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1/*
2 * Transparent proxy support for Linux/iptables
3 *
4 * Copyright (c) 2006-2010 BalaBit IT Ltd.
5 * Author: Balazs Scheidler, Krisztian Kovacs
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 */
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13#include <linux/module.h>
14#include <linux/skbuff.h>
15#include <linux/ip.h>
16#include <net/checksum.h>
17#include <net/udp.h>
18#include <net/tcp.h>
19#include <net/inet_sock.h>
20#include <net/inet_hashtables.h>
21#include <linux/inetdevice.h>
22#include <linux/netfilter/x_tables.h>
23#include <linux/netfilter_ipv4/ip_tables.h>
24
25#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
26
27#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
28#define XT_TPROXY_HAVE_IPV6 1
29#include <net/if_inet6.h>
30#include <net/addrconf.h>
31#include <net/inet6_hashtables.h>
32#include <linux/netfilter_ipv6/ip6_tables.h>
33#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
34#endif
35
36#include <linux/netfilter/xt_TPROXY.h>
37
38enum nf_tproxy_lookup_t {
39 NFT_LOOKUP_LISTENER,
40 NFT_LOOKUP_ESTABLISHED,
41};
42
43static bool tproxy_sk_is_transparent(struct sock *sk)
44{
45 switch (sk->sk_state) {
46 case TCP_TIME_WAIT:
47 if (inet_twsk(sk)->tw_transparent)
48 return true;
49 break;
50 case TCP_NEW_SYN_RECV:
51 if (inet_rsk(inet_reqsk(sk))->no_srccheck)
52 return true;
53 break;
54 default:
55 if (inet_sk(sk)->transparent)
56 return true;
57 }
58
59 sock_gen_put(sk);
60 return false;
61}
62
63static inline __be32
64tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
65{
66 struct in_device *indev;
67 __be32 laddr;
68
69 if (user_laddr)
70 return user_laddr;
71
72 laddr = 0;
73 rcu_read_lock();
74 indev = __in_dev_get_rcu(skb->dev);
75 for_primary_ifa(indev) {
76 laddr = ifa->ifa_local;
77 break;
78 } endfor_ifa(indev);
79 rcu_read_unlock();
80
81 return laddr ? laddr : daddr;
82}
83
84/*
85 * This is used when the user wants to intercept a connection matching
86 * an explicit iptables rule. In this case the sockets are assumed
87 * matching in preference order:
88 *
89 * - match: if there's a fully established connection matching the
90 * _packet_ tuple, it is returned, assuming the redirection
91 * already took place and we process a packet belonging to an
92 * established connection
93 *
94 * - match: if there's a listening socket matching the redirection
95 * (e.g. on-port & on-ip of the connection), it is returned,
96 * regardless if it was bound to 0.0.0.0 or an explicit
97 * address. The reasoning is that if there's an explicit rule, it
98 * does not really matter if the listener is bound to an interface
99 * or to 0. The user already stated that he wants redirection
100 * (since he added the rule).
101 *
102 * Please note that there's an overlap between what a TPROXY target
103 * and a socket match will match. Normally if you have both rules the
104 * "socket" match will be the first one, effectively all packets
105 * belonging to established connections going through that one.
