1GAI.CONF(5) Linux Programmer's Manual GAI.CONF(5)
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6 gai.conf - getaddrinfo(3) configuration file
7
9 A call to getaddrinfo(3) might return multiple answers. According to
10 RFC 3484 these answers must be sorted so that the answer with the high‐
11 est success rate is first in the list. The RFC provides an algorithm
12 for the sorting. The static rules are not always adequate, though.
13 For this reason, the RFC also requires that system administrators
14 should have the possibility to dynamically change the sorting. For the
15 glibc implementation, this can be achieved with the /etc/gai.conf file.
16 Each line in the configuration file consists of a keyword and its
18 parameters. White spaces in any place are ignored. Lines starting
19 with '#' are comments and are ignored.
20 The keywords currently recognized are:
22 label netmask precedence
24 The value is added to the label table used in the RFC 3484 sort‐
25 ing. If any label definition is present in the configuration
26 file, the default table is not used. All the label definitions
27 of the default table which are to be maintained have to be
28 duplicated. Following the keyword, the line has to contain a
29 network mask and a precedence value.
30 precedence netmask precedence
32 This keyword is similar to label, but instead the value is added
33 to the precedence table as specified in RFC 3484. Once again,
34 the presence of a single precedence line in the configuration
35 file causes the default table to not be used.
36 reload <yes|no>
38 This keyword controls whether a process checks whether the con‐
39 figuration file has been changed since the last time it was
40 read. If the value is "yes", the file is reread. This might
41 cause problems in multithreaded applications and is generally a
42 bad idea. The default is "no".
43 scopev4 mask value
45 Add another rule to the RFC 3484 scope table for IPv4 address.
46 By default, the scope IDs described in section 3.2 in RFC 3438
47 are used. Changing these defaults should hardly ever be neces‐
48 sary.
49
51 /etc/gai.conf
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54 The gai.conf file is supported by glibc since version 2.5.
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57 The default table according to RFC 3484 would be specified with the
58 following configuration file:
59 label ::1/128 0
61 label ::/0 1
62 label 2002::/16 2
63 label ::/96 3
64 label ::ffff:0:0/96 4
65 precedence ::1/128 50
66 precedence ::/0 40
67 precedence 2002::/16 30
68 precedence ::/96 20
69 precedence ::ffff:0:0/96 10
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72 getaddrinfo(3), RFC 3484
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75 This page is part of release 5.07 of the Linux man-pages project. A
76 description of the project, information about reporting bugs, and the
77 latest version of this page, can be found at
78 https://www.kernel.org/doc/man-pages/.
79Linux 2020-06-09 GAI.CONF(5)