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
 25static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
 26static DEFINE_SPINLOCK(gre_proto_lock);
 27
 28int 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
 41err_out_unlock:
 42	spin_unlock(&gre_proto_lock);
 43err_out:
 44	return -1;
 45}
 46EXPORT_SYMBOL_GPL(gre_add_protocol);
 47
 48int 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
 62err_out_unlock:
 63	spin_unlock(&gre_proto_lock);
 64err_out:
 65	return -1;
 66}
 67EXPORT_SYMBOL_GPL(gre_del_protocol);
 68
 69static 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
 90drop_unlock:
 91	rcu_read_unlock();
 92drop:
 93	kfree_skb(skb);
 94	return NET_RX_DROP;
 95}
 96
 97static 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
113static const struct net_protocol net_gre_protocol = {
114	.handler     = gre_rcv,
115	.err_handler = gre_err,
116	.netns_ok    = 1,
117};
118
119static 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
131static void __exit gre_exit(void)
132{
133	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
134}
135
136module_init(gre_init);
137module_exit(gre_exit);
138
139MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
140MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
141MODULE_LICENSE("GPL");
142