ip_gre.c

{
	struct ip_tunnel *t = netdev_priv(dev);
	struct iphdr *iph = (struct iphdr *)skb_push(skb, t->hlen);
	__be16 *p = (__be16*)(iph+1);

	memcpy(iph, &t->parms.iph, sizeof(struct iphdr));
	p[0]		= t->parms.o_flags;
	p[1]		= htons(type);

	/*
	 *	Set the source hardware address.
	 */

	if (saddr)
		memcpy(&iph->saddr, saddr, 4);

	if (daddr) {
		memcpy(&iph->daddr, daddr, 4);
		return t->hlen;
	}
	if (iph->daddr && !ipv4_is_multicast(iph->daddr))
		return t->hlen;

	return -t->hlen;
}

static int ipgre_header_parse(const struct sk_buff *skb, unsigned char *haddr)
{
	struct iphdr *iph = (struct iphdr*) skb_mac_header(skb);
	memcpy(haddr, &iph->saddr, 4);
	return 4;
}

static const struct header_ops ipgre_header_ops = {
	.create	= ipgre_header,
	.parse	= ipgre_header_parse,
};

#ifdef CONFIG_NET_IPGRE_BROADCAST
static int ipgre_open(struct net_device *dev)
{
	struct ip_tunnel *t = netdev_priv(dev);

	if (ipv4_is_multicast(t->parms.iph.daddr)) {
		struct flowi fl = { .oif = t->parms.link,
				    .nl_u = { .ip4_u =
					      { .daddr = t->parms.iph.daddr,
						.saddr = t->parms.iph.saddr,
						.tos = RT_TOS(t->parms.iph.tos) } },
				    .proto = IPPROTO_GRE };
		struct rtable *rt;
		if (ip_route_output_key(dev_net(dev), &rt, &fl))
			return -EADDRNOTAVAIL;
		dev = rt->u.dst.dev;
		ip_rt_put(rt);
		if (__in_dev_get_rtnl(dev) == NULL)
			return -EADDRNOTAVAIL;
		t->mlink = dev->ifindex;
		ip_mc_inc_group(__in_dev_get_rtnl(dev), t->parms.iph.daddr);
	}
	return 0;
}

static int ipgre_close(struct net_device *dev)
{
	struct ip_tunnel *t = netdev_priv(dev);
	if (ipv4_is_multicast(t->parms.iph.daddr) && t->mlink) {
		struct in_device *in_dev;
		in_dev = inetdev_by_index(dev_net(dev), t->mlink);
		if (in_dev) {
			ip_mc_dec_group(in_dev, t->parms.iph.daddr);
			in_dev_put(in_dev);
		}
	}
	return 0;
}

#endif

static void ipgre_tunnel_setup(struct net_device *dev)
{
	dev->uninit		= ipgre_tunnel_uninit;
	dev->destructor 	= free_netdev;
	dev->hard_start_xmit	= ipgre_tunnel_xmit;
	dev->do_ioctl		= ipgre_tunnel_ioctl;
	dev->change_mtu		= ipgre_tunnel_change_mtu;

	dev->type		= ARPHRD_IPGRE;
	dev->needed_headroom 	= LL_MAX_HEADER + sizeof(struct iphdr) + 4;
	dev->mtu		= ETH_DATA_LEN - sizeof(struct iphdr) - 4;
	dev->flags		= IFF_NOARP;
	dev->iflink		= 0;
	dev->addr_len		= 4;
	dev->features		|= NETIF_F_NETNS_LOCAL;
}

static int ipgre_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel;
	struct iphdr *iph;

	tunnel = netdev_priv(dev);
	iph = &tunnel->parms.iph;

	tunnel->dev = dev;
	strcpy(tunnel->parms.name, dev->name);

	memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
	memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);

	ipgre_tunnel_bind_dev(dev);

