This new abstraction layer allows multiple implementations of network
devices in a single running process. This will be useful, for example, to
support network devices that are simulated entirely in the running process
or that communicate with other processes over Unix domain sockets, etc.
The reimplemented tap device support in this commit has not been tested.
For consistency, it's best if every netdev function takes a netdev instead
of a device name. The netdev_nodev_*() functions have always been a bit
ugly.
The netdev_nodev_*() functions have always been a bit of a kluge. It's
better to keep a network device open than to open it every time that it is
needed.
Also updates the only user of netdev_find_dev_by_in4().
When there is the possibility of multiple classes of netdevs,
netdev_add_router() needs to know which of these to use, so it needs a
"struct netdev *" parameter.
This new function allows cleanup of code that was using
netdev_nodev_get_flags() or ad-hoc methods to detect whether a network
device with the given name exists.
netdev_open() can always be used in place of netdev_open_tap(). The
former is going to be generalized to support pluggable network device
types, so it makes sense to use it everywhere.
Until now, netdev_get_in4() and netdev_nodev_get_in4() have returned a
bool that represents success or failure. This commit changes the return
value to an int that can indicate what kind of error occurred, which is
both more consistent with the rest of the netdev interfaces and more
meaningful, and updates all callers to the new interface.
(Currently netdev_get_in4() won't ever return an error, but other future
implementations might.)
To make the netdev code more portable, it needs to support returning error
codes from functions that don't have them. This commit changes
netdev_get_mtu() to return an error code and updates its caller.
(Currently netdev_get_mtu() won't ever return an error, but other future
implementations might.)
To make the netdev code more portable, it needs to support returning error
codes from functions that don't have them. This commit changes
netdev_get_etheraddr() to return an error code and updates all of its
callers.
(Currently netdev_get_etheraddr() won't ever return an error, but other
future implementations might.)
In some cases we need to be able to locate a device by its IPv4 address.
There doesn't seem to be an easy way to do this on Linux, so we iterate
through all devices until it's found. The caller can provide a hint as
to the device, so subsequent checks can be quicker.
This checkin also adds nodev versions of functions to lookup ARP entries
and the IPv4 address of a device.
The dpif and netdev code has had various ways to check for changes to
dpifs and netdevs over the course of Open vSwitch development. All of
these have been thus far fairly specific to the Linux implementation. This
commit is the start of a more general API for watching for such changes.
The dpif-related parts seem fairly mature and so they are documented,
the netdev parts will probably need to change somewhat and so they are
not documented yet.
