Listen to TCP :53 in Docker

[dereckson]

Currently the README suggests to run the image like this:

 -p 53:53                                      \
 -p 53:53/udp                                  \

That creates the following bindings:

53/tcp
0.0.0.0:53->53/udp
:::53->53/udp

You can then reach host 53 UDP, but not TCP.

[gc-ss]

You can then reach host 53 UDP, but not TCP.

Is DNS over TCP something gets used? What's your DNS over TCP setup?

[Ajedi32]

DNS over TCP is a mandatory part of the DNS spec: https://datatracker.ietf.org/doc/html/rfc7766#section-5

As for the missing TCP binding, that's very strange since -p 53:53 should bind port 53 TCP. Does it work if you explicitly specify TCP like 53:53/tcp?

[qupfer]

DNS over TCP is a mandatory part of the DNS spec: https://datatracker.ietf.org/doc/html/rfc7766#section-5

I'm not in an academic environment anymore, so maybe I'm wrong.

But RFC 7766 describes DNS over TCP and yes, there is DNS over TCP mandatory :-D But this does not (imho) imply, that DNS MUST use TCP, as DNS must not follow RFC7766 if they don't implement DNS over TCP.