1 files changed, 833 insertions, 0 deletions

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
new file mode 100644
index 00000000000..b788f55e139
--- /dev/null
+++ b/net/ipv6/sit.c
@@ -0,0 +1,833 @@
+/*
+ *	IPv6 over IPv4 tunnel device - Simple Internet Transition (SIT)
+ *	Linux INET6 implementation
+ *
+ *	Authors:
+ *	Pedro Roque		<roque@di.fc.ul.pt>	
+ *	Alexey Kuznetsov	<kuznet@ms2.inr.ac.ru>
+ *
+ *	$Id: sit.c,v 1.53 2001/09/25 05:09:53 davem Exp $
+ *
+ *	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.
+ *
+ *	Changes:
+ * Roger Venning <r.venning@telstra.com>:	6to4 support
+ * Nate Thompson <nate@thebog.net>:		6to4 support
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/sched.h>
+#include <linux/net.h>
+#include <linux/in6.h>
+#include <linux/netdevice.h>
+#include <linux/if_arp.h>
+#include <linux/icmp.h>
+#include <asm/uaccess.h>
+#include <linux/init.h>
+#include <linux/netfilter_ipv4.h>
+
+#include <net/sock.h>
+#include <net/snmp.h>
+
+#include <net/ipv6.h>
+#include <net/protocol.h>
+#include <net/transp_v6.h>
+#include <net/ip6_fib.h>
+#include <net/ip6_route.h>
+#include <net/ndisc.h>
+#include <net/addrconf.h>
+#include <net/ip.h>
+#include <net/udp.h>
+#include <net/icmp.h>
+#include <net/ipip.h>
+#include <net/inet_ecn.h>
+#include <net/xfrm.h>
+#include <net/dsfield.h>
+
+/*
+   This version of net/ipv6/sit.c is cloned of net/ipv4/ip_gre.c
+
+   For comments look at net/ipv4/ip_gre.c --ANK
+ */
+
+#define HASH_SIZE  16
+#define HASH(addr) ((addr^(addr>>4))&0xF)
+
+static int ipip6_fb_tunnel_init(struct net_device *dev);
+static int ipip6_tunnel_init(struct net_device *dev);
+static void ipip6_tunnel_setup(struct net_device *dev);
+
+static struct net_device *ipip6_fb_tunnel_dev;
+
+static struct ip_tunnel *tunnels_r_l[HASH_SIZE];
+static struct ip_tunnel *tunnels_r[HASH_SIZE];
+static struct ip_tunnel *tunnels_l[HASH_SIZE];
+static struct ip_tunnel *tunnels_wc[1];
+static struct ip_tunnel **tunnels[4] = { tunnels_wc, tunnels_l, tunnels_r, tunnels_r_l };
+
+static DEFINE_RWLOCK(ipip6_lock);
+
+static struct ip_tunnel * ipip6_tunnel_lookup(u32 remote, u32 local)
+{
+	unsigned h0 = HASH(remote);
+	unsigned h1 = HASH(local);
+	struct ip_tunnel *t;
+
+	for (t = tunnels_r_l[h0^h1]; t; t = t->next) {
+		if (local == t->parms.iph.saddr &&
+		    remote == t->parms.iph.daddr && (t->dev->flags&IFF_UP))
+			return t;
+	}
+	for (t = tunnels_r[h0]; t; t = t->next) {
+		if (remote == t->parms.iph.daddr && (t->dev->flags&IFF_UP))
+			return t;
+	}
+	for (t = tunnels_l[h1]; t; t = t->next) {
+		if (local == t->parms.iph.saddr && (t->dev->flags&IFF_UP))
+			return t;
+	}
+	if ((t = tunnels_wc[0]) != NULL && (t->dev->flags&IFF_UP))
+		return t;
+	return NULL;
+}
+
+static struct ip_tunnel ** ipip6_bucket(struct ip_tunnel *t)
+{
+	u32 remote = t->parms.iph.daddr;
+	u32 local = t->parms.iph.saddr;
+	unsigned h = 0;
