On Tue, 14 Dec 2021, Dan Ritter wrote:
Vincent Lefevre wrote:
Hi,
When I use USB tethering between my Debian/unstable laptop and my
Samsung Galaxy Note10+ phone (Android 11), everything is OK with
IPv6 connections (e.g. "wget -6"), but IPv4 connections freeze
(e.g. "wget -4" or "ssh -4"). I can notice this in particular when
testing with the same remote server. For instance, with "wget -4",
a few dozens of KB are downloaded, then the connection is completely
frozen.
I don't have any issue with the mobile hotspot (thus wifi between the
laptop and the phone) or with a Cosmo under Android 9 (instead of the
Samsung Galaxy Note10+), but in both cases, this is much slower, and
I sometimes get wifi disconnections.
On my Debian laptop, I'm using NetworkManager (nmcli).
Have you investigated the MTU? This sounds like a mismatch
between what your laptop and phone are using.
Diagnosis (besides looking at connection details on both sides):
ping with increasingly large packet sizes. If it works at small
IPv4 packet sizes and then stops, that's the problem.
Yes, probably - --clamp-mss-to-ptmu in iptables might be what is needed.
The other thing I thought of was dodgy natting somewhere. Especially if
there's a firewall somewhere that drops 'middle of stream' packets where
no SYN has been seen first.
