rtnetlink: support specifying device flags on device creation

commit e8469ed959c373c2ff9e6f488aa5a14971aebe1f
Author: Patrick McHardy <kaber@trash.net>
Date:   Tue Feb 23 20:41:30 2010 +0100

Support specifying the initial device flags when creating a device though
rtnl_link. Devices allocated by rtnl_create_link() are marked as INITIALIZING
in order to surpress netlink registration notifications. To complete setup,
rtnl_configure_link() must be called, which performs the device flag changes
and invokes the deferred notifiers if everything went well.

Two examples:

# add macvlan to eth0
#
$ ip link add link eth0 up allmulticast on type macvlan

[LINK]11: macvlan0@eth0: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether 26:f8:84:02:f9:2a brd ff:ff:ff:ff:ff:ff
[ROUTE]ff00::/8 dev macvlan0  table local  metric 256  mtu 1500 advmss 1440 hoplimit 0
[ROUTE]fe80::/64 dev macvlan0  proto kernel  metric 256  mtu 1500 advmss 1440 hoplimit 0
[LINK]11: macvlan0@eth0: <BROADCAST,MULTICAST,ALLMULTI,UP,LOWER_UP> mtu 1500
    link/ether 26:f8:84:02:f9:2a
[ADDR]11: macvlan0    inet6 fe80::24f8:84ff:fe02:f92a/64 scope link
       valid_lft forever preferred_lft forever
[ROUTE]local fe80::24f8:84ff:fe02:f92a via :: dev lo  table local  proto none  metric 0  mtu 16436 advmss 16376 hoplimit 0
[ROUTE]default via fe80::215:e9ff:fef0:10f8 dev macvlan0  proto kernel  metric 1024  mtu 1500 advmss 1440 hoplimit 0
[NEIGH]fe80::215:e9ff:fef0:10f8 dev macvlan0 lladdr 00:15:e9:f0:10:f8 router STALE
[ROUTE]2001:6f8:974::/64 dev macvlan0  proto kernel  metric 256  expires 0sec mtu 1500 advmss 1440 hoplimit 0
[PREFIX]prefix 2001:6f8:974::/64 dev macvlan0 onlink autoconf valid 14400 preferred 131084
[ADDR]11: macvlan0    inet6 2001:6f8:974:0:24f8:84ff:fe02:f92a/64 scope global dynamic
       valid_lft 86399sec preferred_lft 14399sec

# add VLAN to eth1, eth1 is down
#
$ ip link add link eth1 up type vlan id 1000
RTNETLINK answers: Network is down

<no events>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/veth.c

@@ -333,19 +333,17 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 	struct veth_priv *priv;
 	char ifname[IFNAMSIZ];
 	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp;
+	struct ifinfomsg *ifmp;
 	struct net *net;
 
 	/*
 	 * create and register peer first
-	 *
-	 * struct ifinfomsg is at the head of VETH_INFO_PEER, but we
-	 * skip it since no info from it is useful yet
 	 */
-
 	if (data != NULL && data[VETH_INFO_PEER] != NULL) {
 		struct nlattr *nla_peer;
 
 		nla_peer = data[VETH_INFO_PEER];
+		ifmp = nla_data(nla_peer);
 		err = nla_parse(peer_tb, IFLA_MAX,
 				nla_data(nla_peer) + sizeof(struct ifinfomsg),
 				nla_len(nla_peer) - sizeof(struct ifinfomsg),
@@ -358,8 +356,10 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 			return err;
 
 		tbp = peer_tb;
-	} else
+	} else {
+		ifmp = NULL;
 		tbp = tb;
+	}
 
 	if (tbp[IFLA_IFNAME])
 		nla_strlcpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
@@ -387,6 +387,10 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 
 	netif_carrier_off(peer);
 
+	err = rtnl_configure_link(peer, ifmp);
+	if (err < 0)
+		goto err_configure_peer;
+
 	/*
 	 * register dev last
 	 *
@@ -428,6 +432,7 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 err_register_dev:
 	/* nothing to do */
 err_alloc_name:
+err_configure_peer:
 	unregister_netdevice(peer);
 	return err;
 

include/net/rtnetlink.h

@@ -87,6 +87,8 @@ extern void	rtnl_link_unregister(struct rtnl_link_ops *ops);
 extern struct net *rtnl_link_get_net(struct net *src_net, struct nlattr *tb[]);
 extern struct net_device *rtnl_create_link(struct net *src_net, struct net *net,
 	char *ifname, const struct rtnl_link_ops *ops, struct nlattr *tb[]);
+extern int rtnl_configure_link(struct net_device *dev,
+			       const struct ifinfomsg *ifm);
 extern const struct nla_policy ifla_policy[IFLA_MAX+1];
 
