2 * Transparent proxy support for Linux/iptables
4 * Copyright (c) 2006-2010 BalaBit IT Ltd.
5 * Author: Balazs Scheidler, Krisztian Kovacs
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.
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
16 #include <net/checksum.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>
25 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
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>
36 #include <linux/netfilter/xt_TPROXY.h>
38 enum nf_tproxy_lookup_t {
40 NFT_LOOKUP_ESTABLISHED,
43 static bool tproxy_sk_is_transparent(struct sock *sk)
45 switch (sk->sk_state) {
47 if (inet_twsk(sk)->tw_transparent)
50 case TCP_NEW_SYN_RECV:
51 if (inet_rsk(inet_reqsk(sk))->no_srccheck)
55 if (inet_sk(sk)->transparent)
64 tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
66 struct in_device *indev;
74 indev = __in_dev_get_rcu(skb->dev);
75 for_primary_ifa(indev) {
76 laddr = ifa->ifa_local;
81 return laddr ? laddr : daddr;
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:
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
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).
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.
107 static inline struct sock *
108 nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb, void *hp,
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)
120 switch (lookup_type) {
121 case NFT_LOOKUP_LISTENER:
123 sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
130 /* NOTE: we return listeners even if bound to
131 * 0.0.0.0, those are filtered out in
132 * xt_socket, since xt_TPROXY needs 0 bound
136 case NFT_LOOKUP_ESTABLISHED:
137 sk = inet_lookup_established(net, &tcp_hashinfo,
138 saddr, sport, daddr, dport,
146 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
149 int connected = (sk->sk_state == TCP_ESTABLISHED);
150 int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
152 /* NOTE: we return listeners even if bound to
153 * 0.0.0.0, those are filtered out in
154 * xt_socket, since xt_TPROXY needs 0 bound
157 if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
158 (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
169 pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
170 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
175 #ifdef XT_TPROXY_HAVE_IPV6
176 static inline struct sock *
177 nf_tproxy_get_sock_v6(struct net *net, struct sk_buff *skb, int thoff, void *hp,
179 const struct in6_addr *saddr, const struct in6_addr *daddr,
180 const __be16 sport, const __be16 dport,
181 const struct net_device *in,
182 const enum nf_tproxy_lookup_t lookup_type)
189 switch (lookup_type) {
190 case NFT_LOOKUP_LISTENER:
192 sk = inet6_lookup_listener(net, &tcp_hashinfo, skb,
193 thoff + __tcp_hdrlen(tcph),
198 /* NOTE: we return listeners even if bound to
199 * 0.0.0.0, those are filtered out in
200 * xt_socket, since xt_TPROXY needs 0 bound
204 case NFT_LOOKUP_ESTABLISHED:
205 sk = __inet6_lookup_established(net, &tcp_hashinfo,
206 saddr, sport, daddr, ntohs(dport),
214 sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
217 int connected = (sk->sk_state == TCP_ESTABLISHED);
218 int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr);
220 /* NOTE: we return listeners even if bound to
221 * 0.0.0.0, those are filtered out in
222 * xt_socket, since xt_TPROXY needs 0 bound
225 if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
226 (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
237 pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
238 protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);
245 * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections
246 * @skb: The skb being processed.
247 * @laddr: IPv4 address to redirect to or zero.
248 * @lport: TCP port to redirect to or zero.
249 * @sk: The TIME_WAIT TCP socket found by the lookup.
251 * We have to handle SYN packets arriving to TIME_WAIT sockets
252 * differently: instead of reopening the connection we should rather
253 * redirect the new connection to the proxy if there's a listener
256 * tproxy_handle_time_wait4() consumes the socket reference passed in.
258 * Returns the listener socket if there's one, the TIME_WAIT socket if
259 * no such listener is found, or NULL if the TCP header is incomplete.
