[Bug 1374109] Re: epmd does not support binding to an IPv4 address anymore

[alexander]

@James Page,

on my specific setup epmd was starting just fine if there is no
excplicit IPv6 bind address set (via the ERL_EPMD_ADDRESS env). On
`netstat -ntlp` epmd was visible and listening to ::1. IPv6 on box was
disabled per https://wiki.ubuntu.com/IPv6#Disabling_IPv6

I'll assume it may be working fine for a) if you don't specify a bind
address tough I didn't test this. Unfortunately I've changed my setup
and I'm unable to confirm this.

FTR: upstream packages (via Erlang's Ubuntu repository) are compiled
with IPv4 and this is probably the easiest workaround for the case.

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https://bugs.launchpad.net/bugs/1374109

Title:
  epmd does not support binding to an IPv4 address anymore

Status in “erlang” package in Ubuntu:
  Confirmed

Bug description:
  The bug is actually located in erlang itself. epmd fails to bind to
  any IPv4 address if instructed to do so

  [Impact]
  Users of RabbitMQ in IPv4 environments are unable to start rabbitmq unless the environment variable ERL_EPMD_ADDRESS is unset. In case of disabled IPv6 support there is no valid setting for ERL_EPMD_ADDRESS as
  * IPv4 addresses will be rejected as syntacitcally invalid
  * IPv6 addresses will fail to bind

  [Test Case]
  service rabbitmq-server stop && killall epmd

  ERL_EPMD_ADDRESS="127.0.0.1" epmd
  epmd: Thu Sep 25 21:00:16 2014: cannot parse IP address "127.0.0.1"

  same could be acieved with the epmd's -address option

  In case IPv6 support is disabled:
  ERL_EPMD_ADDRESS="::1" epmd
  epmd: Thu Sep 25 21:01:40 2014: failed to bind socket: Cannot assign requested address

  -- rabbitmq case:
  cat rabbitmq-env.conf
  export RABBITMQ_NODENAME=rabbit at localhost
  export RABBITMQ_NODE_IP_ADDRESS=127.0.0.1
  export ERL_EPMD_ADDRESS=127.0.0.1

  service rabbitmq-server start
   * Starting message broker rabbitmq-server
   * FAILED - check /var/log/rabbitmq/startup_\{log, _err\}                                                        [fail]

  Commenting/removing the "export ERL_EPMD_ADDRESS=127.0.0.1" line
  resolves the issue

  [Possible cause]
  In this bug: https://bugs.launchpad.net/ubuntu/+source/rabbitmq-server/+bug/1312507?comments=all

  The issue was fixed using -DEPMD6" in CPPFLAGS
  (https://bugs.launchpad.net/ubuntu/+source/rabbitmq-
  server/+bug/1312507/comments/5) which perhaps (I speculate only)
  activates some of the erlang's IPV6_V6ONLY definitions.

  There is another complaint regarding the same issue here:
  https://bugs.launchpad.net/ubuntu/+source/rabbitmq-
  server/+bug/1312507/comments/14

  [System info]
  lsb_release -rd
  Description:	Ubuntu 14.04.1 LTS
  Release:	14.04

  apt-cache policy rabbitmq-server
  rabbitmq-server:
    Installed: 3.2.4-1
    Candidate: 3.2.4-1

  
  apt-cache policy erlang-base
  erlang-base:
    Installed: 1:16.b.3-dfsg-1ubuntu2.1
    Candidate: 1:16.b.3-dfsg-1ubuntu2.1

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