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TheProphecy

S7 Android 8 UDP not working over cell interface

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TheProphecy

Good day.

Installed latest (1.1.36) TorGuard Android VPN client. I like it, works fine so far. However, UDP is not working correctly when going thru the cellular interface (works fine via WIFI.) I can connect fine, and the client is able to verify it's external IP address, but when I try to browse to a website, nada - the browser appears to connect (the progress bar advances a little) but then nothing else happens, and the browser eventually reports an error (Google Chrome says I'm disconnected.) Works fine if I use TCP instead.

Found someone on Stack Exchange with a similar issue and someone replied it was possibly related to MTU - with UDP if the packet is too big it's just dropped, whereas with TCP it's resent in smaller units.I can get to /sys/class/net/rmnetN (there are 8 rmnet's) and some have an MTU of 1500 and some 1430 - This looks pretty normal.

I don't know how to open a shell, so unless I install one, I can't use ping to test packet sizes + the phone is not rooted so I can't edit the MTU values for the devices anyway.

Is there anything I can do to make UDP work?

Regards,

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On 10/08/2018 at 7:10 AM, TheProphecy said:

Good day.

Installed latest (1.1.36) TorGuard Android VPN client. I like it, works fine so far. However, UDP is not working correctly when going thru the cellular interface (works fine via WIFI.) I can connect fine, and the client is able to verify it's external IP address, but when I try to browse to a website, nada - the browser appears to connect (the progress bar advances a little) but then nothing else happens, and the browser eventually reports an error (Google Chrome says I'm disconnected.) Works fine if I use TCP instead.

Found someone on Stack Exchange with a similar issue and someone replied it was possibly related to MTU - with UDP if the packet is too big it's just dropped, whereas with TCP it's resent in smaller units.I can get to /sys/class/net/rmnetN (there are 8 rmnet's) and some have an MTU of 1500 and some 1430 - This looks pretty normal.

I don't know how to open a shell, so unless I install one, I can't use ping to test packet sizes + the phone is not rooted so I can't edit the MTU values for the devices anyway.

Is there anything I can do to make UDP work?

Regards,

 

Hi - before we start playing with MTU, does this happen across all ports via UDP?

Regards

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TheProphecy

Yeah, tried different ports, no change. Tried the Stealth port 4443, same issue. Currently using 53 for TLS-Crypt. Also tried from different locations, always the same issue...

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On 15/08/2018 at 4:41 AM, TheProphecy said:

Yeah, tried different ports, no change. Tried the Stealth port 4443, same issue. Currently using 53 for TLS-Crypt. Also tried from different locations, always the same issue...

 

It may just be that UDP is blocked on your Cellular network, what network are you using?

Regards

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TheProphecy

Yeah, but then some apps like music streaming Spotify etc wouldn't work, no? I mean I expect those to be using UDP. I tested all the ports again and discovered that UDP 4443 Stealth with 128 bit AES works, but not with any other encryption settings (like 256 bit AES.) Strange eh? How the hell can it tell which encryption I'm using when the packet is re-encrypted in an SSL layer? I think my network might be actively trying to prevent VPN's from working...

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