set lograte4 { type ipv4_addr; size 65535; flags dynamic; } set lograte6 { type ipv6_addr; size 65535; flags dynamic; } chain block { add @lograte4 { ip saddr limit rate 1/minute } log level warn prefix "block: " add @lograte6 { ip6 saddr limit rate 1/minute } log level warn prefix "block: " counter drop } chain ping-flood { add @lograte4 { ip saddr limit rate 1/minute } log level warn prefix "ping-flood: " add @lograte6 { ip6 saddr limit rate 1/minute } log level warn prefix "ping-flood: " counter drop } chain smurf { add @lograte4 { ip saddr limit rate 1/minute } log level warn prefix "smurf: " add @lograte6 { ip6 saddr limit rate 1/minute } log level warn prefix "smurf: " counter drop } chain bogus-tcp { add @lograte4 { ip saddr limit rate 1/minute } log level warn prefix "bogus-tcp: " add @lograte6 { ip6 saddr limit rate 1/minute } log level warn prefix "bogus-tcp: " counter drop } chain syn-flood { add @lograte4 { ip saddr limit rate 1/minute } log level warn prefix "syn-flood: " add @lograte6 { ip6 saddr limit rate 1/minute } log level warn prefix "syn-flood: " counter drop } chain check-tcp { tcp flags syn tcp option maxseg size != 536-65535 counter goto bogus-tcp tcp flags & (ack|fin) == fin counter goto bogus-tcp tcp flags & (ack|psh) == psh counter goto bogus-tcp tcp flags & (ack|urg) == urg counter goto bogus-tcp tcp flags & (fin|ack) == fin counter goto bogus-tcp tcp flags & (fin|rst) == (fin|rst) counter goto bogus-tcp tcp flags & (fin|psh|ack) == (fin|psh) counter goto bogus-tcp tcp flags & (syn|fin) == (syn|fin) counter goto bogus-tcp comment "SYN-FIN scan" tcp flags & (syn|rst) == (syn|rst) counter goto bogus-tcp comment "SYN-RST scan" tcp flags == (fin|syn|rst|psh|ack|urg) counter goto bogus-tcp comment "XMAS scan" tcp flags == 0x0 counter goto bogus-tcp comment "NULL scan" tcp flags == (fin|urg|psh) counter goto bogus-tcp tcp flags == (fin|urg|psh|syn) counter goto bogus-tcp comment "NMAP-ID" tcp flags == (fin|urg|syn|rst|ack) counter goto bogus-tcp ct state new tcp flags != syn counter goto bogus-tcp tcp sport 0 tcp flags & (fin|syn|rst|ack) == syn counter goto bogus-tcp tcp flags & (fin|syn|rst|ack) == syn counter limit rate over 30/second burst 60 packets goto syn-flood } chain spoofing { add @lograte4 { ip saddr limit rate 1/minute } log level warn prefix "spoofing: " counter drop } chain check-broadcast { #ip saddr 0.0.0.0/32 counter accept comment "DHCP broadcast" fib saddr type broadcast counter goto smurf #ip saddr 224.0.0.0/4 counter goto smurf } chain check-ping { ip protocol icmp icmp type echo-request limit rate over 10/second burst 20 packets goto ping-flood # Note the use `meta nfproto ipv6 meta l4proto ipv6-icmp` # instead of the buggy `ip6 nexthdr ipv6-icmp`. # See https://unix.stackexchange.com/questions/645561/nftables-how-to-set-up-simple-ip-and-port-forwarding#comment1209441_645561 meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type echo-request limit rate over 10/second burst 20 packets goto ping-flood } chain check-public { ip saddr 0.0.0.0/8 counter goto spoofing ip saddr 10.0.0.0/8 counter goto spoofing ip saddr 127.0.0.0/8 counter goto spoofing ip saddr 169.254.0.0/16 counter goto spoofing ip saddr 172.16.0.0/12 counter goto spoofing ip saddr 192.0.2.0/24 counter goto spoofing ip saddr 192.168.0.0/16 counter goto spoofing ip saddr 224.0.0.0/3 counter goto spoofing ip saddr 240.0.0.0/5 counter goto spoofing } chain accept-icmpv6 { # Traffic That Must Not Be Dropped # https://tools.ietf.org/html/rfc4890#section-4.4.1 icmpv6 type destination-unreachable counter accept icmpv6 type packet-too-big counter accept icmpv6 type time-exceeded counter accept icmpv6 type parameter-problem counter accept # Address Configuration and Router Selection messages # (must be received with hop limit = 255) icmpv6 type nd-router-solicit ip6 hoplimit 255 counter accept meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type nd-router-advert ip6 hoplimit 255 counter accept icmpv6 type nd-neighbor-solicit ip6 hoplimit 255 counter accept icmpv6 type nd-neighbor-advert ip6 hoplimit 255 counter accept icmpv6 type nd-redirect ip6 hoplimit 255 log level warn prefix "icmpv6: nd-redirect: " counter drop