From: Daniel Lezcano <dlezcano@fr.ibm.com>

Doing this makes loopback.c a better example of how to do a
simple network device, and it removes the special case
single static allocation of a struct net_device, hopefully
making maintenance easier.

Applies against net-2.6.24

Tested on i386, x86_64
Compiled on ia64, sparc

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Acked-By: Kirill Korotaev <dev@sw.ru>
Acked-by: Benjamin Thery <benjamin.thery@bull.net>
---
 drivers/net/loopback.c           |   63 +++++++++++++++++++++++---------------
 include/linux/netdevice.h        |    2 +-
 net/core/dst.c                   |    8 ++--
 net/decnet/dn_dev.c              |    4 +-
 net/decnet/dn_route.c            |   14 ++++----
 net/ipv4/devinet.c               |    6 ++--
 net/ipv4/ipconfig.c              |    6 ++--
 net/ipv4/ipvs/ip_vs_core.c       |    2 +-
 net/ipv4/route.c                 |   18 +++++-----
 net/ipv4/xfrm4_policy.c          |    2 +-
 net/ipv6/addrconf.c              |   15 +++++---
 net/ipv6/ip6_input.c             |    2 +-
 net/ipv6/netfilter/ip6t_REJECT.c |    2 +-
 net/ipv6/route.c                 |   15 +++-----
 net/ipv6/xfrm6_policy.c          |    2 +-
 net/xfrm/xfrm_policy.c           |    4 +-
 16 files changed, 89 insertions(+), 76 deletions(-)

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 5106c23..3642aff 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -199,44 +199,57 @@ static const struct ethtool_ops loopback_ethtool_ops = {
 	.get_rx_csum		= always_on,
 };
 
-/*
- * The loopback device is special. There is only one instance and
- * it is statically allocated. Don't do this for other devices.
- */
-struct net_device loopback_dev = {
-	.name	 		= "lo",
-	.get_stats		= &get_stats,
-	.mtu			= (16 * 1024) + 20 + 20 + 12,
-	.hard_start_xmit	= loopback_xmit,
-	.hard_header		= eth_header,
-	.hard_header_cache	= eth_header_cache,
-	.header_cache_update	= eth_header_cache_update,
-	.hard_header_len	= ETH_HLEN,	/* 14	*/
-	.addr_len		= ETH_ALEN,	/* 6	*/
-	.tx_queue_len		= 0,
-	.type			= ARPHRD_LOOPBACK,	/* 0x0001*/
-	.rebuild_header		= eth_rebuild_header,
-	.flags			= IFF_LOOPBACK,
-	.features 		= NETIF_F_SG | NETIF_F_FRAGLIST
+static void loopback_setup(struct net_device *dev)
+{
+	dev->get_stats		= &get_stats;
+	dev->mtu		= (16 * 1024) + 20 + 20 + 12;
+	dev->hard_start_xmit	= loopback_xmit;
+	dev->hard_header	= eth_header;
+	dev->hard_header_cache	= eth_header_cache;
+	dev->header_cache_update = eth_header_cache_update;
+	dev->hard_header_len	= ETH_HLEN;	/* 14	*/
+	dev->addr_len		= ETH_ALEN;	/* 6	*/
+	dev->tx_queue_len	= 0;
+	dev->type		= ARPHRD_LOOPBACK;	/* 0x0001*/
+	dev->rebuild_header	= eth_rebuild_header;
+	dev->flags		= IFF_LOOPBACK;
+	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
 #ifdef LOOPBACK_TSO
 				  | NETIF_F_TSO
 #endif
 				  | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA
-				  | NETIF_F_LLTX,
-	.ethtool_ops		= &loopback_ethtool_ops,
-};
+				  | NETIF_F_LLTX;
+	dev->ethtool_ops	= &loopback_ethtool_ops;
+}
 
