LXR linux/net/netfilter/nf_nat

   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        struct nf_conn *ct = exp->master;
  38        union nf_inet_addr newaddr;
  39        u_int16_t port;
  40        unsigned int ret;
  41
  42        /* Reply comes from server. */
  43        newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
  44
  45        exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  46        exp->dir = IP_CT_DIR_REPLY;
  47        exp->expectfn = nf_nat_follow_master;
  48
  49        /* Try to get same port: if not, try to change it. */
  50        for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  51                int ret;
  52
  53                exp->tuple.dst.u.tcp.port = htons(port);
  54                ret = nf_ct_expect_related(exp);
  55                if (ret == 0)
  56                        break;
  57                else if (ret != -EBUSY) {
  58                        port = 0;
  59                        break;
  60                }
  61        }
  62
  63        if (port == 0) {
  64                nf_ct_helper_log(skb, ct, "all ports in use");
  65                return NF_DROP;
  66        }
  67
  68        /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27
  69         * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28
  70         * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
  71         * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
  72         * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
  73         *
  74         * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits,
  75         *                        255.255.255.255==4294967296, 10 digits)
  76         * P:         bound port (min 1 d, max 5d (65635))
  77         * F:         filename   (min 1 d )
  78         * S:         size       (min 1 d )
  79         * 0x01, \n:  terminators
  80         */
  81        /* AAA = "us", ie. where server normally talks to. */
  82        snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port);
  83        pr_debug("nf_nat_irc: inserting '%s' == %pI4, port %u\n",
  84                 buffer, &newaddr.ip, port);
  85
  86        ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
  87                                       matchlen, buffer, strlen(buffer));
  88        if (ret != NF_ACCEPT) {
  89                nf_ct_helper_log(skb, ct, "cannot mangle packet");
  90                nf_ct_unexpect_related(exp);
  91        }
  92
  93        return ret;
  94}
  95
  96static void __exit nf_nat_irc_fini(void)
  97{
  98        RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
  99        synchronize_rcu();
 100}
 101
 102static int __init nf_nat_irc_init(void)
 103{
 104        BUG_ON(nf_nat_irc_hook != NULL);
 105        RCU_INIT_POINTER(nf_nat_irc_hook, help);
 106        return 0;
 107}
 108
 109/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
 110static int warn_set(const char *val, struct kernel_param *kp)
 111{
 112        printk(KERN_INFO KBUILD_MODNAME
 113               ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
 114        return 0;
 115}
 116module_param_call(ports, warn_set, NULL, NULL, 0);
 117
 118module_init(nf_nat_irc_init);
 119module_exit(nf_nat_irc_fini);
 120