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  definition  is
              present  in  the  configuration  file  is  present,  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 label 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  re-read.   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

EXAMPLE

       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

COLOPHON

       This  page  is  part  of  release 3.54 of the Linux man-pages project.  A description of the project, and
       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

Linux                                              2013-02-13                                        GAI.CONF(5)