 /* Setup and register the loopback device. */
 static int __init loopback_init(void)
 {
-	int err = register_netdev(&loopback_dev);
+	struct net_device *dev;
+	int err;
+	
+	err = -ENOMEM;
+	dev = alloc_netdev(0, "lo", loopback_setup);
+	if (!dev)
+		goto out;
+
+	err = register_netdev(dev);
+	if (err)
+		goto out_free_netdev;
 
+	err = 0;
+	loopback_dev = dev;
+
+out:
 	if (err)
 		panic("loopback: Failed to register netdevice: %d\n", err);
-
 	return err;
+out_free_netdev:
+	free_netdev(dev);
+	goto out;
 };
 
-module_init(loopback_init);
+fs_initcall(loopback_init);
 
+struct net_device *loopback_dev;
 EXPORT_SYMBOL(loopback_dev);
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8d12f02..7cd0641 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -680,7 +680,7 @@ struct packet_type {
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
 
-extern struct net_device		loopback_dev;		/* The loopback */
+extern struct net_device		*loopback_dev;		/* The loopback */
 extern struct list_head			dev_base_head;		/* All devices */
 extern rwlock_t				dev_base_lock;		/* Device list lock */
 
diff --git a/net/core/dst.c b/net/core/dst.c
index c6a0587..ad8549e 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -236,13 +236,13 @@ static inline void dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 	if (!unregister) {
 		dst->input = dst->output = dst_discard;
 	} else {
-		dst->dev = &loopback_dev;
-		dev_hold(&loopback_dev);
+		dst->dev = loopback_dev;
+		dev_hold(dst->dev);
 		dev_put(dev);
 		if (dst->neighbour && dst->neighbour->dev == dev) {
-			dst->neighbour->dev = &loopback_dev;
+			dst->neighbour->dev = loopback_dev;
 			dev_put(dev);
-			dev_hold(&loopback_dev);
+			dev_hold(dst->neighbour->dev);
 		}
 	}
 }
diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c
index fa6604f..9fea83e 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -868,10 +868,10 @@ last_chance:
 		rv = dn_dev_get_first(dev, addr);
 		read_unlock(&dev_base_lock);
 		dev_put(dev);
-		if (rv == 0 || dev == &loopback_dev)
+		if (rv == 0 || dev == loopback_dev)
 			return rv;
 	}
-	dev = &loopback_dev;
+	dev = loopback_dev;
 	dev_hold(dev);
 	goto last_chance;
 }
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index a4a6209..8c04ebc 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -883,7 +883,7 @@ static int dn_route_output_slow(struct dst_entry **pprt, const struct flowi *old
 					.scope = RT_SCOPE_UNIVERSE,
 				     } },
 			    .mark = oldflp->mark,
-			    .iif = loopback_dev.ifindex,
+			    .iif = loopback_dev->ifindex,
 			    .oif = oldflp->oif };
 	struct dn_route *rt = NULL;
 	struct net_device *dev_out = NULL, *dev;
@@ -900,7 +900,7 @@ static int dn_route_output_slow(struct dst_entry **pprt, const struct flowi *old
 		       "dn_route_output_slow: dst=%04x src=%04x mark=%d"
 		       " iif=%d oif=%d\n", dn_ntohs(oldflp->fld_dst),
 		       dn_ntohs(oldflp->fld_src),
-		       oldflp->mark, loopback_dev.ifindex, oldflp->oif);
+		       oldflp->mark, loopback_dev->ifindex, oldflp->oif);
 
