mirror of https://github.com/mkerrisk/man-pages
96 lines
3.3 KiB
Groff
96 lines
3.3 KiB
Groff
.\" Copyright (C) 2006 Red Hat, Inc. All rights reserved.
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.\" Author: Ulrich Drepper <drepper@redhat.com>
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.\"
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.\" %%%LICENSE_START(GPLv2_MISC)
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.\" This copyrighted material is made available to anyone wishing to use,
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.\" modify, copy, or redistribute it subject to the terms and conditions of the
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.\" GNU General Public License v.2.
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.\"
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.\" This program is distributed in the hope that it will be useful, but WITHOUT
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.\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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.\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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.\" more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.TH GAI.CONF 5 2013-02-13 "Linux" "Linux Programmer's Manual"
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.SH NAME
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gai.conf \- getaddrinfo(3) configuration file
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.SH DESCRIPTION
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A call to
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.BR getaddrinfo (3)
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might return multiple answers.
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According to RFC\ 3484 these answers must be sorted so that
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the answer with the highest success rate is first in the list.
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The RFC provides an algorithm for the sorting.
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The static rules are not always adequate, though.
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For this reason,
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the RFC also requires that system administrators should have the possibility
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to dynamically change the sorting.
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For the glibc implementation, this can be achieved with the
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.IR /etc/gai.conf
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file.
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.PP
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Each line in the configuration file consists of a keyword and its parameters.
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White spaces in any place are ignored.
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Lines starting with \(aq#\(aq are comments and are ignored.
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.PP
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The keywords currently recognized are:
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.TP
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\fBlabel\fR \fInetmask\fR \fIprecedence\fR
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The value is added to the label table used in the RFC\ 3484 sorting.
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If any \fBlabel\fR definition is present in the configuration file
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is present, the default table is not used.
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All the label definitions
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of the default table which are to be maintained have to be duplicated.
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Following the keyword,
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the line has to contain a network mask and a label value.
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.TP
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\fBprecedence\fR \fInetmask\fR \fIprecedence\fR
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This keyword is similar to \fBlabel\fR, but instead the value is added
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to the precedence table as specified in RFC\ 3484.
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Once again, the
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presence of a single \fBprecedence\fR line in the configuration file
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causes the default table to not be used.
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.TP
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\fBreload\fR <\fByes\fR|\fBno\fR>
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This keyword controls whether a process checks whether the configuration
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file has been changed since the last time it was read.
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If the value is
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"\fByes\fR" the file is re-read.
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This might cause problems in multithreaded
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applications and is generally a bad idea.
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The default is "\fBno\fR".
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.TP
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\fBscopev4\fR \fImask\fR \fIvalue\fR
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Add another rule to the RFC\ 3484 scope table for IPv4 address.
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By default, the scope IDs described in section 3.2 in RFC\ 3438 are used.
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Changing these defaults should hardly ever be necessary.
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.SH FILES
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\fI/etc/gai.conf\fR
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.SH EXAMPLE
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The default table according to RFC\ 3484 would be specified with the
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following configuration file:
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.nf
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label ::1/128 0
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label ::/0 1
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label 2002::/16 2
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label ::/96 3
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label ::ffff:0:0/96 4
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precedence ::1/128 50
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precedence ::/0 40
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precedence 2002::/16 30
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precedence ::/96 20
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precedence ::ffff:0:0/96 10
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.fi
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.\" .SH AUTHOR
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.\" Ulrich Drepper <drepper@redhat.com>
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.\"
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.SH SEE ALSO
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.BR getaddrinfo(3),
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RFC\ 3484
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