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.TH "FILTER-AAAA" "8" "2023-01-12" "9.16.37-Debian" "BIND 9"
.SH NAME
filter-aaaa \- filter AAAA in DNS responses when A is present
.SH SYNOPSIS
.sp
\fBplugin query\fP "filter\-aaaa.so" [{ parameters }];
.SH DESCRIPTION
.sp
\fBfilter\-aaaa.so\fP is a query plugin module for \fBnamed\fP, enabling
\fBnamed\fP to omit some IPv6 addresses when responding to clients.
.sp
Until BIND 9.12, this feature was implemented natively in \fBnamed\fP and
enabled with the \fBfilter\-aaaa\fP ACL and the \fBfilter\-aaaa\-on\-v4\fP and
\fBfilter\-aaaa\-on\-v6\fP options. These options are now deprecated in
\fBnamed.conf\fP but can be passed as parameters to the
\fBfilter\-aaaa.so\fP plugin, for example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
plugin query "/usr/local/lib/filter\-aaaa.so" {
        filter\-aaaa\-on\-v4 yes;
        filter\-aaaa\-on\-v6 yes;
        filter\-aaaa { 192.0.2.1; 2001:db8:2::1; };
};
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
This module is intended to aid transition from IPv4 to IPv6 by
withholding IPv6 addresses from DNS clients which are not connected to
the IPv6 Internet, when the name being looked up has an IPv4 address
available. Use of this module is not recommended unless absolutely
necessary.
.sp
Note: This mechanism can erroneously cause other servers not to give
AAAA records to their clients. If a recursing server with both IPv6 and
IPv4 network connections queries an authoritative server using this
mechanism via IPv4, it is denied AAAA records even if its client is
using IPv6.
.SH OPTIONS
.INDENT 0.0
.TP
.B \fBfilter\-aaaa\fP
This option specifies a list of client addresses for which AAAA filtering is to
be applied. The default is \fBany\fP\&.
.TP
.B \fBfilter\-aaaa\-on\-v4\fP
If set to \fByes\fP, this option indicates that the DNS client is at an IPv4 address, in
\fBfilter\-aaaa\fP\&. If the response does not include DNSSEC
signatures, then all AAAA records are deleted from the response. This
filtering applies to all responses, not only authoritative
ones.
.sp
If set to \fBbreak\-dnssec\fP, then AAAA records are deleted even when
DNSSEC is enabled. As suggested by the name, this causes the response
to fail to verify, because the DNSSEC protocol is designed to detect
deletions.
.sp
This mechanism can erroneously cause other servers not to give AAAA
records to their clients. If a recursing server with both IPv6 and IPv4
network connections queries an authoritative server using this
mechanism via IPv4, it is denied AAAA records even if its client is
using IPv6.
.TP
.B \fBfilter\-aaaa\-on\-v6\fP
This option is identical to \fBfilter\-aaaa\-on\-v4\fP, except that it filters AAAA responses
to queries from IPv6 clients instead of IPv4 clients. To filter all
responses, set both options to \fByes\fP\&.
.UNINDENT
.SH SEE ALSO
.sp
BIND 9 Administrator Reference Manual.
.SH AUTHOR
Internet Systems Consortium
.SH COPYRIGHT
2023, Internet Systems Consortium
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