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
;
73 indev
= __in_dev_get_rcu(skb
->dev
);
74 for_primary_ifa(indev
) {
75 laddr
= ifa
->ifa_local
;
79 return laddr
? laddr
: daddr
;
83 * This is used when the user wants to intercept a connection matching
84 * an explicit iptables rule. In this case the sockets are assumed
85 * matching in preference order:
87 * - match: if there's a fully established connection matching the
88 * _packet_ tuple, it is returned, assuming the redirection
89 * already took place and we process a packet belonging to an
90 * established connection
92 * - match: if there's a listening socket matching the redirection
93 * (e.g. on-port & on-ip of the connection), it is returned,
94 * regardless if it was bound to 0.0.0.0 or an explicit
95 * address. The reasoning is that if there's an explicit rule, it
96 * does not really matter if the listener is bound to an interface
97 * or to 0. The user already stated that he wants redirection
98 * (since he added the rule).
100 * Please note that there's an overlap between what a TPROXY target
101 * and a socket match will match. Normally if you have both rules the
102 * "socket" match will be the first one, effectively all packets
103 * belonging to established connections going through that one.
105 static inline struct sock
*
106 nf_tproxy_get_sock_v4(struct net
*net
, struct sk_buff
*skb
, void *hp
,
108 const __be32 saddr
, const __be32 daddr
,
109 const __be16 sport
, const __be16 dport
,
110 const struct net_device
*in
,
111 const enum nf_tproxy_lookup_t lookup_type
)
118 switch (lookup_type
) {
119 case NFT_LOOKUP_LISTENER
:
121 sk
= inet_lookup_listener(net
, &tcp_hashinfo
, skb
,
128 if (sk
&& !refcount_inc_not_zero(&sk
->sk_refcnt
))
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 if (sk
&& !refcount_inc_not_zero(&sk
->sk_refcnt
))
200 /* NOTE: we return listeners even if bound to
201 * 0.0.0.0, those are filtered out in
202 * xt_socket, since xt_TPROXY needs 0 bound
206 case NFT_LOOKUP_ESTABLISHED
:
207 sk
= __inet6_lookup_established(net
, &tcp_hashinfo
,
208 saddr
, sport
, daddr
, ntohs(dport
),
216 sk
= udp6_lib_lookup(net
, saddr
, sport
, daddr
, dport
,
219 int connected
= (sk
->sk_state
== TCP_ESTABLISHED
);
220 int wildcard
= ipv6_addr_any(&sk
->sk_v6_rcv_saddr
);
222 /* NOTE: we return listeners even if bound to
223 * 0.0.0.0, those are filtered out in
224 * xt_socket, since xt_TPROXY needs 0 bound
227 if ((lookup_type
== NFT_LOOKUP_ESTABLISHED
&& (!connected
|| wildcard
)) ||
228 (lookup_type
== NFT_LOOKUP_LISTENER
&& connected
)) {
239 pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
240 protocol
, saddr
, ntohs(sport
), daddr
, ntohs(dport
), lookup_type
, sk
);
247 * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections
248 * @skb: The skb being processed.
249 * @laddr: IPv4 address to redirect to or zero.
250 * @lport: TCP port to redirect to or zero.
251 * @sk: The TIME_WAIT TCP socket found by the lookup.
253 * We have to handle SYN packets arriving to TIME_WAIT sockets
254 * differently: instead of reopening the connection we should rather
255 * redirect the new connection to the proxy if there's a listener
258 * tproxy_handle_time_wait4() consumes the socket reference passed in.
260 * Returns the listener socket if there's one, the TIME_WAIT socket if
261 * no such listener is found, or NULL if the TCP header is incomplete.
264 tproxy_handle_time_wait4(struct net
*net
, struct sk_buff
*skb
,
265 __be32 laddr
, __be16 lport
, struct sock
*sk
)
267 const struct iphdr
*iph
= ip_hdr(skb
);
268 struct tcphdr _hdr
, *hp
;
270 hp
= skb_header_pointer(skb
, ip_hdrlen(skb
), sizeof(_hdr
), &_hdr
);
272 inet_twsk_put(inet_twsk(sk
));
276 if (hp
->syn
&& !hp
->rst
&& !hp
->ack
&& !hp
->fin
) {
277 /* SYN to a TIME_WAIT socket, we'd rather redirect it
278 * to a listener socket if there's one */
281 sk2
= nf_tproxy_get_sock_v4(net
, skb
, hp
, iph
->protocol
,
282 iph
->saddr
, laddr
? laddr
: iph
->daddr
,
283 hp
->source
, lport
? lport
: hp
->dest
,
284 skb
->dev
, NFT_LOOKUP_LISTENER
);
286 inet_twsk_deschedule_put(inet_twsk(sk
));
294 /* assign a socket to the skb -- consumes sk */
296 nf_tproxy_assign_sock(struct sk_buff
*skb
, struct sock
*sk
)
300 skb
->destructor
= sock_edemux
;
304 tproxy_tg4(struct net
*net
, struct sk_buff
*skb
, __be32 laddr
, __be16 lport
,
305 u_int32_t mark_mask
, u_int32_t mark_value
)
307 const struct iphdr
*iph
= ip_hdr(skb
);
308 struct udphdr _hdr
, *hp
;
311 hp
= skb_header_pointer(skb
, ip_hdrlen(skb
), sizeof(_hdr
), &_hdr
);
315 /* check if there's an ongoing connection on the packet
316 * addresses, this happens if the redirect already happened
317 * and the current packet belongs to an already established
319 sk
= nf_tproxy_get_sock_v4(net
, skb
, hp
, iph
->protocol
,
320 iph
->saddr
, iph
->daddr
,
321 hp
->source
, hp
->dest
,
322 skb
->dev
, NFT_LOOKUP_ESTABLISHED
);
324 laddr
= tproxy_laddr4(skb
, laddr
, iph
->daddr
);
328 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
329 if (sk
&& sk
->sk_state
== TCP_TIME_WAIT
)
330 /* reopening a TIME_WAIT connection needs special handling */
331 sk
= tproxy_handle_time_wait4(net
, skb
, laddr
, lport
, sk
);
333 /* no, there's no established connection, check if
334 * there's a listener on the redirected addr/port */
335 sk
= nf_tproxy_get_sock_v4(net
, skb
, hp
, iph
->protocol
,
338 skb
->dev
, NFT_LOOKUP_LISTENER
);
340 /* NOTE: assign_sock consumes our sk reference */
341 if (sk
&& tproxy_sk_is_transparent(sk
)) {
342 /* This should be in a separate target, but we don't do multiple
343 targets on the same rule yet */
344 skb
->mark
= (skb
->mark
& ~mark_mask
) ^ mark_value
;
346 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
347 iph
->protocol
, &iph
->daddr
, ntohs(hp
->dest
),
348 &laddr
, ntohs(lport
), skb
->mark
);
350 nf_tproxy_assign_sock(skb
, sk
);
354 pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
355 iph
->protocol
, &iph
->saddr
, ntohs(hp
->source
),
356 &iph
->daddr
, ntohs(hp
->dest
), skb
->mark
);
361 tproxy_tg4_v0(struct sk_buff
*skb
, const struct xt_action_param
*par
)
363 const struct xt_tproxy_target_info
*tgi
= par
->targinfo
;
365 return tproxy_tg4(xt_net(par
), skb
, tgi
->laddr
, tgi
->lport
,
366 tgi
->mark_mask
, tgi
->mark_value
);
370 tproxy_tg4_v1(struct sk_buff
*skb
, const struct xt_action_param
*par
)
372 const struct xt_tproxy_target_info_v1
*tgi
= par
->targinfo
;
374 return tproxy_tg4(xt_net(par
), skb
, tgi
->laddr
.ip
, tgi
->lport
,
375 tgi
->mark_mask
, tgi
->mark_value
);
378 #ifdef XT_TPROXY_HAVE_IPV6
380 static inline const struct in6_addr
*
381 tproxy_laddr6(struct sk_buff
*skb
, const struct in6_addr
*user_laddr
,
382 const struct in6_addr
*daddr
)
384 struct inet6_dev
*indev
;
385 struct inet6_ifaddr
*ifa
;
386 struct in6_addr
*laddr
;
388 if (!ipv6_addr_any(user_laddr
))
392 indev
= __in6_dev_get(skb
->dev
);
394 read_lock_bh(&indev
->lock
);
395 list_for_each_entry(ifa
, &indev
->addr_list
, if_list
) {
396 if (ifa
->flags
& (IFA_F_TENTATIVE
| IFA_F_DEPRECATED
))
402 read_unlock_bh(&indev
->lock
);
405 return laddr
? laddr
: daddr
;
409 * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections
410 * @skb: The skb being processed.
