how to debug intermitently slow SSH tunneled VNC session

[Ramiro Aceves <ea1abz%gmail.com@localhost>]

Hello

I am experiencing a weird problem with my RapberryPi4 8 GB RAM setup. RPi4 is connected via ethernet to the home router.


I start an ssh session from my Windows PC at work using Mingw64 to the home RPi4:


ssh -o ServerAliveInterval=60 -p 50006  -L 5901:127.0.0.1:5901 -L 50012:localhost:50012 user@host

Those ports are redirected by the home router to the RPi4 static IP address.


I launch vncserver normally:

netbsd-raspa4$ vncserver

New 'netbsd-raspa4:1 (ramiro)' desktop is netbsd-raspa4:1

Starting applications specified in /home/ramiro/.config/tigervnc/xstartup
Log file is /home/ramiro/.config/tigervnc/netbsd-raspa4:1.log

netbsd-raspa4$ vncserver -list

TigerVNC server sessions:

X DISPLAY #     PROCESS ID
:1              961
netbsd-raspa4$

XFCE4 session is up and running fine.

At work, in a Windows PC, I run Tigervncviewer at localhost:5901.

It starts working well, responsive enough  but some times, many times, it starts going slow, very slow, sometimes
it stucks, after some time it starts working ok, and so on.

When it is stuck, I cannot even write characters in the launched ssh session, or I can write them very very slow.

At that moment, I am able to launch another normal SSH session from the PC at work and works fine, very responsive.

I have also tried this with no appreciable improvements:



$ cat sshraspa4-vnc-gnuradio.sh-comprimido
#!/bin/sh
ssh -C -c chacha20-poly1305%openssh.com@localhost \
        -o ServerAliveInterval=60 \
        -o ServerAliveCountMax=3 \
        -o TCPKeepAlive=yes \
        -o IPQos=lowdelay \
        -p 50006 \
        -L 5901:127.0.0.1:5901 -L 50012:localhost:50012 \
        user@host

I have also tried something like :

ifconfig genet0 mtu 1300 with no improvements.

Any ideas to debug this are appreciated.

I have also noticed the same problem with a NetBSD amd64.

Regards.
Ramiro.