1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* IRC extension for TCP NAT alteration. 3 * 4 * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org> 5 * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation 6 * based on a copy of RR's ip_nat_ftp.c 7 */ 8 9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 10 11 #include <linux/module.h> 12 #include <linux/moduleparam.h> 13 #include <linux/tcp.h> 14 #include <linux/kernel.h> 15 16 #include <net/netfilter/nf_nat.h> 17 #include <net/netfilter/nf_nat_helper.h> 18 #include <net/netfilter/nf_conntrack_helper.h> 19 #include <net/netfilter/nf_conntrack_expect.h> 20 #include <linux/netfilter/nf_conntrack_irc.h> 21 22 #define NAT_HELPER_NAME "irc" 23 24 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 25 MODULE_DESCRIPTION("IRC (DCC) NAT helper"); 26 MODULE_LICENSE("GPL"); 27 MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); 28 29 static struct nf_conntrack_nat_helper nat_helper_irc = 30 NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); 31 32 static unsigned int help(struct sk_buff *skb, 33 enum ip_conntrack_info ctinfo, 34 unsigned int protoff, 35 unsigned int matchoff, 36 unsigned int matchlen, 37 struct nf_conntrack_expect *exp) 38 { 39 char buffer[sizeof("4294967296 65635")]; 40 struct nf_conn *ct = exp->master; 41 union nf_inet_addr newaddr; 42 u_int16_t port; 43 44 /* Reply comes from server. */ 45 newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3; 46 47 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; 48 exp->dir = IP_CT_DIR_REPLY; 49 exp->expectfn = nf_nat_follow_master; 50 51 port = nf_nat_exp_find_port(exp, 52 ntohs(exp->saved_proto.tcp.port)); 53 if (port == 0) { 54 nf_ct_helper_log(skb, ct, "all ports in use"); 55 return NF_DROP; 56 } 57 58 /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27 59 * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28 60 * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26 61 * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26 62 * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27 63 * 64 * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits, 65 * 255.255.255.255==4294967296, 10 digits) 66 * P: bound port (min 1 d, max 5d (65635)) 67 * F: filename (min 1 d ) 68 * S: size (min 1 d ) 69 * 0x01, \n: terminators 70 */ 71 /* AAA = "us", ie. where server normally talks to. */ 72 snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port); 73 pr_debug("inserting '%s' == %pI4, port %u\n", 74 buffer, &newaddr.ip, port); 75 76 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, 77 matchlen, buffer, strlen(buffer))) { 78 nf_ct_helper_log(skb, ct, "cannot mangle packet"); 79 nf_ct_unexpect_related(exp); 80 return NF_DROP; 81 } 82 83 return NF_ACCEPT; 84 } 85 86 static void __exit nf_nat_irc_fini(void) 87 { 88 nf_nat_helper_unregister(&nat_helper_irc); 89 RCU_INIT_POINTER(nf_nat_irc_hook, NULL); 90 synchronize_rcu(); 91 } 92 93 static int __init nf_nat_irc_init(void) 94 { 95 BUG_ON(nf_nat_irc_hook != NULL); 96 nf_nat_helper_register(&nat_helper_irc); 97 RCU_INIT_POINTER(nf_nat_irc_hook, help); 98 return 0; 99 } 100 101 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ 102 static int warn_set(const char *val, const struct kernel_param *kp) 103 { 104 pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); 105 return 0; 106 } 107 module_param_call(ports, warn_set, NULL, NULL, 0); 108 109 module_init(nf_nat_irc_init); 110 module_exit(nf_nat_irc_fini); 111