From ae9a80c1f012686c1f65fce7ce76fdd1b77b0b71 Mon Sep 17 00:00:00 2001
From: Gregor Kleen <gkleen@yggdrasil.li>
Date: Wed, 23 Sep 2026 21:08:35 +0200
Subject: ...

---
 hosts/skadhi/networking/default.nix |  30 +++++
 hosts/skadhi/networking/ruleset.nft | 223 ++++++++++++++++++++++++++++++++++++
 2 files changed, 253 insertions(+)
 create mode 100644 hosts/skadhi/networking/default.nix
 create mode 100644 hosts/skadhi/networking/ruleset.nft

(limited to 'hosts/skadhi/networking')

diff --git a/hosts/skadhi/networking/default.nix b/hosts/skadhi/networking/default.nix
new file mode 100644
index 00000000..ea5a62e2
--- /dev/null
+++ b/hosts/skadhi/networking/default.nix
@@ -0,0 +1,30 @@
+{ flake, config, ... }:
+{
+  imports = with flake.nixosModules.systemProfiles; [
+    networkmanager
+  ];
+
+  config = {
+    environment.persistence."/persistent".directories = [
+      "/etc/NetworkManager/system-connections"
+    ];
+
+    networking = {
+      domain = "yggdrasil";
+      search = [ "yggdrasil" ];
+      hosts = {
+        "127.0.0.1" = [ "${config.networking.hostName}.yggdrasil" config.networking.hostName ];
+        "::1" = [ "${config.networking.hostName}.yggdrasil" config.networking.hostName ];
+      };
+
+      firewall.enable = false;
+      nftables = {
+        enable = true;
+        rulesetFile = ./ruleset.nft;
+      };
+
+      useDHCP = false;
+      useNetworkd = true;
+    };
+  };
+}
diff --git a/hosts/skadhi/networking/ruleset.nft b/hosts/skadhi/networking/ruleset.nft
new file mode 100644
index 00000000..62339f69
--- /dev/null
+++ b/hosts/skadhi/networking/ruleset.nft
@@ -0,0 +1,223 @@
+define icmp_protos = { ipv6-icmp, icmp, igmp }
+
+table arp filter {
+  limit lim_arp {
+    rate over 50 mbytes/second burst 50 mbytes
+  }
+
+  counter arp-rx {}
+  counter arp-tx {}
+
+  counter arp-ratelimit-rx {}
+  counter arp-ratelimit-tx {}
+
+  chain input {
+    type filter hook input priority filter
+    policy accept
+
+    limit name lim_arp counter name arp-ratelimit-rx drop
+
+    counter name arp-rx
+  }
+
+  chain output {
+    type filter hook output priority filter
+    policy accept
+
+    limit name lim_arp counter name arp-ratelimit-tx drop
+
+    counter name arp-tx
+  }
+}
+
+table inet filter {
+  limit lim_reject {
+    rate over 1000/second burst 1000 packets
+  }
+
+  limit lim_icmp {
+    rate over 50 mbytes/second burst 50 mbytes
+  }
+
+  counter invalid-fw {}
+
+  counter fw-lo {}
+
+  counter reject-ratelimit-fw {}
+  counter reject-fw {}
+  counter reject-tcp-fw {}
+  counter reject-icmp-fw {}
+
+
+  counter invalid-rx {}
+  counter rx-lo {}
+  counter invalid-local4-rx {}
+  counter invalid-local6-rx {}
+
+  counter icmp-ratelimit-rx {}
+  counter icmp-rx {}
+
+  counter ssh-rx {}
+  counter mosh-rx {}
+  counter wg-rx {}
+  counter yggdrasil-gre-rx {}
+  counter miniserve-rx {}
+  counter ausweisapp2-rx {}
+
+  counter established-rx {}
+
+  counter reject-ratelimit-rx {}
+  counter reject-rx {}
+  counter reject-tcp-rx {}
+  counter reject-icmp-rx {}
+
+
+  counter tx-lo {}
+
+  counter icmp-ratelimit-tx {}
+  counter icmp-tx {}
+
+  counter ssh-tx {}
+  counter mosh-tx {}
+  counter wg-tx {}
+  counter yggdrasil-gre-tx {}
+  counter miniserve-tx {}
+
+  counter tx {}
+
+  counter fw-libvirt {}
+  counter libvirt-dhcp {}
+  counter libvirt-dns {}
+
+
+  chain forward_tmp {}
+  chain forward {
+    type filter hook forward priority filter
+    policy drop
+
+
+    ct state invalid log level debug prefix "drop invalid forward: " counter name invalid-fw drop
+
+
+    iifname lo counter name fw-lo accept
+
+    jump forward_tmp
+
+    iifname virbr0 oifname != {lo, wgrz, yggdrasil-wg-4, yggdrasil-wg-6, yggdrasil, ip6tnl, ip6gre, yggre-surtr-6, yggre-surtr-4, yggre-vidhar-4} counter name fw-libvirt accept
