[Qemu-devel] [PATCH v3] rtl8139: add vlan support

[Benjamin Poirier <benjamin.poirier@gmail.com>]

I've posted v2 of these patches back in november
http://article.gmane.org/gmane.comp.emulators.qemu/84252

Changes since v2:

insertion:
	* moved insertion later in the process, to handle tso
	* use qemu_sendv_packet() to insert the tag for us
	* added dot1q_buf parameter to rtl8139_do_receive() to avoid some
	  memcpy() in loopback mode. Note that the code path through that
	  function is unchanged when dot1q_buf is NULL.

extraction:
	* reduced the amount of copying by moving the "frame too short" logic
	  after the removal of the vlan tag (as is done in e1000.c for
	  example). Unfortunately, that logic can no longer be shared betwen
	  C+ and C mode.

I've tested on the following combinations of guest and hosts:
host: x86_64, guest: x86_64
host: x86_64, guest: ppc32
host: ppc32, guest: ppc32

Testing on the x86_64 host used '-net tap' and consisted of:
* making an http transfert on the untagged interface.
* ping -s 0-1472 to another host on a vlan.
* making an scp upload to another host on a vlan.

Testing on the ppc32 host used '-net socket' connected to an x86_64 qemu-kvm
running the virtio nic and consisted of:
* establishing an ssh connection between the two using an untagged interface.
* ping -s 0-1472 to the ppc32 using a vlan.
* making an scp transfer in both directions using a vlan.

All that was successful. Nevertheless, it doesn't exercise all code paths so
care is in order.

Please note that the lack of vlan support in rtl8139 has taken a few people
aback:
https://bugzilla.redhat.com/show_bug.cgi?id=516587
http://article.gmane.org/gmane.linux.network.general/14266

Thanks,
-Ben