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, 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}
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(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}
72EXPORT_SYMBOL_GPL(nf_tproxy_laddr4);
73
74struct sock *
75nf_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}
148EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v4);
149
150MODULE_LICENSE("GPL");
151MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
152MODULE_DESCRIPTION("Netfilter IPv4 transparent proxy support");
153