net/ipv4/netfilter/nf_nat_irc.c

   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
  25 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  26 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  27 MODULE_LICENSE("GPL");
  28 MODULE_ALIAS("ip_nat_irc");
  29
  30 static 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
  76 static void __exit nf_nat_irc_fini(void)
  77 {
  78         RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
  79         synchronize_rcu();
  80 }
  81
  82 static 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. */
  90 static 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 }
  96 module_param_call(ports, warn_set, NULL, NULL, 0);
  97
  98 module_init(nf_nat_irc_init);
  99 module_exit(nf_nat_irc_fini);