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Re: 802.1q Was (Re: Plans for 2.5 / 2.6 ???

To: rob@xxxxxxxxxxx
Subject: Re: 802.1q Was (Re: Plans for 2.5 / 2.6 ???
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Fri, 02 Jun 2000 20:32:22 -0700
Cc: buytenh@xxxxxxx, hadi@xxxxxxxxxx, netdev@xxxxxxxxxxx, gleb@xxxxxxxxxxxxxxxxxxxxx
Organization: Candela Technologies
References: <Pine.GSO.4.20.0006020741140.13652-100000@shell.cyberus.ca> <Pine.LNX.4.21.0006021439170.19298-100000@mara.math.leidenuniv.nl> <14647.58672.343104.432906@tungsten.su.valinux.com> <3938611E.D074F254@candelatech.com> <14648.24946.413472.365255@tungsten.su.valinux.com>
Sender: owner-netdev@xxxxxxxxxxx
Rob Walker wrote:

> Ben> On this account, my vlan implementation, and Lenert and Gleb's
> Ben> are almost identical.  Other than some internal issues, I believe
> Ben> the only user-visible difference between my imp and theirs is
> Ben> that they re-write the packet header on the way up the stack so
> Ben> that it looks **exactly** like an ethernet pkt, where as I just
> Ben> leave the header alone and pull 4 extra bytes off of the SKB
> Ben> before giving it to the higher levels.
> 
> Remember how hard *BSD keeps ragging that their stack is faster due to
> "zero copy"?  I can't evaluate whether that statement is true, or if
> the speed advantage has worn off with time, but I do think that the
> faster the implementation, the better.

Yeah, but remember also that Apache, not the fastest, but the most
flexible, rules the web.  A compile-time switch can offer the best
of both worlds..the only question is which one to 'default' to.  If
default to the zero-copy, then dhcpd and others must be fixed (there
is a patch on my web-site that is sorta-kinda fixes dhcpd.)

Of course, maybe these programs should be fixed anyway...

> Maybe a run-time switch could be added to dhcpd, or you could extend
> it to automatically read both types of frames as detected.  Is this
> even possible?

I basically compared the name (vlan* matched) and used that to determine
the behavior for the interface.  I'm sure a more elegant solution could
be contrived...

> 
> rob

-- 
Ben Greear (greearb@xxxxxxxxxxxxxxx)  http://www.candelatech.com
Author of ScryMUD:  scry.wanfear.com 4444        (Released under GPL)
http://scry.wanfear.com               http://scry.wanfear.com/~greear

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