nf_tproxy_ipv4.c

  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	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, ip_hdrlen(skb),
 91					sizeof(struct tcphdr), &_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						  ip_hdrlen(skb) + __tcp_hdrlen(hp),
 99						  saddr, sport, daddr, dport,
100						  in->ifindex, 0);
101
102			if (sk && !refcount_inc_not_zero(&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, 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}
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");