2 * Transparent proxy support for Linux/iptables
4 * Copyright (C) 2007-2008 BalaBit IT Ltd.
5 * Author: 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>
15 #include <linux/netfilter/x_tables.h>
16 #include <linux/netfilter_ipv4/ip_tables.h>
21 #include <net/inet_sock.h>
22 #include <net/netfilter/nf_tproxy_core.h>
23 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
25 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
26 #define XT_SOCKET_HAVE_IPV6 1
27 #include <linux/netfilter_ipv6/ip6_tables.h>
28 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
31 #include <linux/netfilter/xt_socket.h>
33 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
34 #define XT_SOCKET_HAVE_CONNTRACK 1
35 #include <net/netfilter/nf_conntrack.h>
39 xt_socket_put_sk(struct sock *sk)
41 if (sk->sk_state == TCP_TIME_WAIT)
42 inet_twsk_put(inet_twsk(sk));
46 EXPORT_SYMBOL(xt_socket_put_sk);
49 extract_icmp4_fields(const struct sk_buff *skb,
56 unsigned int outside_hdrlen = ip_hdrlen(skb);
57 struct iphdr *inside_iph, _inside_iph;
58 struct icmphdr *icmph, _icmph;
59 __be16 *ports, _ports[2];
61 icmph = skb_header_pointer(skb, outside_hdrlen,
62 sizeof(_icmph), &_icmph);
66 switch (icmph->type) {
67 case ICMP_DEST_UNREACH:
68 case ICMP_SOURCE_QUENCH:
70 case ICMP_TIME_EXCEEDED:
71 case ICMP_PARAMETERPROB:
77 inside_iph = skb_header_pointer(skb, outside_hdrlen +
78 sizeof(struct icmphdr),
79 sizeof(_inside_iph), &_inside_iph);
80 if (inside_iph == NULL)
83 if (inside_iph->protocol != IPPROTO_TCP &&
84 inside_iph->protocol != IPPROTO_UDP)
87 ports = skb_header_pointer(skb, outside_hdrlen +
88 sizeof(struct icmphdr) +
89 (inside_iph->ihl << 2),
90 sizeof(_ports), &_ports);
94 /* the inside IP packet is the one quoted from our side, thus
95 * its saddr is the local address */
96 *protocol = inside_iph->protocol;
97 *laddr = inside_iph->saddr;
99 *raddr = inside_iph->daddr;
106 xt_socket_get4_sk(const struct sk_buff *skb, struct xt_action_param *par)
108 const struct iphdr *iph = ip_hdr(skb);
109 struct udphdr _hdr, *hp = NULL;
111 __be32 uninitialized_var(daddr), uninitialized_var(saddr);
112 __be16 uninitialized_var(dport), uninitialized_var(sport);
113 u8 uninitialized_var(protocol);
114 #ifdef XT_SOCKET_HAVE_CONNTRACK
115 struct nf_conn const *ct;
116 enum ip_conntrack_info ctinfo;
119 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
120 hp = skb_header_pointer(skb, ip_hdrlen(skb),
121 sizeof(_hdr), &_hdr);
125 protocol = iph->protocol;
131 } else if (iph->protocol == IPPROTO_ICMP) {
132 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
139 #ifdef XT_SOCKET_HAVE_CONNTRACK
140 /* Do the lookup with the original socket address in case this is a
141 * reply packet of an established SNAT-ted connection. */
143 ct = nf_ct_get(skb, &ctinfo);
144 if (ct && !nf_ct_is_untracked(ct) &&
145 ((iph->protocol != IPPROTO_ICMP &&
146 ctinfo == IP_CT_ESTABLISHED_REPLY) ||
147 (iph->protocol == IPPROTO_ICMP &&
148 ctinfo == IP_CT_RELATED_REPLY)) &&
149 (ct->status & IPS_SRC_NAT_DONE)) {
151 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
152 dport = (iph->protocol == IPPROTO_TCP) ?
