I've do some other checks concern IPv6 and in/out UDP:
tcpdump -i eth0 -Q in udp port 443 and ip6
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
19:51:42.807541 IP6 2a06:a004:f072::2.58318 >...