[systemd-devel] Extend systemd-resolved service to override DNS response

[Kevin P. Fleming]

On Mon, Feb 13, 2023, at 05:38, Aditya Sharma wrote:
> Hi All,
> 
> We needed help in understanding how systemd-resolved service can be extended to cache DNS responses to protect against DNS server failures.
> We were planning to maintain a cache so that we can override negative responses from the DNS server and replace it with our cached last known good record.

This sounds very dangerous. A 'negative' response from an authoritative DNS server (NXDOMAIN, for example) is authoritative and should not be overridden.

If what you mean is that you want to serve 'stale' records from a cache when their TTLs have expired and the authoritative servers which provided them are not reachable, that's something that a number of existing recursive resolvers are able to do and it could be logical for systemd-resolved to offer it too.
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