LXR linux/net/ipv4/netfilter/nf_nat_masquerade

   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/module.h>
  11#include <linux/atomic.h>
  12#include <linux/inetdevice.h>
  13#include <linux/ip.h>
  14#include <linux/timer.h>
  15#include <linux/netfilter.h>
  16#include <net/protocol.h>
  17#include <net/ip.h>
  18#include <net/checksum.h>
  19#include <net/route.h>
  20#include <linux/netfilter_ipv4.h>
  21#include <linux/netfilter/x_tables.h>
  22#include <net/netfilter/nf_nat.h>
  23#include <net/netfilter/ipv4/nf_nat_masquerade.h>
  24
  25unsigned int
  26nf_nat_masquerade_ipv4(struct sk_buff *skb, unsigned int hooknum,
  27                       const struct nf_nat_range *range,
  28                       const struct net_device *out)
  29{
  30        struct nf_conn *ct;
  31        struct nf_conn_nat *nat;
  32        enum ip_conntrack_info ctinfo;
  33        struct nf_nat_range newrange;
  34        const struct rtable *rt;
  35        __be32 newsrc, nh;
  36
  37        WARN_ON(hooknum != NF_INET_POST_ROUTING);
  38
  39        ct = nf_ct_get(skb, &ctinfo);
  40
  41        WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  42                         ctinfo == IP_CT_RELATED_REPLY)));
  43
  44        /* Source address is 0.0.0.0 - locally generated packet that is
  45         * probably not supposed to be masqueraded.
  46         */
  47        if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
  48                return NF_ACCEPT;
  49
  50        rt = skb_rtable(skb);
  51        nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
  52        newsrc = inet_select_addr(out, nh, RT_SCOPE_UNIVERSE);
  53        if (!newsrc) {
  54                pr_info("%s ate my IP address\n", out->name);
  55                return NF_DROP;
  56        }
  57
  58        nat = nf_ct_nat_ext_add(ct);
  59        if (nat)
  60                nat->masq_index = out->ifindex;
  61
  62        /* Transfer from original range. */
  63        memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
  64        memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
  65        newrange.flags       = range->flags | NF_NAT_RANGE_MAP_IPS;
  66        newrange.min_addr.ip = newsrc;
  67        newrange.max_addr.ip = newsrc;
  68        newrange.min_proto   = range->min_proto;
  69        newrange.max_proto   = range->max_proto;
  70
  71        /* Hand modified range to generic setup. */
  72        return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
  73}
  74EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);
  75
  76static int device_cmp(struct nf_conn *i, void *ifindex)
  77{
  78        const struct nf_conn_nat *nat = nfct_nat(i);
  79
  80        if (!nat)
  81                return 0;
  82        if (nf_ct_l3num(i) != NFPROTO_IPV4)
  83                return 0;
  84        return nat->masq_index == (int)(long)ifindex;
  85}
  86
  87static int masq_device_event(struct notifier_block *this,
  88                             unsigned long event,
  89                             void *ptr)
  90{
  91        const struct net_device *dev = netdev_notifier_info_to_dev(ptr);
  92        struct net *net = dev_net(dev);
  93
  94        if (event == NETDEV_DOWN) {
  95                /* Device was downed.  Search entire table for
  96                 * conntracks which were associated with that device,
  97                 * and forget them.
  98                 */
  99                WARN_ON(dev->ifindex == 0);
 100
 101                nf_ct_iterate_cleanup_net(net, device_cmp,
 102                                          (void *)(long)dev->ifindex, 0, 0);
 103        }
 104
 105        return NOTIFY_DONE;
 106}
 107
 108static int masq_inet_event(struct notifier_block *this,
 109                           unsigned long event,
 110                           void *ptr)
 111{
 112        struct in_device *idev = ((struct in_ifaddr *)ptr)->ifa_dev;
 113        struct netdev_notifier_info info;
 114
 115        /* The masq_dev_notifier will catch the case of the device going
 116         * down.  So if the inetdev is dead and being destroyed we have
 117         * no work to do.  Otherwise this is an individual address removal
 118         * and we have to perform the flush.
 119         */
 120        if (idev->dead)
 121                return NOTIFY_DONE;
 122
 123        netdev_notifier_info_init(&info, idev->dev);
 124        return masq_device_event(this, event, &info);
 125}
 126
 127static struct notifier_block masq_dev_notifier = {
 128        .notifier_call  = masq_device_event,
 129};
 130
 131static struct notifier_block masq_inet_notifier = {
 132        .notifier_call  = masq_inet_event,
 133};
 134
 135static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0);
 136
 137void nf_nat_masquerade_ipv4_register_notifier(void)
 138{
 139        /* check if the notifier was already set */
 140        if (atomic_inc_return(&masquerade_notifier_refcount) > 1)
 141                return;
 142
 143        /* Register for device down reports */
 144        register_netdevice_notifier(&masq_dev_notifier);
 145        /* Register IP address change reports */
 146        register_inetaddr_notifier(&masq_inet_notifier);
 147}
 148EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_register_notifier);
 149
 150void nf_nat_masquerade_ipv4_unregister_notifier(void)
 151{
 152        /* check if the notifier still has clients */
 153        if (atomic_dec_return(&masquerade_notifier_refcount) > 0)
 154                return;
 155
 156        unregister_netdevice_notifier(&masq_dev_notifier);
 157        unregister_inetaddr_notifier(&masq_inet_notifier);
 158}
 159EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_unregister_notifier);
 160
 161MODULE_LICENSE("GPL");
 162MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
 163