Hello Tom,

Tom Herbert [off-list ref] writes:

This patch set adds a new offload type to perform flow dissection for
specific protocols (either by EtherType or by IP protocol). This is
primary useful to crack open UDP encapsulations (like VXLAN, GUE) for
the purposes of parsing the encapsulated packet.

Items in this patch set:
- Constify skb argument to UDP lookup functions
- Create new protocol case in __skb_dissect for ETH_P_TEB. This is based
  on the code in the GRE dissect function and the special handling in
  GRE can now be removed (it sets protocol to ETH_P_TEB and returns so
  goto proto_again is done)
- Add infrastructure for protocol specific flow dissection offload
- Add infrastructure to perform UDP flow dissection. Uses same model of
  GRO where a flow_dissect callback can be associated with a UDP
  socket
- Use the infrastructure to support flow dissection of VXLAN and GUE

Tested:

Forced RPS to call flow dissection for VXLAN, FOU, and GUE. Observed
that inner packet was being properly dissected.

v2: Add signed off

[...]

Can you provide more context on why you did this series? Is the entropy
insufficient you receive via UDP source ports? I assume this is the case
for HW RSS hashing but actually not for the software dissector.

Btw. we forbid hardware to use L4 information if IP_PROTO is UDP but we
allow it in RPS (not in IPv6 if flowlabel is present). Your series could
solve this problem by being more protocol specific and disallow
fragmentation on a particular quadtuple, very much the same like hw
encap offload, where we tell the specific port number to the hardware
and then disallow using L4 information for all other UDP protocols.

Thanks,
Hannes