netdev-dummy: Use netdev_get_devices() instead of a local shash.

When an upcoming commit introduces thread safety into the netdev API, this
allows netdev-dummy to avoid adding more internal locking by taking
advantage of netdev_get_devices() refcounting.

Signed-off-by: Ben Pfaff <blp@nicira.com>
netdev-linux, netdev-bsd: Make access to AF_INET socket thread-safe.

The only uses of 'af_inet_sock', in both drivers, were ioctls, so it seemed
like a good abstraction to write a function that just does such an ioctl,
and to factor out shared code into socket-util.

Signed-off-by: Ben Pfaff <blp@nicira.com>
CC: Ed Maste <emaste@freebsd.org>
netdev-bsd: Make use of AF_LINK socket thread-safe in NetBSD.

Signed-off-by: Ben Pfaff <blp@nicira.com>
CC: Ed Maste <emaste@freebsd.org>
CC: YAMAMOTO Takashi <yamt@mwd.biglobe.ne.jp>
netdev: Adopt four-step alloc/construct/destruct/dealloc lifecycle.

This is the same lifecycle used in the ofproto provider interface.
Compared to the previous netdev provider interface, it has the
advantage that the netdev top layer can control when any given
netdev becomes visible to the outside world.

Signed-off-by: Ben Pfaff <blp@nicira.com>
netdev-vport: Make netdev_vport_patch_peer() return a malloc()'d string.

When threading comes into the picture there arises the possibility of a
race between netdev_vport_patch_peer()'s caller using the returned string
and another caller changing the peer.  It is safer to return a copy.

Signed-off-by: Ben Pfaff <blp@nicira.com>
netdev-linux: Use dedicated netlink notification socket.

The rtnetlink_link asynchronous netlink notifications seem somewhat
troublesome in a threaded environment.  It seems more straightforward
to have netdev-linux fend for itself.

Signed-off-by: Ben Pfaff <blp@nicira.com>
netdev: Make netdev access thread-safe.

Signed-off-by: Ben Pfaff <blp@nicira.com>