root/net/netfilter/nf_nat_irc.c

DEFINITIONS

1. help
2. nf_nat_irc_fini
3. nf_nat_irc_init
4. warn_set

   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);