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Thu, 07 May 2026 03:59:06 -0700 (PDT) MIME-Version: 1.0 References: <CAOq2pXFuE-9e8iuUWaKk7v7eLjgP0g6pgHysH+NykQjRvTkz8g@mail.gmail.com> <284ef9df0bf17daa164f6cf68220de14@riseup.net> <17523398e58dcc6e2a9e42fc0099fada@riseup.net> <c87461626fe2f870464da923a66c989d@riseup.net> In-Reply-To: <c87461626fe2f870464da923a66c989d@riseup.net> From: Sergei Golovan <sgolovan@gmail.com> Date: Thu, 7 May 2026 13:58:54 +0300 X-Gm-Features: AVHnY4LnXXK_YWAfcDWA2wb6FOzLkGd8C9Bfq1cbE7prHtSRLlWXGkLUlnRewrA Message-ID: <CAOq2pXEn89pkjNRxc7Wm1-i9z6+z-SXd_HUdzC2B1BsgVJzzJg@mail.gmail.com> Subject: =?UTF-8?Q?Re=3A_Bug=231135795=3A_=5BPkg=2Derlang=2Ddevel=5D_Bug=231135795=3A_epm?= =?UTF-8?Q?d=2Esocket_fails_to_bind_to_127=2E0=2E0=2E1=3A4369_with_=E2=80=9CAddress_alr?= =?UTF-8?Q?eady_in_use=E2=80=9D_even_when_nothing_is_listening?= To: marvology@riseup.net, 1135795-close@bugs.debian.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi! On Thu, May 7, 2026 at 1:15=E2=80=AFAM <marvology@riseup.net> wrote: > > > It's reasonable if you don't use distributed Erlang. > > Not sure I understand. When I ran "apt install ejabberd", it > auto-installed Erlang via apt. > As far as I know, ejabberd is a distributed XPP server, even if there is a single node, ejabberd uses distributed Erlang. > > > I can reproduce this, as far as I investigated, it is caused by the opt= ion > > BindIPv6Only=3Dboth > > in the socket file. When systemd binds to IPv6 address, it also listens= to IPv4 > > packets, which makes address already in use. > > I was finally able to listen on "127.0.0.1" only, because opening 4369 > publicly is asking for trouble[1]. I guess you should file a bugreport for Erlang developers for that. As for = now I don't know about any exploitable vulnerability in epmd. > > # ss -tulpn|grep epmd > tcp LISTEN 0 4096 127.0.0.1:4369 0.0.0.0:* > users:(("epmd",pid=3D2370007,fd=3D3),("systemd",pid=3D1,fd=3D199)) > > To do this, I had to: > > 1. Run: systemctl edit epmd.socket > 2. Add 2 lines line this: > > ### Editing /etc/systemd/system/epmd.socket.d/override.conf > ### Anything between here and the comment below will become the contents > of the drop-in file > > [Socket] > ListenStream=3D > ListenStream=3D127.0.0.1:4369 You've found another way of teaching epmd.socket to listen only on 12.7.0.0.1, good. > > Anyway, I don't think that's a bug in epmd.socket. It works as intended= . > > I think there is a bug because when I edit like below, epmd failed to > restart. > > [Socket] > ListenStream=3D127.0.0.1:4369 I don't think that I can account for all possible ways the users chose to override the default socket settings. This particular way fails, but there are others, they are documented in /usr/share/doc/erlang-base/README.Debian. > > I need to add "ListenStream=3D" - unsure if this is a correct fix but som= e > people mentioned this on other forums. No, you don't. Please, read the readme in /usr/share/doc/erlang-base/README.Debian, it explains how to make the epmd socket listen only on the lo interface (localhost). As for now, I'm closing this bugreport. Cheers! --=20 Sergei Golovan]