On Mon, Feb 06, 2006 at 02:21:09PM -0800, Nate Lawson wrote:
> Oleg Bulyzhin wrote:
> >On Sun, Feb 05, 2006 at 05:58:17PM -0600, Alan Cox wrote:
> >>Unfortunately, it also breaks NFS over UDP. Let me know if you need
> >>details.
> >>
> >>Alan
> >
> >
> >Fix attached. It's not bge problem it's five years old bug in ip_reass().
> >
> >Index: ip_input.c
> >===================================================================
> >RCS file: /home/ncvs/src/sys/netinet/ip_input.c,v
> >retrieving revision 1.314
> >diff -u -r1.314 ip_input.c
> >--- ip_input.c 2 Feb 2006 03:13:15 -0000 1.314
> >+++ ip_input.c 6 Feb 2006 21:44:45 -0000
> >@@ -982,10 +982,12 @@
> > nq = q->m_nextpkt;
> > q->m_nextpkt = NULL;
> > for (q = nq; q != NULL; q = nq) {
> >+ int sum;
>
> It's not good to declare local variables in the for() context. It's a
> style(9) bug and also costs an extra instruction or two (to decrement
> the stack pointer twice).
You are right, but i was not going to commit this as is. It's just 'proof of
concept' fix.
>
> > nq = q->m_nextpkt;
> > q->m_nextpkt = NULL;
> > m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
> >- m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
> >+ sum = m->m_pkthdr.csum_data + q->m_pkthdr.csum_data;
> >+ m->m_pkthdr.csum_data = (sum & 0xffff) + (sum >> 16);
> > m_cat(m, q);
> > }
> > #ifdef MAC
>
> I'm not familiar with this code. So m->m_pkthdr.csum_data is 32 bits?
> Couldn't the same thing be achieved with making it 16 bits since the add
> will wrap normally?
It will not work cause it's not just a trivial sum it's so called
"1's complement sum" (refer rfc1071 for details).
>
> --
> Nate
--
Oleg.
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