netdev - Re: [PATCH net-next 0/5] SCTP updates

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Message-ID: <53BD4363.70306@redhat.com>
Date:	Wed, 09 Jul 2014 15:28:03 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Neil Horman <nhorman@...driver.com>
CC:	davem@...emloft.net, geirola@...il.com, netdev@...r.kernel.org,
	linux-sctp@...r.kernel.org
Subject: Re: [PATCH net-next 0/5] SCTP updates

On 07/09/2014 12:49 PM, Neil Horman wrote:
> On Wed, Jul 09, 2014 at 11:57:37AM +0200, Daniel Borkmann wrote:
>> On 07/08/2014 04:41 PM, Neil Horman wrote:
>>> On Tue, Jul 08, 2014 at 04:05:26PM +0200, Daniel Borkmann wrote:
>>>> On 07/08/2014 01:14 PM, Neil Horman wrote:
>>>> ...
>>>>> since you're adding cmsg's from rfc6458, do you also want to add some
>>>>> deprecation warnings around the use of SCTP_SNDRCVINFO too, so we can start to
>>>>> schedule its eventual removal?
>>>>
>>>> Sure, we can do that. Do you want me to include it into the set?
>>>
>>> If you're plan is to implement 6458, then yes, I think that would be good.
>>
>> Looking a bit closer at it, all our pr_warn_ratelimited(DEPRECATED ...)
>> warnings in SCTP are being done in 'slowpath' {set,get}sockopt(2) operations
>> only, which is fine. What you're suggesting is to place similar ratelimited
>> warnings (due to different possible pids on the machine) into the 'fastpath'
>> where we get and set cmsg message headers.
>>
>> While that may be fine for {set,get}sockopt(2) that's called once or very few
>> times, I'm not sure this is a good idea in SCTP_SNDRCVINFO as it will yield
>> to unnecessary spamming the klog since up to now this is the only way our
>> users can set or receive this info. I'm not sure we want to annoy users like
>> that ...
>>
> Then we wrap it in a ONCE macro so that it only triggers on the first use
> instance.

I'm not convinced about this so far. The whole point is that we also provide the
pid just as we currently do, so that we give the user a chance to possibly pin
point the process that needs code change to not use the deprecated API anymore.

>> In how many years do you plan a removal ... I think we're stuck with uapi
>> basically forever as we don't want to break old binaries, no? ;/
>>
> I thought we could remove things on a schedule if we followed the deprecation
> process, but that may just be for sysfs.  Regardless, it would still be nice to
> inform people they are using an older api.

I think we rather might be stuck with also the deprecated stuff forever, just
as AF_PACKET still has to carry around the old spkt stuff. :( So if we don't
remove anything, there's actually also no point to spam the log about it, if
everyone can/should read it from the RFC anyway.
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