From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: dhclient, checksum and tap Date: Sun, 27 Jun 2010 11:24:40 +0300 Message-ID: <20100627082439.GA8472@redhat.com> References: <20100625151008.GA17911@redhat.com> <20100625.112152.241921019.davem@davemloft.net> <20100626211419.GA3646@redhat.com> <20100626.200320.43025947.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: herbert.xu@redhat.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:20992 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753184Ab0F0I3n (ORCPT ); Sun, 27 Jun 2010 04:29:43 -0400 Content-Disposition: inline In-Reply-To: <20100626.200320.43025947.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Sat, Jun 26, 2010 at 08:03:20PM -0700, David Miller wrote: > From: "Michael S. Tsirkin" > Date: Sun, 27 Jun 2010 00:14:19 +0300 > > > On Fri, Jun 25, 2010 at 11:21:52AM -0700, David Miller wrote: > >> We added the af_packet status as the migration path to deal with > >> this issue in the cleanest manner possible. Putting a new hack > >> into the TAP driver works contrary to that goal. > > > > Hmm, problem is, using the af_packets status requires > > userspace changes, and so does not help old clients. > > And for virt, clients might be running old kernels without this support. > > qemu has a hack to make old guests running within qemu work. > > I guess I can copy that hack into vhost - a bit ugly as I don't have > > access to the original skb there, so I will have to duplcate some logic, > > but doable. Is this what you suggest? OTOH if we had the workaround in > > tap, this could replace hacks in both vhost and qemu. > > If you add the TAP thing you can _never_ remove it. Exactly for the > same reason that the qemu thing can never be removed. It'll always be > needed for the sake of old guests running old stuff. > > This is why I truly believe that keeping the af_packet status thing as > the only kernel side assist is likely best in the long run. Just to spell it out for me, you think the hack should be done in vhost-net? -- MST