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Date:      Fri, 4 Jun 1999 22:53:59 -0400 (EDT)
From:      Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
To:        Barney Wolff <barney@databus.com>
Cc:        freebsd-net@FreeBSD.ORG
Subject:   Re: subtle SIOCGIFCONF bug
Message-ID:  <199906050253.WAA13064@khavrinen.lcs.mit.edu>
In-Reply-To: <375888260.660a@databus.databus.com>
References:  <375888260.660a@databus.databus.com>

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<<On Fri, 4 Jun 1999 22:01 EDT, Barney Wolff <barney@databus.com> said:

> Gee, I just ran the same .c file on each of them, and it retrieved
> the interface names, addresses and netmasks of every interface.
> Same ioctl's on each system, no ifdefs among 'em.

Obviously you didn't have any other protocols configured.  Oh, and
what did you do skip the link-layer addresses?  Depending on the
implementation, long addresses will either be truncated or not, have
padding or not, have a way to tell how long they are or not, in short
cannot be portably parsed or even skipped past.

> Are you saying that SIOCGIFCONF has a fixed maximum number of interfaces
> it will return, even if you give it a big buffer?

There is no a priori way to know how big a buffer one should use.  The
interface is fundamentally broken.

> Or that you have to get aliases separately?  

What's an `alias'?

-GAWollman

--
Garrett A. Wollman   | O Siem / We are all family / O Siem / We're all the same
wollman@lcs.mit.edu  | O Siem / The fires of freedom 
Opinions not those of| Dance in the burning flame
MIT, LCS, CRS, or NSA|                     - Susan Aglukark and Chad Irschick


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