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NAME | DESCRIPTION | FILES | VERSIONS | EXAMPLES | SEE ALSO | COLOPHON |
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gai.conf(5) File Formats Manual gai.conf(5)
gai.conf - getaddrinfo(3) configuration file
A call to 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
an algorithm for the sorting. The static rules are not always
adequate, though. For this reason, the RFC also requires that
system administrators should have the possibility to dynamically
change the sorting. For the glibc implementation, this can be
achieved with the /etc/gai.conf file.
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.
The keywords currently recognized are:
label netmask precedence
The value is added to the label table used in the RFC 3484
sorting. If any label definition is present in the
configuration file, 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 precedence
value.
precedence netmask precedence
This keyword is similar to label, but instead the value is
added to the precedence table as specified in RFC 3484.
Once again, the presence of a single precedence line in the
configuration file causes the default table to not be used.
reload <yes|no>
This keyword controls whether a process checks whether the
configuration file has been changed since the last time it
was read. If the value is "yes", the file is reread. This
might cause problems in multithreaded applications and is
generally a bad idea. The default is "no".
scopev4 mask value
Add another rule to the RFC 3484 scope table for IPv4
address. By default, the scope IDs described in section
3.2 in RFC 3438 are used. Changing these defaults should
hardly ever be necessary.
/etc/gai.conf
The gai.conf file is supported since glibc 2.5.
The default table according to RFC 3484 would be specified with
the following configuration file:
label ::1/128 0
label ::/0 1
label 2002::/16 2
label ::/96 3
label ::ffff:0:0/96 4
precedence ::1/128 50
precedence ::/0 40
precedence 2002::/16 30
precedence ::/96 20
precedence ::ffff:0:0/96 10
getaddrinfo(3), RFC 3484
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2025-08-11. If you discover any rendering problems in this HTML
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Linux man-pages 6.15 2025-05-17 gai.conf(5)
Pages that refer to this page: pmdanetcheck(1), getaddrinfo(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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