net/ipv4/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/ip.h>
  13
  14 #include <linux/netfilter.h>
  15 #include <net/secure_seq.h>
  16 #include <net/netfilter/nf_nat.h>
  17 #include <net/netfilter/nf_nat_core.h>
  18 #include <net/netfilter/nf_nat_rule.h>
  19 #include <net/netfilter/nf_nat_protocol.h>
  20
  21 bool nf_nat_proto_in_range(const struct nf_conntrack_tuple *tuple,
  22                            enum nf_nat_manip_type maniptype,
  23                            const union nf_conntrack_man_proto *min,
  24                            const union nf_conntrack_man_proto *max)
  25 {
  26         __be16 port;
  27
  28         if (maniptype == IP_NAT_MANIP_SRC)
  29                 port = tuple->src.u.all;
  30         else
  31                 port = tuple->dst.u.all;
  32
  33         return ntohs(port) >= ntohs(min->all) &&
  34                ntohs(port) <= ntohs(max->all);
  35 }
  36 EXPORT_SYMBOL_GPL(nf_nat_proto_in_range);
  37
  38 void nf_nat_proto_unique_tuple(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                                u_int16_t *rover)
  43 {
  44         unsigned int range_size, min, i;
  45         __be16 *portptr;
  46         u_int16_t off;
  47
  48         if (maniptype == IP_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 & IP_NAT_RANGE_PROTO_SPECIFIED)) {
  55                 /* If it's dst rewrite, can't change port */
  56                 if (maniptype == IP_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.all);
  74                 range_size = ntohs(range->max.all) - min + 1;
  75         }
  76
  77         if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
  78                 off = secure_ipv4_port_ephemeral(tuple->src.u3.ip, tuple->dst.u3.ip,
  79                                                  maniptype == IP_NAT_MANIP_SRC
  80                                                  ? tuple->dst.u.all
  81                                                  : tuple->src.u.all);
  82         else
  83                 off = *rover;
  84
  85         for (i = 0; ; ++off) {
  86                 *portptr = htons(min + off % range_size);
  87                 if (++i != range_size && nf_nat_used_tuple(tuple, ct))
  88                         continue;
  89                 if (!(range->flags & IP_NAT_RANGE_PROTO_RANDOM))
  90                         *rover = off;
  91                 return;
  92         }
  93         return;
  94 }
  95 EXPORT_SYMBOL_GPL(nf_nat_proto_unique_tuple);
  96
  97 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
  98 int nf_nat_proto_range_to_nlattr(struct sk_buff *skb,
  99                                  const struct nf_nat_range *range)
 100 {
 101         NLA_PUT_BE16(skb, CTA_PROTONAT_PORT_MIN, range->min.all);
 102         NLA_PUT_BE16(skb, CTA_PROTONAT_PORT_MAX, range->max.all);
 103         return 0;
 104
 105 nla_put_failure:
 106         return -1;
 107 }
 108 EXPORT_SYMBOL_GPL(nf_nat_proto_nlattr_to_range);
 109
 110 int nf_nat_proto_nlattr_to_range(struct nlattr *tb[],
 111                                  struct nf_nat_range *range)
 112 {
 113         if (tb[CTA_PROTONAT_PORT_MIN]) {
 114                 range->min.all = nla_get_be16(tb[CTA_PROTONAT_PORT_MIN]);
 115                 range->max.all = range->min.tcp.port;
 116                 range->flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
 117         }
 118         if (tb[CTA_PROTONAT_PORT_MAX]) {
 119                 range->max.all = nla_get_be16(tb[CTA_PROTONAT_PORT_MAX]);
 120                 range->flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
 121         }
 122         return 0;
 123 }
 124 EXPORT_SYMBOL_GPL(nf_nat_proto_range_to_nlattr);
 125 #endif