Sending an ip6 packet with src_address.as_u64[0,1] = 0xFFFFFFFF FFFFFFFF, dst_address.as_u64 [0,1] = <same> eventually causes mfib_entry_get(...) to ASSERT. 

The ip metadata leaves a certain amount to be desired:

(gdb) p/x vb(b0)->ip
$2 = {adj_index =

{0xffffffff, 0x13131313}

,

{{flow_hash = 0x0,

{ save_protocol = 0x0, fib_index = 0x0}

, save_rewrite_length = 0xe,
rpf_id = 0x0}, icmp = {type = 0x0, code = 0x0, data = 0x0}, reass = {{
next_index = 0x0, estimated_mtu = 0x0}, {fragment_first = 0x0,
fragment_last = 0x0, range_first = 0x0, range_last = 0x0,
next_range_bi = 0xe, ip6_frag_hdr_offset = 0x0}}}}

The attached setup and pcap files reproduce the problem. You'll need to modify the setup script to point to the pcap file.