nftables: rename tcp service chains

nftables-attestation.conf

@@ -40,10 +40,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 80, 443 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 80, 443 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -51,19 +55,26 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 80, 443 } goto input-tcp-service
+        iif lo accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 80, 443 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 80, 443 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 80, 443 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -71,7 +82,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -80,7 +91,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-discuss.conf

@@ -40,10 +40,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 80, 443 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 80, 443 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -51,19 +55,26 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 80, 443 } goto input-tcp-service
+        iif lo accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 80, 443 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 80, 443 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 80, 443 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -71,7 +82,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -80,7 +91,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-mail.conf

@@ -40,10 +40,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 25, 80, 443, 465, 993 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 25, 80, 443, 465, 993 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -51,19 +55,26 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 25, 80, 443, 465, 993 } goto input-tcp-service
+        iif lo accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 25, 80, 443, 465, 993 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 25, 80, 443, 465, 993 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 25, 80, 443, 465, 993 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 25, 80, 443, 465, 993 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 25, 80, 443, 465, 993 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -71,7 +82,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -80,7 +91,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-matrix.conf

@@ -40,10 +40,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 80, 443 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 80, 443 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -51,19 +55,26 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 80, 443 } goto input-tcp-service
+        iif lo accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 80, 443 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 80, 443 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 80, 443 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -71,7 +82,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -80,7 +91,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-network.conf

@@ -42,10 +42,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 80, 443, 7275 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 80, 443, 7275 } tcp flags syn counter notrack accept
+
         udp dport 123 notrack accept
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
@@ -54,20 +58,27 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 80, 443, 7275 } goto input-tcp-service
+        iif lo accept
         udp dport 123 accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443, 7275 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 80, 443, 7275 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 80, 443, 7275 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 80, 443, 7275 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443, 7275 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -75,7 +86,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -84,7 +95,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-ns1.conf

@@ -40,11 +40,16 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
         udp dport 53 notrack accept
+
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 53, 80, 443, 853 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 53, 80, 443, 853 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -52,20 +57,27 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 53, 80, 443, 853 } goto input-tcp-service
+        iif lo accept
         udp dport 53 accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 53, 80, 443, 853 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 53, 80, 443, 853 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 53, 80, 443, 853 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -73,7 +85,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -82,7 +94,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-ns2.conf

@@ -42,14 +42,19 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
         # reject SSH packets via anycast IP
         tcp dport 22 ip daddr 198.251.90.93 reject with tcp reset
 
         udp dport 53 notrack accept
+
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 53, 80, 443, 853 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 53, 80, 443, 853 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -57,20 +62,27 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 53, 80, 443, 853 } goto input-tcp-service
+        iif lo accept
         udp dport 53 accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 53, 80, 443, 853 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 53, 80, 443, 853 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 53, 80, 443, 853 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -78,7 +90,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -87,7 +99,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-social.conf

@@ -40,10 +40,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 80, 443 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 80, 443 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -51,19 +55,26 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 80, 443 } goto input-tcp-service
+        iif lo accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 80, 443 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 80, 443 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 80, 443 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -71,7 +82,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -80,7 +91,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset

nftables-web.conf

@@ -44,10 +44,14 @@ table inet filter {
         iif lo notrack accept
 
         # drop packets to address not configured on incoming interface (strong host model)
+        #
+        # ordered after accepting loopback to permit using external IPs via loopback
         fib daddr . iif type != { local, broadcast, multicast } counter drop
 
+        # handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
         tcp dport { 22, 80, 443 } tcp flags syn limit rate 1024/second burst 128 packets accept
         tcp dport { 22, 80, 443 } tcp flags syn counter notrack accept
+
         meta l4proto { icmp, ipv6-icmp } notrack accept
     }
 
@@ -55,19 +59,26 @@ table inet filter {
         type filter hook input priority filter
         policy drop
 
-        iif lo goto input-loopback
+        tcp dport { 22, 80, 443 } goto input-tcp-service
+        iif lo accept
         meta l4proto { icmp, ipv6-icmp } accept
-        ct state vmap { new : goto input-new, established : goto input-established, related : accept }
+        ct state vmap { new : goto graceful-reject, established : accept, related : accept }
+    }
+
+    chain input-tcp-service {
+        iif lo goto input-tcp-service-loopback
+
+        # for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
+        ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
 
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
         tcp dport { 80, 443 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
-        tcp dport { 22, 80, 443 } synproxy mss 1460 wscale 7 timestamp sack-perm
+        synproxy mss 1460 wscale 7 timestamp sack-perm
     }
 
-    chain input-new {
+    chain input-tcp-service-new {
-        tcp dport != { 22, 80, 443 } goto graceful-reject
         tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
         tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
         tcp dport { 80, 443 } ip saddr @ip-connlimit-main counter reject with tcp reset
@@ -75,7 +86,7 @@ table inet filter {
         accept
     }
 
-    chain input-established {
+    chain input-tcp-service-established {
         ct mark 0x1 accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
@@ -84,7 +95,7 @@ table inet filter {
         ct mark set 0x1 accept
     }
 
-    chain input-loopback {
+    chain input-tcp-service-loopback {
         tcp flags != syn accept
         tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
         tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset