ptr;
216 *ptr = htonl(ntohl(*ptr) -
217 synproxy->tsoff);
218 } else {
219 ptr = (__be32 *)&op[6];
220 old = *ptr;
221 *ptr = htonl(ntohl(*ptr) +
222 synproxy->tsoff);
223 }
224 inet_proto_csum_replace4(&th->check, skb,
225 old, *ptr, false);
226 return 1;
227 }
228 optoff += op[1];
229 }
230 }
231 return 1;
232}
233
234static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
235 .len = sizeof(struct nf_conn_synproxy),
236 .align = __alignof__(struct nf_conn_synproxy),
237 .id = NF_CT_EXT_SYNPROXY,
238};
239
240#ifdef CONFIG_PROC_FS
241static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
242{
243 struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
244 int cpu;
245
246 if (*pos == 0)
247 return SEQ_START_TOKEN;
248
249 for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
250 if (!cpu_possible(cpu))
251 continue;
252 *pos = cpu + 1;
253 return per_cpu_ptr(snet->stats, cpu);
254 }
255
256 return NULL;
257}
258
259static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
260{
261 struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
262 int cpu;
263
264 for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
265 if (!cpu_possible(cpu))
266 continue;
267 *pos = cpu + 1;
268 return per_cpu_ptr(snet->stats, cpu);
269 }
270 (*pos)++;
271 return NULL;
272}
273
274static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
275{
276 return;
277}
278
279static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
280{
281 struct synproxy_stats *stats = v;
282
283 if (v == SEQ_START_TOKEN) {
284 seq_puts(seq, "entries\t\tsyn_received\t"
285 "cookie_invalid\tcookie_valid\t"
286 "cookie_retrans\tconn_reopened\n");
287 return 0;
288 }
289
290 seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
291 stats->syn_received,
292 stats->cookie_invalid,
293 stats->cookie_valid,
294 stats->cookie_retrans,
295 stats->conn_reopened);
296
297 return 0;
298}
299
300static const struct seq_operations synproxy_cpu_seq_ops = {
301 .start = synproxy_cpu_seq_start,
302 .next = synproxy_cpu_seq_next,
303 .stop = synproxy_cpu_seq_stop,
304 .show = synproxy_cpu_seq_show,
305};
306
307static int __net_init synproxy_proc_init(struct net *net)
308{
309 if (!proc_create_net("synproxy", 0444, net->proc_net_stat,
310 &synproxy_cpu_seq_ops, sizeof(struct seq_net_private)))
311 return -ENOMEM;
312 return 0;
313}
314
315static void __net_exit synproxy_proc_exit(struct net *net)
316{
317 remove_proc_entry("synproxy", net->proc_net_stat);
318}
319#else
320static int __net_init synproxy_proc_init(struct net *net)
321{
322 return 0;
323}
324
325static void __net_exit synproxy_proc_exit(struct net *net)
326{
327 return;
328}
329#endif
330
331static int __net_init synproxy_net_init(struct net *net)
332{
333 struct synproxy_net *snet = synproxy_pernet(net);
334 struct nf_conn *ct;
335 int err = -ENOMEM;
336
337 ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL);
338 if (!ct)
339 goto err1;
340
341 if (!nfct_seqadj_ext_add(ct))
342 goto err2;
343 if (!nfct_synproxy_ext_add(ct))
344 goto err2;
345
346 __set_bit(IPS_CONFIRMED_BIT, &ct->status);
347 nf_conntrack_get(&ct->ct_general);
348 snet->tmpl = ct;
349
350 snet->stats = alloc_percpu(struct synproxy_stats);
351 if (snet->stats == NULL)
352 goto err2;
353
354 err = synproxy_proc_init(net);
355 if (err < 0)
356 goto err3;
357
358 return 0;
359
360err3:
361 free_percpu(snet->stats);
362err2:
363 nf_ct_tmpl_free(ct);