+	int prio = 0;
+
+	if (remote) {
+		prio |= 2;
+		h ^= HASH(remote);
+	}
+	if (local) {
+		prio |= 1;
+		h ^= HASH(local);
+	}
+	return &tunnels[prio][h];
+}
+
+static void ipip6_tunnel_unlink(struct ip_tunnel *t)
+{
+	struct ip_tunnel **tp;
+
+	for (tp = ipip6_bucket(t); *tp; tp = &(*tp)->next) {
+		if (t == *tp) {
+			write_lock_bh(&ipip6_lock);
+			*tp = t->next;
+			write_unlock_bh(&ipip6_lock);
+			break;
+		}
+	}
+}
+
+static void ipip6_tunnel_link(struct ip_tunnel *t)
+{
+	struct ip_tunnel **tp = ipip6_bucket(t);
+
+	t->next = *tp;
+	write_lock_bh(&ipip6_lock);
+	*tp = t;
+	write_unlock_bh(&ipip6_lock);
+}
+
+static struct ip_tunnel * ipip6_tunnel_locate(struct ip_tunnel_parm *parms, int create)
+{
+	u32 remote = parms->iph.daddr;
+	u32 local = parms->iph.saddr;
+	struct ip_tunnel *t, **tp, *nt;
+	struct net_device *dev;
+	unsigned h = 0;
+	int prio = 0;
+	char name[IFNAMSIZ];
+
+	if (remote) {
+		prio |= 2;
+		h ^= HASH(remote);
+	}
+	if (local) {
+		prio |= 1;
+		h ^= HASH(local);
+	}
+	for (tp = &tunnels[prio][h]; (t = *tp) != NULL; tp = &t->next) {
+		if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr)
+			return t;
+	}
+	if (!create)
+		goto failed;
+
+	if (parms->name[0])
+		strlcpy(name, parms->name, IFNAMSIZ);
+	else {
+		int i;
+		for (i=1; i<100; i++) {
+			sprintf(name, "sit%d", i);
+			if (__dev_get_by_name(name) == NULL)
+				break;
+		}
+		if (i==100)
+			goto failed;
+	}
+
+	dev = alloc_netdev(sizeof(*t), name, ipip6_tunnel_setup);
+	if (dev == NULL)
+		return NULL;
+
+	nt = dev->priv;
+	dev->init = ipip6_tunnel_init;
+	nt->parms = *parms;
+
+	if (register_netdevice(dev) < 0) {
+		free_netdev(dev);
+		goto failed;
+	}
+
+	dev_hold(dev);
+
+	ipip6_tunnel_link(nt);
+	/* Do not decrement MOD_USE_COUNT here. */
+	return nt;
+
+failed:
+	return NULL;
+}
+
+static void ipip6_tunnel_uninit(struct net_device *dev)
+{
+	if (dev == ipip6_fb_tunnel_dev) {
+		write_lock_bh(&ipip6_lock);
+		tunnels_wc[0] = NULL;
+		write_unlock_bh(&ipip6_lock);
+		dev_put(dev);
+	} else {
+		ipip6_tunnel_unlink((struct ip_tunnel*)dev->priv);
+		dev_put(dev);
+	}
+}
+
+
+static void ipip6_err(struct sk_buff *skb, u32 info)
+{
+#ifndef I_WISH_WORLD_WERE_PERFECT
+
+/* It is not :-( All the routers (except for Linux) return only
+   8 bytes of packet payload. It means, that precise relaying of
+   ICMP in the real Internet is absolutely infeasible.
+ */
+	struct iphdr *iph = (struct iphdr*)skb->data;
+	int type = skb->h.icmph->type;
+	int code = skb->h.icmph->code;
+	struct ip_tunnel *t;
+
+	switch (type) {
+	default:
+	case ICMP_PARAMETERPROB:
+		return;
+
+	case ICMP_DEST_UNREACH:
+		switch (code) {
+		case ICMP_SR_FAILED:
+		case ICMP_PORT_UNREACH:
+			/* Impossible event. */
+			return;
+		case ICMP_FRAG_NEEDED:
+			/* Soft state for pmtu is maintained by IP core. */
+			return;
+		default:
+			/* All others are translated to HOST_UNREACH.
