netdev - Re: [PATCH net 1/2] net/ipv6: delete temporary address if mngtmpaddr is removed or un-mngtmpaddr

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Message-ID: <ZzxDsps3EhGcMamy@fedora>
Date: Tue, 19 Nov 2024 07:52:18 +0000
From: Hangbin Liu <liuhangbin@...il.com>
To: Sam Edwards <cfsworks@...il.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	Maciej Żenczykowski <maze@...gle.com>,
	Xiao Ma <xiaom@...gle.com>, Alex Henrie <alexhenrie24@...il.com>
Subject: Re: [PATCH net 1/2] net/ipv6: delete temporary address if mngtmpaddr
 is removed or un-mngtmpaddr

On Fri, Nov 15, 2024 at 12:46:27PM -0800, Sam Edwards wrote:
> Hi Hangbin,
> 
> It took me a while to grasp but the problem seems to be a confusion
> about what it means to set a temporary's lifetimes to 0/0:
> 1) "The mngtmpaddrs has gone away; this temporary is slated for
> deletion by addrconf_verify_rtnl()"
> 2) "This temporary address itself shall no longer be used, regenerate
> it immediately."
> 
> The existing behavior makes sense for the #2 case, but not for the #1
> case. It seems sensible to me to keep the #2 behavior as-is, because
> userspace might be setting a 0/0 lifetime to forcibly rotate the
> temporary.
> 
> So it sounds like (at least) one of three fixes is in order:
> a) Make ipv6_create_tempaddr() verify that the `ifp` is (still)
> alive+mngtmpaddrs, returning with an error code if not.
> b) Look at the 3 callsites for ipv6_create_tempaddr() and add the
> above verifications before calling.
> c) Add a function that calls ipv6_del_addr(temp) for every temporary
> with a specified ifpub, and use it instead of manage_tempaddrs(..., 0,
> 0, false, ...) when deleting/unflagging a mngtmpaddrs.
> 
> Personally I like option C the best. What are your thoughts?

Hi Sam,

Thanks for the comments. I have no preference. Let me try option C
and update the test case first.

Hangbin