364err1:
365 return err;
366}
367
368static void __net_exit synproxy_net_exit(struct net *net)
369{
370 struct synproxy_net *snet = synproxy_pernet(net);
371
372 nf_ct_put(snet->tmpl);
373 synproxy_proc_exit(net);
374 free_percpu(snet->stats);
375}
376
377static struct pernet_operations synproxy_net_ops = {
378 .init = synproxy_net_init,
379 .exit = synproxy_net_exit,
380 .id = &synproxy_net_id,
381 .size = sizeof(struct synproxy_net),
382};
383
384static int __init synproxy_core_init(void)
385{
386 int err;
387
388 err = nf_ct_extend_register(&nf_ct_synproxy_extend);
389 if (err < 0)
390 goto err1;
391
392 err = register_pernet_subsys(&synproxy_net_ops);
393 if (err < 0)
394 goto err2;
395
396 return 0;
397
398err2:
399 nf_ct_extend_unregister(&nf_ct_synproxy_extend);
400err1:
401 return err;
402}
403
404static void __exit synproxy_core_exit(void)
405{
406 unregister_pernet_subsys(&synproxy_net_ops);
407 nf_ct_extend_unregister(&nf_ct_synproxy_extend);
408}
409
410module_init(synproxy_core_init);
411module_exit(synproxy_core_exit);
412
413static struct iphdr *
414synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
415 __be32 daddr)
416{
417 struct iphdr *iph;
418
419 skb_reset_network_header(skb);
420 iph = skb_put(skb, sizeof(*iph));
421 iph->version = 4;
422 iph->ihl = sizeof(*iph) / 4;
423 iph->tos = 0;
424 iph->id = 0;
425 iph->frag_off = htons(IP_DF);
426 iph->ttl = net->ipv4.sysctl_ip_default_ttl;
427 iph->protocol = IPPROTO_TCP;
428 iph->check = 0;
429 iph->saddr = saddr;
430 iph->daddr = daddr;
431
432 return iph;
433}
434
435static void
436synproxy_send_tcp(struct net *net,
437 const struct sk_buff *skb, struct sk_buff *nskb,
438 struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
439 struct iphdr *niph, struct tcphdr *nth,
440 unsigned int tcp_hdr_size)
441{
442 nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
443 nskb->ip_summed = CHECKSUM_PARTIAL;
444 nskb->csum_start = (unsigned char *)nth - nskb->head;
445 nskb->csum_offset = offsetof(struct tcphdr, check);
446
447 skb_dst_set_noref(nskb, skb_dst(skb));
448 nskb->protocol = htons(ETH_P_IP);
449 if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
450 goto free_nskb;
451
452 if (nfct) {
453 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
454 nf_conntrack_get(nfct);
455 }
456
457 ip_local_out(net, nskb->sk, nskb);
458 return;
459
460free_nskb:
461 kfree_skb(nskb);
462}
463
464void
465synproxy_send_client_synack(struct net *net,
466 const struct sk_buff *skb, const struct tcphdr *th,
467 const struct synproxy_options *opts)
468{
469 struct sk_buff *nskb;
470 struct iphdr *iph, *niph;
471 struct tcphdr *nth;
472 unsigned int tcp_hdr_size;
473 u16 mss = opts->mss_encode;
474
475 iph = ip_hdr(skb);
476
477 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
478 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
479 GFP_ATOMIC);
480 if (!nskb)
481 return;
482 skb_reserve(nskb, MAX_TCP_HEADER);
483
484 niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
485
486 skb_reset_transport_header(nskb);
487 nth = skb_put(nskb, tcp_hdr_size);
488 nth->source = th->dest;
489 nth->dest = th->source;
490 nth->seq = htonl(__cookie_v4_init_sequence(iph, th, &mss));
491 nth->ack_seq = htonl(ntohl(th->seq) + 1);
492 tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
493 if (opts->options & NF_SYNPROXY_OPT_ECN)
494 tcp_flag_word(nth) |= TCP_FLAG_ECE;
