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Linux/net/ipv4/gre_demux.c

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  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");
135 

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