IP: Update packet->len with accumulated fragment size

With packet->len representing the wire length and other places
relying on it, ensure it's updated for fragments as well. This
assumes non-truncated fragments right now. Otherwise we'd need
to teach the FragmentReassembler to somehow track this independently
but it would be a mess.

src/packet_analysis/protocol/ip/IP.cc

@@ -205,6 +205,8 @@ bool IPAnalyzer::AnalyzePacket(size_t len, const uint8_t* data, Packet* packet)
 				}
 
 			packet->cap_len = total_len + hdr_size;
+			// Assumes reassembled packet has wire length == capture length.
+			packet->len = packet->cap_len;
 			}
 		}