| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* IRC extension for TCP NAT alteration. |
| * |
| * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org> |
| * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation |
| * based on a copy of RR's ip_nat_ftp.c |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/module.h> |
| #include <linux/moduleparam.h> |
| #include <linux/tcp.h> |
| #include <linux/kernel.h> |
| |
| #include <net/netfilter/nf_nat.h> |
| #include <net/netfilter/nf_nat_helper.h> |
| #include <net/netfilter/nf_conntrack_helper.h> |
| #include <net/netfilter/nf_conntrack_expect.h> |
| #include <linux/netfilter/nf_conntrack_irc.h> |
| |
| #define NAT_HELPER_NAME "irc" |
| |
| MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); |
| MODULE_DESCRIPTION("IRC (DCC) NAT helper"); |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); |
| |
| static struct nf_conntrack_nat_helper nat_helper_irc = |
| NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); |
| |
| 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; |
| |
| /* 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, 0); |
| 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("inserting '%s' == %pI4, port %u\n", |
| buffer, &newaddr.ip, port); |
| |
| if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, |
| matchlen, buffer, strlen(buffer))) { |
| nf_ct_helper_log(skb, ct, "cannot mangle packet"); |
| nf_ct_unexpect_related(exp); |
| return NF_DROP; |
| } |
| |
| return NF_ACCEPT; |
| } |
| |
| static void __exit nf_nat_irc_fini(void) |
| { |
| nf_nat_helper_unregister(&nat_helper_irc); |
| 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); |
| nf_nat_helper_register(&nat_helper_irc); |
| 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, const struct kernel_param *kp) |
| { |
| pr_info("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); |