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e8439270 KK |
1 | /* |
2 | * Transparent proxy support for Linux/iptables | |
3 | * | |
4 | * Copyright (c) 2006-2007 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 | */ | |
ff67e4e4 | 12 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
e8439270 KK |
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/inet_sock.h> | |
19 | ||
20 | #include <linux/netfilter/x_tables.h> | |
21 | #include <linux/netfilter_ipv4/ip_tables.h> | |
22 | #include <linux/netfilter/xt_TPROXY.h> | |
23 | ||
24 | #include <net/netfilter/ipv4/nf_defrag_ipv4.h> | |
25 | #include <net/netfilter/nf_tproxy_core.h> | |
26 | ||
106e4c26 BS |
27 | /** |
28 | * tproxy_handle_time_wait() - handle TCP TIME_WAIT reopen redirections | |
29 | * @skb: The skb being processed. | |
30 | * @par: Iptables target parameters. | |
31 | * @sk: The TIME_WAIT TCP socket found by the lookup. | |
32 | * | |
33 | * We have to handle SYN packets arriving to TIME_WAIT sockets | |
34 | * differently: instead of reopening the connection we should rather | |
35 | * redirect the new connection to the proxy if there's a listener | |
36 | * socket present. | |
37 | * | |
38 | * tproxy_handle_time_wait() consumes the socket reference passed in. | |
39 | * | |
40 | * Returns the listener socket if there's one, the TIME_WAIT socket if | |
41 | * no such listener is found, or NULL if the TCP header is incomplete. | |
42 | */ | |
43 | static struct sock * | |
44 | tproxy_handle_time_wait(struct sk_buff *skb, const struct xt_action_param *par, struct sock *sk) | |
45 | { | |
46 | const struct iphdr *iph = ip_hdr(skb); | |
47 | const struct xt_tproxy_target_info *tgi = par->targinfo; | |
48 | struct tcphdr _hdr, *hp; | |
49 | ||
50 | hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); | |
51 | if (hp == NULL) { | |
52 | inet_twsk_put(inet_twsk(sk)); | |
53 | return NULL; | |
54 | } | |
55 | ||
56 | if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { | |
57 | /* SYN to a TIME_WAIT socket, we'd rather redirect it | |
58 | * to a listener socket if there's one */ | |
59 | struct sock *sk2; | |
60 | ||
61 | sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, | |
62 | iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr, | |
63 | hp->source, tgi->lport ? tgi->lport : hp->dest, | |
64 | par->in, NFT_LOOKUP_LISTENER); | |
65 | if (sk2) { | |
66 | /* yeah, there's one, let's kill the TIME_WAIT | |
67 | * socket and redirect to the listener | |
68 | */ | |
69 | inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); | |
70 | inet_twsk_put(inet_twsk(sk)); | |
71 | sk = sk2; | |
72 | } | |
73 | } | |
74 | ||
75 | return sk; | |
76 | } | |
77 | ||
e8439270 | 78 | static unsigned int |
4b560b44 | 79 | tproxy_tg(struct sk_buff *skb, const struct xt_action_param *par) |
e8439270 KK |
80 | { |
81 | const struct iphdr *iph = ip_hdr(skb); | |
7eb35586 | 82 | const struct xt_tproxy_target_info *tgi = par->targinfo; |
e8439270 KK |
83 | struct udphdr _hdr, *hp; |
84 | struct sock *sk; | |
85 | ||
86 | hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); | |
87 | if (hp == NULL) | |
88 | return NF_DROP; | |
89 | ||
90 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, | |
106e4c26 BS |
91 | iph->saddr, iph->daddr, |
92 | hp->source, hp->dest, | |
93 | par->in, NFT_LOOKUP_ESTABLISHED); | |
94 | ||
95 | /* UDP has no TCP_TIME_WAIT state, so we never enter here */ | |
96 | if (sk && sk->sk_state == TCP_TIME_WAIT) | |
97 | sk = tproxy_handle_time_wait(skb, par, sk); | |
98 | else if (!sk) | |
99 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, | |
100 | iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr, | |
101 | hp->source, tgi->lport ? tgi->lport : hp->dest, | |
102 | par->in, NFT_LOOKUP_LISTENER); | |
e8439270 KK |
103 | |
104 | /* NOTE: assign_sock consumes our sk reference */ | |
105 | if (sk && nf_tproxy_assign_sock(skb, sk)) { | |
106 | /* This should be in a separate target, but we don't do multiple | |
107 | targets on the same rule yet */ | |
108 | skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; | |
109 | ||
110 | pr_debug("redirecting: proto %u %08x:%u -> %08x:%u, mark: %x\n", | |
111 | iph->protocol, ntohl(iph->daddr), ntohs(hp->dest), | |
112 | ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark); | |
113 | return NF_ACCEPT; | |
114 | } | |
115 | ||
116 | pr_debug("no socket, dropping: proto %u %08x:%u -> %08x:%u, mark: %x\n", | |
117 | iph->protocol, ntohl(iph->daddr), ntohs(hp->dest), | |
118 | ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark); | |
119 | return NF_DROP; | |
120 | } | |
121 | ||
135367b8 | 122 | static int tproxy_tg_check(const struct xt_tgchk_param *par) |
e8439270 | 123 | { |
af5d6dc2 | 124 | const struct ipt_ip *i = par->entryinfo; |
e8439270 KK |
125 | |
126 | if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) | |
127 | && !(i->invflags & IPT_INV_PROTO)) | |
d6b00a53 | 128 | return 0; |
e8439270 | 129 | |
ff67e4e4 | 130 | pr_info("Can be used only in combination with " |
e8439270 | 131 | "either -p tcp or -p udp\n"); |
d6b00a53 | 132 | return -EINVAL; |
e8439270 KK |
133 | } |
134 | ||
135 | static struct xt_target tproxy_tg_reg __read_mostly = { | |
136 | .name = "TPROXY", | |
70a85166 | 137 | .family = NFPROTO_IPV4, |
e8439270 KK |
138 | .table = "mangle", |
139 | .target = tproxy_tg, | |
140 | .targetsize = sizeof(struct xt_tproxy_target_info), | |
141 | .checkentry = tproxy_tg_check, | |
142 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
143 | .me = THIS_MODULE, | |
144 | }; | |
145 | ||
146 | static int __init tproxy_tg_init(void) | |
147 | { | |
148 | nf_defrag_ipv4_enable(); | |
149 | return xt_register_target(&tproxy_tg_reg); | |
150 | } | |
151 | ||
152 | static void __exit tproxy_tg_exit(void) | |
153 | { | |
154 | xt_unregister_target(&tproxy_tg_reg); | |
155 | } | |
156 | ||
157 | module_init(tproxy_tg_init); | |
158 | module_exit(tproxy_tg_exit); | |
159 | MODULE_LICENSE("GPL"); | |
160 | MODULE_AUTHOR("Krisztian Kovacs"); | |
161 | MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); | |
162 | MODULE_ALIAS("ipt_TPROXY"); |