1 /*
2 * Copyright (C) 2007-2008 BalaBit IT Ltd.
3 * Author: Krisztian Kovacs
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 */
10
11 #include <net/netfilter/nf_tproxy.h>
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
14 #include <net/sock.h>
15 #include <net/inet_sock.h>
16 #include <linux/ip.h>
17 #include <net/checksum.h>
18 #include <net/udp.h>
19 #include <net/tcp.h>
20 #include <linux/inetdevice.h>
21
22 struct sock *
nf_tproxy_handle_time_wait4(struct net * net,struct sk_buff * skb,__be32 laddr,__be16 lport,struct sock * sk)23 nf_tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
24 __be32 laddr, __be16 lport, struct sock *sk)
25 {
26 const struct iphdr *iph = ip_hdr(skb);
27 struct tcphdr _hdr, *hp;
28
29 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
30 if (hp == NULL) {
31 inet_twsk_put(inet_twsk(sk));
32 return NULL;
33 }
34
35 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
36 /* SYN to a TIME_WAIT socket, we'd rather redirect it
37 * to a listener socket if there's one */
38 struct sock *sk2;
39
40 sk2 = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
41 iph->saddr, laddr ? laddr : iph->daddr,
42 hp->source, lport ? lport : hp->dest,
43 skb->dev, NF_TPROXY_LOOKUP_LISTENER);
44 if (sk2) {
45 inet_twsk_deschedule_put(inet_twsk(sk));
46 sk = sk2;
47 }
48 }
49
50 return sk;
51 }
52 EXPORT_SYMBOL_GPL(nf_tproxy_handle_time_wait4);
53
nf_tproxy_laddr4(struct sk_buff * skb,__be32 user_laddr,__be32 daddr)54 __be32 nf_tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
55 {
56 struct in_device *indev;
57 __be32 laddr;
58
59 if (user_laddr)
60 return user_laddr;
61
62 laddr = 0;
63 indev = __in_dev_get_rcu(skb->dev);
64 for_primary_ifa(indev) {
65 laddr = ifa->ifa_local;
66 break;
67 } endfor_ifa(indev);
68
69 return laddr ? laddr : daddr;
70 }
71 EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
72
73 struct sock *
nf_tproxy_get_sock_v4(struct net * net,struct sk_buff * skb,const u8 protocol,const __be32 saddr,const __be32 daddr,const __be16 sport,const __be16 dport,const struct net_device * in,const enum nf_tproxy_lookup_t lookup_type)74 nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb,
75 const u8 protocol,
76 const __be32 saddr, const __be32 daddr,
77 const __be16 sport, const __be16 dport,
78 const struct net_device *in,
79 const enum nf_tproxy_lookup_t lookup_type)
80 {
81 struct sock *sk;
82
83 switch (protocol) {
84 case IPPROTO_TCP: {
85 struct tcphdr _hdr, *hp;
86
87 hp = skb_header_pointer(skb, ip_hdrlen(skb),
88 sizeof(struct tcphdr), &_hdr);
89 if (hp == NULL)
90 return NULL;
91
92 switch (lookup_type) {
93 case NF_TPROXY_LOOKUP_LISTENER:
94 sk = inet_lookup_listener(net, &tcp_hashinfo, skb,
95 ip_hdrlen(skb) +
96 __tcp_hdrlen(hp),
97 saddr, sport,
98 daddr, dport,
99 in->ifindex, 0);
100
101 if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
102 sk = NULL;
103 /* NOTE: we return listeners even if bound to
104 * 0.0.0.0, those are filtered out in
105 * xt_socket, since xt_TPROXY needs 0 bound
106 * listeners too
107 */
108 break;
109 case NF_TPROXY_LOOKUP_ESTABLISHED:
110 sk = inet_lookup_established(net, &tcp_hashinfo,
111 saddr, sport, daddr, dport,
112 in->ifindex);
113 break;
114 default:
115 BUG();
116 }
117 break;
118 }
119 case IPPROTO_UDP:
120 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
121 in->ifindex);
122 if (sk) {
123 int connected = (sk->sk_state == TCP_ESTABLISHED);
124 int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
125
126 /* NOTE: we return listeners even if bound to
127 * 0.0.0.0, those are filtered out in
128 * xt_socket, since xt_TPROXY needs 0 bound
129 * listeners too
130 */
131 if ((lookup_type == NF_TPROXY_LOOKUP_ESTABLISHED &&
132 (!connected || wildcard)) ||
133 (lookup_type == NF_TPROXY_LOOKUP_LISTENER && connected)) {
134 sock_put(sk);
135 sk = NULL;
136 }
137 }
138 break;
139 default:
140 WARN_ON(1);
141 sk = NULL;
142 }
143
144 pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
145 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
146
147 return sk;
148 }
149 EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
150
151 MODULE_LICENSE("GPL");
152 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
153 MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
154
