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=202512 header.b=UnVZdoQe; dkim-atps=neutral Received: from mail.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id 8E5645A0271 for ; Tue, 13 Jan 2026 03:49:04 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202512; t=1768272540; bh=bJdRhkTW21Kij9DP/cXYtSg1/Hu/oz7t1/wfQT352iE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UnVZdoQeRmQIdPqUC2wp4e1Rf0gpZi0T3MQPDMzogKhqEsxaTh0HapV7JrUHaeUPI XxbBkJ9jpnSZsYlDFSC7yuj5jOGW5ohimDbz43hfBm62M9RezoqBbzPUn1Asgb91KV t1D2an5zr3DYxPhor2PRqqcF1FrraryMCqe5fRpvmxzA0JKtDa+cTA+WXJFGoEe/pI A2girwJm2/WhqLerPBTZ9ag+JU/UHgL3loXHJENhRfWmnL4bkvbQNZ2SGqnIRCAfp1 JWdCF9dTKdNisCQqmtPP3pOUAoAVF3IrvRkZNamV96/5exlBJRV7UEdo6eemCoYj81 9Xr3YD517Wr1g== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4dqtx85vsJz4wHY; Tue, 13 Jan 2026 13:49:00 +1100 (AEDT) Date: Tue, 13 Jan 2026 13:39:34 +1100 From: David Gibson To: Stefano Brivio Subject: Re: [PATCH] conf, pasta: Add --no-tap option Message-ID: References: <20251229095558.918055-1-yuhuang@redhat.com> <20260110191219.29498050@elisabeth> <20260113011209.3c5ed9f6@elisabeth> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="qIEvF72YwOvjB5ff" Content-Disposition: inline In-Reply-To: <20260113011209.3c5ed9f6@elisabeth> Message-ID-Hash: 2QDW2CJOURVJPBDX7MY6WZV45IP3Y27C X-Message-ID-Hash: 2QDW2CJOURVJPBDX7MY6WZV45IP3Y27C 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: Yumei Huang , 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: --qIEvF72YwOvjB5ff Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jan 13, 2026 at 01:12:09AM +0100, Stefano Brivio wrote: > On Mon, 12 Jan 2026 15:26:14 +1100 > David Gibson wrote: >=20 > > On Sat, Jan 10, 2026 at 07:12:19PM +0100, Stefano Brivio wrote: > > > On Mon, 5 Jan 2026 16:53:49 +0800 > > > Yumei Huang wrote: > > > =20 > > > > On Mon, Jan 5, 2026 at 12:18=E2=80=AFPM David Gibson > > > > wrote: =20 > > > > > > > > > > On Mon, Dec 29, 2025 at 05:55:58PM +0800, Yumei Huang wrote: = =20 > > > > > > > > > > > + if (c->pasta_conf_ns) > > > > > > + die("--no-tap is incompatible with --conf= ig-net"); =20 > > > > > > > > > > I don't think this is right. We still can and should bring up 'l= o' in > > > > > the --no-tap case. =20 > > > >=20 > > > > I see your point, but seems c->pasta_conf_ns is only used for tap as > > > > https://passt.top/passt/tree/pasta.c#n328, 'lo' is configured before > > > > that line. =20 > > >=20 > > > Right, and the reason is that there are basic bits of functionality > > > (probing pipe sizes if I recall correctly, or anyway probing for some > > > kind of capability) that need the loopback interface to be up. =20 > >=20 > > Ah, right. Drat. In general I don't like us touching the guest > > netlink at all if we don't have --config-net. Hrm.. now what exactly > > needs this. It's not anything in sock_probe_features() - that runs in > > the host ns. Not pipe sizes, either - that also takes place in the > > host ns (and netns is irrelevant to pipes, anyway). There could well > > be something, but I'm not sure what it is. >=20 > Actually, I tried, and I don't get any trouble (but I think I had some > error when I added that in 2021). Ok. > But we implicitly break any outbound forwarding because our listening > sockets will be unreachable (bind() succeeds though). Networking doesn't work until you configure networking, that's the normal state for !--config-net. I don't see why that should be different for outbound forwards than anything else. > So... I would be > wary of changing that at this point. There might be users relying on > it, and it's otherwise harmless I guess. I mean.. probably? Almost certainly when pasta is creating the ns - but in that case there's very little reason not to use --config-net anyway. The case I'm concerned about is attaching this to an existing netns: this can alter the existing network config there. --=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 --qIEvF72YwOvjB5ff Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmllsFcACgkQzQJF27ox 2GceAA/+OFMlLMCzfSZQBy+WJGvVtZp8k2lx835IiVSRP/06bTrPAq+ZUXyAdtYw SrUMb8OojzuOGzsD8NkNNRGl6jOseSGIxhesHGqGTatquLiFaQKrySqsZf89YBiF DnhRWOTN3qfL3OxEIYQH1nsAfYrPyFtF1JMjfFUr1QeYLJjj7quYJEUPzZoMvdko JLzE0MXe/gAn65cKnoBWYkv+nCTc5UTbHgjhqZ9loHP3L55RWNPH4hJS5xY8t6Ll a28O6j9nQjaNqNg4565k8TtOVmv1CBdxulmCEyZHxhEFATmEYMHsRRXdGaOkPT3P RuA8gdeYhOMgqBH76XXtO2AuDnfI4eW1/VX5Yh6r8mOxb+GIH4XO1yykhu8GfyEb 6TCkO1B44myY8MzjNk/Wu8I/9eXXwbKF10gr7qxHpbt+R/NoGM0HmAp7bMgWud2+ yyke83rurW0GsF5ojXLnajp2UTRsvx+sV1DdrkuqhI0uF2bl2/9x7qd/4Dfg6czp 10FZ3MwULU2Dg8TdrffIlNM4Vn+rjZycrj+Z6qzR1RungEVQtzgoURinWVrxRMIF g761mFvRNFKf1TxZ9u7J8H4n5/YeovAbLUynct6vHtiGA4LwBVancFf2JZo9D7jF IG+ZeMRnGOYjg9ekDfb/Q2v1lN0g8if6Q1h3hYyGOS9L6o8BnHA= =jnqZ -----END PGP SIGNATURE----- --qIEvF72YwOvjB5ff--