LXR linux/net/ipv4/netfilter/nf_nat

   1/* IRC extension for TCP NAT alteration.
   2 *
   3 * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
   4 * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
   5 * based on a copy of RR's ip_nat_ftp.c
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License
   9 * as published by the Free Software Foundation; either version
  10 * 2 of the License, or (at your option) any later version.
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/moduleparam.h>
  15#include <linux/tcp.h>
  16#include <linux/kernel.h>
  17
  18#include <net/netfilter/nf_nat.h>
  19#include <net/netfilter/nf_nat_helper.h>
  20#include <net/netfilter/nf_nat_rule.h>
  21#include <net/netfilter/nf_conntrack_helper.h>
  22#include <net/netfilter/nf_conntrack_expect.h>
  23#include <linux/netfilter/nf_conntrack_irc.h>
  24
  25MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  26MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  27MODULE_LICENSE("GPL");
  28MODULE_ALIAS("ip_nat_irc");
  29
  30static unsigned int help(struct sk_buff *skb,
  31                         enum ip_conntrack_info ctinfo,
  32                         unsigned int matchoff,
  33                         unsigned int matchlen,
  34                         struct nf_conntrack_expect *exp)
  35{
  36        char buffer[sizeof("4294967296 65635")];
  37        u_int32_t ip;
  38        u_int16_t port;
  39        unsigned int ret;
  40
  41        /* Reply comes from server. */
  42        exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  43        exp->dir = IP_CT_DIR_REPLY;
  44        exp->expectfn = nf_nat_follow_master;
  45
  46        /* Try to get same port: if not, try to change it. */
  47        for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  48                int ret;
  49
  50                exp->tuple.dst.u.tcp.port = htons(port);
  51                ret = nf_ct_expect_related(exp);
  52                if (ret == 0)
  53                        break;
  54                else if (ret != -EBUSY) {
  55                        port = 0;
  56                        break;
  57                }
  58        }
  59
  60        if (port == 0)
  61                return NF_DROP;
  62
  63        ip = ntohl(exp->master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip);
  64        sprintf(buffer, "%u %u", ip, port);
  65        pr_debug("nf_nat_irc: inserting '%s' == %pI4, port %u\n",
  66                 buffer, &ip, port);
  67
  68        ret = nf_nat_mangle_tcp_packet(skb, exp->master, ctinfo,
  69                                       matchoff, matchlen, buffer,
  70                                       strlen(buffer));
  71        if (ret != NF_ACCEPT)
  72                nf_ct_unexpect_related(exp);
  73        return ret;
  74}
  75
  76static void __exit nf_nat_irc_fini(void)
  77{
  78        RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
  79        synchronize_rcu();
  80}
  81
  82static int __init nf_nat_irc_init(void)
  83{
  84        BUG_ON(nf_nat_irc_hook != NULL);
  85        RCU_INIT_POINTER(nf_nat_irc_hook, help);
  86        return 0;
  87}
  88
  89/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
  90static int warn_set(const char *val, struct kernel_param *kp)
  91{
  92        printk(KERN_INFO KBUILD_MODNAME
  93               ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
  94        return 0;
  95}
  96module_param_call(ports, warn_set, NULL, NULL, 0);
  97
  98module_init(nf_nat_irc_init);
  99module_exit(nf_nat_irc_fini);
 100