[ruby-core:63032] [ruby-trunk - Bug #9925] [Open] rsock_addrinfo uses DNS family AF_UNSPEC for lookup causing high IPv6 AAAA volume

Issue #9925 has been reported by Aaron Stone.

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Bug #9925: rsock_addrinfo uses DNS family AF_UNSPEC for lookup causing high IPv6 AAAA volume
https://bugs.ruby-lang.org/issues/9925

* Author: Aaron Stone
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: 2.0.0
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
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In ext/socket/raddrinfo.c, the function rsock_addrinfo() always uses AF_UNSPEC for DNS queries. This is causing me a very high volume of IPv6 DNS lookups. rsock_addrinfo() is used by TCPSocket (and all other Socket base classes, e.g. Socket and UDPSocket), and TCPSocket is used by Net::HTTP.

Remember that DNS does not do negative caching - if a hostname does not have a AAAA record, then DNS will _always_ try to look up that record again!

I propose that the following code should have some way to force IPv4 or IPv6 lookups:

http://rxr.whitequark.org/mri/source/ext/socket/raddrinfo.c
378 struct addrinfo*
379 rsock_addrinfo(VALUE host, VALUE port, int socktype, int flags)
380 {
381     struct addrinfo hints;
382 
383     MEMZERO(&hints, struct addrinfo, 1);
384     hints.ai_family = AF_UNSPEC;
385     hints.ai_socktype = socktype;
386     hints.ai_flags = flags;
387     return rsock_getaddrinfo(host, port, &hints, 1);
388 }

For example, an environment variable named something like RUBY_GAI could be set to "INET" or "INET6" to switch the hints.ai_family away from AF_UNSPEC.



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