Justin C. Walker writes:

The ENOBUFS error crops up when there is no available buffer for some

required use (e.g., failing on the allocation of an mbuf to hold the

packet header). This is done in udp_output(), and un ip_output().

Yeah, I'm an idiot. I'd gotten suspicious of dlil just because its new to me. I had ifq_maxlen set too small & ip_output was dropping things. I'm pretty sure this is what was causing my real problem. Oops..

Is this driver "virtual", or does it deal with hardware?

"yes" ;-) It uses I/O Kit for hardware access only, and is otherwise a pretty much straightforward port of an existing FreeBSD / Tru64 driver with changes for Apple's dlil layer. Thanks for the help.. Drew