RE: dhcpcd not working in simh-vax with xq0:nat networking

[Mark Pizzolato - Info Comm <Mark%infocomm.com@localhost>]

On Friday, December 10, 2021 at 12:07 PM, Rhialto wrote:
> On Fri 10 Dec 2021 at 19:48:43 +0000, Mark Pizzolato - Info Comm wrote:
> > I will track this down if you can provide me with a pointer to a disk image
> > (hopefully compressed) that demonstrates the problem.
> 
> Thanks! I was thinking in first instance it would be a NetBSD weirdness,
> but maybe it isn't. I only tried the microvax3900, not other models.

It may be NetBSD weirdness, or it more likely a general weakness in the 
dhcpd in the simh NAT code.  The NAT code comes from what was originally
slirp.  The NAT dhcp activities under simh haven't generally gotten much (if 
any) exercise since I think that only NetBSD has a dhcp client.  Maybe 
Johnny's RSX TCP stack also has a dhcp client, but users probably haven't been 
using NAT.

As I start to think about this and the digging you already did that observed that 
it worked when tcpdump put the qt interface into promiscuous mode, I'm 
thinking that the default QT initialization of the XQ device isn't configuring an 
appropriate MAC receive address that would match the destination MAC 
address of the slirp dhcp's DHCP response packets.  I haven't looked yet, but 
maybe the slirp dhcp response packets may have a broadcast destination 
address and the interface may not be yet configured with a broadcast 
address in its match list.  

I'll let you know what I find.

- Mark