Bind to all network interfaces for both IPv4 and IPv6

[inistor]

Describe the bug

Desired outcome

Run an input plugin, be it tcp or http, binding to all network interfaces, for both IPv4 and IPv6. This is a docker environment, running the latest fluentd DockerHub image (1.16.2-1, at the time of this writing).

Configuration

  <source>
    @type forward
    bind "[::]"
    port 12345
  </source>

Result

➜  /tmp drit --rm -v /tmp/f2.conf:/f.conf fluentd -c /f.conf
fluentd -c /f.conf
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: parsing config file is succeeded path="/f.conf"
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: gem 'fluentd' version '1.16.2'
2024-07-15 17:00:45 +0000 [trace]: fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 17:00:45 +0000 [trace]: fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 17:00:45 +0000 [debug]: fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: using configuration file: <ROOT>
  <system>
    log_level trace
  </system>
  <source>
    @type forward
    bind ""
    port 12345
  </source>
</ROOT>
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: starting fluentd-1.16.2 pid=7 ruby="3.1.5"
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: spawn command to main:  cmdline=["/usr/bin/ruby", "-Eascii-8bit:ascii-8bit", "/usr/bin/fluentd", "-c", "/f.conf", "--plugin", "/fluentd/plugins", "--under-supervisor"]
2024-07-15 17:00:45 +0000 [info]: #0 fluent/log.rb:362:info: init worker0 logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 17:00:45 +0000 [info]: fluent/log.rb:362:info: adding source type="forward"
2024-07-15 17:00:45 +0000 [trace]: #0 fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 17:00:45 +0000 [trace]: #0 fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 17:00:45 +0000 [debug]: #0 fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 17:00:45 +0000 [info]: #0 fluent/log.rb:362:info: starting fluentd worker pid=16 ppid=7 worker=0
2024-07-15 17:00:45 +0000 [info]: #0 fluent/log.rb:362:info: listening port port=12345 bind=""
2024-07-15 17:00:45 +0000 [info]: #0 fluent/log.rb:362:info: fluentd worker is now running worker=0
^C2024-07-15 17:00:49 +0000 [debug]: #0 fluent/log.rb:341:debug: fluentd main process get SIGINT
2024-07-15 17:00:49 +0000 [info]: fluent/log.rb:362:info: Received graceful stop
2024-07-15 17:00:50 +0000 [debug]: #0 fluent/log.rb:341:debug: fluentd main process get SIGTERM
2024-07-15 17:00:50 +0000 [debug]: #0 fluent/log.rb:341:debug: getting start to shutdown main process
2024-07-15 17:00:50 +0000 [info]: #0 fluent/log.rb:362:info: fluentd worker is now stopping worker=0
2024-07-15 17:00:50 +0000 [info]: #0 fluent/log.rb:362:info: shutting down fluentd worker worker=0
2024-07-15 17:00:50 +0000 [debug]: #0 fluent/log.rb:341:debug: calling stop on input plugin type=:forward plugin_id="object:85c"
2024-07-15 17:00:50 +0000 [debug]: #0 fluent/log.rb:341:debug: preparing shutdown input plugin type=:forward plugin_id="object:85c"
2024-07-15 17:00:50 +0000 [info]: #0 fluent/log.rb:362:info: shutting down input plugin type=:forward plugin_id="object:85c"
2024-07-15 17:00:50 +0000 [debug]: #0 fluent/log.rb:341:debug: calling after_shutdown on input plugin type=:forward plugin_id="object:85c"
2024-07-15 17:00:51 +0000 [debug]: #0 fluent/log.rb:341:debug: closing input plugin type=:forward plugin_id="object:85c"
2024-07-15 17:00:51 +0000 [debug]: #0 fluent/log.rb:341:debug: calling terminate on input plugin type=:forward plugin_id="object:85c"
2024-07-15 17:00:51 +0000 [info]: fluent/log.rb:362:info: Worker 0 finished with status 0
➜  /tmp vi f2.conf 
➜  /tmp drit --rm -v /tmp/f2.conf:/f.conf fluentd -c /f.conf
fluentd -c /f.conf
2024-07-15 17:01:01 +0000 [info]: fluent/log.rb:362:info: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 17:01:01 +0000 [info]: fluent/log.rb:362:info: parsing config file is succeeded path="/f.conf"
2024-07-15 17:01:01 +0000 [info]: fluent/log.rb:362:info: gem 'fluentd' version '1.16.2'
2024-07-15 17:01:01 +0000 [trace]: fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 17:01:01 +0000 [trace]: fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 17:01:01 +0000 [debug]: fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 17:01:01 +0000 [info]: fluent/log.rb:362:info: using configuration file: <ROOT>
  <system>
    log_level trace
  </system>
  <source>
    @type forward
    bind "[::]"
    port 12345
  </source>
</ROOT>
2024-07-15 17:01:01 +0000 [info]: fluent/log.rb:362:info: starting fluentd-1.16.2 pid=7 ruby="3.1.5"
