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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/module.h>
  16 #include <linux/kernel.h>
  17 #include <linux/kmod.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/in.h>
  20 #include <linux/ip.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/spinlock.h>
  23 #include <net/protocol.h>
  24 #include <net/gre.h>
  25
  26
  27 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
  28 static DEFINE_SPINLOCK(gre_proto_lock);
  29
  30 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
  31 {
  32         if (version >= GREPROTO_MAX)
  33                 goto err_out;
  34
  35         spin_lock(&gre_proto_lock);
  36         if (gre_proto[version])
  37                 goto err_out_unlock;
  38
  39         RCU_INIT_POINTER(gre_proto[version], proto);
  40         spin_unlock(&gre_proto_lock);
  41         return 0;
  42
  43 err_out_unlock:
  44         spin_unlock(&gre_proto_lock);
  45 err_out:
  46         return -1;
  47 }
  48 EXPORT_SYMBOL_GPL(gre_add_protocol);
  49
  50 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
  51 {
  52         if (version >= GREPROTO_MAX)
  53                 goto err_out;
  54
  55         spin_lock(&gre_proto_lock);
  56         if (rcu_dereference_protected(gre_proto[version],
  57                         lockdep_is_held(&gre_proto_lock)) != proto)
  58                 goto err_out_unlock;
  59         RCU_INIT_POINTER(gre_proto[version], NULL);
  60         spin_unlock(&gre_proto_lock);
  61         synchronize_rcu();
  62         return 0;
  63
  64 err_out_unlock:
  65         spin_unlock(&gre_proto_lock);
  66 err_out:
  67         return -1;
  68 }
  69 EXPORT_SYMBOL_GPL(gre_del_protocol);
  70
  71 static int gre_rcv(struct sk_buff *skb)
  72 {
  73         const struct gre_protocol *proto;
  74         u8 ver;
  75         int ret;
  76
  77         if (!pskb_may_pull(skb, 12))
  78                 goto drop;
  79
  80         ver = skb->data[1]&0x7f;
  81         if (ver >= GREPROTO_MAX)
  82                 goto drop;
  83
  84         rcu_read_lock();
  85         proto = rcu_dereference(gre_proto[ver]);
  86         if (!proto || !proto->handler)
  87                 goto drop_unlock;
  88         ret = proto->handler(skb);
  89         rcu_read_unlock();
  90         return ret;
  91
  92 drop_unlock:
  93         rcu_read_unlock();
  94 drop:
  95         kfree_skb(skb);
  96         return NET_RX_DROP;
  97 }
  98
  99 static void gre_err(struct sk_buff *skb, u32 info)
 100 {
 101         const struct gre_protocol *proto;
 102         const struct iphdr *iph = (const struct iphdr *)skb->data;
 103         u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
 104
 105         if (ver >= GREPROTO_MAX)
 106                 return;
 107
 108         rcu_read_lock();
 109         proto = rcu_dereference(gre_proto[ver]);
 110         if (proto && proto->err_handler)
 111                 proto->err_handler(skb, info);
 112         rcu_read_unlock();
 113 }
 114
 115 static const struct net_protocol net_gre_protocol = {
 116         .handler     = gre_rcv,
 117         .err_handler = gre_err,
 118         .netns_ok    = 1,
 119 };
 120
 121 static int __init gre_init(void)
 122 {
 123         pr_info("GRE over IPv4 demultiplexor driver\n");
 124
 125         if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
 126                 pr_err("can't add protocol\n");
 127                 return -EAGAIN;
 128         }
 129
 130         return 0;
 131 }
 132
 133 static void __exit gre_exit(void)
 134 {
 135         inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 136 }
 137
 138 module_init(gre_init);
 139 module_exit(gre_exit);
 140
 141 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
 142 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 143 MODULE_LICENSE("GPL");
 144