netdev - Re: [PATCHv2 net 1/2] ipv6: prevent only DAD and RS sending for IFF_NO

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Date:   Fri, 13 Jan 2023 21:33:07 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, davem@...emloft.net,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [PATCHv2 net 1/2] ipv6: prevent only DAD and RS sending for
 IFF_NO_ADDRCONF

On Wed, 11 Jan 2023 19:41:56 -0500 Xin Long wrote:
> So instead of preventing all the ipv6 addrconf, it makes more sense to
> only prevent DAD and RS sending for the slave ports: Firstly, check
> IFF_NO_ADDRCONF in addrconf_dad_completed() to prevent RS as it did in
> commit b52e1cce31ca ("ipv6: Don't send rs packets to the interface of
> ARPHRD_TUNNEL"), and then also check IFF_NO_ADDRCONF where IFA_F_NODAD
> is checked to prevent DAD.

Maybe it's because I'm not an ipv6 expert but it feels to me like we're
getting into intricate / hacky territory. IIUC all addresses on legs of
bond/team will silently get nodad behavior? Isn't that risky for a fix?

Could we instead revert 0aa64df30b38 and take this via net-next?

Alternatively - could the team user space just tell the kernel what
behavior it wants? Instead of always putting the flag up, like we did 
in 0aa64df30b3, do it only when the user space opts in?