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.\" ========================================================================
.\"
.IX Title "Mail::DKIM::DNS 3pm"
.TH Mail::DKIM::DNS 3pm "2020-09-11" "perl v5.30.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
Mail::DKIM::DNS \- performs DNS queries for Mail::DKIM
.SH "VERSION"
.IX Header "VERSION"
version 1.20200907
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is the module that performs \s-1DNS\s0 queries for Mail::DKIM.
.SH "CONFIGURATION"
.IX Header "CONFIGURATION"
This module has a couple configuration settings that the caller
may want to use to customize the behavior of this module.
.ie n .SS "$Mail::DKIM::DNS::TIMEOUT"
.el .SS "\f(CW$Mail::DKIM::DNS::TIMEOUT\fP"
.IX Subsection "$Mail::DKIM::DNS::TIMEOUT"
This global variable specifies the maximum amount of time (in seconds)
to wait for a single \s-1DNS\s0 query to complete. The default is 10.
.SS "\fBMail::DKIM::DNS::resolver()\fP"
.IX Subsection "Mail::DKIM::DNS::resolver()"
Use this global subroutine to get or replace the instance of
Net::DNS::Resolver that Mail::DKIM uses. If set to undef (the default),
then a brand new default instance of Net::DNS::Resolver will be
created the first time a \s-1DNS\s0 query is needed.
.PP
You will call this subroutine if you want to specify non-default options
to Net::DNS::Resolver, such as different timeouts, or to enable use
of a persistent socket. For example:
.PP
.Vb 6
\&  # first, construct a custom DNS resolver
\&  my $res = Net::DNS::Resolver\->new(
\&                    udp_timeout => 3, tcp_timeout => 3, retry => 2,
\&                 );
\&  $res\->udppacketsize(1240);
\&  $res\->persistent_udp(1);
\&
\&  # then, tell Mail::DKIM to use this resolver
\&  Mail::DKIM::DNS::resolver($res);
.Ve
.SS "\fBMail::DKIM::DNS::enable_EDNS0()\fP"
.IX Subsection "Mail::DKIM::DNS::enable_EDNS0()"
This is a convenience subroutine that will construct an appropriate \s-1DNS\s0
resolver that uses \s-1EDNS0\s0 (Extension mechanisms for \s-1DNS\s0) to support large
\&\s-1DNS\s0 replies, and configure Mail::DKIM to use it. (As such, it should \s-1NOT\s0
be used in conjunction with the \fBresolver()\fR subroutine described above.)
.PP
.Vb 1
\&  Mail::DKIM::DNS::enable_EDNS0();
.Ve
.PP
Use of \s-1EDNS0\s0 is recommended, since it reduces the need for falling back to \s-1TCP\s0
when dealing with large \s-1DNS\s0 packets. However, it is not enabled by default
because some Internet firewalls which do deep inspection of packets are not able
to process EDNS0\-enabled packets. When there is a firewall on a path to a \s-1DNS\s0
resolver, the \s-1EDNS0\s0 feature should be specifically tested before enabling.
.SH "AUTHORS"
.IX Header "AUTHORS"
.IP "\(bu" 4
Jason Long <jason@long.name>
.IP "\(bu" 4
Marc Bradshaw <marc@marcbradshaw.net>
.IP "\(bu" 4
Bron Gondwana <brong@fastmailteam.com> (\s-1ARC\s0)
.SH "THANKS"
.IX Header "THANKS"
Work on ensuring that this module passes the \s-1ARC\s0 test suite was
generously sponsored by Valimail (https://www.valimail.com/)
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
.IP "\(bu" 4
Copyright (C) 2013 by Messiah College
.IP "\(bu" 4
Copyright (C) 2010 by Jason Long
.IP "\(bu" 4
Copyright (C) 2017 by Standcore \s-1LLC\s0
.IP "\(bu" 4
Copyright (C) 2020 by FastMail Pty Ltd
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.6 or,
at your option, any later version of Perl 5 you may have available.