+			   rfc2003 contains "deep thoughts" about NET_UNREACH,
+			   I believe they are just ether pollution. --ANK
+			 */
+			break;
+		}
+		break;
+	case ICMP_TIME_EXCEEDED:
+		if (code != ICMP_EXC_TTL)
+			return;
+		break;
+	}
+
+	read_lock(&ipip6_lock);
+	t = ipip6_tunnel_lookup(iph->daddr, iph->saddr);
+	if (t == NULL || t->parms.iph.daddr == 0)
+		goto out;
+	if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
+		goto out;
+
+	if (jiffies - t->err_time < IPTUNNEL_ERR_TIMEO)
+		t->err_count++;
+	else
+		t->err_count = 1;
+	t->err_time = jiffies;
+out:
+	read_unlock(&ipip6_lock);
+	return;
+#else
+	struct iphdr *iph = (struct iphdr*)dp;
+	int hlen = iph->ihl<<2;
+	struct ipv6hdr *iph6;
+	int type = skb->h.icmph->type;
+	int code = skb->h.icmph->code;
+	int rel_type = 0;
+	int rel_code = 0;
+	int rel_info = 0;
+	struct sk_buff *skb2;
+	struct rt6_info *rt6i;
+
+	if (len < hlen + sizeof(struct ipv6hdr))
+		return;
+	iph6 = (struct ipv6hdr*)(dp + hlen);
+
+	switch (type) {
+	default:
+		return;
+	case ICMP_PARAMETERPROB:
+		if (skb->h.icmph->un.gateway < hlen)
+			return;
+
+		/* So... This guy found something strange INSIDE encapsulated
+		   packet. Well, he is fool, but what can we do ?
+		 */
+		rel_type = ICMPV6_PARAMPROB;
+		rel_info = skb->h.icmph->un.gateway - hlen;
+		break;
+
+	case ICMP_DEST_UNREACH:
+		switch (code) {
+		case ICMP_SR_FAILED:
+		case ICMP_PORT_UNREACH:
+			/* Impossible event. */
+			return;
+		case ICMP_FRAG_NEEDED:
+			/* Too complicated case ... */
+			return;
+		default:
+			/* All others are translated to HOST_UNREACH.
+			   rfc2003 contains "deep thoughts" about NET_UNREACH,
+			   I believe, it is just ether pollution. --ANK
+			 */
+			rel_type = ICMPV6_DEST_UNREACH;
+			rel_code = ICMPV6_ADDR_UNREACH;
+			break;
+		}
+		break;
+	case ICMP_TIME_EXCEEDED:
+		if (code != ICMP_EXC_TTL)
+			return;
+		rel_type = ICMPV6_TIME_EXCEED;
+		rel_code = ICMPV6_EXC_HOPLIMIT;
+		break;
+	}
+
+	/* Prepare fake skb to feed it to icmpv6_send */
+	skb2 = skb_clone(skb, GFP_ATOMIC);
+	if (skb2 == NULL)
+		return;
+	dst_release(skb2->dst);
+	skb2->dst = NULL;
+	skb_pull(skb2, skb->data - (u8*)iph6);
+	skb2->nh.raw = skb2->data;
+
+	/* Try to guess incoming interface */
+	rt6i = rt6_lookup(&iph6->saddr, NULL, NULL, 0);
+	if (rt6i && rt6i->rt6i_dev) {
+		skb2->dev = rt6i->rt6i_dev;
+
+		rt6i = rt6_lookup(&iph6->daddr, &iph6->saddr, NULL, 0);
+
+		if (rt6i && rt6i->rt6i_dev && rt6i->rt6i_dev->type == ARPHRD_SIT) {
+			struct ip_tunnel * t = (struct ip_tunnel*)rt6i->rt6i_dev->priv;
