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Date: Sun, 12 Dec 2004 16:55:40 -0500
From: Ken Smith <kensmith@cse.Buffalo.EDU>
To: Wilko Bulte <wb@freebie.xs4all.nl>
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cc: Brooks Davis <brooks@FreeBSD.ORG>
cc: Brooks Davis <brooks@one-eyed-alien.net>
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cc: Ken Smith <kensmith@cse.Buffalo.EDU>
Subject: Re: cvs commit: src/sbin/ifconfig ifconfig.c src/sys/net if.c if.h
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On Sun, Dec 12, 2004 at 10:28:50PM +0100, Wilko Bulte wrote:
> On Sun, Dec 12, 2004 at 12:53:21PM -0800, Brooks Davis wrote..
> > ifi_mtu, etc remain in the same location because the two new variables
> > fill in the hidden padding required to align ifi_mtu.  I've verified
> > that old and new ifconfigs work with old and new kernels.  The change
> 
> Als on 64 bit machines?  Just wondering..

I didn't check as thoroughly as Brooks said he did but I whipped up
a very crude little test and ran it on beast:

#include <sys/param.h>
#include <sys/socket.h>
#include "if.h"

main()
{
        struct if_data foo;
        u_char *addr1, *addr2;

        printf("sizeof if_data %d\n", sizeof(foo));
        addr1 = (u_char *)&foo;
        addr2 = (u_char *)&foo.ifi_mtu;
        printf("offset ifi_mtu %d\n", (int)(addr2 - addr1));
}

It reported no change in the structure size and said the ifi_mtu field
began at the same spot using the old and new versions of if.h.  So,
that *should* indicate Alpha's compiler had been doing the same
invisible padding that i386's had been.

Brooks, sorry about all this.  Just last-second jitters... :-)

-- 
						Ken Smith
- From there to here, from here to      |       kensmith@cse.buffalo.edu
  there, funny things are everywhere.   |
                      - Theodore Geisel |