// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Transparent proxy support for Linux/iptables
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*
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* Copyright (c) 2006-2010 BalaBit IT Ltd.
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* Author: Balazs Scheidler, Krisztian Kovacs
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/ip.h>
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#include <net/checksum.h>
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#include <net/udp.h>
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#include <net/tcp.h>
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#include <net/inet_sock.h>
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#include <net/inet_hashtables.h>
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#include <linux/inetdevice.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
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#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
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#define XT_TPROXY_HAVE_IPV6 1
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#include <net/if_inet6.h>
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#include <net/addrconf.h>
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#include <net/inet6_hashtables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
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#endif
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#include <net/netfilter/nf_tproxy.h>
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#include <linux/netfilter/xt_TPROXY.h>
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static unsigned int
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tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
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u_int32_t mark_mask, u_int32_t mark_value)
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{
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const struct iphdr *iph = ip_hdr(skb);
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struct udphdr _hdr, *hp;
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struct sock *sk;
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hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
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if (hp == NULL)
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return NF_DROP;
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/* check if there's an ongoing connection on the packet
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* addresses, this happens if the redirect already happened
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* and the current packet belongs to an already established
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* connection */
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sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
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iph->saddr, iph->daddr,
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hp->source, hp->dest,
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skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
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laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr);
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if (!lport)
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lport = hp->dest;
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/* UDP has no TCP_TIME_WAIT state, so we never enter here */
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if (sk && sk->sk_state == TCP_TIME_WAIT)
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/* reopening a TIME_WAIT connection needs special handling */
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sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
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else if (!sk)
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/* no, there's no established connection, check if
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* there's a listener on the redirected addr/port */
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sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
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iph->saddr, laddr,
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hp->source, lport,
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skb->dev, NF_TPROXY_LOOKUP_LISTENER);
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/* NOTE: assign_sock consumes our sk reference */
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if (sk && nf_tproxy_sk_is_transparent(sk)) {
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/* This should be in a separate target, but we don't do multiple
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targets on the same rule yet */
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skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
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pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
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iph->protocol, &iph->daddr, ntohs(hp->dest),
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&laddr, ntohs(lport), skb->mark);
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nf_tproxy_assign_sock(skb, sk);
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return NF_ACCEPT;
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}
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pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
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iph->protocol, &iph->saddr, ntohs(hp->source),
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&iph->daddr, ntohs(hp->dest), skb->mark);
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return NF_DROP;
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}
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static unsigned int
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tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
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{
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const struct xt_tproxy_target_info *tgi = par->targinfo;
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return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
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tgi->mark_mask, tgi->mark_value);
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}
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static unsigned int
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tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
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{
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const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
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return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
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tgi->mark_mask, tgi->mark_value);
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}
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#ifdef XT_TPROXY_HAVE_IPV6
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static unsigned int
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tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
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{
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const struct ipv6hdr *iph = ipv6_hdr(skb);
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const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
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struct udphdr _hdr, *hp;
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struct sock *sk;
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const struct in6_addr *laddr;
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__be16 lport;
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int thoff = 0;
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int tproto;
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tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
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if (tproto < 0) {
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pr_debug("unable to find transport header in IPv6 packet, dropping\n");
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return NF_DROP;
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}
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hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
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if (hp == NULL) {
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pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
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return NF_DROP;
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}
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/* check if there's an ongoing connection on the packet
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* addresses, this happens if the redirect already happened
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* and the current packet belongs to an already established
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* connection */
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sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto,
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&iph->saddr, &iph->daddr,
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hp->source, hp->dest,
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xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED);
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laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
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lport = tgi->lport ? tgi->lport : hp->dest;
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/* UDP has no TCP_TIME_WAIT state, so we never enter here */
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if (sk && sk->sk_state == TCP_TIME_WAIT) {
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const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
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/* reopening a TIME_WAIT connection needs special handling */
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sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff,
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xt_net(par),
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&tgi->laddr.in6,
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tgi->lport,
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sk);
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}
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else if (!sk)
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/* no there's no established connection, check if
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* there's a listener on the redirected addr/port */
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sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff,
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tproto, &iph->saddr, laddr,
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hp->source, lport,
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xt_in(par), NF_TPROXY_LOOKUP_LISTENER);
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/* NOTE: assign_sock consumes our sk reference */
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if (sk && nf_tproxy_sk_is_transparent(sk)) {
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/* This should be in a separate target, but we don't do multiple
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targets on the same rule yet */
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skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
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pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
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tproto, &iph->saddr, ntohs(hp->source),
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laddr, ntohs(lport), skb->mark);
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nf_tproxy_assign_sock(skb, sk);
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return NF_ACCEPT;
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}
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pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
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tproto, &iph->saddr, ntohs(hp->source),
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&iph->daddr, ntohs(hp->dest), skb->mark);
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return NF_DROP;
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}
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static int tproxy_tg6_check(const struct xt_tgchk_param *par)
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{
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const struct ip6t_ip6 *i = par->entryinfo;
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int err;
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err = nf_defrag_ipv6_enable(par->net);
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if (err)
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return err;
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if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
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!(i->invflags & IP6T_INV_PROTO))
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return 0;
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pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
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return -EINVAL;
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}
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#endif
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static int tproxy_tg4_check(const struct xt_tgchk_param *par)
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{
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const struct ipt_ip *i = par->entryinfo;
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int err;
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err = nf_defrag_ipv4_enable(par->net);
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if (err)
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return err;
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if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
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&& !(i->invflags & IPT_INV_PROTO))
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return 0;
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pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
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return -EINVAL;
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}
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static struct xt_target tproxy_tg_reg[] __read_mostly = {
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{
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.name = "TPROXY",
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.family = NFPROTO_IPV4,
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.table = "mangle",
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.target = tproxy_tg4_v0,
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.revision = 0,
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.targetsize = sizeof(struct xt_tproxy_target_info),
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.checkentry = tproxy_tg4_check,
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.hooks = 1 << NF_INET_PRE_ROUTING,
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.me = THIS_MODULE,
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},
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{
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.name = "TPROXY",
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.family = NFPROTO_IPV4,
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.table = "mangle",
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.target = tproxy_tg4_v1,
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.revision = 1,
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.targetsize = sizeof(struct xt_tproxy_target_info_v1),
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.checkentry = tproxy_tg4_check,
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.hooks = 1 << NF_INET_PRE_ROUTING,
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.me = THIS_MODULE,
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},
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#ifdef XT_TPROXY_HAVE_IPV6
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{
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.name = "TPROXY",
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.family = NFPROTO_IPV6,
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.table = "mangle",
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.target = tproxy_tg6_v1,
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.revision = 1,
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.targetsize = sizeof(struct xt_tproxy_target_info_v1),
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.checkentry = tproxy_tg6_check,
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.hooks = 1 << NF_INET_PRE_ROUTING,
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.me = THIS_MODULE,
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},
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#endif
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};
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static int __init tproxy_tg_init(void)
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{
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return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
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}
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static void __exit tproxy_tg_exit(void)
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{
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xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
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}
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module_init(tproxy_tg_init);
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module_exit(tproxy_tg_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
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MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
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MODULE_ALIAS("ipt_TPROXY");
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MODULE_ALIAS("ip6t_TPROXY");
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