fix nftables (firewall) mechanism

nftables.conf

@@ -0,0 +1,25 @@
+#!/usr/sbin/nft -f
+
+flush ruleset
+
+table inet filter {
+  chain input {
+    type filter hook input priority 0;
+
+    # accept any localhost traffic
+    iif lo accept
+
+    # accept traffic originated from us
+    ct state established,related accept
+
+    # activate the following line to accept common local services
+    tcp dport { 22 } ct state new accept
+
+    # ICMPv6 packets which must not be dropped, see https://tools.ietf.org/html/rfc4890#section-4.4.1
+    meta nfproto ipv6 icmpv6 type { destination-unreachable, packet-too-big, time-exceeded, parameter-problem, echo-reply, echo-request, nd-router-solicit, nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert, 148, 149 } accept
+    ip6 saddr fe80::/10 icmpv6 type { 130, 131, 132, 143, 151, 152, 153 } accept
+
+    # count and drop any other traffic
+    counter drop
+  }
+}