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

[Dan Streetman]

> It was no "assumption", but an "observation".

no, you are assuming that systemd-resolved is the authoritative
nameserver providing the $(hostname) addresses, which is wrong.
systemd-resolved is a stub nameserver that does no authoritative
resolution itself; it gets its answers from other nameservers.

> Name: xxx # my "$(hostname)"

why are you obfuscating your hostname?  It could be relevant, for
example if you're choosing to use the 'local' domain.


Let's try this instead; do this:

$ sudo systemctl --runtime edit systemd-resolved

in the editor that opens, put this:

[Service]
Environment=SYSTEMD_LOG_LEVEL=debug


then, save it and exit the editor.  Then do:

$ sudo systemctl restart systemd-resolved

and now lookup your name:

$ nslookup $(hostname)

and then do this and paste/attach the results:

$ journalctl -b -u systemd-resolved --no-pager

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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.

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