LXR linux/net/ipv4/netfilter/nf_nat

   1/* Amanda extension for TCP NAT alteration.
   2 * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
   3 * based on a copy of HW's ip_nat_irc.c as well as other modules
   4 *
   5 * This program is free software; you can redistribute it and/or
   6 * modify it under the terms of the GNU General Public License
   7 * as published by the Free Software Foundation; either version
   8 * 2 of the License, or (at your option) any later version.
   9 */
  10
  11#include <linux/kernel.h>
  12#include <linux/module.h>
  13#include <linux/skbuff.h>
  14#include <linux/udp.h>
  15
  16#include <net/netfilter/nf_nat_helper.h>
  17#include <net/netfilter/nf_nat_rule.h>
  18#include <net/netfilter/nf_conntrack_helper.h>
  19#include <net/netfilter/nf_conntrack_expect.h>
  20#include <linux/netfilter/nf_conntrack_amanda.h>
  21
  22MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  23MODULE_DESCRIPTION("Amanda NAT helper");
  24MODULE_LICENSE("GPL");
  25MODULE_ALIAS("ip_nat_amanda");
  26
  27static unsigned int help(struct sk_buff *skb,
  28                         enum ip_conntrack_info ctinfo,
  29                         unsigned int matchoff,
  30                         unsigned int matchlen,
  31                         struct nf_conntrack_expect *exp)
  32{
  33        char buffer[sizeof("65535")];
  34        u_int16_t port;
  35        unsigned int ret;
  36
  37        /* Connection comes from client. */
  38        exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  39        exp->dir = IP_CT_DIR_ORIGINAL;
  40
  41        /* When you see the packet, we need to NAT it the same as the
  42         * this one (ie. same IP: it will be TCP and master is UDP). */
  43        exp->expectfn = nf_nat_follow_master;
  44
  45        /* Try to get same port: if not, try to change it. */
  46        for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  47                exp->tuple.dst.u.tcp.port = htons(port);
  48                if (nf_ct_expect_related(exp) == 0)
  49                        break;
  50        }
  51
  52        if (port == 0)
  53                return NF_DROP;
  54
  55        sprintf(buffer, "%u", port);
  56        ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
  57                                       matchoff, matchlen,
  58                                       buffer, strlen(buffer));
  59        if (ret != NF_ACCEPT)
  60                nf_ct_unexpect_related(exp);
  61        return ret;
  62}
  63
  64static void __exit nf_nat_amanda_fini(void)
  65{
  66        rcu_assign_pointer(nf_nat_amanda_hook, NULL);
  67        synchronize_rcu();
  68}
  69
  70static int __init nf_nat_amanda_init(void)
  71{
  72        BUG_ON(nf_nat_amanda_hook != NULL);
  73        rcu_assign_pointer(nf_nat_amanda_hook, help);
  74        return 0;
  75}
  76
  77module_init(nf_nat_amanda_init);
  78module_exit(nf_nat_amanda_fini);
  79