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

[Vasya Pupkin]

Some more details. Here's a part of my sslh config:

listen:
(
    { host: "0.0.0.0"; port: "443"; },
    { host: "::"; port: "443"; }
);

And here's how it's working:

# ss -tlnp | grep sslh
LISTEN 0      50           0.0.0.0:443        0.0.0.0:*    users:(("sslh-fork",pid=2557,fd=3),("sslh-fork",pid=2556,fd=3),("sslh-fork",pid=2551,fd=3))
LISTEN 0      50              [::]:443           [::]:*    users:(("sslh-fork",pid=2557,fd=4),("sslh-fork",pid=2556,fd=4),("sslh-fork",pid=2551,fd=4))

You can see that it's listening on both 0.0.0.0 and [::] interfaces.

Now here's a piece of my sshd_config:

AddressFamily any
ListenAddress 0.0.0.0
ListenAddress ::

And here's how it's working:

# ss -tlnp | grep sshd
LISTEN 0      8192            [::]:22            [::]:*    users:(("sshd",pid=843,fd=3),("systemd",pid=1,fd=69))


As you can see, it doesn't listen on IPv4 interface at all.

This is clearly a packaging bug because only precompiled binaries are
affected. My sslh binary compiled under Ubuntu 22.04 was doing the same
and was fixed once I compiled it under Ubuntu 24.04.

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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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