Hi,
Well, even in IPv4 you cannot change metric;
same route can be installed e.g., for manual
backup route entry.
But well, NLM_F_REPLACE handler is completely
missing in IPv6. I think we are okay with
"replace" (NLM_F_CREATE|NLM_F_REPLACE) but we
could return "no such route" for "change"
(NLM_F_REPLACE).
--yoshfuji
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