Bip

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=595408

Per Arnaud's comment there:

Tcp will detect such connection breakage only when bip sends data to
your ADSL ip and times out waiting for ACKs. So bip indeed
approximates when the connection is lost. The blreset_on_talk should
be useful to you as bip will replay logs as long as you did not reply
anything.

I don't see any trivial way to implement a better connection loss
detection for backlog reset. It should be feasible to delay backlog
resetting to only when we receive any data from client, which would
prevent some errors of the type you described (but not all).
Another way would be to poll the tcp buffer size and to reset logs
only when it's down to 0. It's probably the best solution.