Re: kern/55800: Data transfers stall when SACK is enabled

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/55800; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/55800: Data transfers stall when SACK is enabled
Date: Thu, 12 Nov 2020 07:08:01 -0000 (UTC)

 kim%netbsd.org@localhost (Kimmo Suominen) writes:
 
 > Sadly this also happens if both ends are running 9.1.  The transfer
 > stalled after about 1 GB of data having been transferred.  After
 > disabling SACK (on the local end) and restarting the transfer, it
 > completed without any stalling (transferring another 9 GB of data).
 
 The tcpdump shows that some packet from the sender gets lost and
 the receiver SACKs subsequent segments. The sender then stops.
 
 After an hour, the receiver pushes an ACK (still only for the
 received segments), but the sender continues sending packets of the
 stream as if nothing has happened. No retry packet is received
 in the sequence.
 
 Is there anything between sender and receiver? firewall? packet filter
 (also on either machine) that could drop the retry packets ?
 
 -- 
 -- 
                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."