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        NF_CT_ASSERT(hooknum == NF_INET_POST_ROUTING);
  38
  39        ct = nf_ct_get(skb, &ctinfo);
  40        nat = nfct_nat(ct);
  41
  42        NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  43                            ctinfo == IP_CT_RELATED_REPLY));
  44
  45        /* Source address is 0.0.0.0 - locally generated packet that is
  46         * probably not supposed to be masqueraded.
  47         */
  48        if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
  49                return NF_ACCEPT;
  50
  51        rt = skb_rtable(skb);
  52        nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
  53        newsrc = inet_select_addr(out, nh, RT_SCOPE_UNIVERSE);
  54        if (!newsrc) {
  55                pr_info("%s ate my IP address\n", out->name);
  56                return NF_DROP;
  57        }
  58
  59        nat->masq_index = out->ifindex;
  60
  61        /* Transfer from original range. */
  62        memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
  63        memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
  64        newrange.flags       = range->flags | NF_NAT_RANGE_MAP_IPS;
  65        newrange.min_addr.ip = newsrc;
  66        newrange.max_addr.ip = newsrc;
  67        newrange.min_proto   = range->min_proto;
  68        newrange.max_proto   = range->max_proto;
  69
  70        /* Hand modified range to generic setup. */
  71        return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
  72}
  73EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);
  74
  75static int device_cmp(struct nf_conn *i, void *ifindex)
  76{
  77        const struct nf_conn_nat *nat = nfct_nat(i);
  78
  79        if (!nat)
  80                return 0;
  81        if (nf_ct_l3num(i) != NFPROTO_IPV4)
  82                return 0;
  83        return nat->masq_index == (int)(long)ifindex;
  84}
  85
  86static int masq_device_event(struct notifier_block *this,
  87                             unsigned long event,
  88                             void *ptr)
  89{
  90        const struct net_device *dev = netdev_notifier_info_to_dev(ptr);
  91        struct net *net = dev_net(dev);
  92
  93        if (event == NETDEV_DOWN) {
  94                /* Device was downed.  Search entire table for
  95                 * conntracks which were associated with that device,
  96                 * and forget them.
  97                 */
  98                NF_CT_ASSERT(dev->ifindex != 0);
  99
 100                nf_ct_iterate_cleanup(net, device_cmp,
 101                                      (void *)(long)dev->ifindex, 0, 0);
 102        }
 103
 104        return NOTIFY_DONE;
 105}
 106
 107static int masq_inet_event(struct notifier_block *this,
 108                           unsigned long event,
 109                           void *ptr)
 110{
 111        struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
 112        struct netdev_notifier_info info;
 113
 114        netdev_notifier_info_init(&info, dev);
 115        return masq_device_event(this, event, &info);
 116}
 117
 118static struct notifier_block masq_dev_notifier = {
 119        .notifier_call  = masq_device_event,
 120};
 121
 122static struct notifier_block masq_inet_notifier = {
 123        .notifier_call  = masq_inet_event,
 124};
 125
 126static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0);
 127
 128void nf_nat_masquerade_ipv4_register_notifier(void)
 129{
 130        /* check if the notifier was already set */
 131        if (atomic_inc_return(&masquerade_notifier_refcount) > 1)
 132                return;
 133
 134        /* Register for device down reports */
 135        register_netdevice_notifier(&masq_dev_notifier);
 136        /* Register IP address change reports */
 137        register_inetaddr_notifier(&masq_inet_notifier);
 138}
 139EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_register_notifier);
 140
 141void nf_nat_masquerade_ipv4_unregister_notifier(void)
 142{
 143        /* check if the notifier still has clients */
 144        if (atomic_dec_return(&masquerade_notifier_refcount) > 0)
 145                return;
 146
 147        unregister_netdevice_notifier(&masq_dev_notifier);
 148        unregister_inetaddr_notifier(&masq_inet_notifier);
 149}
 150EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_unregister_notifier);
 151
 152MODULE_LICENSE("GPL");
 153MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
 154