LXR linux/net/ipv4/netfilter/nf_nat_proto

   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
  20static u_int16_t udp_port_rover;
  21
  22static void
  23udp_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
  31static bool
  32udp_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
  73const 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};
  84