net/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_conntrack_helper.h>
  21 #include <net/netfilter/nf_conntrack_expect.h>
  22 #include <linux/netfilter/nf_conntrack_irc.h>
  23
  24 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  25 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  26 MODULE_LICENSE("GPL");
  27 MODULE_ALIAS("ip_nat_irc");
  28
  29 static 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                 nf_ct_helper_log(skb, exp->master, "all ports in use");
  61                 return NF_DROP;
  62         }
  63
  64         ret = nf_nat_mangle_tcp_packet(skb, exp->master, ctinfo,
  65                                        protoff, matchoff, matchlen, buffer,
  66                                        strlen(buffer));
  67         if (ret != NF_ACCEPT) {
  68                 nf_ct_helper_log(skb, exp->master, "cannot mangle packet");
  69                 nf_ct_unexpect_related(exp);
  70         }
  71         return ret;
  72 }
  73
  74 static void __exit nf_nat_irc_fini(void)
  75 {
  76         RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
  77         synchronize_rcu();
  78 }
  79
  80 static int __init nf_nat_irc_init(void)
  81 {
  82         BUG_ON(nf_nat_irc_hook != NULL);
  83         RCU_INIT_POINTER(nf_nat_irc_hook, help);
  84         return 0;
  85 }
  86
  87 /* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
  88 static int warn_set(const char *val, struct kernel_param *kp)
  89 {
  90         printk(KERN_INFO KBUILD_MODNAME
  91                ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
  92         return 0;
  93 }
  94 module_param_call(ports, warn_set, NULL, NULL, 0);
  95
  96 module_init(nf_nat_irc_init);
  97 module_exit(nf_nat_irc_fini);