merge from in xen-unstable tip (17318:b5fea3aeb04b): hw/rtl8139.c

merge from in xen-unstable tip (17318:b5fea3aeb04b): hw/rtl8139.c

merge this changeset from xen-unstable:

changeset:   12482:075f4ffdbbce5527ba525a515abe320703d17a0e
user:        kfraser@localhost.localdomain
date:        Fri Nov 17 10:34:08 2006 +0000
files:       tools/ioemu/hw/rtl8139.c
description:
[QEMU] rtl8139: Disallow chaining above 64K

As it stands the 8139C+ TX chaining is only bounded by realloc failure.
This is contrary to how the real hardware operates.  It also has DoS
potential when ioemu runs in dom0.

This patch makes any attempt to chain a frame beyond 64K fail
immediately.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>