This commit introduces a new netdev type called "patch". A patch is a
pair of interfaces, in which frames sent through one of the devices
pop out of the other. This is useful for linking together datapaths.
A patch's only argument on creation is "peer", which specifies the other
side of the patch. A patch must be created in pairs, so a second netdev
must be created with the "name" and "peer" values reversed.
The current implementation is built using veth devices. Further, it's
limited to the veth devices which support configuration through sysfs.
This limits the ability to use a "patch" on 2.6.18 kernels using the
veth device we include (read: flavors of XenServer 5.5). In the not too
distant future, the implementation will be modified to use the new
kernel port abstraction introduced by Jesse Gross's forthcoming GRE
work. At that point, patch devices will work on any Linux platform
supported by OVS.
We only reconfigure netdevs if the arguments have changed, which
was previously detected based on a hash. This stores and compares
the full argument list to avoid any chance of missing changes due
to collisions.
We previously maintained a list of open devices inside of the
linux netdev. Since the netdev library now maintains this list,
it is better to use that list instead of our own.
This builds on earlier work that implemented netdev object refcounting.
However, rather than requiring explicit create and destroy calls,
these operations are now performed automatically based on the referenece
count. This is important because in certain situations it is not
possible to know whether a netdev has already been created. A
workaround existed (which looked fairly similar to this paradigm) but
introduced it's own issues. This simplifies and unifies the API.
This implements the userspace portion of GRE on Linux. It communicates
with the kernel module to setup tunnels using either Netlink or ioctls
as appropriate based on the kernel version.
Significant portions of this commit were actually written by
Justin Pettit.
This change adds netdev_create() and netdev_destroy() functions to allow
the creation of network devices through the netdev library. Previously,
network devices had to already exist or be created on demand through
netdev_open(). This caused problems such as not being able to specify
TAP devices as ports in ovs-vswitchd, which this patch fixes.
This also lays the groundwork for adding GRE and VDE support.
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.
