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 and algorithm for the sorting. The static rules are not always adequate, though. For this reason the RFC also requires that system administrators get the chance 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 is present 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 label value.

precedence netmask precedence
    This keyword is similar to label but instead the value is added to the precendence 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 control whether a process checks whether the configuration file has been changes since the last time it was read. If the value is `yes' the file is re-read. This might cause problems in multi-threaded applications and is generally a bad idea. The default is `no'.

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
precendence  ::1/128       50
precendence  ::/0          40
precendence  2002::/16     30
precendence ::/96          20
precendence ::ffff:0:0/96  10

FILES
/etc/gai.conf

AUTHOR
Ulrich Drepper <drepper redhat com>

SEE ALSO
getaddrinfo(3), RFC 3484