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 #if 0
  26 #define DEBUGP printk
  27 #else
  28 #define DEBUGP(format, args...)
  29 #endif
  30
  31 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  32 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  33 MODULE_LICENSE("GPL");
  34 MODULE_ALIAS("ip_nat_irc");
  35
  36 static unsigned int help(struct sk_buff **pskb,
  37                          enum ip_conntrack_info ctinfo,
  38                          unsigned int matchoff,
  39                          unsigned int matchlen,
  40                          struct nf_conntrack_expect *exp)
  41 {
  42         char buffer[sizeof("4294967296 65635")];
  43         u_int32_t ip;
  44         u_int16_t port;
  45         unsigned int ret;
  46
  47         DEBUGP("IRC_NAT: info (seq %u + %u) in %u\n",
  48                expect->seq, exp_irc_info->len, ntohl(tcph->seq));
  49
  50         /* Reply comes from server. */
  51         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  52         exp->dir = IP_CT_DIR_REPLY;
  53         exp->expectfn = nf_nat_follow_master;
  54
  55         /* Try to get same port: if not, try to change it. */
  56         for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  57                 exp->tuple.dst.u.tcp.port = htons(port);
  58                 if (nf_conntrack_expect_related(exp) == 0)
  59                         break;
  60         }
  61
  62         if (port == 0)
  63                 return NF_DROP;
  64
  65         ip = ntohl(exp->master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip);
  66         sprintf(buffer, "%u %u", ip, port);
  67         DEBUGP("nf_nat_irc: inserting '%s' == %u.%u.%u.%u, port %u\n",
  68                buffer, NIPQUAD(ip), port);
  69
  70         ret = nf_nat_mangle_tcp_packet(pskb, exp->master, ctinfo,
  71                                        matchoff, matchlen, buffer,
  72                                        strlen(buffer));
  73         if (ret != NF_ACCEPT)
  74                 nf_conntrack_unexpect_related(exp);
  75         return ret;
  76 }
  77
  78 static void __exit nf_nat_irc_fini(void)
  79 {
  80         rcu_assign_pointer(nf_nat_irc_hook, NULL);
  81         synchronize_rcu();
  82 }
  83
  84 static int __init nf_nat_irc_init(void)
  85 {
  86         BUG_ON(rcu_dereference(nf_nat_irc_hook));
  87         rcu_assign_pointer(nf_nat_irc_hook, help);
  88         return 0;
  89 }
  90
  91 /* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
  92 static int warn_set(const char *val, struct kernel_param *kp)
  93 {
  94         printk(KERN_INFO KBUILD_MODNAME
  95                ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
  96         return 0;
  97 }
  98 module_param_call(ports, warn_set, NULL, NULL, 0);
  99
 100 module_init(nf_nat_irc_init);
 101 module_exit(nf_nat_irc_fini);