- 根目录:
- net
- netfilter
- xt_TPROXY.c
/*
* Transparent proxy support for Linux/iptables
*
* Copyright (c) 2006-2010 BalaBit IT Ltd.
* Author: Balazs Scheidler, Krisztian Kovacs
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#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 <linux/netfilter/xt_TPROXY.h>
enum nf_tproxy_lookup_t {
NFT_LOOKUP_LISTENER,
NFT_LOOKUP_ESTABLISHED,
};
static bool tproxy_sk_is_transparent(struct sock *sk)
{
if (sk->sk_state != TCP_TIME_WAIT) {
if (inet_sk(sk)->transparent)
return true;
sock_put(sk);
} else {
if (inet_twsk(sk)->tw_transparent)
return true;
inet_twsk_put(inet_twsk(sk));
}
return false;
}
static inline __be32
tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
{
struct in_device *indev;
__be32 laddr;
if (user_laddr)
return user_laddr;
laddr = 0;
rcu_read_lock();
indev = __in_dev_get_rcu(skb->dev);
for_primary_ifa(indev) {
laddr = ifa->ifa_local;
break;
} endfor_ifa(indev);
rcu_read_unlock();
return laddr ? laddr : daddr;
}
/*
* This is used when the user wants to intercept a connection matching
* an explicit iptables rule. In this case the sockets are assumed
* matching in preference order:
*
* - match: if there's a fully established connection matching the
* _packet_ tuple, it is returned, assuming the redirection
* already took place and we process a packet belonging to an
* established connection
*
* - match: if there's a listening socket matching the redirection
* (e.g. on-port & on-ip of the connection), it is returned,
* regardless if it was bound to 0.0.0.0 or an explicit
* address. The reasoning is that if there's an explicit rule, it
* does not really matter if the listener is bound to an interface
* or to 0. The user already stated that he wants redirection
* (since he added the rule).
*
* Please note that there's an overlap between what a TPROXY target
* and a socket match will match. Normally if you have both rules the
* "socket" match will be the first one, effectively all packets
* belonging to established connections going through that one.
*/
static inline struct sock *
nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
const __be32 saddr, const __be32 daddr,
const __be16 sport, const __be16 dport,
const struct net_device *in,
const enum nf_tproxy_lookup_t lookup_type)
{
struct sock *sk;
switch (protocol) {
case IPPROTO_TCP:
switch (lookup_type) {
case NFT_LOOKUP_LISTENER:
sk = inet_lookup_listener(net, &tcp_hashinfo,
saddr, sport,
daddr, dport,
in->ifindex);
/* NOTE: we return listeners even if bound to
* 0.0.0.0, those are filtered out in
* xt_socket, since xt_TPROXY needs 0 bound
* listeners too
*/
break;
case NFT_LOOKUP_ESTABLISHED:
sk = inet_lookup_established(net, &tcp_hashinfo,
saddr, sport, daddr, dport,
in->ifindex);
break;
default:
BUG();
}
break;
case IPPROTO_UDP:
sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
in->ifindex);
if (sk) {
int connected = (sk->sk_state == TCP_ESTABLISHED);
int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
/* NOTE: we return listeners even if bound to
* 0.0.0.0, those are filtered out in
* xt_socket, since xt_TPROXY needs 0 bound
* listeners too
*/
if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
(lookup_type == NFT_LOOKUP_LISTENER && connected)) {
sock_put(sk);
sk = NULL;
}
}
break;
default:
WARN_ON(1);
sk = NULL;
}
pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
return sk;
}
#ifdef XT_TPROXY_HAVE_IPV6
static inline struct sock *
nf_tproxy_get_sock_v6(struct net *net, const u8 protocol,
const struct in6_addr *saddr, const struct in6_addr *daddr,
const __be16 sport, const __be16 dport,
const struct net_device *in,
const enum nf_tproxy_lookup_t lookup_type)
{
struct sock *sk;
switch (protocol) {
case IPPROTO_TCP:
switch (lookup_type) {
case NFT_LOOKUP_LISTENER:
sk = inet6_lookup_listener(net, &tcp_hashinfo,
saddr, sport,
daddr, ntohs(dport),
in->ifindex);
/* NOTE: we return listeners even if bound to
* 0.0.0.0, those are filtered out in
* xt_socket, since xt_TPROXY needs 0 bound
* listeners too
*/
break;
case NFT_LOOKUP_ESTABLISHED:
sk = __inet6_lookup_established(net, &tcp_hashinfo,
saddr, sport, daddr, ntohs(dport),
in->ifindex);
break;
default:
BUG();
}
break;
case IPPROTO_UDP:
sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
in->ifindex);
if (sk) {
int connected = (sk->sk_state == TCP_ESTABLISHED);
int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr);
/* NOTE: we return listeners even if bound to
* 0.0.0.0, those are filtered out in
* xt_socket, since xt_TPROXY needs 0 bound
* listeners too
*/
if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
(lookup_type == NFT_LOOKUP_LISTENER && connected)) {
sock_put(sk);
sk = NULL;
}
}
break;
default:
WARN_ON(1);
sk = NULL;
}
pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);
return sk;
}
#endif
/**
* tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections
* @skb: The skb being processed.
* @laddr: IPv4 address to redirect to or zero.
* @lport: TCP port to redirect to or zero.