495 nth->doff = tcp_hdr_size / 4;
496 nth->window = 0;
497 nth->check = 0;
498 nth->urg_ptr = 0;
499
500 synproxy_build_options(nth, opts);
501
502 synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
503 IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
504}
505EXPORT_SYMBOL_GPL(synproxy_send_client_synack);
506
507static void
508synproxy_send_server_syn(struct net *net,
509 const struct sk_buff *skb, const struct tcphdr *th,
510 const struct synproxy_options *opts, u32 recv_seq)
511{
512 struct synproxy_net *snet = synproxy_pernet(net);
513 struct sk_buff *nskb;
514 struct iphdr *iph, *niph;
515 struct tcphdr *nth;
516 unsigned int tcp_hdr_size;
517
518 iph = ip_hdr(skb);
519
520 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
521 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
522 GFP_ATOMIC);
523 if (!nskb)
524 return;
525 skb_reserve(nskb, MAX_TCP_HEADER);
526
527 niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
528
529 skb_reset_transport_header(nskb);
530 nth = skb_put(nskb, tcp_hdr_size);
531 nth->source = th->source;
532 nth->dest = th->dest;
533 nth->seq = htonl(recv_seq - 1);
534
535
536
537 nth->ack_seq = htonl(ntohl(th->ack_seq) - 1);
538 tcp_flag_word(nth) = TCP_FLAG_SYN;
539 if (opts->options & NF_SYNPROXY_OPT_ECN)
540 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
541 nth->doff = tcp_hdr_size / 4;
542 nth->window = th->window;
543 nth->check = 0;
544 nth->urg_ptr = 0;
545
546 synproxy_build_options(nth, opts);
547
548 synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
549 niph, nth, tcp_hdr_size);
550}
551
552static void
553synproxy_send_server_ack(struct net *net,
554 const struct ip_ct_tcp *state,
555 const struct sk_buff *skb, const struct tcphdr *th,
556 const struct synproxy_options *opts)
557{
558 struct sk_buff *nskb;
559 struct iphdr *iph, *niph;
560 struct tcphdr *nth;
561 unsigned int tcp_hdr_size;
562
563 iph = ip_hdr(skb);
564
565 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
566 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
567 GFP_ATOMIC);
568 if (!nskb)
569 return;
570 skb_reserve(nskb, MAX_TCP_HEADER);
571
572 niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
573
574 skb_reset_transport_header(nskb);
575 nth = skb_put(nskb, tcp_hdr_size);
576 nth->source = th->dest;
577 nth->dest = th->source;
578 nth->seq = htonl(ntohl(th->ack_seq));
579 nth->ack_seq = htonl(ntohl(th->seq) + 1);
580 tcp_flag_word(nth) = TCP_FLAG_ACK;
581 nth->doff = tcp_hdr_size / 4;
582 nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
583 nth->check = 0;
584 nth->urg_ptr = 0;
585
586 synproxy_build_options(nth, opts);
587
588 synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
589}
590
591static void
592synproxy_send_client_ack(struct net *net,
593 const struct sk_buff *skb, const struct tcphdr *th,
594 const struct synproxy_options *opts)
595{
596 struct sk_buff *nskb;
597 struct iphdr *iph, *niph;
598 struct tcphdr *nth;
599 unsigned int tcp_hdr_size;
600
601 iph = ip_hdr(skb);
602
603 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
604 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
605 GFP_ATOMIC);
606 if (!nskb)
607 return;
608 skb_reserve(nskb, MAX_TCP_HEADER);
609
610 niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
611
612 skb_reset_transport_header(nskb);
613 nth = skb_put(nskb, tcp_hdr_size);
614 nth->source = th->source;
615 nth->dest = th->dest;
