linux/net/netfilter/nf_nat_proto_udp.c
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   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
  20static u16 udp_port_rover;
  21
  22static void
  23udp_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
  33static bool
  34udp_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                                         0);
  61                if (!hdr->check)
  62                        hdr->check = CSUM_MANGLED_0;
  63        }
  64        *portptr = newport;
  65        return true;
  66}
  67
  68const 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 defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  74        .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  75#endif
  76};
  77
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