On 1/27/17, 3:20 PM, David Ahern wrote: > This series closes a couple of gaps between IPv4 and IPv6 with respect > to multipath routes: > > 1. IPv4 allows all nexthops of multipath routes to be deleted using just > the prefix and length; IPv6 only deletes the first nexthop for the > route if only the prefix and length are given. > > 2. IPv4 returns multipath routes encoded in the RTA_MULTIPATH attribute. > IPv6 returns a series of routes with the same prefix and length - one > for each nexthop. This happens for both dumps and notifications. > > IPv6 does accept RTA_MULTIPATH encoded routes, but installs them as a > series of routes. > > Patch 2 addresses the first item by allowing IPv6 multipath routes to be > deleted using just the prefix and length. Patch 3 addresses the second > allowing IPv6 multipath routes to be returned encoded in the RTA_MULTIPATH. > > Patch 1 adds the NLM_F_APPEND flag to notifications when the flag is > present in the request. The lack of this flag was noted testing route > appends and comparing to IPv4. > > Patch 4 prints IPv6 addresses in compressed format when showing route > replace errors. This was noticed testing REPLACE failures. > > The end result for multipath routes: > 1. Route Add > - one notification with RTA_MULTIPATH attribute > > 2. Route Replace > - notification for first route and all siblings that have > succeeded. This is needed regardless of success of remaining > nexthops to maintain add/delete consistency should a failure > happens on the second or following nexthop (ie., need to tell > userspace that original route has been replaced and then the > failure logic deletes all routes inserted thus far). > > 3. Route Delete > - for multipath route only given nexthops are deleted. This path > is hit when DELETE contains RTA_MULTIPATH. All other route deletes, > all nexthops are deleted for given prefix and length (and any > other specs if given) > > - one notification sent per nexthop deleted. This is unavoidable > since IPv6 alllows a single nexthop to be deleted within a multipath > route > > 4. Route Appends > - IPv6 allows nexthops to be appended to an existing route. In this > case one notification is sent per nexthop added
thanks for listing all of these...I think you mentioned this case to me.. but I don't remember now why this notification is sent per nexthop added. This is an update to an existing multipath route. so seems like the notification should be a RTM_NEWROUTE with the full RTA_MULTIPATH route (similar to route add) Same holds for replace, I know the code might be tricky here...but the route replace is also an update to an existing multipath route and hence should be a RTM_NEWROUTE with the full multipath route (RTA_MULTIPATH) that changed (from userspace semantics POV) I don't have a better solution, but with the above still being different, wondering if its worth the risk changing the api for just a few notifications. > > Addresses some of the inconsistencies also noted by Roopa at netdev0.1: > https://www.netdev01.org/docs/prabhu-linux_ipv4_ipv6_inconsistencies_talk_slides.pdf > > v3 > - removed the need for a user API to opt-in to change. Requiring an > API just shifts the difference from same API with different > behavior to different API to achieve equivalent behavior > > - route notifications changed to use RTA_MULTIPATH for add and replace > > - upated commit messages and cover letter > > v2 > - fixed locking in patch 1 as noted by DaveM > - changed user API for patch 2 to require an rtmsg with RTM_F_ALL_NEXTHOPS > set in rtm_flags > - revamped explanation of patch 2 and cover letter > > David Ahern (4): > net: ipv6: add NLM_F_APPEND in notifications when applicable > net: ipv6: Allow shorthand delete of all nexthops in multipath route > net: ipv6: Add support to dump multipath routes via RTA_MULTIPATH > attribute > net: ipv6: Use compressed IPv6 addresses showing route replace error > > include/net/ip6_fib.h | 4 +- > include/net/netlink.h | 1 + > net/ipv6/ip6_fib.c | 19 +++++- > net/ipv6/route.c | 163 > ++++++++++++++++++++++++++++++++++++++++++++------ > 4 files changed, 165 insertions(+), 22 deletions(-) >
