[Bug 2080216] Re: sshd cannot bind to IPv4 interfaces

[Nick Rosbrook]

Okay, I am not sure why the ipv6 socket is not accepting ipv4, because
AFAICT (and when I test on my machine) the way IPV6_V6ONLY is being set
in the default case, it should allow ipv4.

However, I do think there is a case to be made about the socket unit
being more aligned with the contents of /etc/ssh/sshd_config, and non-
socket activated sshd. E.g., with the default contents of
/etc/ssh/sshd_config, and *non-socket-activated* ssh, we will have two
separate listening addresses, [::]:22 and 0.0.0.0:22 (explicitly, not
via ipv6). We should do the same for socket-activated SSH by default.
And, while we are at it, we need to make sshd-socket-generator honor
AddressFamily.

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https://bugs.launchpad.net/bugs/2080216

Title:
  sshd cannot bind to IPv4 interfaces

Status in openssh package in Ubuntu:
  Confirmed

Bug description:
  After upgrading from 22.04 to 24.04 I noticed that my sshd only
  listening on IPv6 interface (::), while previously it was listening
  both IPv4 (0.0.0.0) and IPv6 (::). I tried to explicitly specify
  ListenAddress 0.0.0.0 (assuming it would bind to IPv4 only) but after
  restart sshd was still listening on IPv6 only.

  This problem affects other packages as well, for example, openvpn.

  Rebuilding applications from sources seems to fix the issue.

  Setting net.ipv6.bindv6only=0 also helps, but that's not a solution.

  ProblemType: Bug
  DistroRelease: Ubuntu 24.04
  Package: openssh-server 1:9.6p1-3ubuntu13.5
  ProcVersionSignature: Ubuntu 6.8.0-41.41-generic 6.8.12
  Uname: Linux 6.8.0-41-generic x86_64
  ApportVersion: 2.28.1-0ubuntu3.1
  Architecture: amd64
  CasperMD5CheckResult: unknown
  Date: Tue Sep 10 16:45:54 2024
  ProcEnviron:
   LANG=C.UTF-8
   PATH=(custom, no user)
   SHELL=/bin/bash
   TERM=screen.xterm-256color
  SourcePackage: openssh
  UpgradeStatus: Upgraded to noble on 2024-09-10 (0 days ago)

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