Re: [RFC v2 6/6] flow_dissector: Parse batman-adv unicast headers

On Wed, Dec 6, 2017 at 8:54 AM, Willem de Bruijn
[off-list ref] wrote:

On Wed, Dec 6, 2017 at 5:26 AM, Sven Eckelmann
[off-list ref] wrote:

quoted

On Dienstag, 5. Dezember 2017 09:19:45 CET Tom Herbert wrote:
[...]

quoted

Switch statements with cases having many LOC is hard to read and
__skb_flow_dissect is aleady quite convoluted to begin with.

I suggest putting this in a static function similar to how MPLS and
GRE are handled.

Perhaps it can even be behind a static key depending on whether any
devices are active, adjusted in batadv_hardif_(en|dis)able_interface.

It's aready in a switch statement so static key shouldn't make a
difference. Also, we have made flow dissector operate indendently of
whether to end protocol is enable (for instance GRE is dissected
regarless of whether and GRE tunnels are configured).

Tom

quoted

Thanks for the feedback.

I was not sure whether "inline" or an extra function would be preferred. I've
then decided to implement it like most of the other protocols. But since an
extra function is the preferred method for handling new protos, I will move it
to an extra function.

The change can already be found in
 https://git.open-mesh.org/linux-merge.git/shortlog/refs/heads/ecsv/flowdissector

I also saw that you've introduced in
commit 823b96939578 ("flow_dissector: Add control/reporting of encapsulation")
a flag to stop dissecting when something encapsulated was detected. It is not
100% clear to me when the  FLOW_DIS_ENCAPSULATION should be set and
FLOW_DISSECTOR_F_STOP_AT_ENCAP be checked. Only when there is IP/eth in IP
(like in the two examples from the commit message) or also when there is a
ethernet header, followed by batman-adv unicast header and again followed by
an ethernet header?

Please implement FLOW_DISSECTOR_F_STOP_AT_ENCAP. It may
be used in more flow dissector paths in the future.

The features are also used by GRE, which can encap Ethernet, for an example
that is closer to this protocol.