2024-07-15 17:01:01 +0000 [info]: fluent/log.rb:362:info: spawn command to main:  cmdline=["/usr/bin/ruby", "-Eascii-8bit:ascii-8bit", "/usr/bin/fluentd", "-c", "/f.conf", "--plugin", "/fluentd/plugins", "--under-supervisor"]
2024-07-15 17:01:02 +0000 [info]: #0 fluent/log.rb:362:info: init worker0 logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 17:01:02 +0000 [info]: fluent/log.rb:362:info: adding source type="forward"
2024-07-15 17:01:02 +0000 [trace]: #0 fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 17:01:02 +0000 [trace]: #0 fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 17:01:02 +0000 [debug]: #0 fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 17:01:02 +0000 [info]: #0 fluent/log.rb:362:info: starting fluentd worker pid=16 ppid=7 worker=0
2024-07-15 17:01:02 +0000 [info]: #0 fluent/log.rb:362:info: listening port port=12345 bind="[::]"
2024-07-15 17:01:02 +0000 [error]: #0 fluent/log.rb:404:error: unexpected error error_class=SocketError error="getaddrinfo: Name does not resolve"
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `tcp'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `server_create_tcp_socket'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:212:in `server_create_for_tcp_connection'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:92:in `server_create_connection'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin/in_forward.rb:172:in `start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:203:in `block in start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:192:in `block (2 levels) in lifecycle'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `each'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `block in lifecycle'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `each'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `lifecycle'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:202:in `start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:248:in `start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:147:in `run'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:617:in `block in run_worker'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:962:in `main_process'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:608:in `run_worker'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/command/fluentd.rb:372:in `<top (required)>'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/bin/fluentd:15:in `<top (required)>'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/bin/fluentd:25:in `load'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/bin/fluentd:25:in `<main>'
2024-07-15 17:01:02 +0000 [error]: #0 fluent/log.rb:404:error: unexpected error error_class=SocketError error="getaddrinfo: Name does not resolve"
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `tcp'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `server_create_tcp_socket'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:212:in `server_create_for_tcp_connection'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:92:in `server_create_connection'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin/in_forward.rb:172:in `start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:203:in `block in start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:192:in `block (2 levels) in lifecycle'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `each'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `block in lifecycle'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `each'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `lifecycle'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:202:in `start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:248:in `start'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:147:in `run'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:617:in `block in run_worker'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:962:in `main_process'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:608:in `run_worker'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/command/fluentd.rb:372:in `<top (required)>'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/bin/fluentd:15:in `<top (required)>'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/bin/fluentd:25:in `load'
  2024-07-15 17:01:02 +0000 [error]: #0 fluent/supervisor.rb:961:main_process: /usr/bin/fluentd:25:in `<main>'
2024-07-15 17:01:02 +0000 [error]: fluent/log.rb:404:error: Worker 0 exited unexpectedly with status 1

