net/ipv4/gre_demux.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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/module.h>
  16 #include <linux/if.h>
  17 #include <linux/icmp.h>
  18 #include <linux/kernel.h>
  19 #include <linux/kmod.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/in.h>
  22 #include <linux/ip.h>
  23 #include <linux/netdevice.h>
  24 #include <linux/if_tunnel.h>
  25 #include <linux/spinlock.h>
  26 #include <net/protocol.h>
  27 #include <net/gre.h>
  28
  29 #include <net/icmp.h>
  30 #include <net/route.h>
  31 #include <net/xfrm.h>
  32
  33 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
  34
  35 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
  36 {
  37         if (version >= GREPROTO_MAX)
  38                 return -EINVAL;
  39
  40         return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
  41                 0 : -EBUSY;
  42 }
  43 EXPORT_SYMBOL_GPL(gre_add_protocol);
  44
  45 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
  46 {
  47         int ret;
  48
  49         if (version >= GREPROTO_MAX)
  50                 return -EINVAL;
  51
  52         ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
  53                 0 : -EBUSY;
  54
  55         if (ret)
  56                 return ret;
  57
  58         synchronize_rcu();
  59         return 0;
  60 }
  61 EXPORT_SYMBOL_GPL(gre_del_protocol);
  62
  63 static int gre_rcv(struct sk_buff *skb)
  64 {
  65         const struct gre_protocol *proto;
  66         u8 ver;
  67         int ret;
  68
  69         if (!pskb_may_pull(skb, 12))
  70                 goto drop;
  71
  72         ver = skb->data[1]&0x7f;
  73         if (ver >= GREPROTO_MAX)
  74                 goto drop;
  75
  76         rcu_read_lock();
  77         proto = rcu_dereference(gre_proto[ver]);
  78         if (!proto || !proto->handler)
  79                 goto drop_unlock;
  80         ret = proto->handler(skb);
  81         rcu_read_unlock();
  82         return ret;
  83
  84 drop_unlock:
  85         rcu_read_unlock();
  86 drop:
  87         kfree_skb(skb);
  88         return NET_RX_DROP;
  89 }
  90
  91 static void gre_err(struct sk_buff *skb, u32 info)
  92 {
  93         const struct gre_protocol *proto;
  94         const struct iphdr *iph = (const struct iphdr *)skb->data;
  95         u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
  96
  97         if (ver >= GREPROTO_MAX)
  98                 return;
  99
 100         rcu_read_lock();
 101         proto = rcu_dereference(gre_proto[ver]);
 102         if (proto && proto->err_handler)
 103                 proto->err_handler(skb, info);
 104         rcu_read_unlock();
 105 }
 106
 107 static const struct net_protocol net_gre_protocol = {
 108         .handler     = gre_rcv,
 109         .err_handler = gre_err,
 110         .netns_ok    = 1,
 111 };
 112
 113 static int __init gre_init(void)
 114 {
 115         pr_info("GRE over IPv4 demultiplexor driver\n");
 116
 117         if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
 118                 pr_err("can't add protocol\n");
 119                 return -EAGAIN;
 120         }
 121         return 0;
 122 }
 123
 124 static void __exit gre_exit(void)
 125 {
 126         inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 127 }
 128
 129 module_init(gre_init);
 130 module_exit(gre_exit);
 131
 132 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
 133 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 134 MODULE_LICENSE("GPL");