From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 582703858D20; Wed, 12 Jul 2023 12:34:54 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 582703858D20
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org;
	s=default; t=1689165294;
	bh=3bNb9q8IO+e7yXDIJKZEmADq2Qs5mEXtY6+zwIL6Fyk=;
	h=From:To:Subject:Date:From;
	b=QD/XseNpulcFsrQfx9eKGh8bFBo4P84ruJszeuVzEgwCJS7AFdPfvt7oztgCR9GaN
	 GRuPny9ZBIFZv9zna58++ONwVQhpVQkbJjKysoIQ367DEX6hZOg3JlFsiArNJVEWPK
	 pKT74k8PKQFoF+QDXBjP65XbV1Nj+g14umNDyMg8=
From: "pemensik at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug network/30631] New: [RFE] option ends0 should allow setting
 optional EDNS0 buffer value
Date: Wed, 12 Jul 2023 12:34:53 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: glibc
X-Bugzilla-Component: network
X-Bugzilla-Version: unspecified
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pemensik at redhat dot com
X-Bugzilla-Status: NEW
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: <bug-30631-131@http.sourceware.org/bugzilla/>
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
List-Id: <glibc-bugs.sourceware.org>

https://sourceware.org/bugzilla/show_bug.cgi?id=3D30631

            Bug ID: 30631
           Summary: [RFE] option ends0 should allow setting optional EDNS0
                    buffer value
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
          Assignee: unassigned at sourceware dot org
          Reporter: pemensik at redhat dot com
  Target Milestone: ---

options edns0 enables outgoing queries to accept responses up to
RESOLV_EDNS_BUFFER_SIZE=3D=3D1200.

I have just found systemd-resolved offers quite big EDNS0 size: 65494.

It is true on lo interface there should not be any fragmentation, which
requires low EDNS0 value (check bug #21361). There is no single value that
would work always. I think it would be great, if edns0 binary option were
expanded to numeric option like timeout:X.

That would allow to set

nameserver 127.0.0.1
options edns0:4096

But would still accept just:

nameserver 8.8.8.8
options edns0

For keeping backward compatibility. Because this actually goes over network,
where on-path MTU is not known and might be changing dynamically, low value
like 1200 is appropriate there to avoid fragmentation.

If the nameserver is on the same LAN, it might be useful to specify edns0:1=
500
for it. On local network only MTU can be derived from the interface leading=
 to
the nameserver. It might delegate on-path measurements to Network Manager
daemon or whatever is configuring /etc/resolv.conf. But currently there is =
no
way to set custom environment or any configuration file.

--=20
You are receiving this mail because:
You are on the CC list for the bug.=