+    oifname virbr0 ct state {established, related} counter name fw-libvirt accept
+
+
+    limit name lim_reject log level debug prefix "drop forward: " counter name reject-ratelimit-fw drop
+    log level debug prefix "reject forward: " counter name reject-fw
+    meta l4proto tcp ct state new counter name reject-tcp-fw reject with tcp reset
+    ct state new counter name reject-icmp-fw reject
+  }
+
+  chain input_tmp {}
+  chain input {
+    type filter hook input priority filter
+    policy drop
+
+
+    ct state invalid log level debug prefix "drop invalid input: " counter name invalid-rx drop
+
+
+    iifname lo counter name rx-lo accept
+    iif != lo ip daddr 127.0.0.1/8 counter name invalid-local4-rx reject
+    iif != lo ip6 daddr ::1/128 counter name invalid-local6-rx reject
+
+    meta l4proto $icmp_protos limit name lim_icmp counter name icmp-ratelimit-rx drop
+    meta l4proto $icmp_protos counter name icmp-rx accept
+
+    jump input_tmp
+
+    tcp dport 22 counter name ssh-rx accept
+    udp dport 60000-61000 counter name mosh-rx accept
+
+    tcp dport 8080 counter name miniserve-rx accept
+    udp dport 24727 counter name ausweisapp2-rx accept
+
+    udp dport 51820-51822 counter name wg-rx accept
+    iifname "yggdrasil-wg-*" meta l4proto gre counter name yggdrasil-gre-rx accept
+
+    iifname virbr0 udp dport 67 counter name libvirt-dhcp accept
+    iifname virbr0 udp dport 547 counter name libvirt-dhcp accept
+    iifname virbr0 udp dport 53 counter name libvirt-dns accept
+    iifname virbr0 tcp dport 53 counter name libvirt-dns accept
+
+    iifname wgrz ip saddr 10.200.116.1 meta l4proto gre counter accept
+
+    ct state {established, related} counter name established-rx accept
+
+
+    limit name lim_reject log level debug prefix "drop input: " counter name reject-ratelimit-rx drop
+    log level debug prefix "reject input: " counter name reject-rx
+    meta l4proto tcp ct state new counter name reject-tcp-rx reject with tcp reset
+    ct state new counter name reject-icmp-rx reject
+  }
+
+  chain output {
+    type filter hook output priority filter
+    policy accept
+
+
+    oifname lo counter name tx-lo accept
+
+    meta l4proto $icmp_protos limit name lim_icmp counter name icmp-ratelimit-tx drop
+    meta l4proto $icmp_protos counter name icmp-tx accept
+
+
+    tcp sport 22 counter name ssh-tx
+    udp sport 60000-61000 counter name mosh-tx
+
+    udp sport 51820-51822 counter name wg-tx
+    iifname "yggdrasil-wg-*" meta l4proto gre counter name yggdrasil-gre-tx
+
+    tcp sport 8080 counter name miniserve-tx accept
+
+    oifname virbr0 udp sport 67 counter name libvirt-dhcp accept
+    oifname virbr0 udp sport 547 counter name libvirt-dhcp accept
+    oifname virbr0 udp sport 53 counter name libvirt-dns accept
+    oifname virbr0 tcp sport 53 counter name libvirt-dns accept
+
+
+    counter name tx
+  }
+}
+
+table ip nat {
+  counter libvirt-nat {}
+
+  chain postrouting_tmp {}
+  chain postrouting {
+    type nat hook postrouting priority srcnat
+    policy accept
+
+    iifname virbr0 oifname != virbr0 counter name libvirt-nat masquerade
+    jump postrouting_tmp
+  }
+}
+
+table ip6 nat {
+  counter libvirt-nat {}
+
+  chain postrouting {
+    type nat hook postrouting priority srcnat
+    policy accept
+
+    iifname virbr0 oifname != virbr0 counter name libvirt-nat masquerade
+  }
+}
+
+table ip mss_clamp {
+  counter libvirt-mss-clamp {}
+
+  chain postrouting_tmp {}
+  chain postrouting {
+    type filter hook postrouting priority mangle
+    policy accept
+
+    iifname virbr0 oifname != virbr0 tcp flags & (syn|rst) == syn counter name libvirt-mss-clamp tcp option maxseg size set rt mtu
+    jump postrouting_tmp
+  }
+}
-- 
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