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// SPDX-License-Identifier: GPL-2.0-only
/*
* Transparent proxy support for Linux/iptables
*
* Copyright (c) 2006-2010 BalaBit IT Ltd.
* Author: Balazs Scheidler, Krisztian Kovacs
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/inet_sock.h>
#include <net/inet_hashtables.h>
#include <linux/inetdevice.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
#define XT_TPROXY_HAVE_IPV6 1
#include <net/if_inet6.h>
#include <net/addrconf.h>
#include <net/inet6_hashtables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
#endif
#include <net/netfilter/nf_tproxy.h>
#include <linux/netfilter/xt_TPROXY.h>
static unsigned int
tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport,
u_int32_t mark_mask, u_int32_t mark_value)
{
const struct iphdr *iph = ip_hdr(skb);
struct udphdr _hdr, *hp;
struct sock *sk;
hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
if (hp == NULL)
return NF_DROP;
/* check if there's an ongoing connection on the packet
* addresses, this happens if the redirect already happened
* and the current packet belongs to an already established
* connection */
sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
iph->saddr, iph->daddr,
hp->source, hp->dest,
skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr);
if (!lport)
lport = hp->dest;
/* UDP has no TCP_TIME_WAIT state, so we never enter here */
if (sk && sk->sk_state == TCP_TIME_WAIT)
/* reopening a TIME_WAIT connection needs special handling */
sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk);
else if (!sk)
/* no, there's no established connection, check if
* there's a listener on the redirected addr/port */
sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol,
iph->saddr, laddr,
hp->source, lport,
skb->dev, NF_TPROXY_LOOKUP_LISTENER);
/* NOTE: assign_sock consumes our sk reference */
if (sk && nf_tproxy_sk_is_transparent(sk)) {
/* This should be in a separate target, but we don't do multiple
targets on the same rule yet */
skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
iph->protocol, &iph->daddr, ntohs(hp->dest),
&laddr, ntohs(lport), skb->mark);
nf_tproxy_assign_sock(skb, sk);
return NF_ACCEPT;
}
pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
iph->protocol, &iph->saddr, ntohs(hp->source),
&iph->daddr, ntohs(hp->dest), skb->mark);
return NF_DROP;
}
static unsigned int
tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct xt_tproxy_target_info *tgi = par->targinfo;
return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport,
tgi->mark_mask, tgi->mark_value);
}
static unsigned int
tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport,
tgi->mark_mask, tgi->mark_value);
}
#ifdef XT_TPROXY_HAVE_IPV6
static unsigned int
tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct ipv6hdr *iph = ipv6_hdr(skb);
const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
struct udphdr _hdr, *hp;
struct sock *sk;
const struct in6_addr *laddr;
__be16 lport;
int thoff = 0;
int tproto;
tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
if (tproto < 0) {
pr_debug("unable to find transport header in IPv6 packet, dropping\n");
return NF_DROP;
}
hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
if (hp == NULL) {
pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
return NF_DROP;
}
/* check if there's an ongoing connection on the packet
* addresses, this happens if the redirect already happened
* and the current packet belongs to an already established
* connection */
sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto,
&iph->saddr, &iph->daddr,
hp->source, hp->dest,
xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED);
laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
lport = tgi->lport ? tgi->lport : hp->dest;
/* UDP has no TCP_TIME_WAIT state, so we never enter here */
if (sk && sk->sk_state == TCP_TIME_WAIT) {
const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
/* reopening a TIME_WAIT connection needs special handling */
sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff,
xt_net(par),
&tgi->laddr.in6,
tgi->lport,
sk);
}
else if (!sk)
/* no there's no established connection, check if
* there's a listener on the redirected addr/port */
sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff,
tproto, &iph->saddr, laddr,
hp->source, lport,
xt_in(par), NF_TPROXY_LOOKUP_LISTENER);
/* NOTE: assign_sock consumes our sk reference */
if (sk && nf_tproxy_sk_is_transparent(sk)) {
/* This should be in a separate target, but we don't do multiple
targets on the same rule yet */
skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
tproto, &iph->saddr, ntohs(hp->source),
laddr, ntohs(lport), skb->mark);
nf_tproxy_assign_sock(skb, sk);
return NF_ACCEPT;
}
pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
tproto, &iph->saddr, ntohs(hp->source),
&iph->daddr, ntohs(hp->dest), skb->mark);
return NF_DROP;
}
static int tproxy_tg6_check(const struct xt_tgchk_param *par)
{
const struct ip6t_ip6 *i = par->entryinfo;
int err;
err = nf_defrag_ipv6_enable(par->net);
if (err)
return err;
if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
!(i->invflags & IP6T_INV_PROTO))
return 0;
pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
return -EINVAL;
}
static void tproxy_tg6_destroy(const struct xt_tgdtor_param *par)
{
nf_defrag_ipv6_disable(par->net);
}
#endif
static int tproxy_tg4_check(const struct xt_tgchk_param *par)
{
const struct ipt_ip *i = par->entryinfo;
int err;
err = nf_defrag_ipv4_enable(par->net);
if (err)
return err;
if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
&& !(i->invflags & IPT_INV_PROTO))
return 0;
pr_info_ratelimited("Can be used only with -p tcp or -p udp\n");
return -EINVAL;
}
static void tproxy_tg4_destroy(const struct xt_tgdtor_param *par)
{
nf_defrag_ipv4_disable(par->net);
}
static struct xt_target tproxy_tg_reg[] __read_mostly = {
{
.name = "TPROXY",
.family = NFPROTO_IPV4,
.table = "mangle",
.target = tproxy_tg4_v0,
.revision = 0,
.targetsize = sizeof(struct xt_tproxy_target_info),
.checkentry = tproxy_tg4_check,
.destroy = tproxy_tg4_destroy,
.hooks = 1 << NF_INET_PRE_ROUTING,
.me = THIS_MODULE,
},
{
.name = "TPROXY",
.family = NFPROTO_IPV4,
.table = "mangle",
.target = tproxy_tg4_v1,
.revision = 1,
.targetsize = sizeof(struct xt_tproxy_target_info_v1),
.checkentry = tproxy_tg4_check,
.destroy = tproxy_tg4_destroy,
.hooks = 1 << NF_INET_PRE_ROUTING,
.me = THIS_MODULE,
},
#ifdef XT_TPROXY_HAVE_IPV6
{
.name = "TPROXY",
.family = NFPROTO_IPV6,
.table = "mangle",
.target = tproxy_tg6_v1,
.revision = 1,
.targetsize = sizeof(struct xt_tproxy_target_info_v1),
.checkentry = tproxy_tg6_check,
.destroy = tproxy_tg6_destroy,
.hooks = 1 << NF_INET_PRE_ROUTING,
.me = THIS_MODULE,
},
#endif
};
static int __init tproxy_tg_init(void)
{
return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
}
static void __exit tproxy_tg_exit(void)
{
xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
}
module_init(tproxy_tg_init);
module_exit(tproxy_tg_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
MODULE_ALIAS("ipt_TPROXY");
MODULE_ALIAS("ip6t_TPROXY");
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