release/src-rt-6.x.4708/linux/linux-2.6.36/net/ipv4/netfilter/nf_nat_proto_udp.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/init.h>
  11 #include <linux/ip.h>
  12 #include <linux/udp.h>
  13
  14 #include <linux/netfilter.h>
  15 #include <net/netfilter/nf_nat.h>
  16 #include <net/netfilter/nf_nat_core.h>
  17 #include <net/netfilter/nf_nat_rule.h>
  18 #include <net/netfilter/nf_nat_protocol.h>
  19
  20 static u_int16_t udp_port_rover;
  21
  22 static void
  23 udp_unique_tuple(struct nf_conntrack_tuple *tuple,
  24                  const struct nf_nat_range *range,
  25                  enum nf_nat_manip_type maniptype,
  26                  const struct nf_conn *ct)
  27 {
  28         nf_nat_proto_unique_tuple(tuple, range, maniptype, ct, &udp_port_rover);
  29 }
  30
  31 static bool
  32 udp_manip_pkt(struct sk_buff *skb,
  33               unsigned int iphdroff,
  34               const struct nf_conntrack_tuple *tuple,
  35               enum nf_nat_manip_type maniptype)
  36 {
  37         const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
  38         struct udphdr *hdr;
  39         unsigned int hdroff = iphdroff + iph->ihl*4;
  40         __be32 oldip, newip;
  41         __be16 *portptr, newport;
  42
  43         if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
  44                 return false;
  45
  46         iph = (struct iphdr *)(skb->data + iphdroff);
  47         hdr = (struct udphdr *)(skb->data + hdroff);
  48
  49         if (maniptype == IP_NAT_MANIP_SRC) {
  50                 /* Get rid of src ip and src pt */
  51                 oldip = iph->saddr;
  52                 newip = tuple->src.u3.ip;
  53                 newport = tuple->src.u.udp.port;
  54                 portptr = &hdr->source;
  55         } else {
  56                 /* Get rid of dst ip and dst pt */
  57                 oldip = iph->daddr;
  58                 newip = tuple->dst.u3.ip;
  59                 newport = tuple->dst.u.udp.port;
  60                 portptr = &hdr->dest;
  61         }
  62         if (hdr->check || skb->ip_summed == CHECKSUM_PARTIAL) {
  63                 inet_proto_csum_replace4(&hdr->check, skb, oldip, newip, 1);
  64                 inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
  65                                          0);
  66                 if (!hdr->check)
  67                         hdr->check = CSUM_MANGLED_0;
  68         }
  69         *portptr = newport;
  70         return true;
  71 }
  72
  73 const struct nf_nat_protocol nf_nat_protocol_udp = {
  74         .protonum               = IPPROTO_UDP,
  75         .me                     = THIS_MODULE,
  76         .manip_pkt              = udp_manip_pkt,
  77         .in_range               = nf_nat_proto_in_range,
  78         .unique_tuple           = udp_unique_tuple,
  79 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  80         .range_to_nlattr        = nf_nat_proto_range_to_nlattr,
  81         .nlattr_to_range        = nf_nat_proto_nlattr_to_range,
  82 #endif
  83 };