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 precedenceThe 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 precedenceThis 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 valueAdd 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.
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
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
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