net/ipv4/gre.c

   1 /*
   2  *      GRE over IPv4 demultiplexer driver
   3  *
   4  *      Authors: Dmitry Kozlov (xeb@mail.ru)
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  *
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/kmod.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/in.h>
  18 #include <linux/ip.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/version.h>
  21 #include <linux/spinlock.h>
  22 #include <net/protocol.h>
  23 #include <net/gre.h>
  24
  25
  26 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
  27 static DEFINE_SPINLOCK(gre_proto_lock);
  28
  29 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
  30 {
  31         if (version >= GREPROTO_MAX)
  32                 goto err_out;
  33
  34         spin_lock(&gre_proto_lock);
  35         if (gre_proto[version])
  36                 goto err_out_unlock;
  37
  38         rcu_assign_pointer(gre_proto[version], proto);
  39         spin_unlock(&gre_proto_lock);
  40         return 0;
  41
  42 err_out_unlock:
  43         spin_unlock(&gre_proto_lock);
  44 err_out:
  45         return -1;
  46 }
  47 EXPORT_SYMBOL_GPL(gre_add_protocol);
  48
  49 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
  50 {
  51         if (version >= GREPROTO_MAX)
  52                 goto err_out;
  53
  54         spin_lock(&gre_proto_lock);
  55         if (rcu_dereference_protected(gre_proto[version],
  56                         lockdep_is_held(&gre_proto_lock)) != proto)
  57                 goto err_out_unlock;
  58         rcu_assign_pointer(gre_proto[version], NULL);
  59         spin_unlock(&gre_proto_lock);
  60         synchronize_rcu();
  61         return 0;
  62
  63 err_out_unlock:
  64         spin_unlock(&gre_proto_lock);
  65 err_out:
  66         return -1;
  67 }
  68 EXPORT_SYMBOL_GPL(gre_del_protocol);
  69
  70 static int gre_rcv(struct sk_buff *skb)
  71 {
  72         const struct gre_protocol *proto;
  73         u8 ver;
  74         int ret;
  75
  76         if (!pskb_may_pull(skb, 12))
  77                 goto drop;
  78
  79         ver = skb->data[1]&0x7f;
  80         if (ver >= GREPROTO_MAX)
  81                 goto drop;
  82
  83         rcu_read_lock();
  84         proto = rcu_dereference(gre_proto[ver]);
  85         if (!proto || !proto->handler)
  86                 goto drop_unlock;
  87         ret = proto->handler(skb);
  88         rcu_read_unlock();
  89         return ret;
  90
  91 drop_unlock:
  92         rcu_read_unlock();
  93 drop:
  94         kfree_skb(skb);
  95         return NET_RX_DROP;
  96 }
  97
  98 static void gre_err(struct sk_buff *skb, u32 info)
  99 {
 100         const struct gre_protocol *proto;
 101         const struct iphdr *iph = (const struct iphdr *)skb->data;
 102         u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
 103
 104         if (ver >= GREPROTO_MAX)
 105                 return;
 106
 107         rcu_read_lock();
 108         proto = rcu_dereference(gre_proto[ver]);
 109         if (proto && proto->err_handler)
 110                 proto->err_handler(skb, info);
 111         rcu_read_unlock();
 112 }
 113
 114 static const struct net_protocol net_gre_protocol = {
 115         .handler     = gre_rcv,
 116         .err_handler = gre_err,
 117         .netns_ok    = 1,
 118 };
 119
 120 static int __init gre_init(void)
 121 {
 122         pr_info("GRE over IPv4 demultiplexor driver");
 123
 124         if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
 125                 pr_err("gre: can't add protocol\n");
 126                 return -EAGAIN;
 127         }
 128
 129         return 0;
 130 }
 131
 132 static void __exit gre_exit(void)
 133 {
 134         inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 135 }
 136
 137 module_init(gre_init);
 138 module_exit(gre_exit);
 139
 140 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
 141 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 142 MODULE_LICENSE("GPL");
 143