[kwlug-disc] Puzzling network issue ...

[Khalid Baheyeldin]

I am having a puzzling issue with my VPN network, which uses Wireguard, and
has been working well for months.
Then a few days ago, things started going wrong.

A service (e.g. Home Assistant, Grafana) would load from my phone, but
fails to load from my laptop.
My phone and my laptop are peers in the Wireguard VPN.

The issue does not seem to be a firewall issue, because I have not changed
that at all, and I do see responses, but no traffic.

When I use curl, I get back a response, which is an HTTP redirect:

$ curl s1.example.com:3000
<a href="/login">Found</a>.

But when I go to that URL, the browser (or curl) hangs there indefinitely.

$ curl s1.example.com:3000/login # Grafana, Hangs

$ curl s1.example.com:8123/ # Home Assistant, Hangs

Again, some requests with errors do send back responses:

$ curl s1.example.com:8123/foo # Home Assistant, with an invalid URL
404: Not Found

But I do see bytes being queued in netstat on the target machine (3rd
column).

tcp 0 5606 10.10.0.4:8123 10.10.0.2:50322 ESTABLISHED 4071/python3

Then it goes from ESTABLISHED to CLOSING to CLOSE_WAIT ...etc.

I restarted the Wireguard tunnels on both machines, just in case:

$ sudo systemctl status wg-quick at wg0

And it made no difference.

This is happening for various services, but only from specific machines,
but not others.

How can one go about troubleshooting this pesky problem?
-- 
Khalid M. Baheyeldin
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