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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 14 15 #include <linux/module.h> 16 #include <linux/moduleparam.h> 17 #include <linux/tcp.h> 18 #include <linux/kernel.h> 19 20 #include <net/netfilter/nf_nat.h> 21 #include <net/netfilter/nf_nat_helper.h> 22 #include <net/netfilter/nf_conntrack_helper.h> 23 #include <net/netfilter/nf_conntrack_expect.h> 24 #include <linux/netfilter/nf_conntrack_irc.h> 25 26 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 27 MODULE_DESCRIPTION("IRC (DCC) NAT helper"); 28 MODULE_LICENSE("GPL"); 29 MODULE_ALIAS("ip_nat_irc"); 30 31 static unsigned int help(struct sk_buff *skb, 32 enum ip_conntrack_info ctinfo, 33 unsigned int protoff, 34 unsigned int matchoff, 35 unsigned int matchlen, 36 struct nf_conntrack_expect *exp) 37 { 38 char buffer[sizeof("4294967296 65635")]; 39 struct nf_conn *ct = exp->master; 40 union nf_inet_addr newaddr; 41 u_int16_t port; 42 43 /* Reply comes from server. */ 44 newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3; 45 46 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; 47 exp->dir = IP_CT_DIR_REPLY; 48 exp->expectfn = nf_nat_follow_master; 49 50 /* Try to get same port: if not, try to change it. */ 51 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { 52 int ret; 53 54 exp->tuple.dst.u.tcp.port = htons(port); 55 ret = nf_ct_expect_related(exp); 56 if (ret == 0) 57 break; 58 else if (ret != -EBUSY) { 59 port = 0; 60 break; 61 } 62 } 63 64 if (port == 0) { 65 nf_ct_helper_log(skb, ct, "all ports in use"); 66 return NF_DROP; 67 } 68 69 /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27 70 * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28 71 * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26 72 * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26 73 * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27 74 * 75 * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits, 76 * 255.255.255.255==4294967296, 10 digits) 77 * P: bound port (min 1 d, max 5d (65635)) 78 * F: filename (min 1 d ) 79 * S: size (min 1 d ) 80 * 0x01, \n: terminators 81 */ 82 /* AAA = "us", ie. where server normally talks to. */ 83 snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port); 84 pr_debug("inserting '%s' == %pI4, port %u\n", 85 buffer, &newaddr.ip, port); 86 87 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, 88 matchlen, buffer, strlen(buffer))) { 89 nf_ct_helper_log(skb, ct, "cannot mangle packet"); 90 nf_ct_unexpect_related(exp); 91 return NF_DROP; 92 } 93 94 return NF_ACCEPT; 95 } 96 97 static void __exit nf_nat_irc_fini(void) 98 { 99 RCU_INIT_POINTER(nf_nat_irc_hook, NULL); 100 synchronize_rcu(); 101 } 102 103 static int __init nf_nat_irc_init(void) 104 { 105 BUG_ON(nf_nat_irc_hook != NULL); 106 RCU_INIT_POINTER(nf_nat_irc_hook, help); 107 return 0; 108 } 109 110 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ 111 static int warn_set(const char *val, const struct kernel_param *kp) 112 { 113 pr_info("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