+			if (rel_type == ICMPV6_TIME_EXCEED && t->parms.iph.ttl) {
+				rel_type = ICMPV6_DEST_UNREACH;
+				rel_code = ICMPV6_ADDR_UNREACH;
+			}
+			icmpv6_send(skb2, rel_type, rel_code, rel_info, skb2->dev);
+		}
+	}
+	kfree_skb(skb2);
+	return;
+#endif
+}
+
+static inline void ipip6_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
+{
+	if (INET_ECN_is_ce(iph->tos))
+		IP6_ECN_set_ce(skb->nh.ipv6h);
+}
+
+static int ipip6_rcv(struct sk_buff *skb)
+{
+	struct iphdr *iph;
+	struct ip_tunnel *tunnel;
+
+	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+		goto out;
+
+	iph = skb->nh.iph;
+
+	read_lock(&ipip6_lock);
+	if ((tunnel = ipip6_tunnel_lookup(iph->saddr, iph->daddr)) != NULL) {
+		secpath_reset(skb);
+		skb->mac.raw = skb->nh.raw;
+		skb->nh.raw = skb->data;
+		memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
+		skb->protocol = htons(ETH_P_IPV6);
+		skb->pkt_type = PACKET_HOST;
+		tunnel->stat.rx_packets++;
+		tunnel->stat.rx_bytes += skb->len;
+		skb->dev = tunnel->dev;
+		dst_release(skb->dst);
+		skb->dst = NULL;
+		nf_reset(skb);
+		ipip6_ecn_decapsulate(iph, skb);
+		netif_rx(skb);
+		read_unlock(&ipip6_lock);
+		return 0;
+	}
+
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0);
+	kfree_skb(skb);
+	read_unlock(&ipip6_lock);
+out:
+	return 0;
+}
+
+/* Returns the embedded IPv4 address if the IPv6 address
+   comes from 6to4 (RFC 3056) addr space */
+
+static inline u32 try_6to4(struct in6_addr *v6dst)
+{
+	u32 dst = 0;
+
+	if (v6dst->s6_addr16[0] == htons(0x2002)) {
+	        /* 6to4 v6 addr has 16 bits prefix, 32 v4addr, 16 SLA, ... */
+		memcpy(&dst, &v6dst->s6_addr16[1], 4);
+	}
+	return dst;
+}
+
+/*
+ *	This function assumes it is being called from dev_queue_xmit()
+ *	and that skb is filled properly by that function.
+ */
+
+static int ipip6_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ip_tunnel *tunnel = (struct ip_tunnel*)dev->priv;
+	struct net_device_stats *stats = &tunnel->stat;
+	struct iphdr  *tiph = &tunnel->parms.iph;
+	struct ipv6hdr *iph6 = skb->nh.ipv6h;
+	u8     tos = tunnel->parms.iph.tos;
+	struct rtable *rt;     			/* Route to the other host */
+	struct net_device *tdev;			/* Device to other host */
+	struct iphdr  *iph;			/* Our new IP header */
+	int    max_headroom;			/* The extra header space needed */
+	u32    dst = tiph->daddr;
+	int    mtu;
+	struct in6_addr *addr6;	
+	int addr_type;
+
+	if (tunnel->recursion++) {
+		tunnel->stat.collisions++;
+		goto tx_error;
+	}
+
+	if (skb->protocol != htons(ETH_P_IPV6))
+		goto tx_error;
+
+	if (!dst)
