[PATCH v4] virtio-network: Clarify VLAN filter table configuration

[Parav Pandit <parav@nvidia.com>]

The filtering behavior of the VLAN filter commands is not very clear as
discussed in thread [1].

Hence, add the command description and device requirements for it.

[1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg912392.html
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/147
Suggested-by: Si-Wei Liu <si-wei.liu@oracle.com>
Signed-off-by: Parav Pandit <parav@nvidia.com>
---
changelog:
v3->v4:
- added description for accepting vlan tagged packets when vlan
  filter is not negotiated
v2->v3:
- corrected grammar
- simplified description for untagged packets
v1->v2:
- adapt to new file path
v0->v1:
- added missing conformance section link
---
 .../virtio-network/device-conformance.tex     |  1 +
 device-types/virtio-network/device.tex        | 22 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/device-types/virtio-network/device-conformance.tex b/device-types/virtio-network/device-conformance.tex
index c686377..54f6783 100644
--- a/device-types/virtio-network/device-conformance.tex
+++ b/device-types/virtio-network/device-conformance.tex
@@ -9,6 +9,7 @@
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Processing of Incoming Packets}
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Packet Receive Filtering}
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Setting MAC Address Filtering}
+\item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / VLAN Filtering}
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Gratuitous Packet Sending}
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode}
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS processing}
diff --git a/device-types/virtio-network/device.tex b/device-types/virtio-network/device.tex
index e7cdd6f..0e6d872 100644
--- a/device-types/virtio-network/device.tex
+++ b/device-types/virtio-network/device.tex
@@ -1210,6 +1210,28 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
 Both the VIRTIO_NET_CTRL_VLAN_ADD and VIRTIO_NET_CTRL_VLAN_DEL
 command take a little-endian 16-bit VLAN id as the command-specific-data.
 
+VIRTIO_NET_CTRL_VLAN_ADD command adds the specified VLAN to the VLAN
+filtering table.
+
+VIRTIO_NET_CTRL_VLAN_DEL command removes specified VLAN from the VLAN
+filtering table which was previously added using
+VIRTIO_NET_CTRL_VLAN_ADD command.
+
+\devicenormative{\subparagraph}{VLAN Filtering}{Device Types / Network Device / Device Operation / Control Virtqueue / VLAN Filtering}
+
+When VIRTIO_NET_F_CTRL_VLAN is not negotiated, the device accepts
+all VLAN tagged packets that matches the device's filter
+configuration.
+
+When VIRTIO_NET_F_CTRL_VLAN is negotiated, the device starts with
+an empty VLAN filtering table.
+
+When VIRTIO_NET_F_CTRL_VLAN is negotiated, the device accepts all
+VLAN tagged packets whose VLAN tag is found in the VLAN filtering
+table; the device should drop all VLAN tagged packets whose VLAN tag
+is not found in the VLAN filtering table. The VLAN filtering table
+applies only to the VLAN tagged packets.
+
 \subparagraph{Legacy Interface: VLAN Filtering}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / VLAN Filtering / Legacy Interface: VLAN Filtering}
 When using the legacy interface, transitional devices and drivers
 MUST format the VLAN id
-- 
2.26.2