Certain network requests error only inside VMs.

[Dor]

Hey,

I have Proxmox 5.2 installed on NUC for over a month and everything work fine.
In the recent days, I decided to create a new workstation VM machine, and noticed something strange.
Certain network request doesn't get finished at all, and it only occurs in VMs inside Proxmox. A specific Github request loads forever and doesn't finish. I couldn't even register to the forum inside the VM, but most of the network requests do work.

The network requests I've found so far:

• Go to any Github repo, with Adblock, uBlock, Ghostery or anything similar disabled. You should see a network requests with the following url: collector.githubapp.com - the requests loads forever until I get empty response in the browser.
  
• A simple registration to this forum doesn't work. The register page do work, but when I'm trying to complete it, I get "Check your internet connection" error.

Here is where I've tried to do the same requests:

• Proxmox - Fresh Arch Linux installation (This is where I've first noticed the issue) - doesn't work.
• Proxmox - Fresh Ubuntu Desktop installation - doesn't work.
• PC - Windows 10 - works fine
• VirtualBox - Fresh Ubuntu installation - work fine.

I can reproduce the issue both with the latest Firefox and Chrome versions, and after waiting long enough I just get an empty response (which is not what it should be).
This is the examples I have for now, I'll try to find more and post them.

Thanks,

Dor

 

[dcsapak]

does it work from the proxmox host? if not, maybe a broken cable/port/nic? or it could be a mtu issue?

 

[Dor]

It does work in the Proxmox host, and all the devices I mentioned earlier use the same MTU (1500).
I used wget to make the request, then tested it again on the VM, but now with wget.
wget worked without a problem. Seems like the problem occurs only when the browsers make the request, weird.

Do you have any idea what could cause this?

 

[Dor]

Any other ideas?
Couldn't find an answer, and it still occurs.