616 nth->seq = htonl(ntohl(th->seq) + 1);
617 nth->ack_seq = th->ack_seq;
618 tcp_flag_word(nth) = TCP_FLAG_ACK;
619 nth->doff = tcp_hdr_size / 4;
620 nth->window = htons(ntohs(th->window) >> opts->wscale);
621 nth->check = 0;
622 nth->urg_ptr = 0;
623
624 synproxy_build_options(nth, opts);
625
626 synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
627 IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
628}
629
630bool
631synproxy_recv_client_ack(struct net *net,
632 const struct sk_buff *skb, const struct tcphdr *th,
633 struct synproxy_options *opts, u32 recv_seq)
634{
635 struct synproxy_net *snet = synproxy_pernet(net);
636 int mss;
637
638 mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
639 if (mss == 0) {
640 this_cpu_inc(snet->stats->cookie_invalid);
641 return false;
642 }
643
644 this_cpu_inc(snet->stats->cookie_valid);
645 opts->mss_option = mss;
646 opts->options |= NF_SYNPROXY_OPT_MSS;
647
648 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
649 synproxy_check_timestamp_cookie(opts);
650
651 synproxy_send_server_syn(net, skb, th, opts, recv_seq);
652 return true;
653}
654EXPORT_SYMBOL_GPL(synproxy_recv_client_ack);
655
656unsigned int
657ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
658 const struct nf_hook_state *nhs)
659{
660 struct net *net = nhs->net;
661 struct synproxy_net *snet = synproxy_pernet(net);
662 enum ip_conntrack_info ctinfo;
663 struct nf_conn *ct;
664 struct nf_conn_synproxy *synproxy;
665 struct synproxy_options opts = {};
666 const struct ip_ct_tcp *state;
667 struct tcphdr *th, _th;
668 unsigned int thoff;
669
670 ct = nf_ct_get(skb, &ctinfo);
671 if (!ct)
672 return NF_ACCEPT;
673
674 synproxy = nfct_synproxy(ct);
675 if (!synproxy)
676 return NF_ACCEPT;
677
678 if (nf_is_loopback_packet(skb) ||
679 ip_hdr(skb)->protocol != IPPROTO_TCP)
680 return NF_ACCEPT;
681
682 thoff = ip_hdrlen(skb);
683 th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
684 if (!th)
685 return NF_DROP;
686
687 state = &ct->proto.tcp;
688 switch (state->state) {
689 case TCP_CONNTRACK_CLOSE:
690 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
691 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
692 ntohl(th->seq) + 1);
693 break;
694 }
695
696 if (!th->syn || th->ack ||
697 CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
698 break;
699
700
701
702
703
704 nf_ct_seqadj_init(ct, ctinfo, 0);
705 synproxy->tsoff = 0;
706 this_cpu_inc(snet->stats->conn_reopened);
707
708
709 case TCP_CONNTRACK_SYN_SENT:
710 if (!synproxy_parse_options(skb, thoff, th, &opts))
711 return NF_DROP;
712
713 if (!th->syn && th->ack &&
714 CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
715
716
717
718
719 if (synproxy_recv_client_ack(net, skb, th, &opts,
720 ntohl(th->seq) + 1)) {
721 this_cpu_inc(snet->stats->cookie_retrans);
722 consume_skb(skb);
723 return NF_STOLEN;
724 } else {
725 return NF_DROP;
726 }
727 }
728
729 synproxy->isn = ntohl(th->ack_seq);
730 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
731 synproxy->its = opts.tsecr;
732
733 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
734 break;
735 case TCP_CONNTRACK_SYN_RECV:
736 if (!th->syn || !th->ack)
737 break;
738
739 if (!synproxy_parse_options(skb, thoff, th, &opts))
740 return NF_DROP;
741
742 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
743 synproxy->tsoff = opts.tsval - synproxy->its;
