boot, tailscale: Apply kernel regression patch instead of workarounds

common/boot.nix

@@ -11,6 +11,19 @@ in
     efi.canTouchEfiVariables = true;
   };
 
+  boot.kernelPatches = [
+    # Fix the /proc/net/tcp seek issue
+    # Impacts tailscale: https://github.com/tailscale/tailscale/issues/16966
+    {
+      name = "proc: fix missing pde_set_flags() for net proc files";
+      patch = pkgs.fetchurl {
+        name = "fix-missing-pde_set_flags-for-net-proc-files.patch";
+        url = "https://patchwork.kernel.org/project/linux-fsdevel/patch/20250821105806.1453833-1-wangzijie1@honor.com/raw/";
+        hash = "sha256-DbQ8FiRj65B28zP0xxg6LvW5ocEH8AHOqaRbYZOTDXg=";
+      };
+    }
+  ];
+
   services.resolved = {
     enable = true;
     fallbackDns = [ ];

common/tailscale.nix

@@ -20,21 +20,4 @@
   };
 
   networking.domain = "birdsong.network";
-
-  # Workaround for: https://github.com/tailscale/tailscale/issues/16966
-  nixpkgs.overlays = [
-    (_: prev: {
-      tailscale = prev.tailscale.overrideAttrs (old: {
-        checkFlags =
-          builtins.map
-            (
-              flag:
-              if prev.lib.hasPrefix "-skip=" flag
-              then flag + "|^TestGetList$|^TestIgnoreLocallyBoundPorts$|^TestPoller$"
-              else flag
-            )
-            old.checkFlags;
-      });
-    })
-  ];
 }