From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH net-next v3 0/4] net: ipv6: Improve user experience with multipath routes Date: Mon, 30 Jan 2017 09:12:05 -0700 Message-ID: References: <1485559258-4856-1-git-send-email-dsa@cumulusnetworks.com> <588D3EB9.1070107@cumulusnetworks.com> <592be6dc-df0e-6185-ba6f-5acf5d042ae5@cumulusnetworks.com> <588E80DB.3070209@cumulusnetworks.com> <71e661bd-e26d-2629-06bb-888f6a09b06d@cumulusnetworks.com> <588EA2E8.2040302@cumulusnetworks.com> <5be4a78e-64b8-abc4-4015-6751a2bab12b@cumulusnetworks.com> <588F607D.2050600@cumulusnetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, nicolas.dichtel@6wind.com To: Roopa Prabhu Return-path: Received: from mail-pg0-f52.google.com ([74.125.83.52]:36088 "EHLO mail-pg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753639AbdA3QMY (ORCPT ); Mon, 30 Jan 2017 11:12:24 -0500 Received: by mail-pg0-f52.google.com with SMTP id 3so43581599pgj.3 for ; Mon, 30 Jan 2017 08:12:07 -0800 (PST) In-Reply-To: <588F607D.2050600@cumulusnetworks.com> Sender: netdev-owner@vger.kernel.org List-ID: On 1/30/17 8:49 AM, Roopa Prabhu wrote: >> Single next hop delete will be around because IPv6 allows it -- and because IPv4 needs to support it. >> > understand single next hop delete for ipv6 will be around..and my only point was to leave it around but not optimize for that case. > I don't think we should support single nexthop delete in ipv4 (I have not seen a requirement for that)... ipv4 is good as it is right now. > the additional complexity is not needed. > IPv4 has a known bug -- delete a virtual interface in a multihop route and the entire route is deleted, including the nexthops for other devices. This does not happen for IPv6. Simple example of that bug: ip li add dummy1 type dummy ip li add dummy2 type dummy ip addr add dev dummy1 10.11.1.1/28 ip li set dummy1 up ip addr add dev dummy2 10.11.2.1/28 ip li set dummy2 up ip ro add 1.1.1.0/24 nexthop via 10.11.1.2 nexthop via 10.11.2.2 ip li del dummy2 --> the entire multipath route has been deleted. And, fixing this bug enables work to make IPv4 append to be sane -- appending a route should modify an existing route by adding the nexthop, not adding a new route that I believe can never actually be hit. Both cases mean modifying an IPv4 route -- adding or removing nexthops -- a capability that IPv6 allows so fixing this means closing another difference between the stacks.