[Dnsmasq-discuss] One Request to Flush Them All

[Gilad Moav]

another weird one: just did a quick `dig tcp3.sub.mov.lat +tcp` which only
has 1 A RR. it successfully resolved and forwarded, but it doesn't show in
the cache.

> Hi, I wanted to share an observation regarding Dnsmasq's cache behavior
> that might warrant attention.
>
> It seems that if a DNS response exceeds the configured cache size, issuing
> a new DNS request causes Dnsmasq to flush its entire cache.
>
> This behavior is easily reproducible:
>
> 1. Request a DNS resolution for kong.sub.mov.lat (ensuring you're using
> EDNS with the truncation flag, or DNS over TCP).
> 2. After the response, request the resolution of any other domain.
>
> Upon doing so, the entire cache is wiped, leaving only the latest response
> in the cache.
>
> From what I’ve gathered, it appears that all entries related to the
> oversized response are treated as a single entity within the cache. When a
> new response is cached, instead of freeing just enough space for the new
> entry, the system flushes the entire cache.
>
> Please let me know your thoughts on this or if further clarification is
> needed.
>
> Best regards,
> Gilad.
>
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