262 tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
263 __be32 laddr, __be16 lport, struct sock *sk)
265 const struct iphdr *iph = ip_hdr(skb);
266 struct tcphdr _hdr, *hp;
268 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
270 inet_twsk_put(inet_twsk(sk));
274 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
275 /* SYN to a TIME_WAIT socket, we'd rather redirect it
276 * to a listener socket if there's one */
279 sk2 = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
280 iph->saddr, laddr ? laddr : iph->daddr,
281 hp->source, lport ? lport : hp->dest,
282 skb->dev, NFT_LOOKUP_LISTENER);
284 inet_twsk_deschedule_put(inet_twsk(sk));
292 /* assign a socket to the skb -- consumes sk */
294 nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
298 skb->destructor = sock_edemux;
302 tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
303 u_int32_t mark_mask, u_int32_t mark_value)
305 const struct iphdr *iph = ip_hdr(skb);
306 struct udphdr _hdr, *hp;
309 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
313 /* check if there's an ongoing connection on the packet
314 * addresses, this happens if the redirect already happened
315 * and the current packet belongs to an already established
317 sk = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
318 iph->saddr, iph->daddr,
319 hp->source, hp->dest,
320 skb->dev, NFT_LOOKUP_ESTABLISHED);
322 laddr = tproxy_laddr4(skb, laddr, iph->daddr);
326 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
327 if (sk && sk->sk_state == TCP_TIME_WAIT)
328 /* reopening a TIME_WAIT connection needs special handling */
329 sk = tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
331 /* no, there's no established connection, check if
332 * there's a listener on the redirected addr/port */
333 sk = nf_tproxy_get_sock_v4(net, skb, hp, iph->protocol,
336 skb->dev, NFT_LOOKUP_LISTENER);
338 /* NOTE: assign_sock consumes our sk reference */
339 if (sk && tproxy_sk_is_transparent(sk)) {
340 /* This should be in a separate target, but we don't do multiple
341 targets on the same rule yet */
342 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
344 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
345 iph->protocol, &iph->daddr, ntohs(hp->dest),
346 &laddr, ntohs(lport), skb->mark);
348 nf_tproxy_assign_sock(skb, sk);
352 pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
353 iph->protocol, &iph->saddr, ntohs(hp->source),
354 &iph->daddr, ntohs(hp->dest), skb->mark);
359 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
361 const struct xt_tproxy_target_info *tgi = par->targinfo;
363 return tproxy_tg4(par->net, skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value);
367 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
369 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
371 return tproxy_tg4(par->net, skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value);
374 #ifdef XT_TPROXY_HAVE_IPV6
376 static inline const struct in6_addr *
377 tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
378 const struct in6_addr *daddr)
380 struct inet6_dev *indev;
381 struct inet6_ifaddr *ifa;
382 struct in6_addr *laddr;
384 if (!ipv6_addr_any(user_laddr))
389 indev = __in6_dev_get(skb->dev);
391 list_for_each_entry(ifa, &indev->addr_list, if_list) {
392 if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
400 return laddr ? laddr : daddr;
404 * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections
405 * @skb: The skb being processed.
406 * @tproto: Transport protocol.
407 * @thoff: Transport protocol header offset.
408 * @par: Iptables target parameters.
409 * @sk: The TIME_WAIT TCP socket found by the lookup.
411 * We have to handle SYN packets arriving to TIME_WAIT sockets
412 * differently: instead of reopening the connection we should rather
413 * redirect the new connection to the proxy if there's a listener
416 * tproxy_handle_time_wait6() consumes the socket reference passed in.
418 * Returns the listener socket if there's one, the TIME_WAIT socket if
419 * no such listener is found, or NULL if the TCP header is incomplete.
