Probable Bug in tcp.h

[Marc Lörner]

On Friday 06 June 2008 14:25, Bruce Evans wrote:
> On Fri, 6 Jun 2008, Marc [iso-8859-1] Lörner wrote:
> > On Friday 06 June 2008 09:52, Peter Jeremy wrote:
> >> I gather from this comment that you have some code using struct tcphdr
> >> that is getting alignment errors.  struct tcphdr is extensively used
> >> in the TCP stack within the kernel so it's likely that any layout or
> >> alignment problem with it would show up there.  I suspect you are
> >> dereferencing a mis-aligned struct tcphdr.
> >
> > The funny thing is that the dereferencing occurs in
> > "/usr/src/sys/netinet/tcp_input.c" in function tcp_input in line 550:
> >
> > 	/*
> > 	 * Check that TCP offset makes sense,
> > 	 * pull out TCP options and adjust length.		XXX
> > 	 */
> > 	off = th->th_off << 2;								<----- here
> > 	if (off < sizeof (struct tcphdr) || off > tlen) {
> > 		tcpstat.tcps_rcvbadoff++;
> > 		goto drop;
> > 	}
> >
> > So the misalignment may probably lie in TCP stack?
>
> Quite likely.  th is normally at offset off0 in ip, where ip is required
> to be 32-bit aligned (see my previous reply).  You can see off0 in a
> stack trace.
>

off0 is 0x14 => no problem with that
but address of ip is 0xe000000021c8706e => not correct aligned to 32-bits

Can anyone tell me, where ip is allocated, so I can do a little bit more 
research?

Marc