netdev - Re: [PATCH net] ipv6: kill sk_dst

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Message-ID: <1448908052.24696.136.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 30 Nov 2015 10:27:32 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Paolo Abeni <pabeni@...hat.com>
Cc:	Dmitry Vyukov <dvyukov@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Vlad Yasevich <vyasevich@...il.com>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] ipv6: kill sk_dst_lock

On Mon, 2015-11-30 at 19:13 +0100, Paolo Abeni wrote:
> On Mon, 2015-11-30 at 08:35 -0800, Eric Dumazet wrote:
> > ip6_sk_dst_lookup_flow() uses sk_dst_check() anyway, so the simplest
> > way to fix the mess is to remove sk_dst_lock completely, as we did for
> > IPv4.
> 
> Probably I'm missing something here, but why we don't need to sync the
> update of sk_dst_cache and of dst_cookie (i.e. put them under the same
> lock)?
> 
> Can't we end up with inconsistent values after concurrent udp
> sendmsg() ? 

I do not think this is an issue. A route is best effort.

If really a packet is dropped during a route flap, no big deal,
especially if this is during a fuzzer test ;)



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