Created attachment 154834 [details]
After some back and forth on the mailing list (freebsd-net) Hans Petter Selasky came up with the attached patch which I tested successfully.

I've noticed that mbuf tags aren't being copied from the leading fragment (header) to the subsequent fragment packets. In other words, one would expect that all fragments of a packet are carrying the same tags that were set on the original packet. I have built a simple test were I use ipfw with ALTQ and sent large packet (bigger then MTU) off that BSD machine. I have observed that the leading fragment (m0) packet is going through the right class although the next fragments are hitting the default class for unclassified packets.