net/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/export.h>
  11 #include <linux/init.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_l3proto.h>
  18 #include <net/netfilter/nf_nat_l4proto.h>
  19
  20 static u16 udp_port_rover;
  21
  22 static void
  23 udp_unique_tuple(const struct nf_nat_l3proto *l3proto,
  24                  struct nf_conntrack_tuple *tuple,
  25                  const struct nf_nat_range *range,
  26                  enum nf_nat_manip_type maniptype,
  27                  const struct nf_conn *ct)
  28 {
  29         nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
  30                                     &udp_port_rover);
  31 }
  32
  33 static bool
  34 udp_manip_pkt(struct sk_buff *skb,
  35               const struct nf_nat_l3proto *l3proto,
  36               unsigned int iphdroff, unsigned int hdroff,
  37               const struct nf_conntrack_tuple *tuple,
  38               enum nf_nat_manip_type maniptype)
  39 {
  40         struct udphdr *hdr;
  41         __be16 *portptr, newport;
  42
  43         if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
  44                 return false;
  45         hdr = (struct udphdr *)(skb->data + hdroff);
  46
  47         if (maniptype == NF_NAT_MANIP_SRC) {
  48                 /* Get rid of src port */
  49                 newport = tuple->src.u.udp.port;
  50                 portptr = &hdr->source;
  51         } else {
  52                 /* Get rid of dst port */
  53                 newport = tuple->dst.u.udp.port;
  54                 portptr = &hdr->dest;
  55         }
  56         if (hdr->check || skb->ip_summed == CHECKSUM_PARTIAL) {
  57                 l3proto->csum_update(skb, iphdroff, &hdr->check,
  58                                      tuple, maniptype);
  59                 inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
  60                                          false);
  61                 if (!hdr->check)
  62                         hdr->check = CSUM_MANGLED_0;
  63         }
  64         *portptr = newport;
  65         return true;
  66 }
  67
  68 const struct nf_nat_l4proto nf_nat_l4proto_udp = {
  69         .l4proto                = IPPROTO_UDP,
  70         .manip_pkt              = udp_manip_pkt,
  71         .in_range               = nf_nat_l4proto_in_range,
  72         .unique_tuple           = udp_unique_tuple,
  73 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
  74         .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  75 #endif
  76 };