> I don't see your argument. Either you want IPv6 for a connection or you don't.
Yes, I want to use dual-stack in general. That's why my application has numerous components which use CURLOPT_IPRESOLVE = AUTO. But if IPv6 doesn't work on a "system level", I want my curl code to be as fast as "IPv4 only" resolve mode without changing anything in my code - like doing detection that IPv6 doesn't work and modifying IP resolve mode in all the places where I create and set an easy handle (that's your suggestion as I understood it). In other words, I want benefits of dual-stack when it works, and I don't want to pay any performance penalties when it doesn't. And I also don't want to pay code change penalties to modify CURLOPT_IPRESOLVE to IPv4 for cases when IPv6 doesn't work in ALL the places where easy handles are created and set up. > . A callback is only useful if the application needs to change something > while a transfer is ongoing The callback I am proposing is a global application callback, not a transfer-specific callback which, indeed, is needed only for transfer-in-progress operations. My callback will be set when application initializes curl via curl_global_init_ipv6() function, and it will be used when a multi handle is created (and before any easy handles are added to it) to set "IPv6 works" mode for the multi-handle . This is very similar to what Curl_ipv6works() currently does, only my proposal will allow to use application-specific function instead of Curl_ipv6works(). Thanks, Dmitry Karpov -----Original Message----- From: curl-library <curl-library-boun...@lists.haxx.se> On Behalf Of Dan Fandrich via curl-library Sent: Tuesday, September 20, 2022 12:58 PM To: libcurl development <curl-library@lists.haxx.se> Cc: Dan Fandrich <d...@coneharvesters.com> Subject: Re: [EXTERNAL] Re: Feature request: provide ability to set a global callback function telling libcurl if IPv6 works on the system On Tue, Sep 20, 2022 at 07:24:42PM +0000, Dmitry Karpov wrote: > Not necessarily. > If we have a bunch of applications on the system with large codebases which > use CURLOPT_IPRESOLVE = AUTO in too many places, then all these places should > detect somehow that "IPv6 doesn't work" and change the resolve mode to IPv4. > It is just not always feasible or desirable. > > The "curl_global_init_ipv6() with callback" solves this problem very easily > and cleanly - as just one global callback can instantly tell all multi > handles created in the application that "IPv6 doesn't work" and let them all > fall back to IPv4. I don't see your argument. Either you want IPv6 for a connection or you don't. Just set the right value using curl_easy_getopt() before you call perform. A callback is only useful if the application needs to change something while a transfer is ongoing, which isn't the case for this option. -- Unsubscribe: https://lists.haxx.se/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.html -- Unsubscribe: https://lists.haxx.se/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.html