153 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
154 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
158 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
159 saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
161 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
162 protocol, &saddr, ntohs(sport),
163 &daddr, ntohs(dport),
164 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
168 EXPORT_SYMBOL(xt_socket_get4_sk);
171 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
172 const struct xt_socket_mtinfo1 *info)
176 sk = xt_socket_get4_sk(skb, par);
179 bool transparent = true;
181 /* Ignore sockets listening on INADDR_ANY */
182 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
183 inet_sk(sk)->inet_rcv_saddr == 0);
185 /* Ignore non-transparent sockets,
186 if XT_SOCKET_TRANSPARENT is used */
187 if (info && info->flags & XT_SOCKET_TRANSPARENT)
188 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
189 inet_sk(sk)->transparent) ||
190 (sk->sk_state == TCP_TIME_WAIT &&
191 inet_twsk(sk)->tw_transparent));
193 xt_socket_put_sk(sk);
195 if (wildcard || !transparent)
203 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
205 return socket_match(skb, par, NULL);
209 socket_mt4_v1(const struct sk_buff *skb, struct xt_action_param *par)
211 return socket_match(skb, par, par->matchinfo);
214 #ifdef XT_SOCKET_HAVE_IPV6
217 extract_icmp6_fields(const struct sk_buff *skb,
218 unsigned int outside_hdrlen,
220 struct in6_addr **raddr,
221 struct in6_addr **laddr,
225 struct ipv6hdr *inside_iph, _inside_iph;
226 struct icmp6hdr *icmph, _icmph;
227 __be16 *ports, _ports[2];
229 __be16 inside_fragoff;
232 icmph = skb_header_pointer(skb, outside_hdrlen,
233 sizeof(_icmph), &_icmph);
237 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
240 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
241 if (inside_iph == NULL)
243 inside_nexthdr = inside_iph->nexthdr;
245 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
246 &inside_nexthdr, &inside_fragoff);
247 if (inside_hdrlen < 0)
248 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
250 if (inside_nexthdr != IPPROTO_TCP &&
251 inside_nexthdr != IPPROTO_UDP)
254 ports = skb_header_pointer(skb, inside_hdrlen,
255 sizeof(_ports), &_ports);
259 /* the inside IP packet is the one quoted from our side, thus
260 * its saddr is the local address */
261 *protocol = inside_nexthdr;
262 *laddr = &inside_iph->saddr;
264 *raddr = &inside_iph->daddr;
271 xt_socket_get6_sk(const struct sk_buff *skb, struct xt_action_param *par)
273 struct ipv6hdr *iph = ipv6_hdr(skb);
274 struct udphdr _hdr, *hp = NULL;
276 struct in6_addr *daddr = NULL, *saddr = NULL;
277 __be16 uninitialized_var(dport), uninitialized_var(sport);
278 int thoff = 0, uninitialized_var(tproto);
280 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
282 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
286 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
287 hp = skb_header_pointer(skb, thoff,
288 sizeof(_hdr), &_hdr);
297 } else if (tproto == IPPROTO_ICMPV6) {
298 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
305 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
306 saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
307 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
308 "(orig %pI6:%hu) sock %p\n",
309 tproto, saddr, ntohs(sport),
311 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
314 EXPORT_SYMBOL(xt_socket_get6_sk);
317 socket_mt6_v1(const struct sk_buff *skb, struct xt_action_param *par)
320 const struct xt_socket_mtinfo1 *info;
322 info = (struct xt_socket_mtinfo1 *) par->matchinfo;
323 sk = xt_socket_get6_sk(skb, par);
326 bool transparent = true;
328 /* Ignore sockets listening on INADDR_ANY */
329 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
330 ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
332 /* Ignore non-transparent sockets,
333 if XT_SOCKET_TRANSPARENT is used */
334 if (info && info->flags & XT_SOCKET_TRANSPARENT)
335 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
336 inet_sk(sk)->transparent) ||
337 (sk->sk_state == TCP_TIME_WAIT &&
338 inet_twsk(sk)->tw_transparent));
340 xt_socket_put_sk(sk);
342 if (wildcard || !transparent)
350 static struct xt_match socket_mt_reg[] __read_mostly = {
354 .family = NFPROTO_IPV4,
355 .match = socket_mt4_v0,
356 .hooks = (1 << NF_INET_PRE_ROUTING) |
357 (1 << NF_INET_LOCAL_IN),
363 .family = NFPROTO_IPV4,
364 .match = socket_mt4_v1,
365 .matchsize = sizeof(struct xt_socket_mtinfo1),
366 .hooks = (1 << NF_INET_PRE_ROUTING) |
367 (1 << NF_INET_LOCAL_IN),
370 #ifdef XT_SOCKET_HAVE_IPV6
374 .family = NFPROTO_IPV6,
375 .match = socket_mt6_v1,
376 .matchsize = sizeof(struct xt_socket_mtinfo1),
377 .hooks = (1 << NF_INET_PRE_ROUTING) |
378 (1 << NF_INET_LOCAL_IN),
384 static int __init socket_mt_init(void)
386 nf_defrag_ipv4_enable();
387 #ifdef XT_SOCKET_HAVE_IPV6
388 nf_defrag_ipv6_enable();
391 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
394 static void __exit socket_mt_exit(void)
396 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
399 module_init(socket_mt_init);
400 module_exit(socket_mt_exit);
402 MODULE_LICENSE("GPL");
403 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
404 MODULE_DESCRIPTION("x_tables socket match module");
405 MODULE_ALIAS("ipt_socket");
406 MODULE_ALIAS("ip6t_socket");