/* IRC extension for TCP NAT alteration. * * (C) 2000-2001 by Harald Welte * (C) 2004 Rusty Russell IBM Corporation * based on a copy of RR's ip_nat_ftp.c * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include #include #include #include #include #include #include #include #include MODULE_AUTHOR("Harald Welte "); MODULE_DESCRIPTION("IRC (DCC) NAT helper"); MODULE_LICENSE("GPL"); MODULE_ALIAS("ip_nat_irc"); static unsigned int help(struct sk_buff *skb, enum ip_conntrack_info ctinfo, unsigned int protoff, unsigned int matchoff, unsigned int matchlen, struct nf_conntrack_expect *exp) { char buffer[sizeof("4294967296 65635")]; struct nf_conn *ct = exp->master; union nf_inet_addr newaddr; u_int16_t port; unsigned int ret; /* Reply comes from server. */ newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3; exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; exp->dir = IP_CT_DIR_REPLY; exp->expectfn = nf_nat_follow_master; /* Try to get same port: if not, try to change it. */ for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { int ret; exp->tuple.dst.u.tcp.port = htons(port); ret = nf_ct_expect_related(exp); if (ret == 0) break; else if (ret != -EBUSY) { port = 0; break; } } if (port == 0) { nf_ct_helper_log(skb, ct, "all ports in use"); return NF_DROP; } /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27 * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28 * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26 * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26 * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27 * * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits, * 255.255.255.255==4294967296, 10 digits) * P: bound port (min 1 d, max 5d (65635)) * F: filename (min 1 d ) * S: size (min 1 d ) * 0x01, \n: terminators */ /* AAA = "us", ie. where server normally talks to. */ snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port); pr_debug("nf_nat_irc: inserting '%s' == %pI4, port %u\n", buffer, &newaddr.ip, port); ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, matchlen, buffer, strlen(buffer)); if (ret != NF_ACCEPT) { nf_ct_helper_log(skb, ct, "cannot mangle packet"); nf_ct_unexpect_related(exp); } return ret; } static void __exit nf_nat_irc_fini(void) { RCU_INIT_POINTER(nf_nat_irc_hook, NULL); synchronize_rcu(); } static int __init nf_nat_irc_init(void) { BUG_ON(nf_nat_irc_hook != NULL); RCU_INIT_POINTER(nf_nat_irc_hook, help); return 0; } /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ static int warn_set(const char *val, struct kernel_param *kp) { printk(KERN_INFO KBUILD_MODNAME ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); return 0; } module_param_call(ports, warn_set, NULL, NULL, 0); module_init(nf_nat_irc_init); module_exit(nf_nat_irc_fini);