Re: [Accel-ppp-users] discarding message with invalid tid 0

[Guillaume N. <g....@al...>]

On Fri, Oct 05, 2018 at 04:29:23PM +0200, Alarig Le Lay wrote:
> On ven.  5 oct. 15:49:48 2018, Guillaume Nault wrote:
> > Thanks for the trace. Do BGP and L2TP run on the same machine? Or is
> > the second "BGP" trace taken from a different machine? I ask because
> > I'm surprised to see incorrect checksums on your second trace. If this
> > machine only acts as a router between your L2TP server and your
> > provider we should have correct checksums, regardless of offloading
> > options.
> 
> They are on different machines. My LNS is a gentoo and my BGP router a
> FreeBSD.
> 
> The offloading on linux doesn’t change anything, but disabling it on the
> router made tunnel going up instantaneously.
> 
Which kernel version is your Gentoo? Could you send a pcap of a
successful tunnel establishment (one from the Gentoo and one from the
FreeBSD, as you did in your previous message)?

> root@bgp-adsl:~ # ifconfig vtnet2 -rxcsum -txcsum -tso -lro
> 
> Thanks for the hint!
> 
> BTW, my other LNS uses xl2tpd (and a patched PPP plus kea for IPv6) and
> wasn’t impacted. I’m not enough skilled to see the differences in the
> code.
> 
I guess something is still wrong. It would be strange if it was the
router that was at fault.
My guess is that, by disabling offloads, the router stopped checking
the UDP checksum of transit packets. If the LAC does not verify UDP
checksums, then invalid checksums don't prevent the LAC and LNS from
communicating. If you capture trafic on the router, do you still see
invalid checksums for packets originated by the LNS? And correct
checksums for packets sent by the other LNS?