106 */
107static inline struct sock *
108nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb, void *hp,
109 const u8 protocol,
110 const __be32 saddr, const __be32 daddr,
111 const __be16 sport, const __be16 dport,
112 const struct net_device *in,
113 const enum nf_tproxy_lookup_t lookup_type)
114{
115 struct sock *sk;
116 struct tcphdr *tcph;
117
118 switch (protocol) {
119 case IPPROTO_TCP:
120 switch (lookup_type) {
121 case NFT_LOOKUP_LISTENER:
122 tcph = hp;
123 sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
124 ip_hdrlen(skb) +
125 __tcp_hdrlen(tcph),
126 saddr, sport,
127 daddr, dport,
128 in->ifindex);
129
130 if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
131 sk = NULL;
132 /* NOTE: we return listeners even if bound to
133 * 0.0.0.0, those are filtered out in
134 * xt_socket, since xt_TPROXY needs 0 bound
135 * listeners too
136 */
137 break;
138 case NFT_LOOKUP_ESTABLISHED:
139 sk = inet_lookup_established(net, &tcp_hashinfo,
140 saddr, sport, daddr, dport,
141 in->ifindex);
142 break;
143 default:
144 BUG();
145 }
146 break;
147 case IPPROTO_UDP:
148 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
149 in->ifindex);
150 if (sk) {
151 int connected = (sk->sk_state == TCP_ESTABLISHED);
152 int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
153
154 /* NOTE: we return listeners even if bound to
155 * 0.0.0.0, those are filtered out in
156 * xt_socket, since xt_TPROXY needs 0 bound
157 * listeners too
158 */
159 if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
160 (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
161 sock_put(sk);
162 sk = NULL;
163 }
164 }
165 break;
166 default:
167 WARN_ON(1);
168 sk = NULL;
169 }
170
171 pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
172 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
173
174 return sk;
175}
176
177#ifdef XT_TPROXY_HAVE_IPV6
178static inline struct sock *
179nf_tproxy_get_sock_v6(struct net *net, struct sk_buff *skb, int thoff, void *hp,
180 const u8 protocol,
181 const struct in6_addr *saddr, const struct in6_addr *daddr,
182 const __be16 sport, const __be16 dport,
183 const struct net_device *in,
184 const enum nf_tproxy_lookup_t lookup_type)
185{
186 struct sock *sk;
187 struct tcphdr *tcph;
188
189 switch (protocol) {
190 case IPPROTO_TCP:
191 switch (lookup_type) {
192 case NFT_LOOKUP_LISTENER:
193 tcph = hp;
194 sk = inet6_lookup_listener(net, &tcp_hashinfo, skb,
195 thoff + __tcp_hdrlen(tcph),
196 saddr, sport,
197 daddr, ntohs(dport),
198 in->ifindex);
199
200 if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
201 sk = NULL;
202 /* NOTE: we return listeners even if bound to
203 * 0.0.0.0, those are filtered out in
204 * xt_socket, since xt_TPROXY needs 0 bound
205 * listeners too
206 */
207 break;
208 case NFT_LOOKUP_ESTABLISHED:
209 sk = __inet6_lookup_established(net, &tcp_hashinfo,
210 saddr, sport, daddr, ntohs(dport),
211 in->ifindex);
212 break;
213 default:
214 BUG();
215 }
216 break;
217 case IPPROTO_UDP:
218 sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
219 in->ifindex);
220 if (sk) {
221 int connected = (sk->sk_state == TCP_ESTABLISHED);
222 int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr);
223
224 /* NOTE: we return listeners even if bound to
225 * 0.0.0.0, those are filtered out in
226 * xt_socket, since xt_TPROXY needs 0 bound
227 * listeners too
228 */
229 if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
230 (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
231 sock_put(sk);
232 sk = NULL;
233 }
234 }
235 break;
236 default:
237 WARN_ON(1);
238 sk = NULL;
239 }
240
241 pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
242 protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);
243
244 return sk;
245}
246#endif
247
248/**
249 * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections
250 * @skb: The skb being processed.
251 * @laddr: IPv4 address to redirect to or zero.
252 * @lport: TCP port to redirect to or zero.
253 * @sk: The TIME_WAIT TCP socket found by the lookup.
254 *
255 * We have to handle SYN packets arriving to TIME_WAIT sockets
256 * differently: instead of reopening the connection we should rather
257 * redirect the new connection to the proxy if there's a listener
258 * socket present.
259 *
260 * tproxy_handle_time_wait4() consumes the socket reference passed in.
261 *
262 * Returns the listener socket if there's one, the TIME_WAIT socket if
263 * no such listener is found, or NULL if the TCP header is incomplete.
