From b5d2d75e079a918be686957b1a8d2f6c5cc95a0a Mon Sep 17 00:00:00 2001 From: David Ahern Date: Sun, 15 Jul 2018 09:35:19 -0700 Subject: [PATCH] net/ipv6: Do not allow device only routes via the multipath API Eric reported that reverting the patch that fixed and simplified IPv6 multipath routes means reverting back to invalid userspace notifications. eg., $ ip -6 route add 2001:db8:1::/64 nexthop dev eth0 nexthop dev eth1 only generates a single notification: 2001:db8:1::/64 dev eth0 metric 1024 pref medium While working on a fix for this problem I found another case that is just broken completely - a multipath route with a gateway followed by device followed by gateway: $ ip -6 ro add 2001:db8:103::/64 nexthop via 2001:db8:1::64 nexthop dev dummy2 nexthop via 2001:db8:3::64 In this case the device only route is dropped completely - no notification to userpsace but no addition to the FIB either: $ ip -6 ro ls 2001:db8:1::/64 dev dummy1 proto kernel metric 256 pref medium 2001:db8:2::/64 dev dummy2 proto kernel metric 256 pref medium 2001:db8:3::/64 dev dummy3 proto kernel metric 256 pref medium 2001:db8:103::/64 metric 1024 nexthop via 2001:db8:1::64 dev dummy1 weight 1 nexthop via 2001:db8:3::64 dev dummy3 weight 1 pref medium fe80::/64 dev dummy1 proto kernel metric 256 pref medium fe80::/64 dev dummy2 proto kernel metric 256 pref medium fe80::/64 dev dummy3 proto kernel metric 256 pref medium Really, IPv6 multipath is just FUBAR'ed beyond repair when it comes to device only routes, so do not allow it all. This change will break any scripts relying on the mpath api for insert, but I don't see any other way to handle the permutations. Besides, since the routes are added to the FIB as standalone (non-multipath) routes the kernel is not doing what the user requested, so it might as well tell the user that. Reported-by: Eric Dumazet Signed-off-by: David Ahern Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/route.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 63f99411f0de..2ce0bd17de4f 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -4388,6 +4388,13 @@ static int ip6_route_multipath_add(struct fib6_config *cfg, rt = NULL; goto cleanup; } + if (!rt6_qualify_for_ecmp(rt)) { + err = -EINVAL; + NL_SET_ERR_MSG(extack, + "Device only routes can not be added for IPv6 using the multipath API."); + fib6_info_release(rt); + goto cleanup; + } rt->fib6_nh.nh_weight = rtnh->rtnh_hops + 1; -- 2.30.2