+		dst = try_6to4(&iph6->daddr);
+
+	if (!dst) {
+		struct neighbour *neigh = NULL;
+
+		if (skb->dst)
+			neigh = skb->dst->neighbour;
+
+		if (neigh == NULL) {
+			if (net_ratelimit())
+				printk(KERN_DEBUG "sit: nexthop == NULL\n");
+			goto tx_error;
+		}
+
+		addr6 = (struct in6_addr*)&neigh->primary_key;
+		addr_type = ipv6_addr_type(addr6);
+
+		if (addr_type == IPV6_ADDR_ANY) {
+			addr6 = &skb->nh.ipv6h->daddr;
+			addr_type = ipv6_addr_type(addr6);
+		}
+
+		if ((addr_type & IPV6_ADDR_COMPATv4) == 0)
+			goto tx_error_icmp;
+
+		dst = addr6->s6_addr32[3];
+	}
+
+	{
+		struct flowi fl = { .nl_u = { .ip4_u =
+					      { .daddr = dst,
+						.saddr = tiph->saddr,
+						.tos = RT_TOS(tos) } },
+				    .oif = tunnel->parms.link,
+				    .proto = IPPROTO_IPV6 };
+		if (ip_route_output_key(&rt, &fl)) {
+			tunnel->stat.tx_carrier_errors++;
+			goto tx_error_icmp;
+		}
+	}
+	if (rt->rt_type != RTN_UNICAST) {
+		ip_rt_put(rt);
+		tunnel->stat.tx_carrier_errors++;
+		goto tx_error_icmp;
+	}
+	tdev = rt->u.dst.dev;
+
+	if (tdev == dev) {
+		ip_rt_put(rt);
+		tunnel->stat.collisions++;
+		goto tx_error;
+	}
+
+	if (tiph->frag_off)
+		mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
+	else
+		mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
+
+	if (mtu < 68) {
+		tunnel->stat.collisions++;
+		ip_rt_put(rt);
+		goto tx_error;
+	}
+	if (mtu < IPV6_MIN_MTU)
+		mtu = IPV6_MIN_MTU;
+	if (tunnel->parms.iph.daddr && skb->dst)
+		skb->dst->ops->update_pmtu(skb->dst, mtu);
+
+	if (skb->len > mtu) {
+		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
+		ip_rt_put(rt);
+		goto tx_error;
+	}
+
+	if (tunnel->err_count > 0) {
+		if (jiffies - tunnel->err_time < IPTUNNEL_ERR_TIMEO) {
+			tunnel->err_count--;
+			dst_link_failure(skb);
+		} else
+			tunnel->err_count = 0;
+	}
+
+	/*
+	 * Okay, now see if we can stuff it in the buffer as-is.
+	 */
+	max_headroom = LL_RESERVED_SPACE(tdev)+sizeof(struct iphdr);
+
+	if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) {
+		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
+		if (!new_skb) {
+			ip_rt_put(rt);
+  			stats->tx_dropped++;
+			dev_kfree_skb(skb);
+			tunnel->recursion--;
+			return 0;
+		}
+		if (skb->sk)
+			skb_set_owner_w(new_skb, skb->sk);
+		dev_kfree_skb(skb);
+		skb = new_skb;
+		iph6 = skb->nh.ipv6h;
+	}
+
+	skb->h.raw = skb->nh.raw;
+	skb->nh.raw = skb_push(skb, sizeof(struct iphdr));
+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+	dst_release(skb->dst);
+	skb->dst = &rt->u.dst;
+
+	/*
+	 *	Push down and install the IPIP header.