the error is getaddrinfo: Name does not resolve in lib/fluent/plugin_helper/server.rb.

Attempting to use bind "::" allows the server to start, but only listens on IPv6.

Additional notes

The same problem error when using an http type input plugin, for instance @type monitor_agent, along with `bind "[::]".
In this case, a slightly stranger thing happens; the stacktrace shows:

2024-07-15 17:05:42 +0000 [debug]: #0 fluent/log.rb:341:debug: listening monitoring http server on http://[::]:12345/api/plugins for worker0
2024-07-15 17:05:42 +0000 [error]: #0 fluent/log.rb:404:error: unexpected error error_class=SocketError error="getaddrinfo: Name does not resolve"
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/3.1.0/socket.rb:227:in `getaddrinfo'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/3.1.0/socket.rb:227:in `foreach'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/3.1.0/socket.rb:763:in `tcp_server_sockets'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/utils.rb:60:in `create_listeners'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/server.rb:130:in `listen'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/server.rb:111:in `initialize'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/httpserver.rb:47:in `initialize'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server/compat/server.rb:47:in `new'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server/compat/server.rb:47:in `initialize'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server.rb:69:in `new'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server.rb:69:in `http_server_create_http_server'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin/in_monitor_agent.rb:213:in `start'
  2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:203:in `block in start'
[...]

Please note that the webrick gem is used, for some reason, instead of async-http - which, in the code, seems to be intended for compatibility with older Ruby versions - see

fluentd/lib/fluent/plugin_helper/http_server.rb

Line 21 in 6d53664

require 'fluent/plugin_helper/http_server/compat/server'

and commit f458fae

For the async-http, at least, the "[::]" has the intended outcome (i.e. both IPv4 and IPv6 listeners on all interfaces); the following code:

require 'async'
require 'async/http/server'
require 'async/http/endpoint'
[...]
endpoint = Async::HTTP::Endpoint.parse('http://[::]:12345')
server = Async::HTTP::Server.new(app, endpoint)

To Reproduce

Create a simple configuration file fluent-test-bind.conf:

<system>
  log_level trace
</system>

<source>
  @type forward
  bind "[::]"
  port 12345
</source>

Start a container, using the newly created config file:
docker run -it --rm -v ./fluent-test-bind.conf:/fluent-test-bind.conf fluentd -c /fluent-test-bind.conf

The error (and stack traces) appear on stdout:

fluentd -c /f.conf
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: parsing config file is succeeded path="/f.conf"
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: gem 'fluentd' version '1.16.2'
2024-07-15 18:03:15 +0000 [trace]: fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 18:03:15 +0000 [trace]: fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 18:03:15 +0000 [debug]: fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: using configuration file: <ROOT>
  <system>
    log_level trace
  </system>
  <source>
    @type forward
    bind "[::]"
    port 12345
  </source>
</ROOT>
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: starting fluentd-1.16.2 pid=7 ruby="3.1.5"
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: spawn command to main:  cmdline=["/usr/bin/ruby", "-Eascii-8bit:ascii-8bit", "/usr/bin/fluentd", "-c", "/f.conf", "--plugin", "/fluentd/plugins", "--under-supervisor"]
2024-07-15 18:03:15 +0000 [info]: #0 fluent/log.rb:362:info: init worker0 logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: adding source type="forward"
2024-07-15 18:03:15 +0000 [trace]: #0 fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 18:03:15 +0000 [trace]: #0 fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 18:03:15 +0000 [debug]: #0 fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 18:03:15 +0000 [info]: #0 fluent/log.rb:362:info: starting fluentd worker pid=16 ppid=7 worker=0
2024-07-15 18:03:15 +0000 [info]: #0 fluent/log.rb:362:info: listening port port=12345 bind="[::]"
2024-07-15 18:03:15 +0000 [error]: #0 fluent/log.rb:404:error: unexpected error error_class=SocketError error="getaddrinfo: Name does not resolve"
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `tcp'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `server_create_tcp_socket'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:212:in `server_create_for_tcp_connection'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:92:in `server_create_connection'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin/in_forward.rb:172:in `start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:203:in `block in start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:192:in `block (2 levels) in lifecycle'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `each'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `block in lifecycle'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `each'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `lifecycle'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:202:in `start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:248:in `start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:147:in `run'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:617:in `block in run_worker'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:962:in `main_process'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:608:in `run_worker'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/command/fluentd.rb:372:in `<top (required)>'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/bin/fluentd:15:in `<top (required)>'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/bin/fluentd:25:in `load'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/bin/fluentd:25:in `<main>'

Expected behavior

It would be desirable to be able to use a single listener entry in the configuration file to listen on both IPv4 and IPv6 interfaces.

It is also expected that bind addresses of the type "[::]" or "[::1]" are allowed - they are permitted by Async::HTTP::Endpoint.parse(), as indicated above.

