> On 26 Feb 2021, at 15.39, David Laight <david.lai...@aculab.com> wrote: > > Some thoughts... > > Does a non-android linux system behave correctly through the same NAT > gateways? > Particularly with a similar kernel version. > > If you have a USB OTG cable and USB ethernet dongle you may be able to get > android to use a wired ethernet connection - excluding any WiFi issues. > (OTG usually works for keyboard and mouse, dunno if ethernet support is > there.) > > Does you android device work on any other networks?
I have done some further tests. I managed to find another Android device (kernel 4.9.113), which thankfully does _not_ send the weird D-SACKs and quickly recovers, so the problem appears to be on the original device. Additionally, I have managed to do a trace on the WLAN AP, where I can confirm that all packets seem to be transferred without unnecessary modifications or re-ordering. Ie. all segments sent from the server make it to the device and any loss will be device local. As such this points to a driver-level issue? I don't have an ethernet dongle ready. I tried to connect using cellular and was unable to replicate the issue, so this further points at a driver-level issue. Given that it now seems relevant, the device is an Android P20 Lite, running a variant of Android 9.1 with an update from this year (kernel was built jan. 05 2021). /Gil
