From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Lebrun Subject: Re: [PATCH 1/9] ipv6: implement dataplane support for rthdr type 4 (Segment Routing Header) Date: Thu, 20 Oct 2016 15:04:59 +0200 Message-ID: <5808C0FB.2050202@uclouvain.be> References: <1476715350-18983-1-git-send-email-david.lebrun@uclouvain.be> <1476715350-18983-2-git-send-email-david.lebrun@uclouvain.be> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kiHK4HScUDNvNv8mXg3Sl4IxwS7NXhvLn" Cc: Linux Kernel Network Developers To: Tom Herbert Return-path: Received: from smtp.sgsi.ucl.ac.be ([130.104.5.67]:37295 "EHLO smtp5.sgsi.ucl.ac.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932543AbcJTND3 (ORCPT ); Thu, 20 Oct 2016 09:03:29 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: --kiHK4HScUDNvNv8mXg3Sl4IxwS7NXhvLn Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 10/17/2016 07:01 PM, Tom Herbert wrote: >> > + >> > + if (skb->ip_summed =3D=3D CHECKSUM_COMPLETE) >> > + skb->ip_summed =3D CHECKSUM_NONE; >> > + > Because the packet is being changed? Would it make sense to update the > checksum complete value based on the changes being made. Consider the > case that the next hop is local to the host (someone may try to > implement network virtualization this way). >=20 Rethinking about that: even if the next hop is local, I am not sure to see the benefits of updating the checksum instead of setting CHECKSUM_NONE. For example, if the next and final hop is local and the packet carries a TCP payload, tcp_checksum_complete() would force the recomputation of the checksum anyway (unless ip_summed =3D=3D CHECKSUM_UNNECESSARY). So I fail to see a path where updating the checksum would be beneficial. Am I missing something ? David --kiHK4HScUDNvNv8mXg3Sl4IxwS7NXhvLn Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iEYEARECAAYFAlgIwPsACgkQjbzn67sZ6ANQCQCeMJ88JkRJmC5dXZ1ixcT60i2W jOwAnAgjWoRs/K1GvYgFDJuPiGyVWtd+ =PVyR -----END PGP SIGNATURE----- --kiHK4HScUDNvNv8mXg3Sl4IxwS7NXhvLn--