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); 98