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 25MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 26MODULE_DESCRIPTION("IRC (DCC) NAT helper"); 27MODULE_LICENSE("GPL"); 28MODULE_ALIAS("ip_nat_irc"); 29 30static 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 exp->tuple.dst.u.tcp.port = htons(port); 49 if (nf_ct_expect_related(exp) == 0) 50 break; 51 } 52 53 if (port == 0) 54 return NF_DROP; 55 56 ip = ntohl(exp->master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip); 57 sprintf(buffer, "%u %u", ip, port); 58 pr_debug("nf_nat_irc: inserting '%s' == %pI4, port %u\n", 59 buffer, &ip, port); 60 61 ret = nf_nat_mangle_tcp_packet(skb, exp->master, ctinfo, 62 matchoff, matchlen, buffer, 63 strlen(buffer)); 64 if (ret != NF_ACCEPT) 65 nf_ct_unexpect_related(exp); 66 return ret; 67} 68 69static void __exit nf_nat_irc_fini(void) 70{ 71 rcu_assign_pointer(nf_nat_irc_hook, NULL); 72 synchronize_rcu(); 73} 74 75static int __init nf_nat_irc_init(void) 76{ 77 BUG_ON(nf_nat_irc_hook != NULL); 78 rcu_assign_pointer(nf_nat_irc_hook, help); 79 return 0; 80} 81 82/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ 83static int warn_set(const char *val, struct kernel_param *kp) 84{ 85 printk(KERN_INFO KBUILD_MODNAME 86 ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); 87 return 0; 88} 89module_param_call(ports, warn_set, NULL, NULL, 0); 90 91module_init(nf_nat_irc_init); 92module_exit(nf_nat_irc_fini); 93