net/netfilter/nf_nat_proto_sctp.c

   1 /*
   2  * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   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/sctp.h>
  11 #include <net/sctp/checksum.h>
  12
  13 #include <net/netfilter/nf_nat_l4proto.h>
  14
  15 static u_int16_t nf_sctp_port_rover;
  16
  17 static void
  18 sctp_unique_tuple(const struct nf_nat_l3proto *l3proto,
  19                   struct nf_conntrack_tuple *tuple,
  20                   const struct nf_nat_range *range,
  21                   enum nf_nat_manip_type maniptype,
  22                   const struct nf_conn *ct)
  23 {
  24         nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
  25                                     &nf_sctp_port_rover);
  26 }
  27
  28 static bool
  29 sctp_manip_pkt(struct sk_buff *skb,
  30                const struct nf_nat_l3proto *l3proto,
  31                unsigned int iphdroff, unsigned int hdroff,
  32                const struct nf_conntrack_tuple *tuple,
  33                enum nf_nat_manip_type maniptype)
  34 {
  35         struct sctphdr *hdr;
  36         int hdrsize = 8;
  37
  38         /* This could be an inner header returned in imcp packet; in such
  39          * cases we cannot update the checksum field since it is outside
  40          * of the 8 bytes of transport layer headers we are guaranteed.
  41          */
  42         if (skb->len >= hdroff + sizeof(*hdr))
  43                 hdrsize = sizeof(*hdr);
  44
  45         if (!skb_make_writable(skb, hdroff + hdrsize))
  46                 return false;
  47
  48         hdr = (struct sctphdr *)(skb->data + hdroff);
  49
  50         if (maniptype == NF_NAT_MANIP_SRC) {
  51                 /* Get rid of src port */
  52                 hdr->source = tuple->src.u.sctp.port;
  53         } else {
  54                 /* Get rid of dst port */
  55                 hdr->dest = tuple->dst.u.sctp.port;
  56         }
  57
  58         if (hdrsize < sizeof(*hdr))
  59                 return true;
  60
  61         if (skb->ip_summed != CHECKSUM_PARTIAL) {
  62                 hdr->checksum = sctp_compute_cksum(skb, hdroff);
  63                 skb->ip_summed = CHECKSUM_NONE;
  64         }
  65
  66         return true;
  67 }
  68
  69 const struct nf_nat_l4proto nf_nat_l4proto_sctp = {
  70         .l4proto                = IPPROTO_SCTP,
  71         .manip_pkt              = sctp_manip_pkt,
  72         .in_range               = nf_nat_l4proto_in_range,
  73         .unique_tuple           = sctp_unique_tuple,
  74 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
  75         .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  76 #endif
  77 };