+	 */
+
+	iph 			=	skb->nh.iph;
+	iph->version		=	4;
+	iph->ihl		=	sizeof(struct iphdr)>>2;
+	if (mtu > IPV6_MIN_MTU)
+		iph->frag_off	=	htons(IP_DF);
+	else
+		iph->frag_off	=	0;
+
+	iph->protocol		=	IPPROTO_IPV6;
+	iph->tos		=	INET_ECN_encapsulate(tos, ipv6_get_dsfield(iph6));
+	iph->daddr		=	rt->rt_dst;
+	iph->saddr		=	rt->rt_src;
+
+	if ((iph->ttl = tiph->ttl) == 0)
+		iph->ttl	=	iph6->hop_limit;
+
+	nf_reset(skb);
+
+	IPTUNNEL_XMIT();
+	tunnel->recursion--;
+	return 0;
+
+tx_error_icmp:
+	dst_link_failure(skb);
+tx_error:
+	stats->tx_errors++;
+	dev_kfree_skb(skb);
+	tunnel->recursion--;
+	return 0;
+}
+
+static int
+ipip6_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
+{
+	int err = 0;
+	struct ip_tunnel_parm p;
+	struct ip_tunnel *t;
+
+	switch (cmd) {
+	case SIOCGETTUNNEL:
+		t = NULL;
+		if (dev == ipip6_fb_tunnel_dev) {
+			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
+				err = -EFAULT;
+				break;
+			}
+			t = ipip6_tunnel_locate(&p, 0);
+		}
+		if (t == NULL)
+			t = (struct ip_tunnel*)dev->priv;
+		memcpy(&p, &t->parms, sizeof(p));
+		if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
+			err = -EFAULT;
+		break;
+
+	case SIOCADDTUNNEL:
+	case SIOCCHGTUNNEL:
+		err = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			goto done;
+
+		err = -EFAULT;
+		if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
+			goto done;
+
+		err = -EINVAL;
+		if (p.iph.version != 4 || p.iph.protocol != IPPROTO_IPV6 ||
+		    p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)))
+			goto done;
+		if (p.iph.ttl)
+			p.iph.frag_off |= htons(IP_DF);
+
+		t = ipip6_tunnel_locate(&p, cmd == SIOCADDTUNNEL);
+
+		if (dev != ipip6_fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {
+			if (t != NULL) {
+				if (t->dev != dev) {
+					err = -EEXIST;
+					break;
+				}
+			} else {
+				if (((dev->flags&IFF_POINTOPOINT) && !p.iph.daddr) ||
+				    (!(dev->flags&IFF_POINTOPOINT) && p.iph.daddr)) {
+					err = -EINVAL;
+					break;
+				}
+				t = (struct ip_tunnel*)dev->priv;
+				ipip6_tunnel_unlink(t);
+				t->parms.iph.saddr = p.iph.saddr;
+				t->parms.iph.daddr = p.iph.daddr;
+				memcpy(dev->dev_addr, &p.iph.saddr, 4);
+				memcpy(dev->broadcast, &p.iph.daddr, 4);
+				ipip6_tunnel_link(t);
+				netdev_state_change(dev);
+			}
+		}
+
+		if (t) {
+			err = 0;
+			if (cmd == SIOCCHGTUNNEL) {
+				t->parms.iph.ttl = p.iph.ttl;
+				t->parms.iph.tos = p.iph.tos;
+			}
+			if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof(p)))
+				err = -EFAULT;
+		} else
+			err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
+		break;
+
+	case SIOCDELTUNNEL:
+		err = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			goto done;
+
+		if (dev == ipip6_fb_tunnel_dev) {
+			err = -EFAULT;
+			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
+				goto done;
+			err = -ENOENT;
+			if ((t = ipip6_tunnel_locate(&p, 0)) == NULL)
+				goto done;
+			err = -EPERM;
+			if (t == ipip6_fb_tunnel_dev->priv)
+				goto done;
+			dev = t->dev;
+		}
+		err = unregister_netdevice(dev);
+		break;
+
+	default:
+		err = -EINVAL;
+	}
+
+done:
+	return err;