icmpv6 type ind-neighbor-solicit ip6 hoplimit 255 counter accept icmpv6 type ind-neighbor-advert ip6 hoplimit 255 counter accept # Link-local multicast receiver notification messages # (must have link-local source address) icmpv6 type mld-listener-query ip6 saddr fe80::/10 counter accept icmpv6 type mld-listener-report ip6 saddr fe80::/10 counter accept icmpv6 type mld-listener-done ip6 saddr fe80::/10 counter accept # https://tools.ietf.org/html/rfc3810 Multicast Listener Discovery Version 2 (MLDv2) for IPv6 icmpv6 type mld2-listener-report ip6 saddr fe80::/10 counter accept # SEND Certificate Path notification messages # (must be received with hop limit = 255) icmpv6 type 148 ip6 hoplimit 255 counter accept comment "certificate-path-solicitation" icmpv6 type 149 ip6 hoplimit 255 counter accept comment "certificate-path-advertisement" # Multicast Router Discovery messages # (must have link-local source address and hop limit = 1) icmpv6 type 151 ip6 saddr fe80::/10 ip6 hoplimit 1 counter accept comment "multicast-router-advertisement" icmpv6 type 152 ip6 saddr fe80::/10 ip6 hoplimit 1 counter accept comment "multicast-router-solicitation" icmpv6 type 153 ip6 saddr fe80::/10 ip6 hoplimit 1 counter accept comment "multicast-router-termination" } chain accept-connectivity-input { # Connectivity checking messages # (multicast) ping ip protocol icmp icmp type echo-reply counter accept # drop packets with rh0 headers rt type 0 jump block rt type 0 jump block rt type 0 jump block # (multicast) ping meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type echo-reply counter accept #ct state invalid counter drop ip protocol icmp icmp type destination-unreachable counter accept ip protocol icmp icmp type time-exceeded counter accept ip protocol icmp icmp type parameter-problem counter accept ip protocol icmp icmp type echo-request limit rate over 10/second burst 20 packets goto ping-flood ip protocol icmp icmp type echo-request counter accept # echo-reply is handled before invalid packets to allow multicast ping # which do not have an associated connection. meta nfproto ipv6 meta l4proto ipv6-icmp jump accept-icmpv6 # Connectivity checking messages icmpv6 type echo-request counter accept # echo-reply is handled before invalid because of multicast } chain accept-connectivity-output { ip protocol icmp counter accept meta skuid 0 udp dport 33434-33523 counter accept comment "traceroute" meta nfproto ipv6 meta l4proto ipv6-icmp jump accept-icmpv6 # Connectivity checking messages meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type echo-request counter accept meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type echo-reply counter accept } chain accept-connectivity-forward { ip protocol icmp icmp type destination-unreachable counter accept ip protocol icmp icmp type time-exceeded counter accept ip protocol icmp icmp type parameter-problem counter accept ip protocol icmp icmp type echo-request counter accept # Traffic That Must Not Be Dropped # https://tools.ietf.org/html/rfc4890#section-4.3.1 meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type destination-unreachable counter accept meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type packet-too-big counter accept meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type time-exceeded counter accept meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type parameter-problem counter accept # Connectivity checking messages meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type echo-request counter accept meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type echo-reply counter accept # Traffic That Normally Should Not Be Dropped # https://tools.ietf.org/html/rfc4890#section-4.3.2 meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type 144 counter accept comment "home-agent-address-discovery-request" meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type 145 counter accept comment "home-agent-address-discovery-reply" meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type 146 counter accept comment "mobile-prefix-solicitation" meta nfproto ipv6 meta l4proto ipv6-icmp icmpv6 type 147 counter accept comment "mobile-prefix-advertisement" }