[Bug nss/29017] New: Change resolv.conf default to single-request

[Bug nss/29017] New: Change resolv.conf default to single-request

[sourceware at psanetra dot de]

https://sourceware.org/bugzilla/show_bug.cgi?id=29017

            Bug ID: 29017
           Summary: Change resolv.conf default to single-request
           Product: glibc
           Version: 2.10
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: nss
          Assignee: unassigned at sourceware dot org
          Reporter: sourceware at psanetra dot de
  Target Milestone: ---

glibc 2.9 introduced "same time" lookup of ipv4 and ipv6 host names via DNS and
glibc 2.10 introduced the option "single-request" to introduce explicit
sequential lookups of those addresses. The default since 2.10 is to send those
lookups in parallel.

A known issue is that some firewalls and DNS servers fail to handle those
parallel requests and return only a single response for one of those requests.
In these cases glibc waits for 5 seconds and then switches to single-request
mode for a specific process.

This default behavior leads to very bad performance on short living processes
and is very hard to debug as specialized knowledge about resolv.conf and glibc
is required.

See reports on Stack Exchange:
https://unix.stackexchange.com/questions/141163/dns-lookups-sometimes-take-5-seconds
https://serverfault.com/questions/906397/how-do-i-set-the-single-request-option-in-networkmanager
https://unix.stackexchange.com/questions/290987/resolving-hostname-takes-5-seconds

In my specific case the parallel lookups work just fine at home, while always
causing issues at work.

We have the year 2022 and these issues still occur, so it was not some kind of
issue that went away by time as it was possibly expected when glibc 2.10 was
released.

I propose to change the default behavior to "single-request" to avoid those
issues by default and optionally introduce a new option to lookup ipv4 and ipv6
addresses in parallel to improve performance, although I do not expect that
this performance gain is really noticable anymore with the internet connections
we have today.

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[Bug nss/29017] Change resolv.conf default to single-request

[sourceware at psanetra dot de]

https://sourceware.org/bugzilla/show_bug.cgi?id=29017

Philip Sanetra <sourceware at psanetra dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sourceware at psanetra dot de

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[Bug network/29017] Change resolv.conf default to single-request

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29017

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com
          Component|nss                         |network
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=31476

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[Bug network/29017] Change resolv.conf default to single-request

[cristian at rodriguez dot im]

https://sourceware.org/bugzilla/show_bug.cgi?id=29017

Cristian Rodríguez <cristian at rodriguez dot im> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |cristian at rodriguez dot im

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[Bug network/29017] Change resolv.conf default to single-request

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29017

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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