RE: Endianness and comparing IP's

Is the BSWAP32 macro a destructive macro . . destructive in the sense that
the value ip is modified?

If so, you run BSWAP32(ip) in the condition and ip is modified.  Conditional
fails . . pass ip through BSWAP32 again and the byte order is back to the
original!

Its quite possible that ip is coming to you in a form that is already
byte-order correct . .

Try this . . remove all the BSWAP32 refs and before the condition put in
this line

log ("server_login: ip=%u con->ip=%u", ip, con->ip);


I'd venture a guess that ip will show as equivalent to con->ip . . so the
use of BSWAP32 here is incorrect


Keith Clayton
Programmer/Analyst, Lake Tahoe Community College
clayton@ltcc.cc.ca.us

"If you don't trust me with your source code, why should I trust you with my
computer"

No electrons were harmed in the creation of this email

-----Original Message-----
From:	alex avriette [SMTP:alex@macachu.yi.org]
Sent:	Friday, January 05, 2001 12:25 PM
To:	linuxppc-dev@lists.linuxppc.org
Cc:	drscholl@users.sourceforge.net
Subject:	Endianness and comparing IP's


I am still working with the opennap software (available at
opennap.sourceforge.net) to resolve a strange issue whereby two IP's are
reported as equal, but fail a conditional for equality. the code in
question is here:

  if (BSWAP32(ip) != con->ip)
  {
    log ("server_login: ip=%u con->ip=%u", BSWAP32(ip), con->ip);
    log ("server_login: %s does not match %s (%s)",
         con->host, fields[0], my_ntoa (ip));
    con->destroy;
    return;
   }

the output of this is here:

server_login: ip=523706576 con->ip=523706576
server_login: 208.32.55.31 does not match cygnus.theblackmoor.net
(208.32.55.31)

so what I see happening is that BSWAP32(ip) doesnt equal con->ip which is
reported by the log (as seen earlier on the list, it uses a v*printf
followed by a fputs) as indeed being equal. I dont have host entries for
this host nor any of the other hosts I am trying to connect to.

Apparently this software is developed on x86 machines and tested in
Solaris on Suns for big endian compatibility. The code works fine on PC's
in this configuration:

    if (ip != BSWAP32 (con->ip))
    {
      log ("server_login: %s does not match %s (%s)",
           con->host, fields[0], my_ntoa (ip));
      con->destroy;
      return;
    }

I am not familiar with the concept of endianness and it hasnt quite been
explained sufficiently to me. I have Cc'ed the primary developer of
opennap on this message, though I am pretty familiar with the concepts and
workings of the code.

Thanks in advance.

alex

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