Re: Some odd TCP behavior (timeouts)

From: Rodney W. Grimes <freebsd-rwg_at_gndrsh.dnsmgr.net>
Date: Wed, 19 May 2021 12:44:40 -0700 (PDT)
> Hello, 
> 
> I'm having a TCP connectivity issue stumping me and driving me crazy.
> The TLDR version: No more printing on my LaserJet (but ping works),
> while printing and the web interfacw works fine under Windows.
> Other TCP connections apparently flawless.
> Wireshark shows FreeBSD performing the three way handshake but
> then ignoring some packets sent from the printer (no ACKs)
> and retransmitting until timeout hits.
>  
> The details with the wireshark logs are on 
> https://superuser.com/questions/1649435/mysterious-tcp-http-issue-accessing-laserjet-web-interface
> 
> I have seen a few commits to CURRENT's tcp and timeout code recently.
> I went back to stable/13 as of two days ago, but still no joy.
> 
> Has anyone else noticed something going on with TCP?
> Especially HTTP/HTTPS, like connections timing out in rare cases?
> If you have a LaserJet (preferably 551dn), can you still access
> its web interface, or get a reply with
> 
>   printf "GET / HTTP/1.0\r\n\r\n" | nc LaserJet 80   # or 443.
> 
> Regards,
>         Jens

One thing that did change that comes to mind is the
fact FreeBSD now drops certain packets if timestamps
got negotiated.  Locally I have that turned off as
an unconfirmed suspect of some connection problems:

	sysctl net.inet.tcp.tolerate_missing_ts=1

You can try that, if it fixes the problem PLEASE let
us know!

> Jens Schweikhardt http://www.schweikhardt.net/
-- 
Rod Grimes                                                 rgrimes_at_freebsd.org
Received on Wed May 19 2021 - 19:44:40 UTC

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