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 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 4.15 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)