root/net/netfilter/xt_TPROXY.c

DEFINITIONS

1. tproxy_tg
2. tproxy_tg_check
3. tproxy_tg_init
4. tproxy_tg_exit

/*
 * Transparent proxy support for Linux/iptables
 *
 * Copyright (c) 2006-2007 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.
 *
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <net/inet_sock.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter/xt_TPROXY.h>

#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
#include <net/netfilter/nf_tproxy_core.h>

static unsigned int
tproxy_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        const struct iphdr *iph = ip_hdr(skb);
        const struct xt_tproxy_target_info *tgi = par->targinfo;
        struct udphdr _hdr, *hp;
        struct sock *sk;

        hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
        if (hp == NULL)
                return NF_DROP;

        sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
                                   iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
                                   hp->source, tgi->lport ? tgi->lport : hp->dest,
                                   par->in, true);

        /* NOTE: assign_sock consumes our sk reference */
        if (sk && nf_tproxy_assign_sock(skb, 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 %u %08x:%u -> %08x:%u, mark: %x\n",
                         iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
                         ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
                return NF_ACCEPT;
        }

        pr_debug("no socket, dropping: proto %u %08x:%u -> %08x:%u, mark: %x\n",
                 iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
                 ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
        return NF_DROP;
}

static bool tproxy_tg_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 true;

        pr_info("xt_TPROXY: Can be used only in combination with "
                "either -p tcp or -p udp\n");
        return false;
}

static struct xt_target tproxy_tg_reg __read_mostly = {
        .name           = "TPROXY",
        .family         = AF_INET,
        .table          = "mangle",
        .target         = tproxy_tg,
        .targetsize     = sizeof(struct xt_tproxy_target_info),
        .checkentry     = tproxy_tg_check,
        .hooks          = 1 << NF_INET_PRE_ROUTING,
        .me             = THIS_MODULE,
};

static int __init tproxy_tg_init(void)
{
        nf_defrag_ipv4_enable();
        return xt_register_target(&tproxy_tg_reg);
}

static void __exit tproxy_tg_exit(void)
{
        xt_unregister_target(&tproxy_tg_reg);
}

module_init(tproxy_tg_init);
module_exit(tproxy_tg_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Krisztian Kovacs");
MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
MODULE_ALIAS("ipt_TPROXY");