Your Environment

- Fluentd version: `1.16.2`
- Package version: `fluentd:v1.16.2-1.1`
- Operating system: `MacOS` / `Docker Desktop 4.32.0`
- Kernel version: `N/A`

Your Configuration

<system>
  log_level trace
</system>

<source>
  @type forward
  bind "[::]"
  port 12345
</source>

Your Error Log

fluentd -c /f.conf
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: parsing config file is succeeded path="/f.conf"
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: gem 'fluentd' version '1.16.2'
2024-07-15 18:03:15 +0000 [trace]: fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 18:03:15 +0000 [trace]: fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 18:03:15 +0000 [debug]: fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: using configuration file: <ROOT>
  <system>
    log_level trace
  </system>
  <source>
    @type forward
    bind "[::]"
    port 12345
  </source>
</ROOT>
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: starting fluentd-1.16.2 pid=7 ruby="3.1.5"
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: spawn command to main:  cmdline=["/usr/bin/ruby", "-Eascii-8bit:ascii-8bit", "/usr/bin/fluentd", "-c", "/f.conf", "--plugin", "/fluentd/plugins", "--under-supervisor"]
2024-07-15 18:03:15 +0000 [info]: #0 fluent/log.rb:362:info: init worker0 logger path=nil rotate_age=nil rotate_size=nil
2024-07-15 18:03:15 +0000 [info]: fluent/log.rb:362:info: adding source type="forward"
2024-07-15 18:03:15 +0000 [trace]: #0 fluent/log.rb:319:trace: registered input plugin 'forward'
2024-07-15 18:03:15 +0000 [trace]: #0 fluent/log.rb:319:trace: registered metrics plugin 'local'
2024-07-15 18:03:15 +0000 [debug]: #0 fluent/log.rb:341:debug: No fluent logger for internal event
2024-07-15 18:03:15 +0000 [info]: #0 fluent/log.rb:362:info: starting fluentd worker pid=16 ppid=7 worker=0
2024-07-15 18:03:15 +0000 [info]: #0 fluent/log.rb:362:info: listening port port=12345 bind="[::]"
2024-07-15 18:03:15 +0000 [error]: #0 fluent/log.rb:404:error: unexpected error error_class=SocketError error="getaddrinfo: Name does not resolve"
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `tcp'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:376:in `server_create_tcp_socket'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:212:in `server_create_for_tcp_connection'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/server.rb:92:in `server_create_connection'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin/in_forward.rb:172:in `start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:203:in `block in start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:192:in `block (2 levels) in lifecycle'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `each'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:191:in `block in lifecycle'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `each'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:178:in `lifecycle'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:202:in `start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:248:in `start'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/engine.rb:147:in `run'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:617:in `block in run_worker'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:962:in `main_process'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/supervisor.rb:608:in `run_worker'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/command/fluentd.rb:372:in `<top (required)>'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: <internal:/usr/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/bin/fluentd:15:in `<top (required)>'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/bin/fluentd:25:in `load'
  2024-07-15 18:03:15 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/bin/fluentd:25:in `<main>'

### Additional context

The same problem error when using an http type input plugin, for instance `@type monitor_agent`, along with `bind "[::]". 
In this case, a slightly stranger thing happens; the stacktrace shows:

2024-07-15 17:05:42 +0000 [debug]: #0 fluent/log.rb:341:debug: listening monitoring http server on http://[::]:12345/api/plugins for worker0
2024-07-15 17:05:42 +0000 [error]: #0 fluent/log.rb:404:error: unexpected error error_class=SocketError error="getaddrinfo: Name does not resolve"
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/3.1.0/socket.rb:227:in getaddrinfo' 2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/3.1.0/socket.rb:227:in foreach'
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/3.1.0/socket.rb:763:in tcp_server_sockets' 2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/utils.rb:60:in create_listeners'
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/server.rb:130:in listen' 2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/server.rb:111:in initialize'
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/httpserver.rb:47:in initialize' 2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server/compat/server.rb:47:in new'
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server/compat/server.rb:47:in initialize' 2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server.rb:69:in new'
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin_helper/http_server.rb:69:in http_server_create_http_server' 2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/plugin/in_monitor_agent.rb:213:in start'
2024-07-15 17:05:42 +0000 [error]: #0 fluent/supervisor.rb:962:main_process: /usr/lib/ruby/gems/3.1.0/gems/fluentd-1.16.2/lib/fluent/root_agent.rb:203:in `block in start'
[...]

