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<p class="MsoNormal"><span lang="EN-US">Hi guys,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I use dnsdist as a protection layer in front of my DNS servers, where I use the packet cache in dnsdist and allow things to be cached up to 5 minutes:<o:p></o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US">pc = newPacketCache(500000, {maxTTL=300, minTTL=0, temporaryFailureTTL=60, staleTTL=60, dontAge=true, maxNegativeTTL=30})<o:p></o:p></span></b></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">This works perfectly fine, and I have a decent cache hit ratio with normal traffic patterns, and obviously a lot higher during high QPS.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Now, the issue is, I have things like Lets Encrypt which does DNS validation by doing a TXT query to _acme-challenge.<domain> and expects a certain value. However, the value might have been cached previously, meaning
it returns the incorrect value for the domain, and thus the validation fail.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Is there any “easy” way to basically disable the packetcache for specific query names (ideally wildcarding the domain part of it), so it always causes a query to the backend/upstream servers?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">For all queries a 5 min TTL is perfectly fine, but for _acme-challenge TXT lookups, I want this to be either not cached at all, or the cache time to be something like 5 seconds instead.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Best Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Lucas Rolff<o:p></o:p></span></p>
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