From 1293f046b500a2cd60ddf195639fae6419163931 Mon Sep 17 00:00:00 2001
From: Izorkin <izorkin@elven.pw>
Date: Sat, 7 Jan 2023 18:54:41 +0300
Subject: [PATCH] nixos/dhcpcd: optimize exitHook

---
 nixos/modules/services/networking/dhcpcd.nix | 32 ++++++++++++--------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/nixos/modules/services/networking/dhcpcd.nix b/nixos/modules/services/networking/dhcpcd.nix
index 266a7ea1435e1..8d5ac02ba88be 100644
--- a/nixos/modules/services/networking/dhcpcd.nix
+++ b/nixos/modules/services/networking/dhcpcd.nix
@@ -13,6 +13,8 @@ let
   enableDHCP = config.networking.dhcpcd.enable &&
         (config.networking.useDHCP || any (i: i.useDHCP == true) interfaces);
 
+  enableNTPService = (config.services.ntp.enable || config.services.ntpd-rs.enable || config.services.openntpd.enable || config.services.chrony.enable);
+
   # Don't start dhcpcd on explicitly configured interfaces or on
   # interfaces that are part of a bridge, bond or sit device.
   ignoredInterfaces =
@@ -89,20 +91,22 @@ let
       ${cfg.extraConfig}
     '';
 
-  exitHook = pkgs.writeText "dhcpcd.exit-hook"
-    ''
+  exitHook = pkgs.writeText "dhcpcd.exit-hook" ''
+    ${optionalString enableNTPService ''
       if [ "$reason" = BOUND -o "$reason" = REBOOT ]; then
-          # Restart ntpd.  We need to restart it to make sure that it
-          # will actually do something: if ntpd cannot resolve the
-          # server hostnames in its config file, then it will never do
-          # anything ever again ("couldn't resolve ..., giving up on
-          # it"), so we silently lose time synchronisation. This also
-          # applies to openntpd.
-          /run/current-system/systemd/bin/systemctl try-reload-or-restart ntpd.service openntpd.service chronyd.service ntpd-rs.service || true
+        # Restart ntpd. We need to restart it to make sure that it will actually do something:
+        # if ntpd cannot resolve the server hostnames in its config file, then it will never do
+        # anything ever again ("couldn't resolve ..., giving up on it"), so we silently lose
+        # time synchronisation. This also applies to openntpd.
+        ${optionalString config.services.ntp.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart ntpd.service || true"}
+        ${optionalString config.services.ntpd-rs.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart ntpd-rs.service || true"}
+        ${optionalString config.services.openntpd.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart openntpd.service || true"}
+        ${optionalString config.services.chrony.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart chronyd.service || true"}
       fi
+    ''}
 
-      ${cfg.runHook}
-    '';
+    ${cfg.runHook}
+  '';
 
 in
 
@@ -232,7 +236,7 @@ in
         wants = [ "network.target" ];
         before = [ "network-online.target" ];
 
-        restartTriggers = [ exitHook ];
+        restartTriggers = optional (enableNTPService || cfg.runHook != "") [ exitHook ];
 
         # Stopping dhcpcd during a reconfiguration is undesirable
         # because it brings down the network interfaces configured by
@@ -261,7 +265,9 @@ in
 
     environment.systemPackages = [ dhcpcd ];
 
-    environment.etc."dhcpcd.exit-hook".source = exitHook;
+    environment.etc."dhcpcd.exit-hook" = mkIf (enableNTPService || cfg.runHook != "") {
+      source = exitHook;
+    };
 
     powerManagement.resumeCommands = mkIf config.systemd.services.dhcpcd.enable
       ''