264 */
265static struct sock *
266tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
267 __be32 laddr, __be16 lport, struct sock *sk)
268{
269 const struct iphdr *iph = ip_hdr(skb);
270 struct tcphdr _hdr, *hp;
271
272 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
273 if (hp == NULL) {
274 inet_twsk_put(inet_twsk(sk));
275 return NULL;
276 }
277
278 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
279 /* SYN to a TIME_WAIT socket, we'd rather redirect it
280 * to a listener socket if there's one */
281 struct sock *sk2;
282
283 sk2 = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
284 iph->saddr, laddr ? laddr : iph->daddr,
285 hp->source, lport ? lport : hp->dest,
286 skb->dev, NFT_LOOKUP_LISTENER);
287 if (sk2) {
288 inet_twsk_deschedule_put(inet_twsk(sk));
289 sk = sk2;
290 }
291 }
292
293 return sk;
294}
295
296/* assign a socket to the skb -- consumes sk */
297static void
298nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
299{
300 skb_orphan(skb);
301 skb->sk = sk;
302 skb->destructor = sock_edemux;
303}
304
305static unsigned int
306tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
307 u_int32_t mark_mask, u_int32_t mark_value)
308{
309 const struct iphdr *iph = ip_hdr(skb);
310 struct udphdr _hdr, *hp;
311 struct sock *sk;
312
313 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
314 if (hp == NULL)
315 return NF_DROP;
316
317 /* check if there's an ongoing connection on the packet
318 * addresses, this happens if the redirect already happened
319 * and the current packet belongs to an already established
320 * connection */
321 sk = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
322 iph->saddr, iph->daddr,
323 hp->source, hp->dest,
324 skb->dev, NFT_LOOKUP_ESTABLISHED);
325
326 laddr = tproxy_laddr4(skb, laddr, iph->daddr);
327 if (!lport)
328 lport = hp->dest;
329
330 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
331 if (sk && sk->sk_state == TCP_TIME_WAIT)
332 /* reopening a TIME_WAIT connection needs special handling */
333 sk = tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
334 else if (!sk)
335 /* no, there's no established connection, check if
336 * there's a listener on the redirected addr/port */
337 sk = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
338 iph->saddr, laddr,
339 hp->source, lport,
340 skb->dev, NFT_LOOKUP_LISTENER);
341
342 /* NOTE: assign_sock consumes our sk reference */
343 if (sk && tproxy_sk_is_transparent(sk)) {
344 /* This should be in a separate target, but we don't do multiple
345 targets on the same rule yet */
346 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
347
348 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
349 iph->protocol, &iph->daddr, ntohs(hp->dest),
350 &laddr, ntohs(lport), skb->mark);
351
352 nf_tproxy_assign_sock(skb, sk);
353 return NF_ACCEPT;
354 }
355
356 pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
357 iph->protocol, &iph->saddr, ntohs(hp->source),
358 &iph->daddr, ntohs(hp->dest), skb->mark);
359 return NF_DROP;
360}
361
362static unsigned int
363tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
364{
365 const struct xt_tproxy_target_info *tgi = par->targinfo;
366
367 return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
368 tgi->mark_mask, tgi->mark_value);
369}
370
371static unsigned int
372tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
373{
374 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
375
376 return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
377 tgi->mark_mask, tgi->mark_value);
378}
379
380#ifdef XT_TPROXY_HAVE_IPV6
381
382static inline const struct in6_addr *
383tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
384 const struct in6_addr *daddr)
385{
386 struct inet6_dev *indev;
387 struct inet6_ifaddr *ifa;
388 struct in6_addr *laddr;
389
390 if (!ipv6_addr_any(user_laddr))
391 return user_laddr;
392 laddr = NULL;
393
394 rcu_read_lock();
395 indev = __in6_dev_get(skb->dev);
396 if (indev)
397 list_for_each_entry(ifa, &indev->addr_list, if_list) {
398 if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
399 continue;
400
401 laddr = &ifa->addr;
402 break;
403 }
404 rcu_read_unlock();
405
406 return laddr ? laddr : daddr;
407}
408
409/**
410 * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections
411 * @skb: The skb being processed.
412 * @tproto: Transport protocol.
413 * @thoff: Transport protocol header offset.
414 * @par: Iptables target parameters.
415 * @sk: The TIME_WAIT TCP socket found by the lookup.
416 *
417 * We have to handle SYN packets arriving to TIME_WAIT sockets
418 * differently: instead of reopening the connection we should rather
419 * redirect the new connection to the proxy if there's a listener
420 * socket present.
421 *
422 * tproxy_handle_time_wait6() consumes the socket reference passed in.
423 *
424 * Returns the listener socket if there's one, the TIME_WAIT socket if
425 * no such listener is found, or NULL if the TCP header is incomplete.
