nixos/scion: use RuntimeDirectory instead of StateDirectory (#323200)

It was wrong to use StateDirectory to keep the scion-control and
scion-router runtime databases on disk for the next run. I observed that
doing this means a reboot, or power outage can corrupt the temporary
runtime databases for the next service start, leading scion ping and
other functionality to stop working permanently, since those files are
not managed in an atomic manner by the golang code.

nixos/modules/services/networking/scion/scion-control.nix

@@ -12,13 +12,13 @@ let
       reconnect_to_dispatcher = true;
     };
     beacon_db = {
-      connection = "/var/lib/scion-control/control.beacon.db";
+      connection = "/run/scion-control/control.beacon.db";
     };
     path_db = {
-      connection = "/var/lib/scion-control/control.path.db";
+      connection = "/run/scion-control/control.path.db";
     };
     trust_db = {
-      connection = "/var/lib/scion-control/control.trust.db";
+      connection = "/run/scion-control/control.trust.db";
     };
     log.console = {
       level = "info";
@@ -35,7 +35,7 @@ in
       example = literalExpression ''
         {
           path_db = {
-            connection = "/var/lib/scion-control/control.path.db";
+            connection = "/run/scion-control/control.path.db";
           };
           log.console = {
             level = "info";
@@ -62,7 +62,7 @@ in
         DynamicUser = true;
         Restart = "on-failure";
         BindPaths = [ "/dev/shm:/run/shm" ];
-        StateDirectory = "scion-control";
+        RuntimeDirectory = "scion-control";
       };
     };
   };

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

@@ -12,10 +12,10 @@ let
       reconnect_to_dispatcher = true;
     };
     path_db = {
-      connection = "/var/lib/scion-daemon/sd.path.db";
+      connection = "/run/scion-daemon/sd.path.db";
     };
     trust_db = {
-      connection = "/var/lib/scion-daemon/sd.trust.db";
+      connection = "/run/scion-daemon/sd.trust.db";
     };
     log.console = {
       level = "info";
@@ -32,7 +32,7 @@ in
       example = literalExpression ''
         {
           path_db = {
-            connection = "/var/lib/scion-daemon/sd.path.db";
+            connection = "/run/scion-daemon/sd.path.db";
           };
           log.console = {
             level = "info";
@@ -57,7 +57,7 @@ in
         ExecStart = "${pkgs.scion}/bin/scion-daemon --config ${configFile}";
         Restart = "on-failure";
         DynamicUser = true;
-        StateDirectory = "scion-daemon";
+        RuntimeDirectory = "scion-daemon";
       };
     };
   };

nixos/modules/services/networking/scion/scion-dispatcher.nix

@@ -66,7 +66,7 @@ in
         ExecStartPre = "${pkgs.coreutils}/bin/rm -rf /run/shm/dispatcher";
         ExecStart = "${pkgs.scion}/bin/scion-dispatcher --config ${configFile}";
         Restart = "on-failure";
-        StateDirectory = "scion-dispatcher";
+        RuntimeDirectory = "scion-dispatcher";
       };
     };
   };

nixos/modules/services/networking/scion/scion-router.nix

@@ -42,7 +42,7 @@ in
         ExecStart = "${pkgs.scion}/bin/scion-router --config ${configFile}";
         Restart = "on-failure";
         DynamicUser = true;
-        StateDirectory = "scion-router";
+        RuntimeDirectory = "scion-router";
       };
     };
   };