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>
18 #include <net/inet_sock.h>
20 #include <linux/netfilter/x_tables.h>
21 #include <linux/netfilter_ipv4/ip_tables.h>
22 #include <linux/netfilter_ipv6/ip6_tables.h>
23 #include <linux/netfilter/xt_TPROXY.h>
25 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
26 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
27 #include <net/netfilter/nf_tproxy_core.h>
30 * tproxy_handle_time_wait4() - handle IPv4 TCP TIME_WAIT reopen redirections
31 * @skb: The skb being processed.
32 * @laddr: IPv4 address to redirect to or zero.
33 * @lport: TCP port to redirect to or zero.
34 * @sk: The TIME_WAIT TCP socket found by the lookup.
36 * We have to handle SYN packets arriving to TIME_WAIT sockets
37 * differently: instead of reopening the connection we should rather
38 * redirect the new connection to the proxy if there's a listener
41 * tproxy_handle_time_wait4() consumes the socket reference passed in.
43 * Returns the listener socket if there's one, the TIME_WAIT socket if
44 * no such listener is found, or NULL if the TCP header is incomplete.
47 tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport,
50 const struct iphdr *iph = ip_hdr(skb);
51 struct tcphdr _hdr, *hp;
53 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
55 inet_twsk_put(inet_twsk(sk));
59 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
60 /* SYN to a TIME_WAIT socket, we'd rather redirect it
61 * to a listener socket if there's one */
64 sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
65 iph->saddr, laddr ? laddr : iph->daddr,
66 hp->source, lport ? lport : hp->dest,
67 skb->dev, NFT_LOOKUP_LISTENER);
69 inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row);
70 inet_twsk_put(inet_twsk(sk));
79 * tproxy_handle_time_wait6() - handle IPv6 TCP TIME_WAIT reopen redirections
80 * @skb: The skb being processed.
81 * @tproto: Transport protocol.
82 * @thoff: Transport protocol header offset.
83 * @par: Iptables target parameters.
84 * @sk: The TIME_WAIT TCP socket found by the lookup.
86 * We have to handle SYN packets arriving to TIME_WAIT sockets
87 * differently: instead of reopening the connection we should rather
88 * redirect the new connection to the proxy if there's a listener
91 * tproxy_handle_time_wait6() consumes the socket reference passed in.
93 * Returns the listener socket if there's one, the TIME_WAIT socket if
94 * no such listener is found, or NULL if the TCP header is incomplete.
97 tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
98 const struct xt_action_param *par,
101 const struct ipv6hdr *iph = ipv6_hdr(skb);
102 struct tcphdr _hdr, *hp;
103 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
105 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
107 inet_twsk_put(inet_twsk(sk));
111 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
112 /* SYN to a TIME_WAIT socket, we'd rather redirect it
113 * to a listener socket if there's one */
116 sk2 = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
118 !ipv6_addr_any(&tgi->laddr.in6) ? &tgi->laddr.in6 : &iph->daddr,
120 tgi->lport ? tgi->lport : hp->dest,
121 skb->dev, NFT_LOOKUP_LISTENER);
123 inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row);
124 inet_twsk_put(inet_twsk(sk));
133 tproxy_tg4(struct sk_buff *skb, __be32 laddr, __be16 lport,
134 u_int32_t mark_mask, u_int32_t mark_value)
136 const struct iphdr *iph = ip_hdr(skb);
137 struct udphdr _hdr, *hp;
140 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
144 /* check if there's an ongoing connection on the packet
145 * addresses, this happens if the redirect already happened
146 * and the current packet belongs to an already established
148 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
149 iph->saddr, iph->daddr,
150 hp->source, hp->dest,
151 skb->dev, NFT_LOOKUP_ESTABLISHED);
153 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
154 if (sk && sk->sk_state == TCP_TIME_WAIT)
155 /* reopening a TIME_WAIT connection needs special handling */
156 sk = tproxy_handle_time_wait4(skb, laddr, lport, sk);
158 /* no, there's no established connection, check if
159 * there's a listener on the redirected addr/port */
160 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
161 iph->saddr, laddr ? laddr : iph->daddr,
162 hp->source, lport ? lport : hp->dest,
163 skb->dev, NFT_LOOKUP_LISTENER);
165 /* NOTE: assign_sock consumes our sk reference */
166 if (sk && nf_tproxy_assign_sock(skb, sk)) {
167 /* This should be in a separate target, but we don't do multiple
168 targets on the same rule yet */
