From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E160C433B4 for ; Thu, 8 Apr 2021 17:10:26 +0000 (UTC) Received: from lists.zx2c4.com (lists.zx2c4.com [165.227.139.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4374D610CC for ; Thu, 8 Apr 2021 17:10:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4374D610CC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=wireguard-bounces@lists.zx2c4.com Received: by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTP id e3ebc8e7; Thu, 8 Apr 2021 17:10:23 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTPS id 1fad5fa4 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO) for ; Thu, 8 Apr 2021 17:10:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Mime-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kGkngEqQ/+881LoOH3774Xn7LJ85jj7dIGzCLptAQxQ=; b=dhuDCWQq8E9xmIHoxKZMCjRd3R 9dYiVMh5jdYn8nyYdbWcOI+KGPQBVb9/sslInGXg+8WrkIbSKS5o1iP3Ofj1DnK5WuAaJLDb3Fj3E /9d8Qj80VUIlFsb8DRSVEcIubwQcnXyOLoF9gk1/JT8t200ANveBd3hCUrcgoPU6t1pOMaIy8LbLX TO5v2FGsldCjKK+32a6ZVKP2w9cWcIREtWV9oRwoVaJybHdCUvGOkVgi+OMda3DqlHKeKCC6q9hoJ HZHOLLiypFODfGh8OXJxrS/S/NxOiqaE/0PT/TtNX4BYyVOSs8BdvZbIEEydrFr8KKKDI3KdBnXoI Q/3Iesdw==; Received: from dyn-234.woodhou.se ([90.155.92.234] helo=u3832b3a9db3152.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lUYAe-008k7w-34; Thu, 08 Apr 2021 17:10:20 +0000 Message-ID: <1f5dfe333c4e8d228773241cffadc9913d7829c7.camel@infradead.org> Subject: Re: Allowing space for packet headers in Wintun Tx/Rx From: David Woodhouse To: Daniel Lenski Cc: WireGuard mailing list Date: Thu, 08 Apr 2021 18:10:19 +0100 In-Reply-To: References: <6e259ab359c7f93f8f1119df0ba7b285cd4f53d1.camel@infradead.org> <26fc1c68fa495407b5c4c46a56abdb5dfe639280.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-IPJt60f/PKARL0Uh4u+D" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" --=-IPJt60f/PKARL0Uh4u+D Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2021-04-08 at 09:42 -0700, Daniel Lenski wrote: > On Thu, Apr 8, 2021 at 7:37 AM David Woodhouse wrot= e: > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > PPP over DTLS > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > >=20 > > We just added support for the PPP-based protocols (Fortinet, F5) and > > I'm not sure we even know what the DTLS-based version looks like on the > > wire, do we? If the header is 4 bytes or fewer, the same nasty trick > > works that I suggest for Cisco DTLS above. And a PPP header even with > > accomp and pfcomp *would* fit in 4 bytes. For the TCP transports we > > have an additional framing but I'm hoping those aren't there in DTLS? > >=20 > > If we do need a header larger than 4 bytes, then we are forced to do > > things properly by adding support in the kernel driver instead of just > > abusing the existing header while we know the kernel isn't looking at > > it. >=20 > This is probably too much "inside baseball" for the non-(OpenConnect > developers) here, but I *have* confirmed that the PPP-over-DTLS > encapsulation is identical to the PPP-over-TLS encapsulation for the 2 > PPP-based protocols that we support already. Both F5 and Fortinet > essentially opted for the thinnest veneer of UDP-ization possible for > their protocols. Ok, so that's the PPP header plus either 6 bytes for Fortinet or 4 bytes for F5? The important part for the purpose of this conversation is "more than four". > The tl;dr for OpenConnect is that we really would need support for > arbitrary head/tail space in order not to have to do *any* memcpy. Right. I'm almost relieved at that, since it's certainly a lot *nicer* to do it that way than any of the hacks I just described. We can extend the TUN_PACKET header structure to have Headroom and Tailroom fields, then add a new ioctl which enables the new TUN_PACKET format and sets the headroom/tailroom to be used in the Rx ring. Implementing that should be relatively simple and unintrusive; the trickiest part of it is maintaining backward compatibility with the existing TUN_PACKET structure. --=-IPJt60f/PKARL0Uh4u+D Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCECow ggUcMIIEBKADAgECAhEA4rtJSHkq7AnpxKUY8ZlYZjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgG A1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhl bnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTkwMTAyMDAwMDAwWhcNMjIwMTAxMjM1 OTU5WjAkMSIwIAYJKoZIhvcNAQkBFhNkd213MkBpbmZyYWRlYWQub3JnMIIBIjANBgkqhkiG9w0B AQEFAAOCAQ8AMIIBCgKCAQEAsv3wObLTCbUA7GJqKj9vHGf+Fa+tpkO+ZRVve9EpNsMsfXhvFpb8 RgL8vD+L133wK6csYoDU7zKiAo92FMUWaY1Hy6HqvVr9oevfTV3xhB5rQO1RHJoAfkvhy+wpjo7Q 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