Re: IPv6 checksum errors with divert

From: Peter <>
Date: Sat, 30 Oct 2021 23:33:23 UTC
Hi Andrey, hi all,

  there is at least one further issue with divert (and dummynet)
and IPv6:
If I put EITHER a divert OR a dummynet pipe/queue into the OUTgoing
(layer3) ruleset to the uplink interface, then Youtube is not able to
insert their advertisments into playback, and may hang entirly on

That seems to not happen due to timing or bandwith issues, but due to
the sheer existance of a dummynet (or divert). And if I move the
dummynet to the incoming, INTRAnet-facing side of the router, the
problem does not appear.

So there must still be some other bit in the IPv6 (or in the mbuf?)
that gets improperly mangled during divert and also during dummynet.

It appears a bit difficult to hunt that one down, due to the sheer
amount of traffic involved in YT streaming, and also since I do not
know exactly for what to look...

Any helpful ideas are welcome.