169 skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
171 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
172 iph->protocol, &iph->daddr, ntohs(hp->dest),
173 &laddr, ntohs(lport), skb->mark);
177 pr_debug("no socket, dropping: proto %hhu %08x:%hu -> %08x:%hu, mark: %x\n",
178 iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
179 ntohl(laddr), ntohs(lport), skb->mark);
184 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
186 const struct xt_tproxy_target_info *tgi = par->targinfo;
188 return tproxy_tg4(skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value);
192 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
194 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
196 return tproxy_tg4(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value);
199 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
201 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
203 const struct ipv6hdr *iph = ipv6_hdr(skb);
204 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
205 struct udphdr _hdr, *hp;
210 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL);
212 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
216 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
218 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
222 /* check if there's an ongoing connection on the packet
223 * addresses, this happens if the redirect already happened
224 * and the current packet belongs to an already established
226 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
227 &iph->saddr, &iph->daddr,
228 hp->source, hp->dest,
229 par->in, NFT_LOOKUP_ESTABLISHED);
231 /* UDP has no TCP_TIME_WAIT state, so we never enter here */
232 if (sk && sk->sk_state == TCP_TIME_WAIT)
233 /* reopening a TIME_WAIT connection needs special handling */
234 sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk);
236 /* no there's no established connection, check if
237 * there's a listener on the redirected addr/port */
238 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
240 !ipv6_addr_any(&tgi->laddr.in6) ? &tgi->laddr.in6 : &iph->daddr,
242 tgi->lport ? tgi->lport : hp->dest,
243 par->in, NFT_LOOKUP_LISTENER);
245 /* NOTE: assign_sock consumes our sk reference */
246 if (sk && nf_tproxy_assign_sock(skb, sk)) {
247 /* This should be in a separate target, but we don't do multiple
248 targets on the same rule yet */
249 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
251 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
252 tproto, &iph->saddr, ntohs(hp->dest),
253 &tgi->laddr.in6, ntohs(tgi->lport), skb->mark);
257 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
258 tproto, &iph->saddr, ntohs(hp->dest),
259 &tgi->laddr.in6, ntohs(tgi->lport), skb->mark);
263 static int tproxy_tg6_check(const struct xt_tgchk_param *par)
265 const struct ip6t_ip6 *i = par->entryinfo;
267 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
268 && !(i->flags & IP6T_INV_PROTO))
271 pr_info("Can be used only in combination with "
272 "either -p tcp or -p udp\n");
277 static int tproxy_tg4_check(const struct xt_tgchk_param *par)
279 const struct ipt_ip *i = par->entryinfo;
281 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
282 && !(i->invflags & IPT_INV_PROTO))
285 pr_info("Can be used only in combination with "
286 "either -p tcp or -p udp\n");
290 static struct xt_target tproxy_tg_reg[] __read_mostly = {
293 .family = NFPROTO_IPV4,
295 .target = tproxy_tg4_v0,
297 .targetsize = sizeof(struct xt_tproxy_target_info),
298 .checkentry = tproxy_tg4_check,
299 .hooks = 1 << NF_INET_PRE_ROUTING,
304 .family = NFPROTO_IPV4,
306 .target = tproxy_tg4_v1,
308 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
309 .checkentry = tproxy_tg4_check,
310 .hooks = 1 << NF_INET_PRE_ROUTING,
313 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
316 .family = NFPROTO_IPV6,
318 .target = tproxy_tg6_v1,
320 .targetsize = sizeof(struct xt_tproxy_target_info_v1),
321 .checkentry = tproxy_tg6_check,
322 .hooks = 1 << NF_INET_PRE_ROUTING,
329 static int __init tproxy_tg_init(void)
331 nf_defrag_ipv4_enable();
332 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
333 nf_defrag_ipv6_enable();
336 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
339 static void __exit tproxy_tg_exit(void)
341 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
344 module_init(tproxy_tg_init);
345 module_exit(tproxy_tg_exit);
346 MODULE_LICENSE("GPL");
347 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
348 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
349 MODULE_ALIAS("ipt_TPROXY");
350 MODULE_ALIAS("ip6t_TPROXY");