From eea16ca2760ecc4e879e7f654334004978ee3157 Mon Sep 17 00:00:00 2001
From: Simon Bruder <simon@sbruder.de>
Date: Tue, 27 Aug 2024 16:37:48 +0200
Subject: [PATCH] shinobu/router: Add ability to bypass HE tunnel

---
 machines/shinobu/services/router/default.nix | 13 +++++++
 machines/shinobu/services/router/dnsmasq.nix |  9 +++++
 machines/shinobu/services/router/rules.nft   | 36 ++++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/machines/shinobu/services/router/default.nix b/machines/shinobu/services/router/default.nix
index 8710a6a..aa44a79 100644
--- a/machines/shinobu/services/router/default.nix
+++ b/machines/shinobu/services/router/default.nix
@@ -110,6 +110,19 @@ in
             UseDNS = "no";
             UseGateway = false; # should not be used by default for routing (wg-he takes precendence)
           };
+          routingPolicyRules = lib.singleton {
+            routingPolicyRuleConfig = {
+              Family = "ipv6";
+              FirewallMark = 31092; # 0x7974
+              Table = 31092; # 0x7974
+            };
+          };
+          routes = lib.singleton {
+            routeConfig = {
+              Gateway = "_ipv6ra";
+              Table = 31092; # 0x7974
+            };
+          };
         };
         physical-lan = {
           name = "enp2s0";
diff --git a/machines/shinobu/services/router/dnsmasq.nix b/machines/shinobu/services/router/dnsmasq.nix
index 7b3e432..a447154 100644
--- a/machines/shinobu/services/router/dnsmasq.nix
+++ b/machines/shinobu/services/router/dnsmasq.nix
@@ -5,6 +5,11 @@
 { config, lib, pkgs, ... }:
 let
   cfg = pkgs.callPackage ./common.nix { };
+
+  bypassHe = [
+    "googlevideo.com"
+    "youtube.com"
+  ];
 in
 {
   services.dnsmasq = {
@@ -51,6 +56,10 @@ in
         ])
         cfg.vlan);
 
+      nftset = [
+        "/${lib.concatStringsSep "/" bypassHe}/6#ip6#he-bypass#addresses"
+      ];
+
       server = [
         "127.0.0.1#5053"
       ];
diff --git a/machines/shinobu/services/router/rules.nft b/machines/shinobu/services/router/rules.nft
index 05cdaed..9acc1b3 100644
--- a/machines/shinobu/services/router/rules.nft
+++ b/machines/shinobu/services/router/rules.nft
@@ -41,6 +41,42 @@ table ip nat {
 	}
 }
 
+# Bypass HE tunnel by setting a firewall mark.
+# This acts in two places that are handled separatly by nftables:
+# Packets from the local host (output hook) and forwared packets (prerouting hook).
+# To simplify the handling,
+# there is a single chain that handles both,
+# which is jumped to from the specific chains.
+# Additionally, masquerading is allowed for all packages with a destination of the dynamic set.
+table ip6 he-bypass {
+	# Dynamically managed by dnsmasq (based on resolved addresses).
+	set addresses {
+		type ipv6_addr
+		comment "IPv6 addresses for which the HE tunnel should be bypassed by using NAT on wan instead"
+	}
+
+	# This must be of type route, otherwise no route lookup will be performed
+	chain output {
+		type route hook output priority mangle
+		jump common
+	}
+
+	# This does not need to be of type route
+	chain prerouting {
+		type filter hook prerouting priority mangle
+		jump common
+	}
+
+	chain common {
+		ip6 daddr @addresses mark set 0x7974 counter
+	}
+
+	chain postrouting {
+		type nat hook postrouting priority filter; policy accept
+		oifname $NAT_WAN_IFACES ip6 daddr @addresses masquerade
+	}
+}
+
 table ip6 public-access {
 	chain input {
 		type filter hook input priority filter; policy accept