From: ebiederm@xmission•com (Eric W. Biederman)
To: Ben Greear <greearb@candelatech•com>
Cc: netdev@vger•kernel.org, "David S. Miller" <davem@davemloft•net>,
Eric Dumazet <eric.dumazet@gmail•com>,
Patrick McHardy <kaber@trash•net>, Ilia K <mail4ilia@gmail•com>,
Tom Goff <thomas.goff@boeing•com>
Subject: Re: [RFC][PATCH] ipmr: Fix struct mfcctl to be independent of MAXVIFS v2
Date: Tue, 06 Apr 2010 10:23:08 -0700 [thread overview]
Message-ID: <m14ojo7awz.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <4BBB67FE.6020209@candelatech.com> (Ben Greear's message of "Tue\, 06 Apr 2010 09\:57\:34 -0700")
Ben Greear <greearb@candelatech•com> writes:
> On 04/06/2010 08:38 AM, Eric W. Biederman wrote:
>>
>> Right now if you recompile the kernel increasing MAXVIFS
>> to support more VIFS users of the MRT_ADD_VIF and MRT_DEL_VIF
>> will break because the ABI changed.
>>
>> My goal is an API that works with just a recompile of existing
>> applications, and an ABI that continues to work for old
>> applications.
>>
>> The unused/dead fields at the end of struct mfcctl make this
>> exercise more difficult than it should be.
>>
>> - Rename the existing struct mfcctl mfcctl_old.
>> - Define a new and larger struct mfcctl that we can detect
>> by size.
>>
>> The new and larger struct mfcctl won't have trailing garbage
>> fields so we can accept anything of that size or larger,
>> and simply ignore the entries that are above MAXVIFS.
>>
>> My new struct mfcctl is now 128 bytes which is noticeable on
>> the stack but should still be small enough not to cause problems.
>>
>> v2: Rework the support larger arrays so that most/all? existing
>> applications can simply be recompiled and work with a larger
>> maximum number of VIFS.
>
> If we're going to change the ABI, can we not support an arbitrary
> number of VIFS instead of just a larger fixed maximum?
The ABI as I have specified should work for any larger structure than
I have specified. But like select many applications will limit themselves
to use the definition of struct mfcctl that is passed to them.
Eric
prev parent reply other threads:[~2010-04-06 17:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-06 12:16 [RFC][PATCH] ipmr: Fix struct mfcctl to be independent of MAXVIFS Eric W. Biederman
2010-04-06 15:38 ` [RFC][PATCH] ipmr: Fix struct mfcctl to be independent of MAXVIFS v2 Eric W. Biederman
2010-04-06 16:57 ` Ben Greear
2010-04-06 17:23 ` Eric W. Biederman [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=m14ojo7awz.fsf@fess.ebiederm.org \
--to=ebiederm@xmission$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=greearb@candelatech$(echo .)com \
--cc=kaber@trash$(echo .)net \
--cc=mail4ilia@gmail$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=thomas.goff@boeing$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox