Interoperability between v1.17.0 vs v1.0.0

Hi there, I am running latest v1.17.0 on my androids (they see each other) and v1.0.0 on debian stable systems. The android-debian route worked a month ago, but not now (it might be that either some android or debian update broke something). Are these two version supposed to interact?

On debian console I see warning about TLS version, but I do not know whether it’s a grave issue:

[4NM4R] 17:19:58 INFO: Listen (BEP/tcp): TLS handshake: tls: received record with version 301 when expecting version 303

(I know that there is debian specific repo for syncthing but for other reasons I would like to avoid using it).

The newest Syncthing only accepts tls1.3 connections, with an opt-in advanced flag to keep accepting tls1.2. See Consider removing support for TLS <1.3 on sync connections · Issue #7594 · syncthing/syncthing · GitHub
I would advice to upgrade the device on v1.0.0 though.

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I think this was a bad decision, because it broke sync between all Debian Buster installations (relying on the distro package) and Android clients.

Why didn’t you make the upgrade to TLSv1.3 optional for those updating the Android app?

I am fortunate that nothing happened in the last week during which sync was not working and I did not notice…

There’s more info about this e.g. here: server selected unsupported protocol version 303 or here: #7598 broke compatibility · Issue #7767 · syncthing/syncthing · GitHub

dobro mil: Thank you for this post. I have been unable to add a remote device to a Debian Buster machine for a couple days now. Remote device = v1.17.0, while my Buster device still sits at v1.0.0, as you know. Adding either device from either side would not work. I noticed the same “version 301 when expecting version 303” message as you, and found your post. Now I know why I’m unable to add the devices as expected.

bt90 Bug Reporter: Thank you for the great link on how to add the latest stable syncthing to Buster. I followed the straight-forward steps, and now I am running v.1.17.0 on Buster!

As a result, my previous connection attempts simply started working immediately following the last installation of syncthing and all is good.