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 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 96 static void __exit nf_nat_irc_fini(void) 97 { 98 RCU_INIT_POINTER(nf_nat_irc_hook, NULL); 99 synchronize_rcu(); 100 } 101 102 static 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. */ 110 static 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 } 116 module_param_call(ports, warn_set, NULL, NULL, 0); 117 118 module_init(nf_nat_irc_init); 119 module_exit(nf_nat_irc_fini); 120