1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2007-2008 BalaBit IT Ltd.
4 * Author: Krisztian Kovacs
5 */
6
7 #include <net/netfilter/nf_tproxy.h>
8 #include <linux/module.h>
9 #include <linux/skbuff.h>
10 #include <net/sock.h>
11 #include <net/inet_sock.h>
12 #include <linux/ip.h>
13 #include <net/checksum.h>
14 #include <net/udp.h>
15 #include <net/tcp.h>
16 #include <linux/inetdevice.h>
17
18 struct sock *
nf_tproxy_handle_time_wait4(struct net * net,struct sk_buff * skb,__be32 laddr,__be16 lport,struct sock * sk)19 nf_tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
20 __be32 laddr, __be16 lport, struct sock *sk)
21 {
22 const struct iphdr *iph = ip_hdr(skb);
23 struct tcphdr _hdr, *hp;
24
25 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
26 if (hp == NULL) {
27 inet_twsk_put(inet_twsk(sk));
28 return NULL;
29 }
30
31 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
32 /* SYN to a TIME_WAIT socket, we'd rather redirect it
33 * to a listener socket if there's one */
34 struct sock *sk2;
35
36 sk2 = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
37 iph->saddr, laddr ? laddr : iph->daddr,
38 hp->source, lport ? lport : hp->dest,
39 skb->dev, NF_TPROXY_LOOKUP_LISTENER);
40 if (sk2) {
41 nf_tproxy_twsk_deschedule_put(inet_twsk(sk));
42 sk = sk2;
43 }
44 }
45
46 return sk;
47 }
48 EXPORT_SYMBOL_GPL(nf_tproxy_handle_time_wait4);
49
nf_tproxy_laddr4(struct sk_buff * skb,__be32 user_laddr,__be32 daddr)50 __be32 nf_tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
51 {
52 const struct in_ifaddr *ifa;
53 struct in_device *indev;
54 __be32 laddr;
55
56 if (user_laddr)
57 return user_laddr;
58
59 laddr = 0;
60 indev = __in_dev_get_rcu(skb->dev);
61
62 in_dev_for_each_ifa_rcu(ifa, indev) {
63 if (ifa->ifa_flags & IFA_F_SECONDARY)
64 continue;
65
66 laddr = ifa->ifa_local;
67 break;
68 }
69
70 return laddr ? laddr : daddr;
71 }
72 EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
73
74 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)75 nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb,
76 const u8 protocol,
77 const __be32 saddr, const __be32 daddr,
78 const __be16 sport, const __be16 dport,
79 const struct net_device *in,
80 const enum nf_tproxy_lookup_t lookup_type)
81 {
82 struct inet_hashinfo *hinfo = net->ipv4.tcp_death_row.hashinfo;
83 struct sock *sk;
84
85 switch (protocol) {
86 case IPPROTO_TCP: {
87 struct tcphdr _hdr, *hp;
88
89 hp = skb_header_pointer(skb, ip_hdrlen(skb),
90 sizeof(struct tcphdr), &_hdr);
91 if (hp == NULL)
92 return NULL;
93
94 switch (lookup_type) {
95 case NF_TPROXY_LOOKUP_LISTENER:
96 sk = inet_lookup_listener(net, hinfo, skb,
97 ip_hdrlen(skb) + __tcp_hdrlen(hp),
98 saddr, sport, 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, hinfo, saddr, sport,
111 daddr, dport, in->ifindex);
112 break;
113 default:
114 BUG();
115 }
116 break;
117 }
118 case IPPROTO_UDP:
119 sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
120 in->ifindex);
121 if (sk) {
122 int connected = (sk->sk_state == TCP_ESTABLISHED);
123 int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
124
125 /* NOTE: we return listeners even if bound to
126 * 0.0.0.0, those are filtered out in
127 * xt_socket, since xt_TPROXY needs 0 bound
128 * listeners too
129 */
130 if ((lookup_type == NF_TPROXY_LOOKUP_ESTABLISHED &&
131 (!connected || wildcard)) ||
132 (lookup_type == NF_TPROXY_LOOKUP_LISTENER && connected)) {
133 sock_put(sk);
134 sk = NULL;
135 }
136 }
137 break;
138 default:
139 WARN_ON(1);
140 sk = NULL;
141 }
142
143 pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
144 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
145
146 return sk;
147 }
148 EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
149
150 MODULE_LICENSE("GPL");
151 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
152 MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
153
