Hi Derek, the ARP request routine will allow the control transfer, in the same way that takes place during the dump itself. The "flag_panic_dump_in_progress" flag is already set and the routine kdp_arp_request (line 1277) calls kdp_poll which will cause the transfer (test around line 678) if a packet is received.
The other testing etc I deliberately left alone as much as possible - my thought way to make the minimal set of changes necessary, rather than do a more extensive change which would be harder to integrate (or even accept). Also, some changes might have ramifications elsewhere and I wanted that risk to be as small as possible. For example, I considered and then rejected the temptation to allow a port-number specification as part of the _panicd_ip address, the reason being that it would require a change to the parser for boot-args (16 character limit, this arg could be 22). So, even though there are some redundancies, they were deliberate in order to make the changes easier to review and evaluate.