SkyDNS can't listen on 0.0.0.0:53 in CoreOS 1151.0.0

[steveeJ]

CoreOS Version

1151.0.0

$ cat /etc/os-release
NAME=CoreOS
...
BUG_REPORT_URL="https://github.com/coreos/bugs/issues"

Environment

I have a SkyDNS container that uses --net=host and attempts to listen on 0.0.0.0:53.

Expected Behavior

SkyDNS works.

Actual Behavior

SkyDNS doesn't work, because systemd-resolved is listening on 127.0.0.53:53, causing SkyDNS to fail.

Reproduction Steps

1. Boot CoreOS 1151.0.0
2. etcdctl set /skydns/config {"dns_addr":"0.0.0.0:53"}
3. sudo /usr/bin/rkt run --debug --net=host docker://skynetservices/skydns --insecure-options=image

Other Information

This has worked in the past without any configuration change.

Feature Request

Disable systemd-resolved by default, or revert whatever caused it to claim that socket.

[dm0-]

We discussed this, and I will send a PR upstream shortly to make enabling the stub resolver configurable. I'll leave it enabled by default for upstream consistency, but we will disable it on CoreOS.

[philips]

And as a workaround doing systemctl mask systemd-resolved works if you are running your own full resolver. However, if you rely on /etc/resolv.conf entries from DHCP it will break.

Also, this issue will be fixed before Beta and we will default this behavior to off.

[dm0-]

We are unconditionally disabling the DNS stub resolver's listening ports on the next alpha and beta, until upstream agrees on a configurable option.