ipv6: fix ECMP route replacement
When replacing an IPv6 multipath route with "ip route replace", i.e. NLM_F_CREATE | NLM_F_REPLACE, fib6_add_rt2node() replaces only first matching route without fixing its siblings, resulting in corrupted siblings linked list; removing one of the siblings can then end in an infinite loop. IPv6 ECMP implementation is a bit different from IPv4 so that route replacement cannot work in exactly the same way. This should be a reasonable approximation: 1. If the new route is ECMP-able and there is a matching ECMP-able one already, replace it and all its siblings (if any). 2. If the new route is ECMP-able and no matching ECMP-able route exists, replace first matching non-ECMP-able (if any) or just add the new one. 3. If the new route is not ECMP-able, replace first matching non-ECMP-able route (if any) or add the new route. We also need to remove the NLM_F_REPLACE flag after replacing old route(s) by first nexthop of an ECMP route so that each subsequent nexthop does not replace previous one. Fixes: 51ebd318 ("ipv6: add support of equal cost multipath (ECMP)") Signed-off-by: NMichal Kubecek <mkubecek@suse.cz> Acked-by: NNicolas Dichtel <nicolas.dichtel@6wind.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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