LXR linux/net/netfilter/xt

   1/*
   2 * Transparent proxy support for Linux/iptables
   3 *
   4 * Copyright (c) 2006-2007 BalaBit IT Ltd.
   5 * Author: Balazs Scheidler, Krisztian Kovacs
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/skbuff.h>
  15#include <linux/ip.h>
  16#include <net/checksum.h>
  17#include <net/udp.h>
  18#include <net/inet_sock.h>
  19
  20#include <linux/netfilter/x_tables.h>
  21#include <linux/netfilter_ipv4/ip_tables.h>
  22#include <linux/netfilter/xt_TPROXY.h>
  23
  24#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  25#include <net/netfilter/nf_tproxy_core.h>
  26
  27static unsigned int
  28tproxy_tg(struct sk_buff *skb, const struct xt_target_param *par)
  29{
  30        const struct iphdr *iph = ip_hdr(skb);
  31        const struct xt_tproxy_target_info *tgi = par->targinfo;
  32        struct udphdr _hdr, *hp;
  33        struct sock *sk;
  34
  35        hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
  36        if (hp == NULL)
  37                return NF_DROP;
  38
  39        sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
  40                                   iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
  41                                   hp->source, tgi->lport ? tgi->lport : hp->dest,
  42                                   par->in, true);
  43
  44        /* NOTE: assign_sock consumes our sk reference */
  45        if (sk && nf_tproxy_assign_sock(skb, sk)) {
  46                /* This should be in a separate target, but we don't do multiple
  47                   targets on the same rule yet */
  48                skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
  49
  50                pr_debug("redirecting: proto %u %08x:%u -> %08x:%u, mark: %x\n",
  51                         iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
  52                         ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
  53                return NF_ACCEPT;
  54        }
  55
  56        pr_debug("no socket, dropping: proto %u %08x:%u -> %08x:%u, mark: %x\n",
  57                 iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),
  58                 ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);
  59        return NF_DROP;
  60}
  61
  62static bool tproxy_tg_check(const struct xt_tgchk_param *par)
  63{
  64        const struct ipt_ip *i = par->entryinfo;
  65
  66        if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
  67            && !(i->invflags & IPT_INV_PROTO))
  68                return true;
  69
  70        pr_info("xt_TPROXY: Can be used only in combination with "
  71                "either -p tcp or -p udp\n");
  72        return false;
  73}
  74
  75static struct xt_target tproxy_tg_reg __read_mostly = {
  76        .name           = "TPROXY",
  77        .family         = AF_INET,
  78        .table          = "mangle",
  79        .target         = tproxy_tg,
  80        .targetsize     = sizeof(struct xt_tproxy_target_info),
  81        .checkentry     = tproxy_tg_check,
  82        .hooks          = 1 << NF_INET_PRE_ROUTING,
  83        .me             = THIS_MODULE,
  84};
  85
  86static int __init tproxy_tg_init(void)
  87{
  88        nf_defrag_ipv4_enable();
  89        return xt_register_target(&tproxy_tg_reg);
  90}
  91
  92static void __exit tproxy_tg_exit(void)
  93{
  94        xt_unregister_target(&tproxy_tg_reg);
  95}
  96
  97module_init(tproxy_tg_init);
  98module_exit(tproxy_tg_exit);
  99MODULE_LICENSE("GPL");
 100MODULE_AUTHOR("Krisztian Kovacs");
 101MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
 102MODULE_ALIAS("ipt_TPROXY");
 103