On Wed, 7 Dec 2022, Dmitry Karpov via curl-library wrote:
Exactly! Honoring exact TTLs will be a very good feature. I heard complaints
from some backend services who manipulated DNS records for load balancing
and used 20s TTL that libcurl didn't honor it and it created performance
issues. So, it will be definitely a good addition to the library.
Sure, just a little complicated.
A primary reason the default name resolving in libcurl is still done with
getaddrinfo() and not with a third party library like c-ares is that it is
mighty hard to replicate its functionality. And getaddrinfo() does not return
TTL.
If we want to know the TTL for A and AAAA records while remaining 100%
compatible with names used all over, we need to use getaddrinfo() *AND* do a
separate lookup for the A and AAAA entries and use any possible TTL values we
get back. Double the number of DNS requests. Not ideal.
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