in_forward plugin bind on both ipv4 and ipv6

[inistor]

Describe the bug While using the in_forward plugin, I’m trying to have it bind on both IPv4 and IPv6 addresses (for dual-stack systems); typically, when using. “::” for bind config parameter, the socket api will bind to both (as long as AF_INET6 is used). However, if I use “::” for bind config parameter, an IPv6 only socket will be created. With the default value of bind (“0.0.0.0”), an IPv4 only socket is created.

To Reproduce Using the configuration below:

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

ipv6 works

[root@centos8-ion ~]# telnet -6 localhost 24224
Trying ::1...
Connected to localhost.
Escape character is '^]'.

ipv4 does not:

[root@centos8-ion ~]# telnet -4 localhost 24224
Trying 127.0.0.1...
telnet: connect to address 127.0.0.1: Connection refused

A workaround is to use two sections:

<source>
        @type forward
        bind "::"
</source>
<source>
        @type forward
        bind "0.0.0.0"
</source>

Expected behavior When binding on "::" (IPv6 name for any address), IPv4 should also be bound on any address. Your Environment

• Fluentd or td-agent version: fluentd --version or td-agent --version

  [root@centos8-ion ~]# fluentd --version
  fluentd 1.10.4

• Operating system: cat /etc/os-release

  
  [root@centos8-ion ~]# cat /etc/os-release 
  NAME="CentOS Linux"
  VERSION="8 (Core)"
  ID="centos"
  ID_LIKE="rhel fedora"
  VERSION_ID="8"
  PLATFORM_ID="platform:el8"
  PRETTY_NAME="CentOS Linux 8 (Core)"
  ANSI_COLOR="0;31"
  CPE_NAME="cpe:/o:centos:centos:8"
  HOME_URL="https://www.centos.org/"
  BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-8" CENTOS_MANTISBT_PROJECT_VERSION="8" REDHAT_SUPPORT_PRODUCT="centos" REDHAT_SUPPORT_PRODUCT_VERSION="8"

- Kernel version: `uname -r`

[root@centos8-ion ~]# uname -r 4.18.0-147.8.1.el8_1.x86_64

**Your Configuration**

    @type forward
    bind "::"

Issue discussed on fluentd Google Group [here](https://groups.google.com/forum/#!topic/fluentd/3lyJkd2wHPY).

[inistor]

Hi there,

Has anyone taken a look over the issue described above?

Thanks, Ion

[github-actions[bot]]

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[inistor]

@repeatedly hi there; any updates here?

[minusbat]

Just found this, as hitting the same issue. No updates I assume ?

[ashie]

FYI: From #2902

Describe the solution you'd like

• When specifying a hostname like localhost, all relevant addresses are listend/bound. For example:

irb(main):016:0> Addrinfo.getaddrinfo('localhost', 5140).select { |x| x.socktype == Socket::SOCK_DGRAM }           
=> [#<Addrinfo: [::1]:5140 UDP (localhost)>, #<Addrinfo: 127.0.0.1:5140 UDP (localhost)>]

[ashie]

We need to modify ServerEngine to realize it:

https://github.com/treasure-data/serverengine/blob/08193f12e8a36518a35244b94f2865d974538450/lib/serverengine/socket_manager_unix.rb#L52-L70

[jaymzh]

So #2902 got de-duped here, which is cool, but I wanna clarify there's 2 different use-cases being discussed:

1. :: should be all-families, all-addresses
2. should be all families that a name resolves to (ala comment https://github.com/fluent/fluentd/issues/3001#issuecomment-850160870 where @ashie is quoting my other ticket)

The first is table-stakes, but the latter should also work.

[inistor]

Correct - the first item refers to how a numeric address is handled, while the second involves DNS resolution.

[soostdijck]

I just ran into this on a v6 only k8s cluster. It's been a while, is this going to make the roadmap any time soon?