GAI.CONF(5)                         Linux Programmer's 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 implementa‐
       tion, this can be achieved with the /etc/gai.conf file.

       Each line in the configuration file consists of a keyword and its parameters.  White  spa‐
       ces 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 main‐
              tained 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
              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

EXAMPLE
       The default table according to RFC 3484 would be specified with the  following  configura‐
       tion 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 3.74 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 http://www.kernel.org/doc/man-pages/.



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