gre.c
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/*
* GRE over IPv4 demultiplexer driver
*
* Authors: Dmitry Kozlov (xeb@mail.ru)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <linux/spinlock.h>
#include <net/protocol.h>
#include <net/gre.h>
static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
static DEFINE_SPINLOCK(gre_proto_lock);
int gre_add_protocol(const struct gre_protocol *proto, u8 version)
{
if (version >= GREPROTO_MAX)
goto err_out;
spin_lock(&gre_proto_lock);
if (gre_proto[version])
goto err_out_unlock;
rcu_assign_pointer(gre_proto[version], proto);
spin_unlock(&gre_proto_lock);
return 0;
err_out_unlock:
spin_unlock(&gre_proto_lock);
err_out:
return -1;
}
EXPORT_SYMBOL_GPL(gre_add_protocol);
int gre_del_protocol(const struct gre_protocol *proto, u8 version)
{
if (version >= GREPROTO_MAX)
goto err_out;
spin_lock(&gre_proto_lock);
if (rcu_dereference_protected(gre_proto[version],
lockdep_is_held(&gre_proto_lock)) != proto)
goto err_out_unlock;
rcu_assign_pointer(gre_proto[version], NULL);
spin_unlock(&gre_proto_lock);
synchronize_rcu();
return 0;
err_out_unlock:
spin_unlock(&gre_proto_lock);
err_out:
return -1;
}
EXPORT_SYMBOL_GPL(gre_del_protocol);
static int gre_rcv(struct sk_buff *skb)
{
const struct gre_protocol *proto;
u8 ver;
int ret;
if (!pskb_may_pull(skb, 12))
goto drop;
ver = skb->data[1]&0x7f;
if (ver >= GREPROTO_MAX)
goto drop;
rcu_read_lock();
proto = rcu_dereference(gre_proto[ver]);
if (!proto || !proto->handler)
goto drop_unlock;
ret = proto->handler(skb);
rcu_read_unlock();
return ret;
drop_unlock:
rcu_read_unlock();
drop:
kfree_skb(skb);
return NET_RX_DROP;
}
static void gre_err(struct sk_buff *skb, u32 info)
{
const struct gre_protocol *proto;
const struct iphdr *iph = (const struct iphdr *)skb->data;
u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
if (ver >= GREPROTO_MAX)
return;
rcu_read_lock();
proto = rcu_dereference(gre_proto[ver]);
if (proto && proto->err_handler)
proto->err_handler(skb, info);
rcu_read_unlock();
}
static const struct net_protocol net_gre_protocol = {
.handler = gre_rcv,
.err_handler = gre_err,
.netns_ok = 1,
};
static int __init gre_init(void)
{
pr_info("GRE over IPv4 demultiplexor driver");
if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
pr_err("gre: can't add protocol\n");
return -EAGAIN;
}
return 0;
}
static void __exit gre_exit(void)
{
inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
}
module_init(gre_init);
module_exit(gre_exit);
MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
MODULE_LICENSE("GPL");