Unable to enable IPv6 for telnet server

Question

I am trying to enable IPv6 on the telnet server running on Ubuntu 16.04, but I cannot.

My configuration files look like the following.

/etc/xinetd.d/telnet

service telnet
{
        disable         = no
        socket_type     = stream
        protocol        = tcp
        wait            = no
        flags           = REUSE IPv6
}

/etc/inetd.conf

telnet stream tcp nowait telnetd /usr/sbin/tcpd /usr/sbin/in.telnetd

After /etc/init.d/xinetd restart, the telnet server is listening on only IPv4 address, not IPv6 address:

# netstat -nap|grep xinet
tcp        0      0 0.0.0.0:23              0.0.0.0:*               LISTEN      4592/xinetd     
unix  2      [ ]         DGRAM                    31655    4592/xinetd 

As a result, when I telnet, I see this error message:

# telnet -6 ::1
Trying ::1...
telnet: Unable to connect to remote host: Connection refused

On the server, I have an active network interface with IPv6 address enabled, and I have been running IPv6-enabled SSH server without any problem. But somehow I cannot enable IPv6 for telnet server.

Any help is appreciated.

Answer 1

I saw this solution here where The problem is solved by adding flags = IPv6 line to /etc/xinetd.d/echo file (but in your case it would be /etc/xinetd.d/telent:

service echo
{
    disable     = no
    type        = INTERNAL
    id      = echo-stream
    socket_type = stream
    protocol    = tcp
        flags           = IPv6  
    user        = root
    wait        = no
}                                                                               


service echo
{
    disable     = no
    type        = INTERNAL
    id      = echo-dgram
    socket_type = dgram
    protocol    = udp
        flags           = IPv6  
    user        = root
    wait        = yes
}   

Answer 2

I faced this issue too. I was able to resolve it by adding the following lines in /etc/xinetd.conf, and do, service xinetd restart.

service telnet

         {
                 socket_type         = stream
                 wait                = no
                 nice                = 10
                 user                = root
                 server              = /usr/sbin/in.telnetd
                 flags               = IPv6
          }

Thanks