426 */
427static struct sock *
428tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
429 const struct xt_action_param *par,
430 struct sock *sk)
431{
432 const struct ipv6hdr *iph = ipv6_hdr(skb);
433 struct tcphdr _hdr, *hp;
434 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
435
436 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
437 if (hp == NULL) {
438 inet_twsk_put(inet_twsk(sk));
439 return NULL;
440 }
441
442 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
443 /* SYN to a TIME_WAIT socket, we'd rather redirect it
444 * to a listener socket if there's one */
445 struct sock *sk2;
446
447 sk2 = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, hp, tproto,
448 &iph->saddr,
449 tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr),
450 hp->source,
451 tgi->lport ? tgi->lport : hp->dest,
452 skb->dev, NFT_LOOKUP_LISTENER);
453 if (sk2) {
454 inet_twsk_deschedule_put(inet_twsk(sk));
455 sk = sk2;
456 }
457 }
458
459 return sk;
460}
461
462static unsigned int
463tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
464{
465 const struct ipv6hdr *iph = ipv6_hdr(skb);
466 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
467 struct udphdr _hdr, *hp;
468 struct sock *sk;
469 const struct in6_addr *laddr;
470 __be16 lport;
471 int thoff = 0;
472 int tproto;
473
474 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
475 if (tproto < 0) {
476 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
477 return NF_DROP;
478 }
479
480 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
481 if (hp == NULL) {
482 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
483 return NF_DROP;
484 }
485
486 /* check if there's an ongoing connection on the packet
487 * addresses, this happens if the redirect already happened
488 * and the current packet belongs to an already established
489 * connection */
490 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, hp, tproto,
491 &iph->saddr, &iph->daddr,
492 hp->source, hp->dest,
493 xt_in(par), NFT_LOOKUP_ESTABLISHED);
494
495 laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
496 lport = tgi->lport ? tgi->lport : hp->dest;
497
498 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
499 if (sk && sk->sk_state == TCP_TIME_WAIT)
500 /* reopening a TIME_WAIT connection needs special handling */
501 sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk);
502 else if (!sk)
503 /* no there's no established connection, check if
504 * there's a listener on the redirected addr/port */
505 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, hp,
506 tproto, &iph->saddr, laddr,
507 hp->source, lport,
508 xt_in(par), NFT_LOOKUP_LISTENER);
509
510 /* NOTE: assign_sock consumes our sk reference */
511 if (sk && tproxy_sk_is_transparent(sk)) {
512 /* This should be in a separate target, but we don't do multiple
513 targets on the same rule yet */
514 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
515
516 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
517 tproto, &iph->saddr, ntohs(hp->source),
518 laddr, ntohs(lport), skb->mark);
519
520 nf_tproxy_assign_sock(skb, sk);
521 return NF_ACCEPT;
522 }
523
524 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
525 tproto, &iph->saddr, ntohs(hp->source),
526 &iph->daddr, ntohs(hp->dest), skb->mark);
527
528 return NF_DROP;
529}
530
531static int tproxy_tg6_check(const struct xt_tgchk_param *par)
532{
533 const struct ip6t_ip6 *i = par->entryinfo;
534 int err;
535
536 err = nf_defrag_ipv6_enable(par->net);
537 if (err)
538 return err;
539
540 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
541 !(i->invflags & IP6T_INV_PROTO))
542 return 0;
543
544 pr_info("Can be used only in combination with "
545 "either -p tcp or -p udp\n");
546 return -EINVAL;
547}
548#endif
549
550static int tproxy_tg4_check(const struct xt_tgchk_param *par)
551{
552 const struct ipt_ip *i = par->entryinfo;
553 int err;
554
555 err = nf_defrag_ipv4_enable(par->net);
556 if (err)
557 return err;
558
559 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
560 && !(i->invflags & IPT_INV_PROTO))
561 return 0;
562
563 pr_info("Can be used only in combination with "
564 "either -p tcp or -p udp\n");
565 return -EINVAL;
566}
567
568static struct xt_target tproxy_tg_reg[] __read_mostly = {
569 {
570 .name = "TPROXY",
571 .family = NFPROTO_IPV4,
572 .table = "mangle",
573 .target = tproxy_tg4_v0,
574 .revision = 0,
575 .targetsize = sizeof(struct xt_tproxy_target_info),
576 .checkentry = tproxy_tg4_check,
577 .hooks = 1 << NF_INET_PRE_ROUTING,
578 .me = THIS_MODULE,
579 },
580 {
581 .name = "TPROXY",
582 .family = NFPROTO_IPV4,
583 .table = "mangle",
584 .target = tproxy_tg4_v1,
585 .revision = 1,
586 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
587 .checkentry = tproxy_tg4_check,
588 .hooks = 1 << NF_INET_PRE_ROUTING,
589 .me = THIS_MODULE,
590 },
591#ifdef XT_TPROXY_HAVE_IPV6
592 {
593 .name = "TPROXY",
594 .family = NFPROTO_IPV6,
595 .table = "mangle",
596 .target = tproxy_tg6_v1,
597 .revision = 1,
598 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
599 .checkentry = tproxy_tg6_check,
600 .hooks = 1 << NF_INET_PRE_ROUTING,
601 .me = THIS_MODULE,
602 },
603#endif
604
605};
606
607static int __init tproxy_tg_init(void)
608{
609 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
610}
611
612static void __exit tproxy_tg_exit(void)
613{
614 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
615}
616
617module_init(tproxy_tg_init);
618module_exit(tproxy_tg_exit);
619MODULE_LICENSE("GPL");
620MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
621MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
622MODULE_ALIAS("ipt_TPROXY");
623MODULE_ALIAS("ip6t_TPROXY");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Transparent proxy support for Linux/iptables
4 *
5 * Copyright (c) 2006-2010 BalaBit IT Ltd.