* @sk: The TIME_WAIT TCP socket found by the lookup.
*
* We have to handle SYN packets arriving to TIME_WAIT sockets
* differently: instead of reopening the connection we should rather
* redirect the new connection to the proxy if there's a listener
* socket present.
*
* tproxy_handle_time_wait4() consumes the socket reference passed in.
*
* Returns the listener socket if there's one, the TIME_WAIT socket if
* no such listener is found, or NULL if the TCP header is incomplete.
*/
static struct sock *
tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport,
struct sock *sk)
{
const struct iphdr *iph = ip_hdr(skb);
struct tcphdr _hdr, *hp;
hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
if (hp == NULL) {
inet_twsk_put(inet_twsk(sk));
return NULL;
}
if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
/* SYN to a TIME_WAIT socket, we'd rather redirect it
* to a listener socket if there's one */
struct sock *sk2;
sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
iph->saddr, laddr ? laddr : iph->daddr,
hp->source, lport ? lport : hp->dest,
skb->dev, NFT_LOOKUP_LISTENER);
if (sk2) {
inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row);
inet_twsk_put(inet_twsk(sk));
sk = sk2;
}
}
return sk;
}
/* assign a socket to the skb -- consumes sk */
static void
nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
{
skb_orphan(skb);
skb->sk = sk;
skb->destructor = sock_edemux;
}
static unsigned int
tproxy_tg4(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(dev_net(skb->dev), iph->protocol,
iph->saddr, iph->daddr,
hp->source, hp->dest,
skb->dev, NFT_LOOKUP_ESTABLISHED);
laddr = 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 = tproxy_handle_time_wait4(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(dev_net(skb->dev), iph->protocol,
iph->saddr, laddr,
hp->source, lport,
skb->dev, NFT_LOOKUP_LISTENER);
/* NOTE: assign_sock consumes our sk reference */
if (sk && 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(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(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value);
}
#ifdef XT_TPROXY_HAVE_IPV6
static inline const struct in6_addr *
tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
const struct in6_addr *daddr)
{
struct inet6_dev *indev;
struct inet6_ifaddr *ifa;
struct in6_addr *laddr;
if (!ipv6_addr_any(user_laddr))
return user_laddr;
laddr = NULL;
rcu_read_lock();
indev = __in6_dev_get(skb->dev);
if (indev)
list_for_each_entry(ifa, &indev->addr_list, if_list) {
if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
continue;
laddr = &ifa->addr;
break;
}
rcu_read_unlock();
return laddr ? laddr : daddr;
}
/**
* tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections
* @skb: The skb being processed.
* @tproto: Transport protocol.
* @thoff: Transport protocol header offset.
* @par: Iptables target parameters.
* @sk: The TIME_WAIT TCP socket found by the lookup.
*
* We have to handle SYN packets arriving to TIME_WAIT sockets
* differently: instead of reopening the connection we should rather
* redirect the new connection to the proxy if there's a listener
* socket present.
*
* tproxy_handle_time_wait6() consumes the socket reference passed in.
*
* Returns the listener socket if there's one, the TIME_WAIT socket if
* no such listener is found, or NULL if the TCP header is incomplete.
*/
static struct sock *
tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
const struct xt_action_param *par,
struct sock *sk)
{
const struct ipv6hdr *iph = ipv6_hdr(skb);
struct tcphdr _hdr, *hp;
const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
if (hp == NULL) {
inet_twsk_put(inet_twsk(sk));
return NULL;
}
if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
/* SYN to a TIME_WAIT socket, we'd rather redirect it
* to a listener socket if there's one */
struct sock *sk2;
sk2 = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
&iph->saddr,
tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr),
hp->source,
tgi->lport ? tgi->lport : hp->dest,
skb->dev, NFT_LOOKUP_LISTENER);
if (sk2) {
inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row);
inet_twsk_put(inet_twsk(sk));
sk = sk2;
}
}
return sk;
}
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(dev_net(skb->dev), tproto,
&iph->saddr, &iph->daddr,
hp->source, hp->dest,
par->in, NFT_LOOKUP_ESTABLISHED);
laddr = 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)
/* reopening a TIME_WAIT connection needs special handling */
sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, 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(dev_net(skb->dev), tproto,
&iph->saddr, laddr,
hp->source, lport,
par->in, NFT_LOOKUP_LISTENER);
/* NOTE: assign_sock consumes our sk reference */
if (sk && 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;
if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
&& !(i->flags & IP6T_INV_PROTO))
return 0;
pr_info("Can be used only in combination with "
"either -p tcp or -p udp\n");
return -EINVAL;
}
#endif
static int tproxy_tg4_check(const struct xt_tgchk_param *par)
{
const struct ipt_ip *i = par->entryinfo;
if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
&& !(i->invflags & IPT_INV_PROTO))
return 0;
pr_info("Can be used only in combination with "
"either -p tcp or -p udp\n");
return -EINVAL;
}
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,
.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,
.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,
.hooks = 1 << NF_INET_PRE_ROUTING,
.me = THIS_MODULE,
},
#endif
};
static int __init tproxy_tg_init(void)
{
nf_defrag_ipv4_enable();
#ifdef XT_TPROXY_HAVE_IPV6
nf_defrag_ipv6_enable();
#endif
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");