411 * @tproto: Transport protocol.
412 * @thoff: Transport protocol header offset.
413 * @par: Iptables target parameters.
414 * @sk: The TIME_WAIT TCP socket found by the lookup.
416 * We have to handle SYN packets arriving to TIME_WAIT sockets
417 * differently: instead of reopening the connection we should rather
418 * redirect the new connection to the proxy if there's a listener
421 * tproxy_handle_time_wait6() consumes the socket reference passed in.
423 * Returns the listener socket if there's one, the TIME_WAIT socket if
424 * no such listener is found, or NULL if the TCP header is incomplete.
427 tproxy_handle_time_wait6(struct sk_buff
*skb
, int tproto
, int thoff
,
428 const struct xt_action_param
*par
,
431 const struct ipv6hdr
*iph
= ipv6_hdr(skb
);
432 struct tcphdr _hdr
, *hp
;
433 const struct xt_tproxy_target_info_v1
*tgi
= par
->targinfo
;
435 hp
= skb_header_pointer(skb
, thoff
, sizeof(_hdr
), &_hdr
);
437 inet_twsk_put(inet_twsk(sk
));
441 if (hp
->syn
&& !hp
->rst
&& !hp
->ack
&& !hp
->fin
) {
442 /* SYN to a TIME_WAIT socket, we'd rather redirect it
443 * to a listener socket if there's one */
446 sk2
= nf_tproxy_get_sock_v6(xt_net(par
), skb
, thoff
, hp
, tproto
,
448 tproxy_laddr6(skb
, &tgi
->laddr
.in6
, &iph
->daddr
),
450 tgi
->lport
? tgi
->lport
: hp
->dest
,
451 skb
->dev
, NFT_LOOKUP_LISTENER
);
453 inet_twsk_deschedule_put(inet_twsk(sk
));
462 tproxy_tg6_v1(struct sk_buff
*skb
, const struct xt_action_param
*par
)
464 const struct ipv6hdr
*iph
= ipv6_hdr(skb
);
465 const struct xt_tproxy_target_info_v1
*tgi
= par
->targinfo
;
466 struct udphdr _hdr
, *hp
;
468 const struct in6_addr
*laddr
;
473 tproto
= ipv6_find_hdr(skb
, &thoff
, -1, NULL
, NULL
);
475 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
479 hp
= skb_header_pointer(skb
, thoff
, sizeof(_hdr
), &_hdr
);
481 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
485 /* check if there's an ongoing connection on the packet
486 * addresses, this happens if the redirect already happened
487 * and the current packet belongs to an already established
489 sk
= nf_tproxy_get_sock_v6(xt_net(par
), skb
, thoff
, hp
, tproto
,
490 &iph
->saddr
, &iph
->daddr
,
491 hp
->source
, hp
->dest
,
492 xt_in(par
), NFT_LOOKUP_ESTABLISHED
);
494 laddr
= tproxy_laddr6(skb
, &tgi
->laddr
.in6
, &iph
->daddr
);
495 lport
= tgi
->lport
? tgi
->lport
: hp
->dest
;
497 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
498 if (sk
&& sk
->sk_state
== TCP_TIME_WAIT
)
499 /* reopening a TIME_WAIT connection needs special handling */
500 sk
= tproxy_handle_time_wait6(skb
, tproto
, thoff
, par
, sk
);
502 /* no there's no established connection, check if
