# gai.conf

## 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 since glibc 2.5.
    


## EXAMPLES



           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
    


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