man > gai.conf(5)

gai.conf(5)                              File Formats Manual                             gai.conf(5)

NAME
       gai.conf - getaddrinfo(3) configuration file

DESCRIPTION
       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 def‐
              inition  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  dupli‐
              cated.  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 ta‐
              ble 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.

FILES
       /etc/gai.conf

VERSIONS
       The gai.conf file is supported since glibc 2.5.

EXAMPLES
       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
       getaddrinfo(3), RFC 3484

Linux man-pages 6.7                          2023-10-31                                  gai.conf(5)