[Bug 1853669] Re: systemd resolves own hostname to link local ipv6 address

[Andreas L]

> If you manually configure your network, ...

Ok, so adding it to /etc/resolv.conf is actually one of the supported ways.
Thanks (for info). I'll stick to that.


> Why is it wrong?

try connecting to that address:


avl at fpc:~$ telnet fe80::4687:fcff:fe9e:4ac7 22
Trying fe80::4687:fcff:fe9e:4ac7...
telnet: Unable to connect to remote host: Invalid argument


The link local inet6 address alone is useless information,...


avl at fpc:~$ telnet fe80::4687:fcff:fe9e:4ac7%enp4s0 22
Trying fe80::4687:fcff:fe9e:4ac7%enp4s0...
Connected to fe80::4687:fcff:fe9e:4ac7%enp4s0.
Escape character is '^]'.
SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3


... unless the network device name (enp4s0 on my machine) is
attached to the inet6 address.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1853669

Title:
  systemd resolves own hostname to link local ipv6 address

Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  I've got an ethernet-device that only has a configured ipv4 address,
  and some auto-generated link-local (aka "scope link") ipv6 address.

  Any tool doing a DNS query (and /lib/systemd/systemd-resolved is the
  DNS-server listening on 127.0.0.53) for this host's hostname gets back
  two addresses: the correct ipv4 address, and a broken ipv6 address.

  Unlike on ipv4,  it is possible for the same ipv6-address to be
  assigned to multiple devices, and therefore the address is only valid
  in the context of the eth-device.

  Now, if "ifconfig" shows "inet6 fe80::4687:fcff:fe9e:4ac7  prefixlen 64  scopeid 0x20<link>"
  then "fe80::4687:fcff:fe9e:4ac7" is NOT a connectable address, and syscall connect() typically fails with EINVAL.

  To make it a valid address, it needs to be suffixed with a "%" and the device name, like:
  fe80::4687:fcff:fe9e:4ac7%enp4s0

  Either the resolver can return the link name attached to the address
  separated with a "%" char, or it needs to ignore link-local inet6
  addresses.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1853669/+subscriptions