treewide: fix fallout of ip-up deprecation

See #18319 for details. Starting network-online.target manually does not
work as it hangs indefinitely.

Additionally, don't treat avahi and dhcpcd special and sync their systemd units
with the respective upstream suggestion.

nixos/modules/services/networking/avahi-daemon.nix

@@ -7,10 +7,6 @@ let
 
   cfg = config.services.avahi;
 
-  # We must escape interfaces due to the systemd interpretation
-  subsystemDevice = interface:
-    "sys-subsystem-net-devices-${utils.escapeSystemdPath interface}.device";
-
   avahiDaemonConf = with cfg; pkgs.writeText "avahi-daemon.conf" ''
     [server]
     ${# Users can set `networking.hostName' to the empty string, when getting
@@ -180,14 +176,8 @@ in
     environment.systemPackages = [ pkgs.avahi ];
 
     systemd.services.avahi-daemon =
-      let
-        deps = optionals (cfg.interfaces!=null) (map subsystemDevice cfg.interfaces);
-      in
       { description = "Avahi daemon";
-        wantedBy = [ "ip-up.target" ];
-        bindsTo = deps;
-        after = deps;
-        before = [ "ip-up.target" ];
+        wantedBy = [ "multi-user.target" ];
         # Receive restart event after resume
         partOf = [ "post-resume.target" ];
 

nixos/modules/services/networking/dhcpcd.nix

@@ -147,10 +147,9 @@ in
     systemd.services.dhcpcd =
       { description = "DHCP Client";
 
-        wantedBy = [ "network.target" ];
-        # Work-around to deal with problems where the kernel would remove &
-        # re-create Wifi interfaces early during boot.
-        after = [ "network-interfaces.target" ];
+        wantedBy = [ "multi-user.target" ];
+        wants = [ "network.target" ];
+        before = [ "network.target" ];
 
         # Stopping dhcpcd during a reconfiguration is undesirable
         # because it brings down the network interfaces configured by

nixos/modules/services/networking/networkmanager.nix

@@ -52,13 +52,6 @@ let
     });
   '';
 
-  ipUpScript = writeScript "01nixos-ip-up" ''
-    #!/bin/sh
-    if test "$2" = "up"; then
-      ${config.systemd.package}/bin/systemctl start network-online.target
-    fi
-  '';
-
   ns = xs: writeText "nameservers" (
     concatStrings (map (s: "nameserver ${s}\n") xs)
   );
@@ -187,9 +180,6 @@ in {
     boot.kernelModules = [ "ppp_mppe" ]; # Needed for most (all?) PPTP VPN connections.
 
     environment.etc = with cfg.basePackages; [
-      { source = ipUpScript;
-        target = "NetworkManager/dispatcher.d/01nixos-ip-up";
-      }
       { source = configFile;
         target = "NetworkManager/NetworkManager.conf";
       }

nixos/modules/system/boot/systemd.nix

@@ -727,8 +727,6 @@ in
         unitConfig.X-StopOnReconfiguration = true;
       };
 
-    systemd.targets.network-online.after = [ "ip-up.target" ];
-
     systemd.units =
       mapAttrs' (n: v: nameValuePair "${n}.target" (targetToUnit n v)) cfg.targets
       // mapAttrs' (n: v: nameValuePair "${n}.service" (serviceToUnit n v)) cfg.services

nixos/modules/tasks/network-interfaces-scripted.nix

@@ -142,7 +142,6 @@ in
                     # (Flushing this interface may have removed it.)
                     ${config.systemd.package}/bin/systemctl try-restart --no-block network-setup.service
                   fi
-                  ${config.systemd.package}/bin/systemctl start network-online.target
                 '';
             preStop = flip concatMapStrings (ips) (ip:
                 let