Date: Tue, 26 Aug 2008 17:56:13 -0700 From: Sam Leffler <sam@freebsd.org> To: gnn@freebsd.org Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, net@freebsd.org Subject: Re: Small patch to multicast code... Message-ID: <48B4A62D.3080300@freebsd.org> In-Reply-To: <m2abezwojl.wl%gnn@neville-neil.com> References: <m27iaa6v43.wl%gnn@neville-neil.com> <20080821203519.GA51534@onelab2.iet.unipi.it> <m23aky6ncl.wl%gnn@neville-neil.com> <48AE23FF.9070009@FreeBSD.org> <m2tzdd6j36.wl%gnn@neville-neil.com> <48AF08B7.4090804@FreeBSD.org> <m2fxowhgq8.wl%gnn@neville-neil.com> <48AF330B.4010802@FreeBSD.org> <m28wuohfm5.wl%gnn@neville-neil.com> <20080825190207.GA73478@zibbi.meraka.csir.co.za> <20080825194038.GA75840@zibbi.meraka.csir.co.za> <m2y72jx33z.wl%gnn@neville-neil.com> <20080826144130.S66593@maildrop.int.zabbadoz.net> <m2abezwojl.wl%gnn@neville-neil.com>
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gnn@freebsd.org wrote:
> At Tue, 26 Aug 2008 14:50:33 +0000 (UTC),
> Bjoern A. Zeeb wrote:
>
>> On Tue, 26 Aug 2008, George V. Neville-Neil wrote:
>>
>> Hi,
>>
>>
>>> At Mon, 25 Aug 2008 21:40:38 +0200,
>>> John Hay wrote:
>>>
>>>> I have tried it and it does fix my problem. RIP2 over multicast works
>>>> again. :-)
>>>>
>>> Good to hear. I'm waiting on a bit more feedback but I think I'll be
>>> checking this in soon, with a big comment talking about the
>>> performance implications etc.
>>>
>> So wait a second; what was the m_pullup vs. m_dup thing? Has anyone
>> actually tried that? I mean using a sledgehammer if a mitten would be
>> enough is kind of .. uhm. You get it.
>>
>
> Perhaps I'm confused, I've been off dealing with other issues for a
> few days, but m_pullup doesn't make a copy of the packet or its
> fields, only makes sure that it's contiguous in memory. Am I wrong in that?
>
> Since the bug is that two pieces of code modify the same data, in ways
> that interfere, I'm not sure how we can avoid making a copy. It might
> be nice to limit the copy, but we'd still need two copies, one for the
> loopback device and one for the real device.
>
>
pull the headers up. copy just the headers. no deep copy.
Sam
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