[GH-ISSUE #298] Listen to TCP :53 in Docker #154

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opened 2026-03-13 15:57:54 +03:00 by kerem · 3 comments

kerem commented

2026-03-13 15:57:54 +03:00

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Originally created by @dereckson on GitHub (Mar 18, 2022).
Original GitHub issue: https://github.com/acme-dns/acme-dns/issues/298

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.

Originally created by @dereckson on GitHub (Mar 18, 2022). Original GitHub issue: https://github.com/acme-dns/acme-dns/issues/298 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.

kerem commented

2026-03-13 15:58:00 +03:00

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@gc-ss commented on GitHub (Mar 19, 2022):

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

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

@gc-ss commented on GitHub (Mar 19, 2022): > You can then reach host 53 UDP, but not TCP. Is DNS over TCP something gets used? What's your DNS over TCP setup?

kerem commented

2026-03-13 15:58:05 +03:00

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@Ajedi32 commented on GitHub (Mar 30, 2022):

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?

@Ajedi32 commented on GitHub (Mar 30, 2022): 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`?

kerem commented

2026-03-13 15:58:10 +03:00

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@qupfer commented on GitHub (Aug 9, 2022):

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.

@qupfer commented on GitHub (Aug 9, 2022): > 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.