linux/net/netfilter/nf_nat_irc.c
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   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_conntrack_helper.h>
  21#include <net/netfilter/nf_conntrack_expect.h>
  22#include <linux/netfilter/nf_conntrack_irc.h>
  23
  24MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  25MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  26MODULE_LICENSE("GPL");
  27MODULE_ALIAS("ip_nat_irc");
  28
  29static unsigned int help(struct sk_buff *skb,
  30                         enum ip_conntrack_info ctinfo,
  31                         unsigned int protoff,
  32                         unsigned int matchoff,
  33                         unsigned int matchlen,
  34                         struct nf_conntrack_expect *exp)
  35{
  36        char buffer[sizeof("4294967296 65635")];
  37        u_int16_t port;
  38        unsigned int ret;
  39
  40        /* Reply comes from server. */
  41        exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  42        exp->dir = IP_CT_DIR_REPLY;
  43        exp->expectfn = nf_nat_follow_master;
  44
  45        /* Try to get same port: if not, try to change it. */
  46        for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  47                int ret;
  48
  49                exp->tuple.dst.u.tcp.port = htons(port);
  50                ret = nf_ct_expect_related(exp);
  51                if (ret == 0)
  52                        break;
  53                else if (ret != -EBUSY) {
  54                        port = 0;
  55                        break;
  56                }
  57        }
  58
  59        if (port == 0)
  60                return NF_DROP;
  61
  62        ret = nf_nat_mangle_tcp_packet(skb, exp->master, ctinfo,
  63                                       protoff, matchoff, matchlen, buffer,
  64                                       strlen(buffer));
  65        if (ret != NF_ACCEPT)
  66                nf_ct_unexpect_related(exp);
  67        return ret;
  68}
  69
  70static void __exit nf_nat_irc_fini(void)
  71{
  72        RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
  73        synchronize_rcu();
  74}
  75
  76static int __init nf_nat_irc_init(void)
  77{
  78        BUG_ON(nf_nat_irc_hook != NULL);
  79        RCU_INIT_POINTER(nf_nat_irc_hook, help);
  80        return 0;
  81}
  82
  83/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
  84static int warn_set(const char *val, struct kernel_param *kp)
  85{
  86        printk(KERN_INFO KBUILD_MODNAME
  87               ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
  88        return 0;
  89}
  90module_param_call(ports, warn_set, NULL, NULL, 0);
  91
  92module_init(nf_nat_irc_init);
  93module_exit(nf_nat_irc_fini);
  94
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