From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id BA1A23858C52; Fri, 1 Apr 2022 17:15:03 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org BA1A23858C52 From: "sourceware at psanetra dot de" To: glibc-bugs@sourceware.org Subject: [Bug nss/29017] New: Change resolv.conf default to single-request Date: Fri, 01 Apr 2022 17:15:03 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: nss X-Bugzilla-Version: 2.10 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: sourceware at psanetra dot de X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: glibc-bugs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Glibc-bugs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Apr 2022 17:15:03 -0000 https://sourceware.org/bugzilla/show_bug.cgi?id=3D29017 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 th= ose 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 reques= ts. 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 process= es and is very hard to debug as specialized knowledge about resolv.conf and gl= ibc 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-op= tion-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 alwa= ys 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 connect= ions we have today. --=20 You are receiving this mail because: You are on the CC list for the bug.=