744 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
745 }
746
747 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
748 NF_SYNPROXY_OPT_WSCALE |
749 NF_SYNPROXY_OPT_SACK_PERM);
750
751 swap(opts.tsval, opts.tsecr);
752 synproxy_send_server_ack(net, state, skb, th, &opts);
753
754 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
755 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
756
757 swap(opts.tsval, opts.tsecr);
758 synproxy_send_client_ack(net, skb, th, &opts);
759
760 consume_skb(skb);
761 return NF_STOLEN;
762 default:
763 break;
764 }
765
766 synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
767 return NF_ACCEPT;
768}
769EXPORT_SYMBOL_GPL(ipv4_synproxy_hook);
770
771static const struct nf_hook_ops ipv4_synproxy_ops[] = {
772 {
773 .hook = ipv4_synproxy_hook,
774 .pf = NFPROTO_IPV4,
775 .hooknum = NF_INET_LOCAL_IN,
776 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
777 },
778 {
779 .hook = ipv4_synproxy_hook,
780 .pf = NFPROTO_IPV4,
781 .hooknum = NF_INET_POST_ROUTING,
782 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
783 },
784};
785
786int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net)
787{
788 int err;
789
790 if (snet->hook_ref4 == 0) {
791 err = nf_register_net_hooks(net, ipv4_synproxy_ops,
792 ARRAY_SIZE(ipv4_synproxy_ops));
793 if (err)
794 return err;
795 }
796
797 snet->hook_ref4++;
798 return 0;
799}
800EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_init);
801
802void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net)
803{
804 snet->hook_ref4--;
805 if (snet->hook_ref4 == 0)
806 nf_unregister_net_hooks(net, ipv4_synproxy_ops,
807 ARRAY_SIZE(ipv4_synproxy_ops));
808}
809EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_fini);
810
811#if IS_ENABLED(CONFIG_IPV6)
812static struct ipv6hdr *
813synproxy_build_ip_ipv6(struct net *net, struct sk_buff *skb,
814 const struct in6_addr *saddr,
815 const struct in6_addr *daddr)
816{
817 struct ipv6hdr *iph;
818
819 skb_reset_network_header(skb);
820 iph = skb_put(skb, sizeof(*iph));
821 ip6_flow_hdr(iph, 0, 0);
822 iph->hop_limit = net->ipv6.devconf_all->hop_limit;
823 iph->nexthdr = IPPROTO_TCP;
824 iph->saddr = *saddr;
825 iph->daddr = *daddr;
826
827 return iph;
828}
829
830static void
831synproxy_send_tcp_ipv6(struct net *net,
832 const struct sk_buff *skb, struct sk_buff *nskb,
833 struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
834 struct ipv6hdr *niph, struct tcphdr *nth,
835 unsigned int tcp_hdr_size)
836{
837 struct dst_entry *dst;
838 struct flowi6 fl6;
839 int err;
840
841 nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
842 nskb->ip_summed = CHECKSUM_PARTIAL;
843 nskb->csum_start = (unsigned char *)nth - nskb->head;
844 nskb->csum_offset = offsetof(struct tcphdr, check);
845
846 memset(&fl6, 0, sizeof(fl6));
847 fl6.flowi6_proto = IPPROTO_TCP;
848 fl6.saddr = niph->saddr;
849 fl6.daddr = niph->daddr;
850 fl6.fl6_sport = nth->source;
851 fl6.fl6_dport = nth->dest;
852 security_skb_classify_flow((struct sk_buff *)skb,
853 flowi6_to_flowi(&fl6));
854 err = nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
855 if (err) {
856 goto free_nskb;
857 }
858
859 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
860 if (IS_ERR(dst))
861 goto free_nskb;
862
863 skb_dst_set(nskb, dst);
864
865 if (nfct) {
866 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
867 nf_conntrack_get(nfct);
868 }
869
870 ip6_local_out(net, nskb->sk, nskb);
