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Date: Tue, 26 Aug 2008 17:56:13 -0700
From: Sam Leffler <sam@freebsd.org>
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Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, net@freebsd.org
Subject: Re: Small patch to multicast code...
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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