6 * Author: Balazs Scheidler, Krisztian Kovacs
7 */
8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9#include <linux/module.h>
10#include <linux/skbuff.h>
11#include <linux/ip.h>
12#include <net/checksum.h>
13#include <net/udp.h>
14#include <net/tcp.h>
15#include <net/inet_sock.h>
16#include <net/inet_hashtables.h>
17#include <linux/inetdevice.h>
18#include <linux/netfilter/x_tables.h>
19#include <linux/netfilter_ipv4/ip_tables.h>
20
21#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
22
23#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
24#define XT_TPROXY_HAVE_IPV6 1
25#include <net/if_inet6.h>
26#include <net/addrconf.h>
27#include <net/inet6_hashtables.h>
28#include <linux/netfilter_ipv6/ip6_tables.h>
29#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
30#endif
31
32#include <net/netfilter/nf_tproxy.h>
33#include <linux/netfilter/xt_TPROXY.h>
34
35static unsigned int
36tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
37 u_int32_t mark_mask, u_int32_t mark_value)
38{
39 const struct iphdr *iph = ip_hdr(skb);
40 struct udphdr _hdr, *hp;
41 struct sock *sk;
42
43 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
44 if (hp == NULL)
45 return NF_DROP;
46
47 /* check if there's an ongoing connection on the packet
48 * addresses, this happens if the redirect already happened
49 * and the current packet belongs to an already established
50 * connection */
51 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
52 iph->saddr, iph->daddr,
53 hp->source, hp->dest,
54 skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
55
56 laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr);
57 if (!lport)
58 lport = hp->dest;
59
60 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
61 if (sk && sk->sk_state == TCP_TIME_WAIT)
62 /* reopening a TIME_WAIT connection needs special handling */
63 sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
64 else if (!sk)
65 /* no, there's no established connection, check if
66 * there's a listener on the redirected addr/port */
67 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
68 iph->saddr, laddr,
69 hp->source, lport,
70 skb->dev, NF_TPROXY_LOOKUP_LISTENER);
71
72 /* NOTE: assign_sock consumes our sk reference */
73 if (sk && nf_tproxy_sk_is_transparent(sk)) {
74 /* This should be in a separate target, but we don't do multiple
75 targets on the same rule yet */
76 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
77 nf_tproxy_assign_sock(skb, sk);
78 return NF_ACCEPT;
79 }
80
81 return NF_DROP;
82}
83
84static unsigned int
85tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
86{
87 const struct xt_tproxy_target_info *tgi = par->targinfo;
88
89 return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
90 tgi->mark_mask, tgi->mark_value);
91}
92
93static unsigned int
94tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
95{
96 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
97
98 return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
99 tgi->mark_mask, tgi->mark_value);
100}
101
102#ifdef XT_TPROXY_HAVE_IPV6
103
104static unsigned int
105tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
106{
107 const struct ipv6hdr *iph = ipv6_hdr(skb);
108 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
109 struct udphdr _hdr, *hp;
110 struct sock *sk;
111 const struct in6_addr *laddr;
112 __be16 lport;
113 int thoff = 0;
114 int tproto;
115
116 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
117 if (tproto < 0)
118 return NF_DROP;
119
120 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
121 if (!hp)
122 return NF_DROP;
123
124 /* check if there's an ongoing connection on the packet
125 * addresses, this happens if the redirect already happened
126 * and the current packet belongs to an already established
127 * connection */
128 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto,
129 &iph->saddr, &iph->daddr,