871 return;
872
873free_nskb:
874 kfree_skb(nskb);
875}
876
877void
878synproxy_send_client_synack_ipv6(struct net *net,
879 const struct sk_buff *skb,
880 const struct tcphdr *th,
881 const struct synproxy_options *opts)
882{
883 struct sk_buff *nskb;
884 struct ipv6hdr *iph, *niph;
885 struct tcphdr *nth;
886 unsigned int tcp_hdr_size;
887 u16 mss = opts->mss_encode;
888
889 iph = ipv6_hdr(skb);
890
891 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
892 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
893 GFP_ATOMIC);
894 if (!nskb)
895 return;
896 skb_reserve(nskb, MAX_TCP_HEADER);
897
898 niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
899
900 skb_reset_transport_header(nskb);
901 nth = skb_put(nskb, tcp_hdr_size);
902 nth->source = th->dest;
903 nth->dest = th->source;
904 nth->seq = htonl(nf_ipv6_cookie_init_sequence(iph, th, &mss));
905 nth->ack_seq = htonl(ntohl(th->seq) + 1);
906 tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
907 if (opts->options & NF_SYNPROXY_OPT_ECN)
908 tcp_flag_word(nth) |= TCP_FLAG_ECE;
909 nth->doff = tcp_hdr_size / 4;
910 nth->window = 0;
911 nth->check = 0;
912 nth->urg_ptr = 0;
913
914 synproxy_build_options(nth, opts);
915
916 synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
917 IP_CT_ESTABLISHED_REPLY, niph, nth,
918 tcp_hdr_size);
919}
920EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);
921
922static void
923synproxy_send_server_syn_ipv6(struct net *net, const struct sk_buff *skb,
924 const struct tcphdr *th,
925 const struct synproxy_options *opts, u32 recv_seq)
926{
927 struct synproxy_net *snet = synproxy_pernet(net);
928 struct sk_buff *nskb;
929 struct ipv6hdr *iph, *niph;
930 struct tcphdr *nth;
931 unsigned int tcp_hdr_size;
932
933 iph = ipv6_hdr(skb);
934
935 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
936 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
937 GFP_ATOMIC);
938 if (!nskb)
939 return;
940 skb_reserve(nskb, MAX_TCP_HEADER);
941
942 niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
943
944 skb_reset_transport_header(nskb);
945 nth = skb_put(nskb, tcp_hdr_size);
946 nth->source = th->source;
947 nth->dest = th->dest;
948 nth->seq = htonl(recv_seq - 1);
949
950
951
952 nth->ack_seq = htonl(ntohl(th->ack_seq) - 1);
953 tcp_flag_word(nth) = TCP_FLAG_SYN;
954 if (opts->options & NF_SYNPROXY_OPT_ECN)
955 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
956 nth->doff = tcp_hdr_size / 4;
957 nth->window = th->window;
958 nth->check = 0;
959 nth->urg_ptr = 0;
960
961 synproxy_build_options(nth, opts);
962
963 synproxy_send_tcp_ipv6(net, skb, nskb, &snet->tmpl->ct_general,
964 IP_CT_NEW, niph, nth, tcp_hdr_size);
965}
966
967static void
968synproxy_send_server_ack_ipv6(struct net *net, const struct ip_ct_tcp *state,
969 const struct sk_buff *skb,
970 const struct tcphdr *th,
971 const struct synproxy_options *opts)
972{
973 struct sk_buff *nskb;
974 struct ipv6hdr *iph, *niph;
975 struct tcphdr *nth;
976 unsigned int tcp_hdr_size;
977
978 iph = ipv6_hdr(skb);
979
980 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
981 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
982 GFP_ATOMIC);
983 if (!nskb)
984 return;
985 skb_reserve(nskb, MAX_TCP_HEADER);
986
987 niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
988
989 skb_reset_transport_header(nskb);
990 nth = skb_put(nskb, tcp_hdr_size);
