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Re: [EXTERNAL] Re: HTTPS records
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From: Daniel F via curl-library <curl-library_at_lists.haxx.se>
Date: Thu, 08 Dec 2022 08:15:40 +0100
W dniu 2022-12-07 23:52, Daniel Stenberg via curl-library napisał(a):
> 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.
You can also try to use res_query, which returns TTL as well. It is part
of 4.3BSD standard, so should be available on may *nix systems. Here is
example how to use it to get TTL:
https://stackoverflow.com/questions/18772674/extracting-ttl-value-of-a-dns-a-record
Date: Thu, 08 Dec 2022 08:15:40 +0100
W dniu 2022-12-07 23:52, Daniel Stenberg via curl-library napisał(a):
> 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.
You can also try to use res_query, which returns TTL as well. It is part
of 4.3BSD standard, so should be available on may *nix systems. Here is
example how to use it to get TTL:
https://stackoverflow.com/questions/18772674/extracting-ttl-value-of-a-dns-a-record
-- Regards Daniel -- Unsubscribe: https://lists.haxx.se/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.htmlReceived on 2022-12-08