tree 2f00af36865d6a122b74e6a86c49e6dbc09f7216
parent 0e05ee7d90e110c8aae99754cd87b58970449ce2
author mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> 1476147499 +0000
committer mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> 1476147499 +0000

virtio-net: add Max MTU configuration field

It is helpful for a host to indicate it's MTU to be set on guest NICs
other than the assumed 1500 byte value.  This helps in situations where
the host network is using Jumbo Frames, or aiding in PMTU discovery by
configuring a homogenous network.  It is also helpful for sizing receive
buffers correctly.

The change adds a new field to configuration area of network
devices.  It will be used to pass a maximum MTU from the device to
the driver.  This will be used by the driver as a maximum value for
packet sizes during transmission, without segmentation offloading.

In addition, in order to support backward and forward compatibility,
we introduce a new feature bit called VIRTIO_NET_F_MTU.

VIRTIO-152

Signed-off-by: Aaron Conole <aconole@redhat.com>
Cc: Victor Kaplansky <victork@redhat.com>
Reviewed-by: Hannes Reiencke <hare@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@585 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652