991 nth->source = th->dest;
992 nth->dest = th->source;
993 nth->seq = htonl(ntohl(th->ack_seq));
994 nth->ack_seq = htonl(ntohl(th->seq) + 1);
995 tcp_flag_word(nth) = TCP_FLAG_ACK;
996 nth->doff = tcp_hdr_size / 4;
997 nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
998 nth->check = 0;
999 nth->urg_ptr = 0;
1000
1001 synproxy_build_options(nth, opts);
1002
1003 synproxy_send_tcp_ipv6(net, skb, nskb, NULL, 0, niph, nth,
1004 tcp_hdr_size);
1005}
1006
1007static void
1008synproxy_send_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
1009 const struct tcphdr *th,
1010 const struct synproxy_options *opts)
1011{
1012 struct sk_buff *nskb;
1013 struct ipv6hdr *iph, *niph;
1014 struct tcphdr *nth;
1015 unsigned int tcp_hdr_size;
1016
1017 iph = ipv6_hdr(skb);
1018
1019 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
1020 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
1021 GFP_ATOMIC);
1022 if (!nskb)
1023 return;
1024 skb_reserve(nskb, MAX_TCP_HEADER);
1025
1026 niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
1027
1028 skb_reset_transport_header(nskb);
1029 nth = skb_put(nskb, tcp_hdr_size);
1030 nth->source = th->source;
1031 nth->dest = th->dest;
1032 nth->seq = htonl(ntohl(th->seq) + 1);
1033 nth->ack_seq = th->ack_seq;
1034 tcp_flag_word(nth) = TCP_FLAG_ACK;
1035 nth->doff = tcp_hdr_size / 4;
1036 nth->window = htons(ntohs(th->window) >> opts->wscale);
1037 nth->check = 0;
1038 nth->urg_ptr = 0;
1039
1040 synproxy_build_options(nth, opts);
1041
1042 synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
1043 IP_CT_ESTABLISHED_REPLY, niph, nth,
1044 tcp_hdr_size);
1045}
1046
1047bool
1048synproxy_recv_client_ack_ipv6(struct net *net,
1049 const struct sk_buff *skb,
1050 const struct tcphdr *th,
1051 struct synproxy_options *opts, u32 recv_seq)
1052{
1053 struct synproxy_net *snet = synproxy_pernet(net);
1054 int mss;
1055
1056 mss = nf_cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
1057 if (mss == 0) {
1058 this_cpu_inc(snet->stats->cookie_invalid);
1059 return false;
1060 }
1061
1062 this_cpu_inc(snet->stats->cookie_valid);
1063 opts->mss_option = mss;
1064 opts->options |= NF_SYNPROXY_OPT_MSS;
1065
1066 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
1067 synproxy_check_timestamp_cookie(opts);
1068
1069 synproxy_send_server_syn_ipv6(net, skb, th, opts, recv_seq);
1070 return true;
1071}
1072EXPORT_SYMBOL_GPL(synproxy_recv_client_ack_ipv6);
1073
1074unsigned int
1075ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
1076 const struct nf_hook_state *nhs)
1077{
1078 struct net *net = nhs->net;
1079 struct synproxy_net *snet = synproxy_pernet(net);
1080 enum ip_conntrack_info ctinfo;
1081 struct nf_conn *ct;
1082 struct nf_conn_synproxy *synproxy;
1083 struct synproxy_options opts = {};
1084 const struct ip_ct_tcp *state;
1085 struct tcphdr *th, _th;
1086 __be16 frag_off;
1087 u8 nexthdr;
1088 int thoff;
1089
1090 ct = nf_ct_get(skb, &ctinfo);
1091 if (!ct)
1092 return NF_ACCEPT;
1093
1094 synproxy = nfct_synproxy(ct);
1095 if (!synproxy)
1096 return NF_ACCEPT;
1097
1098 if (nf_is_loopback_packet(skb))
1099 return NF_ACCEPT;
1100
1101 nexthdr = ipv6_hdr(skb)->nexthdr;
1102 thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
1103 &frag_off);
1104 if (thoff < 0 || nexthdr != IPPROTO_TCP)
1105 return NF_ACCEPT;
1106
1107 th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
1108 if (!th)
1109 return NF_DROP;
