On Tue, 1 Apr 2003, Rask Ingemann Lambertsen wrote:
> Is a network device driver allowed to modify dev->flags? For example:
> if (dev->flags & IFF_ALLMULTI)
> dev->flags |= IFF_PROMISC;
You must be looking at the atp.c driver, or a driver that cribbed from
it. (Is anyone still running a parallel port Ethernet device?!)
Alan Cox added this code to atp.c because the chip doesn't have a
reasonable multicast filter. The only way to receive all multicast
traffic was to turn on promiscuous mode. But that caused a problem
with some parts of the protocol stack were passed traffic not intended
for the local host.
A better solution (which is usually easier to see later) is to have
the driver do the trivial final packet filtering itself.
> I've found it to cause the IFF_PROMISC flag to stick when using
> "tcpdump -p", which to my surprice sets the IFF_ALLMULTI flag.
Which driver are you using?
Donald Becker becker@xxxxxxxxx
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Scyld Beowulf cluster system
Annapolis MD 21403 410-990-9993