 	/* If we have an output interface, verify its a DECnet device */
 	if (oldflp->oif) {
@@ -953,7 +953,7 @@ source_ok:
 		err = -EADDRNOTAVAIL;
 		if (dev_out)
 			dev_put(dev_out);
-		dev_out = &loopback_dev;
+		dev_out = loopback_dev;
 		dev_hold(dev_out);
 		if (!fl.fld_dst) {
 			fl.fld_dst =
@@ -962,7 +962,7 @@ source_ok:
 			if (!fl.fld_dst)
 				goto out;
 		}
-		fl.oif = loopback_dev.ifindex;
+		fl.oif = loopback_dev->ifindex;
 		res.type = RTN_LOCAL;
 		goto make_route;
 	}
@@ -1008,7 +1008,7 @@ source_ok:
 					if (dev_out)
 						dev_put(dev_out);
 					if (dn_dev_islocal(neigh->dev, fl.fld_dst)) {
-						dev_out = &loopback_dev;
+						dev_out = loopback_dev;
 						res.type = RTN_LOCAL;
 					} else {
 						dev_out = neigh->dev;
@@ -1029,7 +1029,7 @@ source_ok:
 		/* Possible improvement - check all devices for local addr */
 		if (dn_dev_islocal(dev_out, fl.fld_dst)) {
 			dev_put(dev_out);
-			dev_out = &loopback_dev;
+			dev_out = loopback_dev;
 			dev_hold(dev_out);
 			res.type = RTN_LOCAL;
 			goto select_source;
@@ -1065,7 +1065,7 @@ select_source:
 			fl.fld_src = fl.fld_dst;
 		if (dev_out)
 			dev_put(dev_out);
-		dev_out = &loopback_dev;
+		dev_out = loopback_dev;
 		dev_hold(dev_out);
 		fl.oif = dev_out->ifindex;
 		if (res.fi)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 5b77bda..808f529 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -203,7 +203,7 @@ static void inetdev_destroy(struct in_device *in_dev)
 	ASSERT_RTNL();
 
 	dev = in_dev->dev;
-	if (dev == &loopback_dev)
+	if (dev == loopback_dev)
 		return;
 
 	in_dev->dead = 1;
@@ -1058,7 +1058,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 			in_dev = inetdev_init(dev);
 			if (!in_dev)
 				return notifier_from_errno(-ENOMEM);
-			if (dev == &loopback_dev) {
+			if (dev == loopback_dev) {
 				IN_DEV_CONF_SET(in_dev, NOXFRM, 1);
 				IN_DEV_CONF_SET(in_dev, NOPOLICY, 1);
 			}
@@ -1074,7 +1074,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 	case NETDEV_UP:
 		if (dev->mtu < 68)
 			break;
-		if (dev == &loopback_dev) {
+		if (dev == loopback_dev) {
 			struct in_ifaddr *ifa;
 			if ((ifa = inet_alloc_ifa()) != NULL) {
 				ifa->ifa_local =
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index c5b2470..3ec7690 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -189,11 +189,11 @@ static int __init ic_open_devs(void)
 	rtnl_lock();
 
 	/* bring loopback device up first */
-	if (dev_change_flags(&loopback_dev, loopback_dev.flags | IFF_UP) < 0)
-		printk(KERN_ERR "IP-Config: Failed to open %s\n", loopback_dev.name);
+	if (dev_change_flags(loopback_dev, loopback_dev->flags | IFF_UP) < 0)
+		printk(KERN_ERR "IP-Config: Failed to open %s\n", loopback_dev->name);
 
 	for_each_netdev(dev) {
-		if (dev == &loopback_dev)
+		if (dev == loopback_dev)
 			continue;
 		if (user_dev_name[0] ? !strcmp(dev->name, user_dev_name) :
 		    (!(dev->flags & IFF_LOOPBACK) &&
diff --git a/net/ipv4/ipvs/ip_vs_core.c b/net/ipv4/ipvs/ip_vs_core.c
index f005a2f..7450326 100644
--- a/net/ipv4/ipvs/ip_vs_core.c
+++ b/net/ipv4/ipvs/ip_vs_core.c
@@ -961,7 +961,7 @@ ip_vs_in(unsigned int hooknum, struct sk_buff **pskb,
 	 *	... don't know why 1st test DOES NOT include 2nd (?)
 	 */
 	if (unlikely(skb->pkt_type != PACKET_HOST
-		     || skb->dev == &loopback_dev || skb->sk)) {
+