Bug#1117594: openssh-client: interactive session traffic slow and erratic

Package: openssh-client
Version: 1:10.1p1-1
Severity: grave
Justification: renders package unusable
X-Debbugs-Cc: [email protected]

Dear Maintainer,

   * What led up to the situation?
     Installing the latest openssh-client package in unstable
     (1:10.1p1-1). all
   * What exactly did you do (or not do) that was effective (or
     ineffective)?
     My interactive connections to SSH servers are not working well. All
     keys and commands are being displayed with a very long delay.
     The connection seems to freeze, but if I type a lot of keys, my
     previous commands are eventually displayed.
     I suspect this is related to the IP QoS changes introduced in openssh 10.1.
     Sending many keys/commands causes a local buffer to fill and the
     packet eventually gets sent. But this is not a sustainable way to
     use SSH interactively.

     Tried different settings for the IPQoS option, but it did not make a
     difference.

     Reverting to a previous version of the package
     (openssh-client 1:10.0p1-8 from testing/forky) fixed the issue.

-- System Information:
Debian Release: forky/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 6.16.10+deb14-amd64 (SMP w/8 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_FIRMWARE_WORKAROUND, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages openssh-client depends on:
ii  adduser              3.153
ii  init-system-helpers  1.69
ii  libc6                2.41-12
ii  libedit2             3.1-20250104-1
ii  libfido2-1           1.16.0-2
ii  libgssapi-krb5-2     1.21.3-5
ii  libselinux1          3.8.1-1
ii  libssl3t64           3.5.4-1
ii  passwd               1:4.18.0-1
ii  zlib1g               1:1.3.dfsg+really1.3.1-1+b1

Versions of packages openssh-client recommends:
ii  xauth  1:1.1.2-1.1

Versions of packages openssh-client suggests:
pn  keychain      <none>
pn  libpam-ssh    <none>
pn  monkeysphere  <none>
pn  ssh-askpass   <none>

-- no debconf information