	if (iph->daddr) {
#ifdef CONFIG_NET_IPGRE_BROADCAST
		if (ipv4_is_multicast(iph->daddr)) {
			if (!iph->saddr)
				return -EINVAL;
			dev->flags = IFF_BROADCAST;
			dev->header_ops = &ipgre_header_ops;
			dev->open = ipgre_open;
			dev->stop = ipgre_close;
		}
#endif
	} else
		dev->header_ops = &ipgre_header_ops;

	return 0;
}

static int ipgre_fb_tunnel_init(struct net_device *dev)
{
	struct ip_tunnel *tunnel = netdev_priv(dev);
	struct iphdr *iph = &tunnel->parms.iph;
	struct ipgre_net *ign = net_generic(dev_net(dev), ipgre_net_id);

	tunnel->dev = dev;
	strcpy(tunnel->parms.name, dev->name);

	iph->version		= 4;
	iph->protocol		= IPPROTO_GRE;
	iph->ihl		= 5;
	tunnel->hlen		= sizeof(struct iphdr) + 4;

	dev_hold(dev);
	ign->tunnels_wc[0]	= tunnel;
	return 0;
}


static struct net_protocol ipgre_protocol = {
	.handler	=	ipgre_rcv,
	.err_handler	=	ipgre_err,
	.netns_ok	=	1,
};

static void ipgre_destroy_tunnels(struct ipgre_net *ign)
{
	int prio;

	for (prio = 0; prio < 4; prio++) {
		int h;
		for (h = 0; h < HASH_SIZE; h++) {
			struct ip_tunnel *t;
			while ((t = ign->tunnels[prio][h]) != NULL)
				unregister_netdevice(t->dev);
		}
	}
}

static int ipgre_init_net(struct net *net)
{
	int err;
	struct ipgre_net *ign;

	err = -ENOMEM;
	ign = kzalloc(sizeof(struct ipgre_net), GFP_KERNEL);
	if (ign == NULL)
		goto err_alloc;

	err = net_assign_generic(net, ipgre_net_id, ign);
	if (err < 0)
		goto err_assign;

	ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "gre0",
					   ipgre_tunnel_setup);
	if (!ign->fb_tunnel_dev) {
		err = -ENOMEM;
		goto err_alloc_dev;
	}

	ign->fb_tunnel_dev->init = ipgre_fb_tunnel_init;
	dev_net_set(ign->fb_tunnel_dev, net);

	if ((err = register_netdev(ign->fb_tunnel_dev)))
		goto err_reg_dev;

	return 0;

err_reg_dev:
	free_netdev(ign->fb_tunnel_dev);
err_alloc_dev:
	/* nothing */
err_assign:
	kfree(ign);
err_alloc:
	return err;
}

static void ipgre_exit_net(struct net *net)
{
	struct ipgre_net *ign;

	ign = net_generic(net, ipgre_net_id);
	rtnl_lock();
	ipgre_destroy_tunnels(ign);
	rtnl_unlock();
	kfree(ign);
}

static struct pernet_operations ipgre_net_ops = {
	.init = ipgre_init_net,
	.exit = ipgre_exit_net,
};

/*
 *	And now the modules code and kernel interface.
 */

static int __init ipgre_init(void)
{
	int err;

	printk(KERN_INFO "GRE over IPv4 tunneling driver\n");

	if (inet_add_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) {
		printk(KERN_INFO "ipgre init: can't add protocol\n");
		return -EAGAIN;
	}

	err = register_pernet_gen_device(&ipgre_net_id, &ipgre_net_ops);
	if (err < 0)
		inet_del_protocol(&ipgre_protocol, IPPROTO_GRE);

	return err;
}

static void __exit ipgre_fini(void)
{
	if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
		printk(KERN_INFO "ipgre close: can't remove protocol\n");

	unregister_pernet_gen_device(ipgre_net_id, &ipgre_net_ops);
}

module_init(ipgre_init);
module_exit(ipgre_fini);
MODULE_LICENSE("GPL");