[Dnsmasq-discuss] Extend server to accept hostnames for upstream resolver

[Dominik Derigs]

Dear Simon,

In docker swarm and compose configurations, other containers are
only reachable via hostnames. It is not always possible to assign
IP addresses beforehand. Hence, the upstream server IP is not
known at dnsmasq start when the upstream is part of the deployed
configuration, e.g., a local cloudflared or unbound container.

So far, getting dnsmasq to run in such a case requires hacks that
somehow try to determine the IP address before starting dnsmasq.
An example for such a hack (not invented by me):
https://github.com/tschaffter/docker-dnsmasq/blob/54b5d5d551746b6f1708fbf4a705e2de66c2eaee/docker-entrypoint.sh#L14-L23

This patch implements name resolution functionality for
server=... by querying the system resolver for a hostname. It is
only used when a user supplied something that is not a valid IP
address (dnsmasq currently fails hard in this case so this isn't
a breaking change) and can be omitted by a compile time flag (I
think it's worthwhile to have it).

I know my proposal does sound somewhat strange (resolving a DNS
server name) but this is something that is somewhat frequently
needed and currently only possible through external hacks.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-Extend-server-to-accept.patch
Type: text/x-patch
Size: 5766 bytes
Desc: not available
URL: <http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/attachments/20220402/959421e9/attachment.bin>