1 #ifndef _NF_TPROXY_CORE_H
2 #define _NF_TPROXY_CORE_H
3
4 #include <linux/types.h>
5 #include <linux/in.h>
6 #include <linux/skbuff.h>
7 #include <net/sock.h>
8 #include <net/inet_hashtables.h>
9 #include <net/inet6_hashtables.h>
10 #include <net/tcp.h>
11
12 #define NFT_LOOKUP_ANY 0
13 #define NFT_LOOKUP_LISTENER 1
14 #define NFT_LOOKUP_ESTABLISHED 2
15
16 /* look up and get a reference to a matching socket */
17
18
19 /* This function is used by the 'TPROXY' target and the 'socket'
20 * match. The following lookups are supported:
21 *
22 * Explicit TProxy target rule
23 * ===========================
24 *
25 * This is used when the user wants to intercept a connection matching
26 * an explicit iptables rule. In this case the sockets are assumed
27 * matching in preference order:
28 *
29 * - match: if there's a fully established connection matching the
30 * _packet_ tuple, it is returned, assuming the redirection
31 * already took place and we process a packet belonging to an
32 * established connection
33 *
34 * - match: if there's a listening socket matching the redirection
35 * (e.g. on-port & on-ip of the connection), it is returned,
36 * regardless if it was bound to 0.0.0.0 or an explicit
37 * address. The reasoning is that if there's an explicit rule, it
38 * does not really matter if the listener is bound to an interface
39 * or to 0. The user already stated that he wants redirection
40 * (since he added the rule).
41 *
42 * "socket" match based redirection (no specific rule)
43 * ===================================================
44 *
45 * There are connections with dynamic endpoints (e.g. FTP data
46 * connection) that the user is unable to add explicit rules
47 * for. These are taken care of by a generic "socket" rule. It is
48 * assumed that the proxy application is trusted to open such
49 * connections without explicit iptables rule (except of course the
50 * generic 'socket' rule). In this case the following sockets are
51 * matched in preference order:
52 *
53 * - match: if there's a fully established connection matching the
54 * _packet_ tuple
55 *
56 * - match: if there's a non-zero bound listener (possibly with a
57 * non-local address) We don't accept zero-bound listeners, since
58 * then local services could intercept traffic going through the
59 * box.
60 *
61 * Please note that there's an overlap between what a TPROXY target
62 * and a socket match will match. Normally if you have both rules the
63 * "socket" match will be the first one, effectively all packets
64 * belonging to established connections going through that one.
65 */
66 static inline struct sock *
nf_tproxy_get_sock_v4(struct net * net,const u8 protocol,const __be32 saddr,const __be32 daddr,const __be16 sport,const __be16 dport,const struct net_device * in,int lookup_type)67 nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
68 const __be32 saddr, const __be32 daddr,
69 const __be16 sport, const __be16 dport,
70 const struct net_device *in, int lookup_type)
71 {
72 struct sock *sk;
73
74 /* look up socket */
75 switch (protocol) {
76 case IPPROTO_TCP:
77 switch (lookup_type) {
78 case NFT_LOOKUP_ANY:
79 sk = __inet_lookup(net, &tcp_hashinfo,
80 saddr, sport, daddr, dport,
81 in->ifindex);
82 break;
83 case NFT_LOOKUP_LISTENER:
84 sk = inet_lookup_listener(net, &tcp_hashinfo,
85 daddr, dport,
86 in->ifindex);
87
88 /* NOTE: we return listeners even if bound to
89 * 0.0.0.0, those are filtered out in
90 * xt_socket, since xt_TPROXY needs 0 bound
91 * listeners too */
92
93 break;
94 case NFT_LOOKUP_ESTABLISHED:
95 sk = inet_lookup_established(net, &tcp_hashinfo,
96 saddr, sport, daddr, dport,
97 in->ifindex);
98 break;
99 default:
100 WARN_ON(1);
101 sk = NULL;
102 break;
103 }
104 break;
105 case IPPROTO_UDP:
106 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
107 in->ifindex);
108 if (sk && lookup_type != NFT_LOOKUP_ANY) {
109 int connected = (sk->sk_state == TCP_ESTABLISHED);
110 int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
111
112 /* NOTE: we return listeners even if bound to
113 * 0.0.0.0, those are filtered out in
114 * xt_socket, since xt_TPROXY needs 0 bound
115 * listeners too */
116 if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
117 (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
118 sock_put(sk);
119 sk = NULL;
120 }
121 }
122 break;
123 default:
124 WARN_ON(1);
125 sk = NULL;
126 }
127
128 pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
129 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
130
131 return sk;
132 }
133
134 #if IS_ENABLED(CONFIG_IPV6)
135 static inline struct sock *
nf_tproxy_get_sock_v6(struct net * net,const u8 protocol,const struct in6_addr * saddr,const struct in6_addr * daddr,const __be16 sport,const __be16 dport,const struct net_device * in,int lookup_type)136 nf_tproxy_get_sock_v6(struct net *net, const u8 protocol,
137 const struct in6_addr *saddr, const struct in6_addr *daddr,
138 const __be16 sport, const __be16 dport,
139 const struct net_device *in, int lookup_type)
140 {
141 struct sock *sk;
142
143 /* look up socket */
144 switch (protocol) {
145 case IPPROTO_TCP:
146 switch (lookup_type) {
147 case NFT_LOOKUP_ANY:
148 sk = inet6_lookup(net, &tcp_hashinfo,
149 saddr, sport, daddr, dport,
150 in->ifindex);
151 break;
152 case NFT_LOOKUP_LISTENER:
153 sk = inet6_lookup_listener(net, &tcp_hashinfo,
154 daddr, ntohs(dport),
155 in->ifindex);
156
157 /* NOTE: we return listeners even if bound to
158 * 0.0.0.0, those are filtered out in
159 * xt_socket, since xt_TPROXY needs 0 bound
160 * listeners too */
161
162 break;
163 case NFT_LOOKUP_ESTABLISHED:
164 sk = __inet6_lookup_established(net, &tcp_hashinfo,
165 saddr, sport, daddr, ntohs(dport),
166 in->ifindex);
167 break;
168 default:
169 WARN_ON(1);
170 sk = NULL;
171 break;
172 }
173 break;
174 case IPPROTO_UDP:
175 sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
176 in->ifindex);
177 if (sk && lookup_type != NFT_LOOKUP_ANY) {
178 int connected = (sk->sk_state == TCP_ESTABLISHED);
179 int wildcard = ipv6_addr_any(&inet6_sk(sk)->rcv_saddr);
180
181 /* NOTE: we return listeners even if bound to
182 * 0.0.0.0, those are filtered out in
183 * xt_socket, since xt_TPROXY needs 0 bound
184 * listeners too */
185 if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
186 (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
187 sock_put(sk);
188 sk = NULL;
189 }
190 }
191 break;
192 default:
193 WARN_ON(1);
194 sk = NULL;
195 }
196
197 pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
198 protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);
199
200 return sk;
201 }
202 #endif
203
204 /* assign a socket to the skb -- consumes sk */
205 void
206 nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk);
207
208 #endif
209