On Fri, Dec 15, 2017 at 1:23 PM, Sven Eckelmann
[off-list ref] wrote:

Hi,

we are currently starting to use batman-adv as mesh protocol on multicore
embedded devices. These usually don't have a lot of CPU power per core but
are reasonable fast when using multiple cores.

It was noticed that sending was working very well but receiving was
basically only using on CPU core per neighbor. The reason for that is
format of the (normal) incoming packet:

  +--------------------+
  | ip(v6)hdr          |
  +--------------------+
  | inner ethhdr       |
  +--------------------+
  | batadv unicast hdr |
  +--------------------+
  | outer ethhdr       |
  +--------------------+

The flow dissector will therefore stop after parsing the outer ethernet
header and will not parse the actual ipv(4|6)/... header of the packet. Our
assumption was now that it would help us to add minimal support to the flow
dissector to jump over the batman-adv unicast and inner ethernet header
(like in gre ETH_P_TEB). The patch was implemented in a slightly hacky
way [1] and the results looked quite promising.

I didn't get any feedback how the files should actually be named and I am
not really happy with the current names - so please feel free to propose
better names.

The discussion of the RFC v2 can be found in the related patches of
https://patchwork.ozlabs.org/cover/844783/


Changes in v3:
==============

* removed change of uapi/linux/batman_adv.h to uapi/linux/batadv_genl.h
  - requested by Willem de Bruijn [off-list ref]
* removed naming fixes for enums/defines in uapi/linux/batadv_genl.h
  - requested by Willem de Bruijn [off-list ref]
* renamed uapi/linux/batadv.h to uapi/linux/batadv_packet.h
* moved batadv dissector functionality in own function
  - requested by Tom Herbert [off-list ref]
* added support for flags FLOW_DISSECTOR_F_STOP_AT_ENCAP and
  FLOW_DIS_ENCAPSULATION
  - requested by Willem de Bruijn [off-list ref]

Thanks for making these changes. The flow dissection looks good to me.

One possible issue is that this exposes kernel fixed width types u8/u16/..
to userspace. For posix compatibility reasons, uapi headers use the
variant with underscores.