illumos gate

During my testing of #2554 I noticed that using DHCP (IPv4) over IPMP is not working.

Trying to configure a DHCP address on the IPMP group interface (ifconfig ipmp0 dhcp) results in DHCP DISCOVER and/or REQUEST packets being sent out on the underlying interfaces. dhcpagent(1M) doesn't set the hardware address in the packets, but it does set a unique CLIENT_ID (or could use IAID/DUID as per #8518). The DHCP server on my network (ISC DHCP on NetBSD 9.2, in case it matters) sends REPLY packets to the MAC broadcast address (ff:ff:ff:ff:ff:ff) as it doesn't know the hardware address. It doesn't include the CLIENT_ID in its response, but the transaction ID is set correctly, which is really all there's needed.

The DHCP responses can be seen using snoop(1M) or tcpdump on the underlying interfaces, but dhcpagent(1M) is apparently unable to pick them up. I don't see them on the IPMP group interface, but I don't see any packets on the group interface at all, so that probably doesn't mean much.