Please note that the `webrick` gem is used, for some reason, instead of `async-http` - which, in the code, seems to be intended for compatibility with older Ruby versions - see https://github.com/fluent/fluentd/blob/6d53664d34113381f1c3048c2569ff9e405b456b/lib/fluent/plugin_helper/http_server.rb#L21 and commit f458fae29717ee75840ce60972638818803f2d78

For the `async-http`, at least, the "[::]" has the intended outcome (i.e. both IPv4 and IPv6 listeners on all interfaces); the following code:
```ruby
require 'async'
require 'async/http/server'
require 'async/http/endpoint'
[...]
endpoint = Async::HTTP::Endpoint.parse('http://[::]:12345')
server = Async::HTTP::Server.new(app, endpoint)

Also, the same problem is encountered for external plugins, such as fluentd-plugin-prometheus. Example config:

<system>
  log_level trace
</system>

<source>
  @type prometheus
  bind "[::]"
  port 9000
  metrics_path /metrics
</source>

[kenhys]

reproduced with v1.16.5 and v1.17.0.

[daipom]

Looks like ipv6 is not supported in case of single worker.

https://github.com/fluent/fluentd/blob/v1.17.0/lib/fluent/plugin_helper/server.rb#L370-L383

[daipom]

Looks like ipv6 is not supported in case of single worker.

https://github.com/fluent/fluentd/blob/v1.17.0/lib/fluent/plugin_helper/server.rb#L370-L383

Hmm, we can't add brackets?

Addrinfo.tcp("::", 20000)
=> #<Addrinfo: [::]:20000 TCP>
Addrinfo.tcp("[::]", 20000)
(irb):1:in `tcp': getaddrinfo: Name or service not known (SocketError)
	from (irb):1:in `<main>'
	from /home/daipom/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/irb-1.13.1/exe/irb:9:in `<top (required)>'
	from /home/daipom/.rbenv/versions/3.2.2/bin/irb:25:in `load'
	from /home/daipom/.rbenv/versions/3.2.2/bin/irb:25:in `<main>'

[daipom]

Hmm, we can't add brackets?

This works.

  <source>
    @type forward
    bind "::"
    port 12345
  </source>

[daipom]

Hmm, we can't add brackets?

This works.

  <source>
    @type forward
    bind "::"
    port 12345
  </source>

@inistor Please try an address with no brackets.

[inistor]

Already did - it only listens on IPv6:

f.conf:

  <source>
    @type forward
    bind "::"
    port 12345
  </source>

➜  /tmp docker run -it --rm --name fluentd-ipv6-test -v /tmp/f.conf:/f.conf fluentd:v1.16-1 -c /f.conf
fluentd -c /f.conf
2024-07-18 05:30:38 +0000 [info]: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2024-07-18 05:30:38 +0000 [info]: parsing config file is succeeded path="/f.conf"
2024-07-18 05:30:38 +0000 [info]: gem 'fluentd' version '1.16.2'
2024-07-18 05:30:38 +0000 [info]: using configuration file: <ROOT>
  <source>
    @type forward
    bind "::"
    port 12345
  </source>
</ROOT>
2024-07-18 05:30:38 +0000 [info]: starting fluentd-1.16.2 pid=6 ruby="3.1.5"
[...]

➜  ~ docker exec -it fluentd-ipv6-test sh
/ $ nc -vz 127.0.0.1 12345
/ $ nc -vz ::1 12345
::1 ([::1]:12345) open
/ $ 

And the reason appears to be the way the URL is formed. At least from Async::HTTP::Endpoint.parse()s point of view:

• endpoint = Async::HTTP::Endpoint.parse('http://[::]:12345') - listens on both IPv4 and IPv6
• endpoint = Async::HTTP::Endpoint.parse('http://:::12345') - listens on IPv6 only

True, in the case of @type forward, Async::HTTP::Endpoint is not involved (it's a TCP socket, not HTTP), but I believe the underlying socket API is the same (my Ruby is quite Rusty - forgive the pun ;-) ).

[inistor]

Please see my report from 2020: #3001

[inistor]

Any comments on this one? Is there any way I may be of assistance?

[daipom]

I see. So we need this feature.

It would be desirable to be able to use a single listener entry in the configuration file to listen on both IPv4 and IPv6 interfaces.