Re: [PATCH net-next 4/4] net/sched: act_mirred: Implement ingress actions

Hi,

On Thu, 22 Sep 2016 19:40:15 -0400 Jamal Hadi Salim [off-list ref] wrote:

On 16-09-22 09:21 AM, Shmulik Ladkani wrote:

quoted

From: Shmulik Ladkani <redacted>

Up until now, 'action mirred' supported only egress actions (either
TCA_EGRESS_REDIR or TCA_EGRESS_MIRROR).

This patch implements the corresponding ingress actions
TCA_INGRESS_REDIR and TCA_INGRESS_MIRROR.

This allows attaching filters whose target is to hand matching skbs into
the rx processing of a specified device.

Thank you for doing this. There was something that made me remove
initial support for this feature - I am blanking out right now but
will find my notes and give more details.

Thanks Jamal, appreciate any details.

Was wondering why it's missing, googled a bit with no meaningful
results, so speculated the following:

Some time long ago, initial 'mirred' purpose was to facilitate ifb.
Therefore 'egress redirect' was implemented. Jamal probably left the
'ingress' support for a later time :)

One interesting usecase for 'ingress redirect' is creating "rx bouncing"
construct (like macvlan/macvtap/ipvlan) but applied according to custom
logic.

It may be around preventing loops maybe.

Could be, but personally, I treat these constructs as (powerful)
building blocks, and "with great power comes great responsibility".

Even today, one may create loops using existing 'egress redirect',
e.g. this rediculously errorneous construct:

 # ip l add v0 type veth peer name v0p 
 # tc filter add dev v0p parent ffff: basic \
    action mirred egress redirect dev v0

Regards,
Shmulik