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Re: Tulip and IP aliasing

To: Jeff Garzik <jgarzik@xxxxxxxxxxxxxxxx>
Subject: Re: Tulip and IP aliasing
From: Andi Kleen <ak@xxxxxx>
Date: Thu, 15 Jun 2000 23:32:17 +0200
Cc: netdev@xxxxxxxxxxx
In-reply-to: <3948D602.CA56CF00@xxxxxxxxxxxxxxxx>; from Jeff Garzik on Thu, Jun 15, 2000 at 05:00:17PM +0200
References: <200006151255.QAA29302@xxxxxxxxxxxxx> <3948D602.CA56CF00@xxxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
On Thu, Jun 15, 2000 at 05:00:17PM +0200, Jeff Garzik wrote:
> I got a report saying that Tulip was slow when IP aliasing for a large
> number of hosts was in effect.  This report was from a guy running a Web
> server which binds to a ton of IP aliases in order to do its virtual
> hosts.
> 
> Talking with jamal on IRC he mentioned that IP aliases matching occurs
> through a linear search.
> 
> Can someone point me to this code?  I grepped for CONFIG_IP_ALIAS in
> 2.4.x but that seemed only to encompass very small bits of code, and not
> the actual IP matching code I am searching for.

Linear search only occurs in obscure cases. For all normal paths
local IPs are looked up via special local routes in the routing cache 
and the FIB hash. About the only thing that could do something like
a linear alias search during normal operation (not configuration)
is inet_select_addr(),  but it should not be called frequently.


-Andi

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