![KOVACS Krisztian](/assets/img/avatar_default.png)
The TPROXY target implements redirection of non-local TCP/UDP traffic to local sockets. Additionally, it's possible to manipulate the packet mark if and only if a socket has been found. (We need this because we cannot use multiple targets in the same iptables rule.) Signed-off-by: KOVACS Krisztian <hidden@sch.bme.hu> Signed-off-by: Patrick McHardy <kaber@trash.net>
113 lines
3 KiB
C
113 lines
3 KiB
C
/*
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* Transparent proxy support for Linux/iptables
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*
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* Copyright (c) 2006-2007 BalaBit IT Ltd.
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* Author: Balazs Scheidler, Krisztian Kovacs
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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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/inet_sock.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 <linux/netfilter/xt_TPROXY.h>
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#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
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#include <net/netfilter/nf_tproxy_core.h>
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static unsigned int
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tproxy_tg(struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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unsigned int hooknum,
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const struct xt_target *target,
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const void *targinfo)
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{
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const struct iphdr *iph = ip_hdr(skb);
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const struct xt_tproxy_target_info *tgi = targinfo;
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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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sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
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iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
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hp->source, tgi->lport ? tgi->lport : hp->dest,
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in, true);
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/* NOTE: assign_sock consumes our sk reference */
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if (sk && nf_tproxy_assign_sock(skb, 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 %u %08x:%u -> %08x:%u, mark: %x\n",
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iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
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ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
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return NF_ACCEPT;
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}
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pr_debug("no socket, dropping: proto %u %08x:%u -> %08x:%u, mark: %x\n",
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iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
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ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
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return NF_DROP;
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}
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static bool
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tproxy_tg_check(const char *tablename,
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const void *entry,
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const struct xt_target *target,
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void *targetinfo,
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unsigned int hook_mask)
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{
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const struct ipt_ip *i = entry;
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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 true;
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pr_info("xt_TPROXY: Can be used only in combination with "
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"either -p tcp or -p udp\n");
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return false;
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}
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static struct xt_target tproxy_tg_reg __read_mostly = {
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.name = "TPROXY",
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.family = AF_INET,
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.table = "mangle",
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.target = tproxy_tg,
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.targetsize = sizeof(struct xt_tproxy_target_info),
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.checkentry = tproxy_tg_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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static int __init tproxy_tg_init(void)
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{
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nf_defrag_ipv4_enable();
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return xt_register_target(&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_target(&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("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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