422 tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
423 const struct xt_action_param *par,
426 const struct ipv6hdr *iph = ipv6_hdr(skb);
427 struct tcphdr _hdr, *hp;
428 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
430 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
432 inet_twsk_put(inet_twsk(sk));
436 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
437 /* SYN to a TIME_WAIT socket, we'd rather redirect it
438 * to a listener socket if there's one */
441 sk2 = nf_tproxy_get_sock_v6(par->net, skb, thoff, hp, tproto,
443 tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr),
445 tgi->lport ? tgi->lport : hp->dest,
446 skb->dev, NFT_LOOKUP_LISTENER);
448 inet_twsk_deschedule_put(inet_twsk(sk));
457 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
459 const struct ipv6hdr *iph = ipv6_hdr(skb);
460 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
461 struct udphdr _hdr, *hp;
463 const struct in6_addr *laddr;
468 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
470 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
474 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
476 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
480 /* check if there's an ongoing connection on the packet
481 * addresses, this happens if the redirect already happened
482 * and the current packet belongs to an already established
484 sk = nf_tproxy_get_sock_v6(par->net, skb, thoff, hp, tproto,
485 &iph->saddr, &iph->daddr,
486 hp->source, hp->dest,
487 par->in, NFT_LOOKUP_ESTABLISHED);
489 laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
490 lport = tgi->lport ? tgi->lport : hp->dest;
492 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
493 if (sk && sk->sk_state == TCP_TIME_WAIT)
494 /* reopening a TIME_WAIT connection needs special handling */
495 sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk);
497 /* no there's no established connection, check if
498 * there's a listener on the redirected addr/port */
499 sk = nf_tproxy_get_sock_v6(par->net, skb, thoff, hp,
500 tproto, &iph->saddr, laddr,
502 par->in, NFT_LOOKUP_LISTENER);
504 /* NOTE: assign_sock consumes our sk reference */
505 if (sk && tproxy_sk_is_transparent(sk)) {
506 /* This should be in a separate target, but we don't do multiple
507 targets on the same rule yet */
508 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
510 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
511 tproto, &iph->saddr, ntohs(hp->source),
512 laddr, ntohs(lport), skb->mark);
514 nf_tproxy_assign_sock(skb, sk);
518 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
519 tproto, &iph->saddr, ntohs(hp->source),
520 &iph->daddr, ntohs(hp->dest), skb->mark);
525 static int tproxy_tg6_check(const struct xt_tgchk_param *par)
527 const struct ip6t_ip6 *i = par->entryinfo;
529 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
530 !(i->invflags & IP6T_INV_PROTO))
533 pr_info("Can be used only in combination with "
534 "either -p tcp or -p udp\n");
539 static int tproxy_tg4_check(const struct xt_tgchk_param *par)
541 const struct ipt_ip *i = par->entryinfo;
543 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
544 && !(i->invflags & IPT_INV_PROTO))
547 pr_info("Can be used only in combination with "
548 "either -p tcp or -p udp\n");
552 static struct xt_target tproxy_tg_reg[] __read_mostly = {
555 .family = NFPROTO_IPV4,
557 .target = tproxy_tg4_v0,
559 .targetsize = sizeof(struct xt_tproxy_target_info),
560 .checkentry = tproxy_tg4_check,
561 .hooks = 1 << NF_INET_PRE_ROUTING,
566 .family = NFPROTO_IPV4,
568 .target = tproxy_tg4_v1,
570 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
571 .checkentry = tproxy_tg4_check,
572 .hooks = 1 << NF_INET_PRE_ROUTING,
575 #ifdef XT_TPROXY_HAVE_IPV6
578 .family = NFPROTO_IPV6,
580 .target = tproxy_tg6_v1,
582 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
583 .checkentry = tproxy_tg6_check,
584 .hooks = 1 << NF_INET_PRE_ROUTING,
591 static int __init tproxy_tg_init(void)
593 nf_defrag_ipv4_enable();
594 #ifdef XT_TPROXY_HAVE_IPV6
595 nf_defrag_ipv6_enable();
598 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
601 static void __exit tproxy_tg_exit(void)
603 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
606 module_init(tproxy_tg_init);
607 module_exit(tproxy_tg_exit);
608 MODULE_LICENSE("GPL");
609 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
610 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
611 MODULE_ALIAS("ipt_TPROXY");
612 MODULE_ALIAS("ip6t_TPROXY");