[35809] in North American Network Operators' Group
Re: Statements against new.net?
daemon@ATHENA.MIT.EDU (Michael Shields)
Fri Mar 16 04:12:10 2001
To: "Mathias Koerber" <mathias@koerber.org>
Cc: "Simon Higgs" <simon@higgs.com>,
"Nanog@Merit. Edu" <nanog@merit.edu>
From: Michael Shields <shields@msrl.com>
Date: 16 Mar 2001 08:50:17 +0000
In-Reply-To: "Mathias Koerber"'s message of "Fri, 16 Mar 2001 13:40:36 +0800"
Message-ID: <87g0geayie.fsf@challah.msrl.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Errors-To: owner-nanog-outgoing@merit.edu
In article <NEBBLGLDKLMMGKEMEFMFAEBNCFAA.mathias@koerber.org>,
"Mathias Koerber" <mathias@koerber.org> wrote:
> Because it does not matter whether it's network byte order or not?
16.1.16.1 is sensitive to network byte order; this program
demonstrates that:
#include <stdio.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
int
main(void)
{
struct in_addr sin;
if (inet_aton("16.1.16.1", &sin) < 0) {
perror("inet_aton failed");
exit(1);
}
printf("Host byte order: %10lu 0x%08lx\n",
sin.s_addr, sin.s_addr);
printf("Network byte order: %10lu 0x%08lx\n",
htonl(sin.s_addr), htonl(sin.s_addr));
return(0);
}
On IA32 this outputs:
Host byte order: 17826064 0x01100110
Network byte order: 268505089 0x10011001
and on sun4c:
Host byte order: 268505089 0x10011001
Network byte order: 268505089 0x10011001
This occurs because the MSB vs. LSB conversion reorders at byte units,
but the mental reordering we perform while looking at a hexadecimal
representation occurs at the four-bit unit represented by one hex digit.
16.1.1.16 would be a palindrome at the byte level (0x10010110), and so
htonl() will be a no-op on it even on a little-endian machine.
I hope this clears things up. Let's run some networks now.
--
Shields.
