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
18struct sock *
19nf_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, offset: ip_hdrlen(skb), len: sizeof(_hdr), buffer: &_hdr);
26 if (hp == NULL) {
27 inet_twsk_put(tw: 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, protocol: iph->protocol,
37 saddr: iph->saddr, daddr: laddr ? laddr : iph->daddr,
38 sport: hp->source, dport: lport ? lport : hp->dest,
39 in: skb->dev, lookup_type: NF_TPROXY_LOOKUP_LISTENER);
40 if (sk2) {
41 nf_tproxy_twsk_deschedule_put(tw: inet_twsk(sk));
42 sk = sk2;
43 }
44 }
45
46 return sk;
47}
48EXPORT_SYMBOL_GPL(nf_tproxy_handle_time_wait4);
49
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(dev: skb->dev);
61 if (!indev)
62 return daddr;
63
64 in_dev_for_each_ifa_rcu(ifa, indev) {
65 if (ifa->ifa_flags & IFA_F_SECONDARY)
66 continue;
67
68 laddr = ifa->ifa_local;
69 break;
70 }
71
72 return laddr ? laddr : daddr;
73}
74EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
75
76struct sock *
77nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb,
78 const u8 protocol,
79 const __be32 saddr, const __be32 daddr,
80 const __be16 sport, const __be16 dport,
81 const struct net_device *in,
82 const enum nf_tproxy_lookup_t lookup_type)
83{
84 struct sock *sk;
85
86 switch (protocol) {
87 case IPPROTO_TCP: {
88 struct tcphdr _hdr, *hp;
89
90 hp = skb_header_pointer(skb, offset: ip_hdrlen(skb),
91 len: sizeof(struct tcphdr), buffer: &_hdr);
92 if (hp == NULL)
93 return NULL;
94
95 switch (lookup_type) {
96 case NF_TPROXY_LOOKUP_LISTENER:
97 sk = inet_lookup_listener(net, skb,
98 doff: ip_hdrlen(skb) + __tcp_hdrlen(th: hp),
99 saddr, sport, daddr, dport,
100 dif: in->ifindex, sdif: 0);
101
102 if (sk && !refcount_inc_not_zero(r: &sk->sk_refcnt))
103 sk = NULL;
104 /* NOTE: we return listeners even if bound to
105 * 0.0.0.0, those are filtered out in
106 * xt_socket, since xt_TPROXY needs 0 bound
107 * listeners too
108 */
109 break;
110 case NF_TPROXY_LOOKUP_ESTABLISHED:
111 sk = inet_lookup_established(net, saddr, sport,
112 daddr, dport, dif: 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 dif: 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}
149EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
150
151MODULE_LICENSE("GPL");
152MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
153MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
154

source code of linux/net/ipv4/netfilter/nf_tproxy_ipv4.c