Once I do netstat -tn, I constantly see quite a lot of connections from a number of ipv6 addresses (the fe80:: ones; normally round or precisely 4096 of them). I am unable to seek out the addresses on WHOIS, and blocking them by way of ufw or iptables would not appear to work. Am I being attacked? Is it a SYN flood?

tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:41510 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:50782 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:27544 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:44052 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:49154 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:26306 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:61276 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:36288 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::a236:9fff:f:32822 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:33540 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:46254 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:34114 SYN_RECV
tcp6       0      0 2a01:4f8:141:1d3::2:443 fe80::b696:91ff:f:39238 SYN_RECV

Simon Fredsted is a brand new contributor to this website. Take care in asking for clarification, commenting, and answering.
Take a look at our Code of Conduct.