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

[Alarig Le L. <al...@sw...>]

On ven.  5 oct. 17:41:12 2018, Guillaume Nault wrote:
> 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)?

My Gentoo runs 4.14.65.
The offload on it is currently configured as following:
lns02 ~ # ethtool -k eth2 | grep offload
tcp-segmentation-offload: on
udp-fragmentation-offload: off
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: off [fixed]
l2-fwd-offload: off [fixed]
hw-tc-offload: off [fixed]
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: off [fixed]

The pcap for the Gentoo (LNS) and the FreeBSD (BGP) are here:
https://bulbizarre.swordarmor.fr/garbage/documents/l2tp-bgp-up.pcap
https://bulbizarre.swordarmor.fr/garbage/documents/l2tp-lns-up.pcap

> 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?

On the other LNS, I see [no chksum] for the L2TP packets, but [udp sum
ok] for the packets inside the L2TP.
10:29:30.286075 IP (tos 0x0, ttl 64, id 62207, offset 0, flags [DF], proto UDP (17), length 78)
    lns01.grifon.fr.l2tp > asr1002-2.par05.phibee-telecom.net.l2tp: [no cksum]  l2tp:[](4864/27122) {IP (tos 0x0, ttl 247, id 35539, offset 0, flags [none], proto TCP (6), length 40)
    www.planet-cards.com.https > 89.234.186.36.50369: Flags [.], cksum 0x71eb (correct), seq 315777840, ack 2253755653, win 51060, length 0}
10:29:30.294650 IP (tos 0x0, ttl 64, id 62216, offset 0, flags [DF], proto UDP (17), length 1416)
    lns01.grifon.fr.l2tp > asr1002-2.par05.phibee-telecom.net.l2tp: [no cksum]  l2tp:[](4864/14578) {IP (tos 0x0, ttl 58, id 0, offset 0, flags [DF], proto UDP (17), length 1378)
    213.152.1.79.static.not.updated.as8218.eu.https > 35.186.234.89.in-addr.arpa.48535: [udp sum ok] UDP, length 1350}

-- 
Alarig