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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   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.

FILES

   /etc/gai.conf

VERSIONS

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

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 4.09 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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