netdev - IFA_F_OPTIMISTIC is not supported?

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Date:   Fri, 08 Sep 2017 10:29:03 -0400
From:   soohoon.lee@...com
To:     netdev@...r.kernel.org
Subject: IFA_F_OPTIMISTIC is not supported?

rtm_newaddr masks off OPTIMISTIC.

inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh)
...
        /* We ignore other flags so far. */
        ifa_flags &= IFA_F_NODAD | IFA_F_HOMEADDRESS | IFA_F_MANAGETEMPADDR |
                     IFA_F_NOPREFIXROUTE;

Is there any problem or not allowed?

I need to do something like adding a route for the address after adding the address but fails because the address is not useable yet.
I tried NODAD but there's still little delay until IFA_F_TENTATIVE is cleared.
	- rtm_newaddr sets IFA_F_TENTATIVE
	- set a timer for dad start with delay=0
	- some delay
	- dad starts but ends immediately because of NODAD flag, and clears TENTATIVE.

And it looks like OPTIMISTIC does what I need but kind of disabled like the code above.

Thanks,
Soohoon.