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Linux/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c

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  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 
 25 unsigned int
 26 nf_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 }
 74 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);
 75 
 76 static 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 
 87 static 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 
108 static 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 
127 static struct notifier_block masq_dev_notifier = {
128         .notifier_call  = masq_device_event,
129 };
130 
131 static struct notifier_block masq_inet_notifier = {
132         .notifier_call  = masq_inet_event,
133 };
134 
135 static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0);
136 
137 void 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 }
148 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_register_notifier);
149 
150 void 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 }
159 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_unregister_notifier);
160 
161 MODULE_LICENSE("GPL");
162 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
163 

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