linux-kernel - Re: [PATCH] net: neigh: disallow state transition DELAY->STALE in neigh

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Date:	Mon, 25 Jul 2016 21:45:39 +0900
From:	吉藤英明 <hideaki.yoshifuji@...aclelinux.com>
To:	Chunhui He <hchunhui@...l.ustc.edu.cn>
Cc:	ja@....bg, David Miller <davem@...emloft.net>,
	dsa@...ulusnetworks.com, nicolas.dichtel@...nd.com,
	roopa@...ulusnetworks.com, rshearma@...cade.com,
	dbarroso@...tly.com, martinbj2008@...il.com, rick.jones2@...com,
	koct9i@...il.com, edumazet@...gle.com, tgraf@...g.ch,
	ebiederm@...ssion.com, YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>,
	network dev <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: neigh: disallow state transition DELAY->STALE in neigh_update()

Hi,

2016-07-25 17:13 GMT+09:00 Chunhui He <hchunhui@...l.ustc.edu.cn>:
>>> The NEIGH_UPDATE_F_WEAK_OVERRIDE is confusing to me, so I choose not to deal
>>> with the flag.
>>
>> IPv6 depends on WEAK_OVERRIDE.  Please do not change.
>>
>
> It seems like IPv6 always sets WEAK_OVERRIDE.
>

Yes.

> As Julian said, maybe there is no good reason to set NUD_STALE for any state
> that is NUD_VALID if address is not changed, even WEAK_OVERRIDE is not set.
> So we may eliminate WEAK_OVERRIDE in that branch.
>
> I think this change should not break IPv6.

OK, following blocks are "no-op" and we will get same result.

Well, please do not try changing several things at the same time and
you could say:

if (ladder == neigh->ha && new == NUD_STALE &&
    !(flags & NUD_UPDATE_F_ADMIN))
        new = old;

I think I tried to maintain our traditional IPv4 behavior (e.g. as of
2.2 era), BTW...

--yoshfuji