[ovs-dev] [PATCH] netdev-linux: do not send packets to down tap ifaces.

[Ben Pfaff]

On Wed, Jan 10, 2018 at 02:06:43PM -0200, Flavio Leitner wrote:
> Today OVS pushes packets to the TAP interface ignoring its
> current state. That works because the kernel will return -EIO
> when it's not UP and OVS will just ignore that as it is not
> an OVS issue.
> 
> However, it causes a huge impact when broadcasts happen when
> using userspace datapath accelerated with DPDK (e.g.: action
> NORMAL).  This patch improves the situation by checking the
> TAP's interface state before issueing any syscall.
> 
> However, there might be use-cases moving interfaces to other
> networking namespaces and in that case, OVS can't retrieve
> the iface state (sets it to DOWN). That would stop the traffic
> breaking the use-case. This patch relies on netlink notifications
> to find out if the device is local or not. When it's local, the
> device state is checked otherwise it will behave as before.
> 
> Signed-off-by: Flavio Leitner <fbl at sysclose.org>

Can you help me understand the "huge impact"?  What kind of impact?

Thanks,

Ben.