net/ipv4/netfilter/ip_nat_irc.c

   1 /* IRC extension for TCP NAT alteration.
   2  * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
   3  * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
   4  * based on a copy of RR's ip_nat_ftp.c
   5  *
   6  * ip_nat_irc.c,v 1.16 2001/12/06 07:42:10 laforge Exp
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/netfilter_ipv4.h>
  16 #include <linux/ip.h>
  17 #include <linux/tcp.h>
  18 #include <linux/kernel.h>
  19 #include <net/tcp.h>
  20 #include <linux/netfilter_ipv4/ip_nat.h>
  21 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  22 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  23 #include <linux/netfilter_ipv4/ip_conntrack_irc.h>
  24 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  25 #include <linux/moduleparam.h>
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  34 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  35 MODULE_LICENSE("GPL");
  36
  37 static unsigned int help(struct sk_buff **pskb,
  38                          enum ip_conntrack_info ctinfo,
  39                          unsigned int matchoff,
  40                          unsigned int matchlen,
  41                          struct ip_conntrack_expect *exp)
  42 {
  43         u_int16_t port;
  44         unsigned int ret;
  45
  46         /* "4294967296 65635 " */
  47         char buffer[18];
  48
  49         DEBUGP("IRC_NAT: info (seq %u + %u) in %u\n",
  50                expect->seq, exp_irc_info->len,
  51                ntohl(tcph->seq));
  52
  53         /* Reply comes from server. */
  54         exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  55         exp->dir = IP_CT_DIR_REPLY;
  56
  57         /* When you see the packet, we need to NAT it the same as the
  58          * this one. */
  59         exp->expectfn = ip_nat_follow_master;
  60
  61         /* Try to get same port: if not, try to change it. */
  62         for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  63                 exp->tuple.dst.u.tcp.port = htons(port);
  64                 if (ip_conntrack_expect_related(exp) == 0)
  65                         break;
  66         }
  67
  68         if (port == 0) {
  69                 ip_conntrack_expect_free(exp);
  70                 return NF_DROP;
  71         }
  72
  73         /*      strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27
  74          *      strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28
  75          *      strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
  76          *      strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
  77          *      strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
  78          *              AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits,
  79          *                      255.255.255.255==4294967296, 10 digits)
  80          *              P:         bound port (min 1 d, max 5d (65635))
  81          *              F:         filename   (min 1 d )
  82          *              S:         size       (min 1 d )
  83          *              0x01, \n:  terminators
  84          */
  85
  86         /* AAA = "us", ie. where server normally talks to. */
  87         sprintf(buffer, "%u %u",
  88                 ntohl(exp->master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip),
  89                 port);
  90         DEBUGP("ip_nat_irc: Inserting '%s' == %u.%u.%u.%u, port %u\n",
  91                buffer, NIPQUAD(exp->tuple.src.ip), port);
  92
  93         ret = ip_nat_mangle_tcp_packet(pskb, exp->master, ctinfo,
  94                                        matchoff, matchlen, buffer,
  95                                        strlen(buffer));
  96         if (ret != NF_ACCEPT)
  97                 ip_conntrack_unexpect_related(exp);
  98         return ret;
  99 }
 100
 101 static void __exit fini(void)
 102 {
 103         ip_nat_irc_hook = NULL;
 104         /* Make sure noone calls it, meanwhile. */
 105         synchronize_net();
 106 }
 107
 108 static int __init init(void)
 109 {
 110         BUG_ON(ip_nat_irc_hook);
 111         ip_nat_irc_hook = help;
 112         return 0;
 113 }
 114
 115 /* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
 116 static int warn_set(const char *val, struct kernel_param *kp)
 117 {
 118         printk(KERN_INFO __stringify(KBUILD_MODNAME)
 119                ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
 120         return 0;
 121 }
 122 module_param_call(ports, warn_set, NULL, NULL, 0);
 123
 124 module_init(init);
 125 module_exit(fini);