f638d68ebb
https://tools.ietf.org/html/rfc4944#section-5.3 says: > If a link fragment that overlaps another fragment is received, as > identified above, and differs in either the size or datagram_offset > of the overlapped fragment, the fragment(s) already accumulated in > the reassembly buffer SHALL be discarded. A fresh reassembly may be > commenced with the most recently received link fragment.