130 hp->source, hp->dest,
131 xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED);
132
133 laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
134 lport = tgi->lport ? tgi->lport : hp->dest;
135
136 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
137 if (sk && sk->sk_state == TCP_TIME_WAIT) {
138 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
139 /* reopening a TIME_WAIT connection needs special handling */
140 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff,
141 xt_net(par),
142 &tgi->laddr.in6,
143 tgi->lport,
144 sk);
145 }
146 else if (!sk)
147 /* no there's no established connection, check if
148 * there's a listener on the redirected addr/port */
149 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff,
150 tproto, &iph->saddr, laddr,
151 hp->source, lport,
152 xt_in(par), NF_TPROXY_LOOKUP_LISTENER);
153
154 /* NOTE: assign_sock consumes our sk reference */
155 if (sk && nf_tproxy_sk_is_transparent(sk)) {
156 /* This should be in a separate target, but we don't do multiple
157 targets on the same rule yet */
158 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
159 nf_tproxy_assign_sock(skb, sk);
160 return NF_ACCEPT;
161 }
162
163 return NF_DROP;
164}
165
166static int tproxy_tg6_check(const struct xt_tgchk_param *par)
167{
168 const struct ip6t_ip6 *i = par->entryinfo;
169 int err;
170
171 err = nf_defrag_ipv6_enable(par->net);
172 if (err)
173 return err;
174
175 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
176 !(i->invflags & IP6T_INV_PROTO))
177 return 0;
178
179 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
180 return -EINVAL;
181}
182
183static void tproxy_tg6_destroy(const struct xt_tgdtor_param *par)
184{
185 nf_defrag_ipv6_disable(par->net);
186}
187#endif
188
189static int tproxy_tg4_check(const struct xt_tgchk_param *par)
190{
191 const struct ipt_ip *i = par->entryinfo;
192 int err;
193
194 err = nf_defrag_ipv4_enable(par->net);
195 if (err)
196 return err;
197
198 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
199 && !(i->invflags & IPT_INV_PROTO))
200 return 0;
201
202 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
203 return -EINVAL;
204}
205
206static void tproxy_tg4_destroy(const struct xt_tgdtor_param *par)
207{
208 nf_defrag_ipv4_disable(par->net);
209}
210
211static struct xt_target tproxy_tg_reg[] __read_mostly = {
212 {
213 .name = "TPROXY",
214 .family = NFPROTO_IPV4,
215 .table = "mangle",
216 .target = tproxy_tg4_v0,
217 .revision = 0,
218 .targetsize = sizeof(struct xt_tproxy_target_info),
219 .checkentry = tproxy_tg4_check,
220 .destroy = tproxy_tg4_destroy,
221 .hooks = 1 << NF_INET_PRE_ROUTING,
222 .me = THIS_MODULE,
223 },
224 {
225 .name = "TPROXY",
226 .family = NFPROTO_IPV4,
227 .table = "mangle",
228 .target = tproxy_tg4_v1,
229 .revision = 1,
230 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
231 .checkentry = tproxy_tg4_check,
232 .destroy = tproxy_tg4_destroy,
233 .hooks = 1 << NF_INET_PRE_ROUTING,
234 .me = THIS_MODULE,
235 },
236#ifdef XT_TPROXY_HAVE_IPV6
237 {
238 .name = "TPROXY",
239 .family = NFPROTO_IPV6,
240 .table = "mangle",
241 .target = tproxy_tg6_v1,
242 .revision = 1,
243 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
244 .checkentry = tproxy_tg6_check,
245 .destroy = tproxy_tg6_destroy,
246 .hooks = 1 << NF_INET_PRE_ROUTING,
247 .me = THIS_MODULE,
248 },
249#endif
250
251};
252
253static int __init tproxy_tg_init(void)
254{
255 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
256}
257
258static void __exit tproxy_tg_exit(void)
259{
260 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
261}
262
263module_init(tproxy_tg_init);
264module_exit(tproxy_tg_exit);
265MODULE_LICENSE("GPL");
266MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
267MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
268MODULE_ALIAS("ipt_TPROXY");
269MODULE_ALIAS("ip6t_TPROXY");