 #define MODULE_ALIAS_RTNL_LINK(kind) MODULE_ALIAS("rtnl-link-" kind)

net/core/rtnetlink.c

@@ -549,6 +549,19 @@ static void set_operstate(struct net_device *dev, unsigned char transition)
 	}
 }
 
+static unsigned int rtnl_dev_combine_flags(const struct net_device *dev,
+					   const struct ifinfomsg *ifm)
+{
+	unsigned int flags = ifm->ifi_flags;
+
+	/* bugwards compatibility: ifi_change == 0 is treated as ~0 */
+	if (ifm->ifi_change)
+		flags = (flags & ifm->ifi_change) |
+			(dev->flags & ~ifm->ifi_change);
+
+	return flags;
+}
+
 static void copy_rtnl_link_stats(struct rtnl_link_stats *a,
 				 const struct net_device_stats *b)
 {
@@ -904,13 +917,7 @@ static int do_setlink(struct net_device *dev, struct ifinfomsg *ifm,
 	}
 
 	if (ifm->ifi_flags || ifm->ifi_change) {
-		unsigned int flags = ifm->ifi_flags;
-
-		/* bugwards compatibility: ifi_change == 0 is treated as ~0 */
-		if (ifm->ifi_change)
-			flags = (flags & ifm->ifi_change) |
-				(dev->flags & ~ifm->ifi_change);
-		err = dev_change_flags(dev, flags);
+		err = dev_change_flags(dev, rtnl_dev_combine_flags(dev, ifm));
 		if (err < 0)
 			goto errout;
 	}
@@ -1053,6 +1060,26 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	return 0;
 }
 
+int rtnl_configure_link(struct net_device *dev, const struct ifinfomsg *ifm)
+{
+	unsigned int old_flags;
+	int err;
+
+	old_flags = dev->flags;
+	if (ifm && (ifm->ifi_flags || ifm->ifi_change)) {
+		err = __dev_change_flags(dev, rtnl_dev_combine_flags(dev, ifm));
+		if (err < 0)
+			return err;
+	}
+
+	dev->rtnl_link_state = RTNL_LINK_INITIALIZED;
+	rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
+
+	__dev_notify_flags(dev, old_flags);
+	return 0;
+}
+EXPORT_SYMBOL(rtnl_configure_link);
+
 struct net_device *rtnl_create_link(struct net *src_net, struct net *net,
 	char *ifname, const struct rtnl_link_ops *ops, struct nlattr *tb[])
 {
@@ -1074,6 +1101,7 @@ struct net_device *rtnl_create_link(struct net *src_net, struct net *net,
 
 	dev_net_set(dev, net);
 	dev->rtnl_link_ops = ops;
+	dev->rtnl_link_state = RTNL_LINK_INITIALIZING;
 	dev->real_num_tx_queues = real_num_queues;
 
 	if (strchr(dev->name, '%')) {
@@ -1203,7 +1231,7 @@ replay:
 		if (!(nlh->nlmsg_flags & NLM_F_CREATE))
 			return -ENODEV;
 
-		if (ifm->ifi_index || ifm->ifi_flags || ifm->ifi_change)
+		if (ifm->ifi_index)
 			return -EOPNOTSUPP;
 		if (tb[IFLA_MAP] || tb[IFLA_MASTER] || tb[IFLA_PROTINFO])
 			return -EOPNOTSUPP;
@@ -1234,9 +1262,15 @@ replay:
 			err = ops->newlink(net, dev, tb, data);
 		else
 			err = register_netdevice(dev);
-		if (err < 0 && !IS_ERR(dev))
+		if (err < 0 && !IS_ERR(dev)) {
 			free_netdev(dev);
+			goto out;
+		}
 
+		err = rtnl_configure_link(dev, ifm);
+		if (err < 0)
+			unregister_netdevice(dev);
+out:
 		put_net(dest_net);
 		return err;
 	}