From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E62732459C6; Fri, 2 Jan 2026 20:18:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767385134; cv=none; b=fyojiCqx/JlEaqdntEf3+/BPIp/4qBVyFku9VptlsWxyz8diqSZtB+pWobUunWqu6jlmenlsygzYc5o447uEtwc3iP6iK7YmmbLk9QUtdYH6gHVzNV0DRj9Dvl5VEKK9s5g7mjaHWunSeBAcqhalz7NzyzI8UrlPbQe30d2wAOU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767385134; c=relaxed/simple; bh=+agCO8qgZzoCTvxk+09fXoc+5YuFE6U+k7GKWMlCFsk=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=UFe3SDlKHL3fYdV6/du3APPYJ4hGW0rUjAkjtvJWsTStUr/9vUgcGvkdj9MlgbAU+vU1SzaTC/sXGOvTMb6kSWGCdBT0eqg+NTvQsQCWAXEp1kSG2HHVbgXClk3yLpm8lXNkXak8G7tSGdHkaT+4RQiLQ9/gGQnaH9wMFkk6XIc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org; spf=none smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=aPqhpcYz; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="aPqhpcYz" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=QRmCVPeP+RIEBMuUcBbI7kHMTrc6nq0oB8Cnpy0O4B8=; b=aPqhpcYzztDJKxwcg3YQlMqpo6 vK9a2edoBrl7cVNq8xCxQkas8x+azHFteFeqnv8pxJdPq1UlhCVebzsuJzFRlqz+nH86g1OHUG/Ay zMVVkrxdtwb6oDve6WocaiPqEXqQPudX1mzkViAaCyMAmUpBqQj0RdYZtPqiZtU7QmGmDLDiU++cL OG3eZ7eRi8zPjXhNymG9887x9uhU4z3XJJ165S7vY4VdwhE4eJBkYAYXGnMIt4erdk/KcAwbsxEZF w4KteSo5qRGYgWow1eqzJ7n2HcFhSo2VVlxkqeTB5SRTJmvsWQQPgN+YHmP3LBlqXwNJMcK3tUbL/ gaxHsCfw==; Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1vblbU-00Eir4-JI; Fri, 02 Jan 2026 20:18:32 +0000 Message-ID: <27c249d80c346a258cfbf32f1d131ad4fe64e77c.camel@debian.org> Subject: Re: [regression 5.10.y] Libvirt can no longer delete macvtap devices after backport of a6cec0bcd342 ("net: rtnetlink: add bulk delete support flag") to 5.10.y series (Debian 11) From: Ben Hutchings To: Thorsten Leemhuis , Roland Schwarzkopf , Nikolay Aleksandrov , David Ahern , "David S. Miller" , Sasha Levin , debian-kernel@lists.debian.org, Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, regressions@lists.linux.dev, 1124549@bugs.debian.org Date: Fri, 02 Jan 2026 21:18:26 +0100 In-Reply-To: References: <0b06eb09-b1a9-41f9-8655-67397be72b22@mathematik.uni-marburg.de> <176608738558.457059.16166844651150713799@eldamar.lan> Organization: Debian Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-OII6/htffjAg1Djg2KhL" User-Agent: Evolution 3.56.2-7 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Debian-User: benh --=-OII6/htffjAg1Djg2KhL Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi all, On Fri, 2025-12-19 at 10:19 +0100, Thorsten Leemhuis wrote: > On 12/18/25 20:50, Salvatore Bonaccorso wrote: > >=20 > > Is there soemthing missing? > >=20 > > Roland I think it would be helpful if you can test as well more recent > > stable series versions to confirm if the issue is present there as > > well or not, which might indicate a 5.10.y specific backporting > > problem. >=20 > FWIW, it (as usual) would be very important to know if this happens with > mainline as well, as that determines if it's a general problem or a > backporting problem [...] The bug is this: - libvirtd wrongly used to use NLM_F_CREATE (0x400) and NLM_F_EXCL (0x200) flags on an RTM_DELLINK operation. These flags are only semantically valid for NEW-type operations. - rtnetlink is rather lax about checking the flags on operations, so these unsupported flags had no effect. - rtnetlink can now support NLM_F_BULK (0x200) on some DEL-type operations. If the flag is used but is not valid for the specific operation then the operation now fails with EOPNOTSUPP. Since NLM_F_EXCL =3D=3D NLM_F_BULK and RTM_DELLINK does not support bulk operations, libvirtd now hits this error case. I have not tested with mainline, but in principle the same issue should occur with any other kernel version that has commit=C2=A0a6cec0bcd342 "net: rtnetlink: add bulk delete support flag" together with an older version of libvirt. This was fixed in libvirt commit 1334002340b, which appears to have gone into version 7.1.0, but Debian 11 "bullseye" has 7.0.0. We can certainly fix the libvirt side of this in Debian, but this also sounds like a case where the kernel should work around known buggy user- space. On the other hand, this has been upstream for over 3 years so maybe it doesn't make sense now. Please let me know whether I (or anyone) should try to implement a workaround for this in the kernel. Ben. --=20 Ben Hutchings - Debian developer, member of kernel, installer and LTS teams --=-OII6/htffjAg1Djg2KhL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEErCspvTSmr92z9o8157/I7JWGEQkFAmlYKBIACgkQ57/I7JWG EQnD0A//T7s2mc8lgDzrecnjiCAaxAAnYMYUy/UhgiuFea9wFuXqo76ucc0paWs7 YmvABwnDSiyl9lq4WfN5CGTmai+arF4PMLQLlmRXslato+22hVK/731P62DfzW+6 Mx5pPyDGaVAkFQHe/hOku64F9/NHbC3ZptPXVoxLeQDTTkTPP+y7G7mxZJUp/KOu YsnMQdDvnqiZsjSyEddi+HDast2K7bxm+iDZ8qJm8crzYux4kXeRo1b+Pug72f1k XErFYPSw8DtQw1OOdxRtP2id4dMhLaXzkde8VFky6jowAFLk3dwV0YwsYm9OAkEQ 8pdQ+7C/JTKznJFeJQjVz5P9TDevqDK+v4PkGPia+KSQN1rcxVRHX9h7Ci5ongk3 l3gTy4U8nz4Mw+ap0qWAmgidfkqcL2Kp/GY0ck8uPXUjtPYWE288KOtMK/z+R8vk B7KcU4YmIvqxEAVMPARatHO4ElUhdzNhj0+vRlr00zHumWZb+Cu6Sk5QC9aTCUVJ gNi/tveeZwcbKWpnyaUr7CdLwgLVXhi7k6KDw+UCMWYrOqMiLsjgFa9QMHqK9bKG FETqDyYvkGnU0Yb4itsE5hTkh9pqNTp3nkIxn0YI7RUF8kYEstV4DW3jjMVjIMad PLiW1gtAOxADHaHuFlqcpbCI1SRsS56ID5r0dgZPjaNoUmbJVR0= =AH7O -----END PGP SIGNATURE----- --=-OII6/htffjAg1Djg2KhL--