Re: TCP connection closed without FIN or RST

On Wed, 2017-11-01 at 22:22 +0000, Vitaly Davidovich wrote:

Eric,

Yes I agree.  However the thing I’m still puzzled about is the client
application is not reading/draining the recvq - ok, the client tcp
stack should start advertising a 0 window size.  Does a 0 window size
count against the tcp_retries2? Is that what you were alluding to in
your first reply?

Every time we receive an (valid) ACK, with a win 0 or not, the counter
of attempts is cleared, given the opportunity for the sender to send 15
more probes.

If it *does* count towards the retries limit then a RST doesn’t seem
like a bad idea.  The client is responding with segments but the user
app there just isn’t draining the data.  Presumably that RST has a
good chance of reaching the client and then unblocking the read()
there with a peer reset error.  Or am I missing something?


If it doesn’t count towards the limit then I need to figure out why
the 0 window size segments weren’t being sent by the client.

Yes please :)

I will try to double check that the client was indeed advertising 0
window size.  There’s nothing special about that machine - it’s a
4.1.35 kernel as well.  I wouldn’t expect the tcp stack there to be
unresponsive just because the user app is sleeping.