net/netfilter/nf_nat_proto_common.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   3  * (C) 2008 Patrick McHardy <kaber@trash.net>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/random.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/export.h>
  14
  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 bool nf_nat_l4proto_in_range(const struct nf_conntrack_tuple *tuple,
  21                              enum nf_nat_manip_type maniptype,
  22                              const union nf_conntrack_man_proto *min,
  23                              const union nf_conntrack_man_proto *max)
  24 {
  25         __be16 port;
  26
  27         if (maniptype == NF_NAT_MANIP_SRC)
  28                 port = tuple->src.u.all;
  29         else
  30                 port = tuple->dst.u.all;
  31
  32         return ntohs(port) >= ntohs(min->all) &&
  33                ntohs(port) <= ntohs(max->all);
  34 }
  35 EXPORT_SYMBOL_GPL(nf_nat_l4proto_in_range);
  36
  37 void nf_nat_l4proto_unique_tuple(const struct nf_nat_l3proto *l3proto,
  38                                  struct nf_conntrack_tuple *tuple,
  39                                  const struct nf_nat_range *range,
  40                                  enum nf_nat_manip_type maniptype,
  41                                  const struct nf_conn *ct,
  42                                  u16 *rover)
  43 {
  44         unsigned int range_size, min, max, i;
  45         __be16 *portptr;
  46         u_int16_t off;
  47
  48         if (maniptype == NF_NAT_MANIP_SRC)
  49                 portptr = &tuple->src.u.all;
  50         else
  51                 portptr = &tuple->dst.u.all;
  52
  53         /* If no range specified... */
  54         if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED)) {
  55                 /* If it's dst rewrite, can't change port */
  56                 if (maniptype == NF_NAT_MANIP_DST)
  57                         return;
  58
  59                 if (ntohs(*portptr) < 1024) {
  60                         /* Loose convention: >> 512 is credential passing */
  61                         if (ntohs(*portptr) < 512) {
  62                                 min = 1;
  63                                 range_size = 511 - min + 1;
  64                         } else {
  65                                 min = 600;
  66                                 range_size = 1023 - min + 1;
  67                         }
  68                 } else {
  69                         min = 1024;
  70                         range_size = 65535 - 1024 + 1;
  71                 }
  72         } else {
  73                 min = ntohs(range->min_proto.all);
  74                 max = ntohs(range->max_proto.all);
  75                 if (unlikely(max < min))
  76                         swap(max, min);
  77                 range_size = max - min + 1;
  78         }
  79
  80         if (range->flags & NF_NAT_RANGE_PROTO_RANDOM) {
  81                 off = l3proto->secure_port(tuple, maniptype == NF_NAT_MANIP_SRC
  82                                                   ? tuple->dst.u.all
  83                                                   : tuple->src.u.all);
  84         } else if (range->flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY) {
  85                 off = prandom_u32();
  86         } else {
  87                 off = *rover;
  88         }
  89
  90         for (i = 0; ; ++off) {
  91                 *portptr = htons(min + off % range_size);
  92                 if (++i != range_size && nf_nat_used_tuple(tuple, ct))
  93                         continue;
  94                 if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM_ALL))
  95                         *rover = off;
  96                 return;
  97         }
  98 }
  99 EXPORT_SYMBOL_GPL(nf_nat_l4proto_unique_tuple);
 100
 101 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 102 int nf_nat_l4proto_nlattr_to_range(struct nlattr *tb[],
 103                                    struct nf_nat_range *range)
 104 {
 105         if (tb[CTA_PROTONAT_PORT_MIN]) {
 106                 range->min_proto.all = nla_get_be16(tb[CTA_PROTONAT_PORT_MIN]);
 107                 range->max_proto.all = range->min_proto.all;
 108                 range->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
 109         }
 110         if (tb[CTA_PROTONAT_PORT_MAX]) {
 111                 range->max_proto.all = nla_get_be16(tb[CTA_PROTONAT_PORT_MAX]);
 112                 range->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
 113         }
 114         return 0;
 115 }
 116 EXPORT_SYMBOL_GPL(nf_nat_l4proto_nlattr_to_range);
 117 #endif