xde_rx should set packet info to help out mac #746
Description
Once a packet is parsed, modified, etc. on the inbound path (or hairpinned on tx), XDE calls mac_rx with the target packet. With some of the parsing reworks in illumos itself, proto fanout calls mac_ether_offload_info to determine how packets should be sorted. illumos does this both for delivery to zones (Nexus, NTP, ...) and to viona. Viona itself would like this info to help emulate LSO for GRO-unfriendly guests.
We should fill out this information when possible to remove these reparsing costs.