LXR linux/net/ipv4/netfilter/nf_nat_proto

   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/init.h>
  11#include <linux/random.h>
  12#include <linux/ip.h>
  13#include <linux/udp.h>
  14
  15#include <linux/netfilter.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
  21static int
  22udp_in_range(const struct nf_conntrack_tuple *tuple,
  23             enum nf_nat_manip_type maniptype,
  24             const union nf_conntrack_man_proto *min,
  25             const union nf_conntrack_man_proto *max)
  26{
  27        __be16 port;
  28
  29        if (maniptype == IP_NAT_MANIP_SRC)
  30                port = tuple->src.u.udp.port;
  31        else
  32                port = tuple->dst.u.udp.port;
  33
  34        return ntohs(port) >= ntohs(min->udp.port) &&
  35               ntohs(port) <= ntohs(max->udp.port);
  36}
  37
  38static int
  39udp_unique_tuple(struct nf_conntrack_tuple *tuple,
  40                 const struct nf_nat_range *range,
  41                 enum nf_nat_manip_type maniptype,
  42                 const struct nf_conn *ct)
  43{
  44        static u_int16_t port;
  45        __be16 *portptr;
  46        unsigned int range_size, min, i;
  47
  48        if (maniptype == IP_NAT_MANIP_SRC)
  49                portptr = &tuple->src.u.udp.port;
  50        else
  51                portptr = &tuple->dst.u.udp.port;
  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 0;
  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.udp.port);
  74                range_size = ntohs(range->max.udp.port) - min + 1;
  75        }
  76
  77        if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
  78                port = net_random();
  79
  80        for (i = 0; i < range_size; i++, port++) {
  81                *portptr = htons(min + port % range_size);
  82                if (!nf_nat_used_tuple(tuple, ct))
  83                        return 1;
  84        }
  85        return 0;
  86}
  87
  88static int
  89udp_manip_pkt(struct sk_buff *skb,
  90              unsigned int iphdroff,
  91              const struct nf_conntrack_tuple *tuple,
  92              enum nf_nat_manip_type maniptype)
  93{
  94        struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
  95        struct udphdr *hdr;
  96        unsigned int hdroff = iphdroff + iph->ihl*4;
  97        __be32 oldip, newip;
  98        __be16 *portptr, newport;
  99
 100        if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
 101                return 0;
 102
 103        iph = (struct iphdr *)(skb->data + iphdroff);
 104        hdr = (struct udphdr *)(skb->data + hdroff);
 105
 106        if (maniptype == IP_NAT_MANIP_SRC) {
 107                /* Get rid of src ip and src pt */
 108                oldip = iph->saddr;
 109                newip = tuple->src.u3.ip;
 110                newport = tuple->src.u.udp.port;
 111                portptr = &hdr->source;
 112        } else {
 113                /* Get rid of dst ip and dst pt */
 114                oldip = iph->daddr;
 115                newip = tuple->dst.u3.ip;
 116                newport = tuple->dst.u.udp.port;
 117                portptr = &hdr->dest;
 118        }
 119        if (hdr->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 120                nf_proto_csum_replace4(&hdr->check, skb, oldip, newip, 1);
 121                nf_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
 122                                       0);
 123                if (!hdr->check)
 124                        hdr->check = CSUM_MANGLED_0;
 125        }
 126        *portptr = newport;
 127        return 1;
 128}
 129
 130struct nf_nat_protocol nf_nat_protocol_udp = {
 131        .name                   = "UDP",
 132        .protonum               = IPPROTO_UDP,
 133        .me                     = THIS_MODULE,
 134        .manip_pkt              = udp_manip_pkt,
 135        .in_range               = udp_in_range,
 136        .unique_tuple           = udp_unique_tuple,
 137#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 138        .range_to_nlattr        = nf_nat_port_range_to_nlattr,
 139        .nlattr_to_range        = nf_nat_port_nlattr_to_range,
 140#endif
 141};
 142