Bug 19697 - /etc/gai.conf option to configure AF_UNSPEC lookups
Summary: /etc/gai.conf option to configure AF_UNSPEC lookups
Status: NEW
Alias: None
Product: glibc
Classification: Unclassified
Component: network (show other bugs)
Version: 2.24
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-02-20 14:22 UTC by Florian Weimer
Modified: 2020-08-17 10:07 UTC (History)
1 user (show)

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Last reconfirmed:
fweimer: security-

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Description Florian Weimer 2016-02-20 14:22:27 UTC 
Systems without IPv6 connectivity may still run software which uses AF_UNSPEC lookups.  Such systems may want to skip the AAAA lookup in getaddrinfo.

Similarly, IPv6-only systems might want to avoid the A lookups.

Therefore, configuration options like “af_unspec both“ (the default), “af_unspec af_inet” and “af_unspec af_inet6” make a lot of sense to me.
Comment 1 Walter Doekes 2020-08-17 10:07:27 UTC 
Seeing that this is still an issue and this bug is referenced here and there, I'd like to shamelessly plug nss-dns4only [1] which uses the nsswitch subsystem to replace AF_UNSPEC queries.

You may find it useful.

Cheers,
Walter Doekes
OSSO B.V.

[1] https://github.com/ossobv/nss-dns4only