gai.conf(5) — Linux manual page


GAI.CONF(5)               Linux Programmer's Manual              GAI.CONF(5)

NAME         top

       gai.conf - getaddrinfo(3) configuration file

DESCRIPTION         top

       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

FILES         top


VERSIONS         top

       The gai.conf file is supported by glibc since version 2.5.

EXAMPLES         top

       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

SEE ALSO         top

       getaddrinfo(3), RFC 3484

COLOPHON         top

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       latest version of this page, can be found at

Linux                            2020-06-09                      GAI.CONF(5)

Pages that refer to this page: pmdanetcheck(1)freeaddrinfo(3)gai_strerror(3)getaddrinfo(3)