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 /* Try to get same port: if not, try to change it. */ 52 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { 53 int ret; 54 55 exp->tuple.dst.u.tcp.port = htons(port); 56 ret = nf_ct_expect_related(exp, 0); 57 if (ret == 0) 58 break; 59 else if (ret != -EBUSY) { 60 port = 0; 61 break; 62 } 63 } 64 65 if (port == 0) { 66 nf_ct_helper_log(skb, ct, "all ports in use"); 67 return NF_DROP; 68 } 69 70 /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27 71 * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28 72 * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26 73 * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26 74 * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27 75 * 76 * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits, 77 * 255.255.255.255==4294967296, 10 digits) 78 * P: bound port (min 1 d, max 5d (65635)) 79 * F: filename (min 1 d ) 80 * S: size (min 1 d ) 81 * 0x01, \n: terminators 82 */ 83 /* AAA = "us", ie. where server normally talks to. */ 84 snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port); 85 pr_debug("inserting '%s' == %pI4, port %u\n", 86 buffer, &newaddr.ip, port); 87 88 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, 89 matchlen, buffer, strlen(buffer))) { 90 nf_ct_helper_log(skb, ct, "cannot mangle packet"); 91 nf_ct_unexpect_related(exp); 92 return NF_DROP; 93 } 94 95 return NF_ACCEPT; 96 } 97 98 static void __exit nf_nat_irc_fini(void) 99 { 100 nf_nat_helper_unregister(&nat_helper_irc); 101 RCU_INIT_POINTER(nf_nat_irc_hook, NULL); 102 synchronize_rcu(); 103 } 104 105 static int __init nf_nat_irc_init(void) 106 { 107 BUG_ON(nf_nat_irc_hook != NULL); 108 nf_nat_helper_register(&nat_helper_irc); 109 RCU_INIT_POINTER(nf_nat_irc_hook, help); 110 return 0; 111 } 112 113 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ 114 static int warn_set(const char *val, const struct kernel_param *kp) 115 { 116 pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); 117 return 0; 118 } 119 module_param_call(ports, warn_set, NULL, NULL, 0); 120 121 module_init(nf_nat_irc_init); 122 module_exit(nf_nat_irc_fini); 123