Re: [PATCH] Remove useless variable assignment in tcpip.cc

[Kris Katterjohn <kjak () ispwest com>]

Andreas Ericsson wrote:
> On Tue, Mar 14, 2006 at 02:32:01PM -0600, Kris Katterjohn wrote:
> > The attached patch removes a useless assignment to a variable.
> >
> >
> > Thanks,
> > Kris
>
> > --- tcpip.cc.orig    2006-03-08 15:29:54.000000000 -0600
> > +++ tcpip.cc 2006-03-14 12:36:09.000000000 -0600
> > @@ -1179,7 +1179,6 @@ char *ping = (char *) &pingpkt;
> >  pingpkt.code = 0;
> >  pingpkt.id = id;
> >  pingpkt.seq = seq;
> > -pingpkt.checksum = 0;
> >  pingpkt.checksum = in_cksum((unsigned short *)ping, icmplen);
> >  
>
>
> This is actually necessary. Since 'char *ping' points to pingpkt the
> checksum has to be zero before calculating it. See RFC 791 or 792
> (I think both have identical texts, or 792 references 791) for details.
>
> It doesn't matter if pingpkt is in the bss but relying on such
> things will cause hard-to-find bugs when bitrot strikes (nmap will
> look like it's working, but some devices may refuse to respond when
> the checksum is bogus).

Ah, I found it in RFC 791.

Thanks,
Kris


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