1110
1111 state = &ct->proto.tcp;
1112 switch (state->state) {
1113 case TCP_CONNTRACK_CLOSE:
1114 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
1115 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
1116 ntohl(th->seq) + 1);
1117 break;
1118 }
1119
1120 if (!th->syn || th->ack ||
1121 CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
1122 break;
1123
1124
1125
1126
1127
1128 nf_ct_seqadj_init(ct, ctinfo, 0);
1129 synproxy->tsoff = 0;
1130 this_cpu_inc(snet->stats->conn_reopened);
1131
1132
1133 case TCP_CONNTRACK_SYN_SENT:
1134 if (!synproxy_parse_options(skb, thoff, th, &opts))
1135 return NF_DROP;
1136
1137 if (!th->syn && th->ack &&
1138 CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
1139
1140
1141
1142
1143 if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
1144 ntohl(th->seq) + 1)) {
1145 this_cpu_inc(snet->stats->cookie_retrans);
1146 consume_skb(skb);
1147 return NF_STOLEN;
1148 } else {
1149 return NF_DROP;
1150 }
1151 }
1152
1153 synproxy->isn = ntohl(th->ack_seq);
1154 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
1155 synproxy->its = opts.tsecr;
1156
1157 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1158 break;
1159 case TCP_CONNTRACK_SYN_RECV:
1160 if (!th->syn || !th->ack)
1161 break;
1162
1163 if (!synproxy_parse_options(skb, thoff, th, &opts))
1164 return NF_DROP;
1165
1166 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
1167 synproxy->tsoff = opts.tsval - synproxy->its;
1168 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1169 }
1170
1171 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
1172 NF_SYNPROXY_OPT_WSCALE |
1173 NF_SYNPROXY_OPT_SACK_PERM);
1174
1175 swap(opts.tsval, opts.tsecr);
1176 synproxy_send_server_ack_ipv6(net, state, skb, th, &opts);
1177
1178 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
1179 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
1180
1181 swap(opts.tsval, opts.tsecr);
1182 synproxy_send_client_ack_ipv6(net, skb, th, &opts);
1183
1184 consume_skb(skb);
1185 return NF_STOLEN;
1186 default:
1187 break;
1188 }
1189
1190 synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
1191 return NF_ACCEPT;
1192}
1193EXPORT_SYMBOL_GPL(ipv6_synproxy_hook);
1194
1195static const struct nf_hook_ops ipv6_synproxy_ops[] = {
1196 {
1197 .hook = ipv6_synproxy_hook,
1198 .pf = NFPROTO_IPV6,
1199 .hooknum = NF_INET_LOCAL_IN,
1200 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1201 },
1202 {
1203 .hook = ipv6_synproxy_hook,
1204 .pf = NFPROTO_IPV6,
1205 .hooknum = NF_INET_POST_ROUTING,
1206 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1207 },
1208};
1209
1210int
1211nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net)
1212{
1213 int err;
1214
1215 if (snet->hook_ref6 == 0) {
1216 err = nf_register_net_hooks(net, ipv6_synproxy_ops,
1217 ARRAY_SIZE(ipv6_synproxy_ops));
1218 if (err)
1219 return err;
1220 }
1221
1222 snet->hook_ref6++;
1223 return 0;
1224}
1225EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_init);
1226
1227void
1228nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net)
1229{
1230 snet->hook_ref6--;
1231 if (snet->hook_ref6 == 0)
1232 nf_unregister_net_hooks(net, ipv6_synproxy_ops,
1233 ARRAY_SIZE(ipv6_synproxy_ops));
1234}
1235EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_fini);
1236#endif
1237
1238MODULE_LICENSE("GPL");
1239MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
1240
