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 high-
       est  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 sort-
	      ing.  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 con-
	      figuration 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 neces-
	      sary.

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 4.10 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/.



Linux				  2016-03-15			   GAI.CONF(5)