[Bug 1875129] [NEW] [SRU] Regression in socat 1.7.3.3, please sync 1.7.3.4

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Alkis Georgopoulos (alkisg):

[Impact]
The socat version in Focal, 1.7.3.3, has a regression that breaks the "remote terminal" functionality of the "epoptes" package.

I reported it to Debian, and the Debian maintainer packaged the new socat 1.7.3.4 which solves the issue:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=958452

This new upstream version is a bug fixing release which I believe can be considered a microrelease:
https://wiki.ubuntu.com/StableReleaseUpdates#New_upstream_microreleases

Please sync it to focal-proposed.

[Test case]
Here are the regression details, in order to be able to reproduce it:

Epoptes is a computer lab management tool, I'm upstream and Debian
maintainer for it. Among other things, it uses socat to forward a
"student" terminal to the "teacher". To reproduce the issue without
installing Epoptes, the following similar commands may be used instead:

Teacher (just run it in a terminal tab):
xterm -e socat tcp-listen:1234,reuseaddr,keepalive=1 stdio,raw,echo=0

Student (just run it in another terminal tab):
TERM=xterm socat EXEC:'screen bash -l',pty,stderr tcp:localhost:1234

This works fine with all socat versions except 1.7.3.3.
In 1.7.3.3, it's like line buffering is enabled or something similar, and pressing for example the up arrow in the keyboard shows "^[OA" instead of displaying the last bash command. Thus, the forwarded xterm is almost unusable.

[Regression potential]
Low. It's a bug fixing upstream release.
I have compiled 1.7.3.4 from source and I've been using it for about a month with no visible issues. I also installed the .deb from sid to my focal box today and it appears to work fine.
Note though that https://tracker.debian.org/pkg/socat shows a unit test failure on arm64 (networkd-test.py), I don't know if that was the case with previous versions or not.

** Affects: socat (Ubuntu)
     Importance: Undecided
         Status: New

-- 
[SRU] Regression in socat 1.7.3.3, please sync 1.7.3.4
https://bugs.launchpad.net/bugs/1875129
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