IMAP fails trying to connect to IPv6 host

Technical assistance
1

Infos:

  • Used Zammad version: 3.3
  • Used Zammad installation source: (source, package, …) Package
  • Operating system: Centos8
  • Browser + version: Brave

I see that when Zammad tries to connect to an IMAP server, it tries to use the IPv6 address which is resolved even though IPv6 is disabled/not available on the host.

I, [2020-06-08T11:01:45.889192 #17293-47324879262320]  INFO -- : fetching imap (imap.gmail.com/sales@ port=993,ssl=true,starttls=false,folder=INBOX,keep_on_server=true)
E, [2020-06-08T11:01:45.890996 #17293-47324879262320] ERROR -- : Can't use Channel::Driver::Imap: #<Errno::EADDRNOTAVAIL: Cannot assign requested address - connect(2) for [2a00:1450:4025:402::6d]:993>
E, [2020-06-08T11:01:45.891048 #17293-47324879262320] ERROR -- : Cannot assign requested address - connect(2) for [2a00:1450:4025:402::6d]:993 (Errno::EADDRNOTAVAIL)
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:1213:in `__connect_nonblock'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:1213:in `connect_nonblock'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:56:in `connect_internal'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:137:in `connect'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:641:in `block in tcp'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:227:in `each'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:227:in `foreach'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/socket.rb:631:in `tcp'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/net/imap.rb:1132:in `tcp_socket'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/net/imap.rb:1089:in `initialize'
/opt/zammad/app/models/channel/driver/imap.rb:107:in `new'
/opt/zammad/app/models/channel/driver/imap.rb:107:in `block in fetch'
/opt/zammad/app/models/channel/driver/imap.rb:517:in `block in timeout'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/timeout.rb:93:in `block in timeout'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/timeout.rb:33:in `block in catch'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/timeout.rb:33:in `catch'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/timeout.rb:33:in `catch'
/opt/zammad/vendor/ruby-2.5.5/lib/ruby/2.5.0/timeout.rb:108:in `timeout'
/opt/zammad/app/models/channel/driver/imap.rb:516:in `timeout'
/opt/zammad/app/models/channel/driver/imap.rb:106:in `fetch'
/opt/zammad/app/models/channel.rb:56:in `fetch'
/opt/zammad/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.3/lib/active_record/relation/delegation.rb:71:in `each'
/opt/zammad/vendor/bundle/ruby/2.5.0/gems/activerecord-5.2.4.3/lib/active_record/relation/delegation.rb:71:in `each'
/opt/zammad/app/models/channel.rb:30:in `fetch'
(eval):1:in `_start_job'
/opt/zammad/app/models/scheduler.rb:287:in `eval'
/opt/zammad/app/models/scheduler.rb:287:in `_start_job'
/opt/zammad/app/models/scheduler.rb:239:in `block (2 levels) in start_job'
/opt/zammad/app/models/scheduler.rb:237:in `loop'
/opt/zammad/app/models/scheduler.rb:237:in `block in start_job'
/opt/zammad/vendor/bundle/ruby/2.5.0/gems/logging-2.2.2/lib/logging/diagnostic_context.rb:474:in `block in create_with_logging_context'
2

This is because your DNS server still returns an IPv6 address which ruby eventually will try to priotize over IPv4. After talking to a developer, ruby technically -theoretically- should also not use IPv6 as soon as the support for it is disabled on system level.

Ensure:
That you did reboot after disabling IPv6 support.
If you didn’t, the change will not be fully active.

This is proberbly rather a ruby issue over an application issue.

3

No problem, Ill give this a go and check all areas of IPv6 on the system have been disabled.

Most DNS providers will return a V6 address if its available.

4

I have rebooted and checked the interfaces which have no IPv6 addresses anymore etc.

Zammad still tries to use V6 when connecting to an IMAP server.

5

Sorry, I currently am missing time capacity to reproduce this.
However, when I last used ipv6 mail servers on an ipv4 only system it was working without any issues on a stable 3.3.

This might be a combination of configuration I currently can’t dig deeper into. Sorry.

6

It does eventually collect over v4, but I thought id bring this to the forum for their review

8

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