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