[RFC] content: explicitly document the VLAN filtering as best-effort

[Tiwei Bie <tiwei.bie@intel.com>]

Similar to the MAC address based filtering, the VLAN filtering
is also best-effort in implementations, but it's not quite clear
in the spec. So document this behaviour explicitly to reflect
the way implementations behave.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
---
This is a RFC for now (Comments would be appreciated!).
More details can be found here:
https://patchwork.ozlabs.org/patch/1113538/

 content.tex | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/content.tex b/content.tex
index 8f0498e..783322b 100644
--- a/content.tex
+++ b/content.tex
@@ -3530,6 +3530,11 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
 If the driver negotiates the VIRTION_NET_F_CTRL_VLAN feature, it
 can control a VLAN filter table in the device.
 
+\begin{note}
+Similar to the MAC address based filtering, the VLAN filtering
+is also best-effort: unwanted packets could still arrive.
+\end{note}
+
 \begin{lstlisting}
 #define VIRTIO_NET_CTRL_VLAN       2
  #define VIRTIO_NET_CTRL_VLAN_ADD             0
-- 
2.17.1