From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202508 header.b=wjda2/qk; dkim-atps=neutral Received: from mail.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id 2705E5A0279 for ; Wed, 10 Sep 2025 05:33:58 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202508; t=1757475234; bh=5gZZreInZS/yXMinhQfUsyodexm0iGn18u5SuxxoeLA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=wjda2/qkdDzRkTrgLEKxttZcUHEC4SzrryI2pCcA1YNBnh5qZyMe+d5hcjImsVfQi LPlpj/0hyRrdpFqRrMU/Um7uGvejDpOj034n162ULXHWJvmPtOP2Ni6BZ0ATKixypk 2hrhZ7fKLOCdEFS/IuC/ieHCI7pem/dkuREbO8Z9Y6GXgoj3U4+Fx/SOnOTWeJqk3c BBdO9Ti0zgJqssfqDJ/buBQHBzILllowSYwHOXSm3UmLY+jHTTmk1P+t6FFdT+inkW XzZ9fmdXUJ4mGi4ZeMn3bt86j1K0TIi7zbiONbrvhD6XiirEVBYyS8d5ddP8MjiwjT shF9AEQ8XDzvg== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4cM5rf65Vhz4wB6; Wed, 10 Sep 2025 13:33:54 +1000 (AEST) Date: Wed, 10 Sep 2025 13:33:48 +1000 From: David Gibson To: Stefano Brivio Subject: Re: [PATCH v2] Send an initial ARP request to resolve the guest IP address Message-ID: References: <20250908092038.405194-1-v@njh.eu> <20250908092429.406248-2-v@njh.eu> <20250909175530.7fc950bc@elisabeth> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="k2zcgndd0jsYCD3p" Content-Disposition: inline In-Reply-To: <20250909175530.7fc950bc@elisabeth> Message-ID-Hash: HRTL5ZTWSG3RR6DH3N4VTNJZCC7UIIQ2 X-Message-ID-Hash: HRTL5ZTWSG3RR6DH3N4VTNJZCC7UIIQ2 X-MailFrom: dgibson@gandalf.ozlabs.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Volker Diels-Grabsch , passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --k2zcgndd0jsYCD3p Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Sep 09, 2025 at 05:55:30PM +0200, Stefano Brivio wrote: > On Tue, 9 Sep 2025 12:10:45 +0200 > Volker Diels-Grabsch wrote: >=20 > > David Gibson wrote: > > > Looks good to me. It would be nice to also send an Neighbour > > > Discovery request to accomplish the same thing for IPv6 only guests, > > > but that could be a separate patch. =20 > >=20 > > Good point! I'd prefer to do it in the same patch, as I'd also like > > fix another minor detail in this one. > >=20 > > Just for the sake of clarity: I had a look at RFC4861 and there are > > many types of Neighbour Discovery requests. For our purpose, I believe > > that we want to send a "Neighbor Solicitation Message" described in > > section 4.3: > >=20 > > https://datatracker.ietf.org/doc/html/rfc4861#section-4.3 > >=20 > > Do you agree, or did you have something else in mind? >=20 > I was about to comment on this, but from the new patch you sent, I see > you already figured out it's a Neighbour Solicitation and that we > already have some bits of code for that. :) >=20 > > > Note that even with this patch, active TCP connections (and in some > > > cases UDP flows) will be broken by a passt restart. =20 > >=20 > > Indeed, that is unavoidable for a user-space tool opening TCP and UDP > > connections, I guess, unless "passt" itself is wrapped into another > > process or system tool that keeps those connections open. But let's > > not go into that. >=20 > Actually, it's not really unavoidable, in the sense that we recently > added (see migrate.c, repair.c, passt-repair.c, and passt-repair(1)) > support for migration of live TCP connections triggered by vhost-user > commands: Right, but doing this requires knowing in advance, support from qemu and a bunch of infrastructure. It's not going to work if you just kill and restart passt. --=20 David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson --k2zcgndd0jsYCD3p Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmjA8ZsACgkQzQJF27ox 2GfrdQ/9E7H+K5PzrY+Lq3v280a+QqtU6SQwxHDWGZ4tmaTe7KFmtZkner6lp7CC K6RhcbPRYkESbXCGExwJM3A9gOZ/lFHapCCU+kHEyI34IiFjmAvPFUvSlm45RCC2 R9AY3KQ0vow0f24z7YbbhjGotQ+WrbEfHP6fAitpcFy1GPBWoqjcV0IA6bOyEGWb jyTbsGHJesaIgUhTcB3EMCgjL5/2X3wZ3jYkgtsDTCUmxEvmP1xZGNhoZNkXEVop k8sChdKtGB0xyd+8OxUqCD/J07iDahZouhV1OYOTDEQ2RPBdGtu0+hFF+bp/xSeX 5pjaiQP/qS7JmcYCFrf63IZOYutnTGkSqYoMb0TvTTsytTWhyOzsEFePgXhD1KzK 9S8BpvK2XjyyWRYV04q8KOT0i6xh8V49vtgAkcP34O38P8k+b4aIhYudJMZmiW+P mkz+zyhf6FcQmPcuJaFZiHjKau9xAVA4eQvzYfhWi0/DkiqB64h529MsFXBTuhVo taCJASwYHcVw+z4RlZp96SGpYpL2lBCy0n1RqM2z3jdVy5HIJDluQTU9V9iT2j3k DELJdB4b7Bu043TfzB4gMNpjqDo13+sBlB36yWSVaxauFkGzt+2jyVTC7Ec/PeRZ EjJXYwdg58cE1VxFMOqw+CBkhPPVLbV0WG+AhNMC/b11bGIgG34= =czYj -----END PGP SIGNATURE----- --k2zcgndd0jsYCD3p--