+}
+
+static struct net_device_stats *ipip6_tunnel_get_stats(struct net_device *dev)
+{
+	return &(((struct ip_tunnel*)dev->priv)->stat);
+}
+
+static int ipip6_tunnel_change_mtu(struct net_device *dev, int new_mtu)
+{
+	if (new_mtu < IPV6_MIN_MTU || new_mtu > 0xFFF8 - sizeof(struct iphdr))
+		return -EINVAL;
+	dev->mtu = new_mtu;
+	return 0;
+}
+
+static void ipip6_tunnel_setup(struct net_device *dev)
+{
+	SET_MODULE_OWNER(dev);
+	dev->uninit		= ipip6_tunnel_uninit;
+	dev->destructor 	= free_netdev;
+	dev->hard_start_xmit	= ipip6_tunnel_xmit;
+	dev->get_stats		= ipip6_tunnel_get_stats;
+	dev->do_ioctl		= ipip6_tunnel_ioctl;
+	dev->change_mtu		= ipip6_tunnel_change_mtu;
+
+	dev->type		= ARPHRD_SIT;
+	dev->hard_header_len 	= LL_MAX_HEADER + sizeof(struct iphdr);
+	dev->mtu		= 1500 - sizeof(struct iphdr);
+	dev->flags		= IFF_NOARP;
+	dev->iflink		= 0;
+	dev->addr_len		= 4;
+}
+
+static int ipip6_tunnel_init(struct net_device *dev)
+{
+	struct net_device *tdev = NULL;
+	struct ip_tunnel *tunnel;
+	struct iphdr *iph;
+
+	tunnel = (struct ip_tunnel*)dev->priv;
+	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);
+
+	if (iph->daddr) {
+		struct flowi fl = { .nl_u = { .ip4_u =
+					      { .daddr = iph->daddr,
+						.saddr = iph->saddr,
+						.tos = RT_TOS(iph->tos) } },
+				    .oif = tunnel->parms.link,
+				    .proto = IPPROTO_IPV6 };
+		struct rtable *rt;
+		if (!ip_route_output_key(&rt, &fl)) {
+			tdev = rt->u.dst.dev;
+			ip_rt_put(rt);
+		}
+		dev->flags |= IFF_POINTOPOINT;
+	}
+
+	if (!tdev && tunnel->parms.link)
+		tdev = __dev_get_by_index(tunnel->parms.link);
+
+	if (tdev) {
+		dev->hard_header_len = tdev->hard_header_len + sizeof(struct iphdr);
+		dev->mtu = tdev->mtu - sizeof(struct iphdr);
+		if (dev->mtu < IPV6_MIN_MTU)
+			dev->mtu = IPV6_MIN_MTU;
+	}
+	dev->iflink = tunnel->parms.link;
+
+	return 0;
+}
+
+int __init ipip6_fb_tunnel_init(struct net_device *dev)
+{
+	struct ip_tunnel *tunnel = dev->priv;
+	struct iphdr *iph = &tunnel->parms.iph;
+
+	tunnel->dev = dev;
+	strcpy(tunnel->parms.name, dev->name);
+
+	iph->version		= 4;
+	iph->protocol		= IPPROTO_IPV6;
+	iph->ihl		= 5;
+	iph->ttl		= 64;
+
+	dev_hold(dev);
+	tunnels_wc[0]		= tunnel;
+	return 0;
+}
+
+static struct net_protocol sit_protocol = {
+	.handler	=	ipip6_rcv,
+	.err_handler	=	ipip6_err,
+};
+
+void __exit sit_cleanup(void)
+{
+	inet_del_protocol(&sit_protocol, IPPROTO_IPV6);
+	unregister_netdev(ipip6_fb_tunnel_dev);
+}
+
+int __init sit_init(void)
+{
+	int err;
+
+	printk(KERN_INFO "IPv6 over IPv4 tunneling driver\n");
+
+	if (inet_add_protocol(&sit_protocol, IPPROTO_IPV6) < 0) {
+		printk(KERN_INFO "sit init: Can't add protocol\n");
+		return -EAGAIN;
+	}
+
+	ipip6_fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "sit0", 
+					   ipip6_tunnel_setup);
+	if (!ipip6_fb_tunnel_dev) {
+		err = -ENOMEM;
+		goto err1;
+	}
+
+	ipip6_fb_tunnel_dev->init = ipip6_fb_tunnel_init;
+
+	if ((err =  register_netdev(ipip6_fb_tunnel_dev)))
+		goto err2;
+
+ out:
+	return err;
+ err2:
+	free_netdev(ipip6_fb_tunnel_dev);
+ err1:
+	inet_del_protocol(&sit_protocol, IPPROTO_IPV6);
+	goto out;
+}