503 * there's a listener on the redirected addr/port */
504 sk
= nf_tproxy_get_sock_v6(xt_net(par
), skb
, thoff
, hp
,
505 tproto
, &iph
->saddr
, laddr
,
507 xt_in(par
), NFT_LOOKUP_LISTENER
);
509 /* NOTE: assign_sock consumes our sk reference */
510 if (sk
&& tproxy_sk_is_transparent(sk
)) {
511 /* This should be in a separate target, but we don't do multiple
512 targets on the same rule yet */
513 skb
->mark
= (skb
->mark
& ~tgi
->mark_mask
) ^ tgi
->mark_value
;
515 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
516 tproto
, &iph
->saddr
, ntohs(hp
->source
),
517 laddr
, ntohs(lport
), skb
->mark
);
519 nf_tproxy_assign_sock(skb
, sk
);
523 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
524 tproto
, &iph
->saddr
, ntohs(hp
->source
),
525 &iph
->daddr
, ntohs(hp
->dest
), skb
->mark
);
530 static int tproxy_tg6_check(const struct xt_tgchk_param
*par
)
532 const struct ip6t_ip6
*i
= par
->entryinfo
;
535 err
= nf_defrag_ipv6_enable(par
->net
);
539 if ((i
->proto
== IPPROTO_TCP
|| i
->proto
== IPPROTO_UDP
) &&
540 !(i
->invflags
& IP6T_INV_PROTO
))
543 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
548 static int tproxy_tg4_check(const struct xt_tgchk_param
*par
)
550 const struct ipt_ip
*i
= par
->entryinfo
;
553 err
= nf_defrag_ipv4_enable(par
->net
);
557 if ((i
->proto
== IPPROTO_TCP
|| i
->proto
== IPPROTO_UDP
)
558 && !(i
->invflags
& IPT_INV_PROTO
))
561 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
565 static struct xt_target tproxy_tg_reg
[] __read_mostly
= {
568 .family
= NFPROTO_IPV4
,
570 .target
= tproxy_tg4_v0
,
572 .targetsize
= sizeof(struct xt_tproxy_target_info
),
573 .checkentry
= tproxy_tg4_check
,
574 .hooks
= 1 << NF_INET_PRE_ROUTING
,
579 .family
= NFPROTO_IPV4
,
581 .target
= tproxy_tg4_v1
,
583 .targetsize
= sizeof(struct xt_tproxy_target_info_v1
),
584 .checkentry
= tproxy_tg4_check
,
585 .hooks
= 1 << NF_INET_PRE_ROUTING
,
588 #ifdef XT_TPROXY_HAVE_IPV6
591 .family
= NFPROTO_IPV6
,
593 .target
= tproxy_tg6_v1
,
595 .targetsize
= sizeof(struct xt_tproxy_target_info_v1
),
596 .checkentry
= tproxy_tg6_check
,
597 .hooks
= 1 << NF_INET_PRE_ROUTING
,
604 static int __init
tproxy_tg_init(void)
606 return xt_register_targets(tproxy_tg_reg
, ARRAY_SIZE(tproxy_tg_reg
));
609 static void __exit
tproxy_tg_exit(void)
611 xt_unregister_targets(tproxy_tg_reg
, ARRAY_SIZE(tproxy_tg_reg
));
614 module_init(tproxy_tg_init
);
615 module_exit(tproxy_tg_exit
);
616 MODULE_LICENSE("GPL");
617 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
618 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
619 MODULE_ALIAS("ipt_TPROXY");
620 MODULE_ALIAS("ip6t_TPROXY");