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.\" A man page for gai.conf. -*- nroff -*-
.\"
.\" Copyright (C) 2006 Red Hat, Inc. All rights reserved.
.\"
.\" This copyrighted material is made available to anyone wishing to use,
.\" modify, copy, or redistribute it subject to the terms and conditions of the
.\" GNU General Public License v.2.
.\"
.\" This program is distributed in the hope that it will be useful, but WITHOUT
.\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
.\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
.\" more details.
.\"
.\" You should have received a copy of the GNU General Public License along
.\" with this program; if not, write to the Free Software Foundation, Inc.,
.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
.\"
.\" Author: Ulrich Drepper <drepper@redhat.com>
.TH gai.conf 5 "May 2006" gai.conf

.SH NAME
gai.conf \- getaddrinfo(3) configuration file

.SH DESCRIPTION
A call to
.BR getaddrinfo (3)
might return multiple answers.  According to RFC 3484 these answers must
be sorted so that the answer with the highest success rate is first in
the list.  The RFC provides and algorithm for the sorting.  The static
rules are not always adequate, though.  For this reason the RFC also
requires that system administrators get the chance to dynamically change
the sorting.  For the glibc implementation this can be achieved with
the
.BR /etc/gai.conf
file.
.PP
Each line in the configuration file consists of a keyword and its
parameters.  White spaces in any place are ignored.  Lines starting
with `#' are comments and are ignored.
.PP
The keywords currently recognized are:
.TP
\fBlabel\fR \fInetmask\fR \fIprecedence\fR
The value is added to the label table used in the RFC 3484 sorting.
If any \fBlabel\fR definition is present in the configuration file
is present the default table is not used.  All the label definitions
of the default table which are to be maintained have to be duplicated.
Following the keyword the line has to contain a network mask and a label
value.

.TP
\fBprecedence\fR \fInetmask\fR \fIprecedence\fR
This  keyword is similar to \fBlabel\fR but instead the value is added
to the precendence table as specified in RFC 3484.  Once again, the
presence of a single \fBprecedence\fR line in the configuration file
causes the default table to not be used.

.TP
\fBreload\fR <\fByes\fR|\fBno\fR>
This keyword control whether a process checks whether the configuration
file has been changes since the last time it was read.  If the value is
`\fByes\fR' the file is re-read.  This might cause problems in multi-threaded
applications and is generally a bad idea.  The default is `\fBno\fR'.


.SH EXAMPLE

The default table according to RFC 3484 would be specified with the
following configuration file:

.nf
label  ::1/128       0
label  ::/0          1
label  2002::/16     2
label ::/96          3
label ::ffff:0:0/96  4
precendence  ::1/128       50
precendence  ::/0          40
precendence  2002::/16     30
precendence ::/96          20
precendence ::ffff:0:0/96  10


.SH FILES
\fI/etc/gai.conf\fR

.SH AUTHOR
Ulrich Drepper <drepper@redhat.com>

.SH SEE ALSO
.BR getaddrinfo(3),
RFC 3484