tree 3b817e829128b4e2ac572681d6b0eece28fb1c83
parent cfe0ed63faadb7fd2bca336410ebce4d623e3e67
author Harald Welte <laforge@osmocom.org> 1612463178 +0100
committer Harald Welte <laforge@osmocom.org> 1612463282 +0100

gb: frame_relay: Detect link outage on "last receive seq nr == 0"

this is a bit of a hack.  Q.933 explicitly forbids either side from ever
sending a sequence number of '0'.  Values start from '1' and are modulo 256,
but '0' is always skipped.  So if the peer is sending us a "last received
sequence number of '0' it means it has not yet received any packets from us,
which in turn can only mean that it has just been restarted.  Let's treat
this as "service affecting condition" and notify upper layers.  This helps
particularly in recovering from rapidly re-starting peers, where the Q.933
nor NS have time to actually detect the connection was lost.

Change-Id: I960a7b17f2550cb49a7b9d72ed87cd271bb64122
Related: OS#4974