tests: add simple networking test

Just a test that pings one machine from another.

tests/default.nix

@@ -11,6 +11,7 @@ let
     ./bash.nix
     ./hello.nix
     ./log.nix
+    ./networking.nix
     ./solo5/multi.nix
     ./vmm_x86.nix
     ./x86.nix

tests/networking.nix

@@ -0,0 +1,45 @@
+{
+  name = "networking";
+  nodes = {
+
+    a = { pkgs, ... }: { imports = [ ../nixos-modules/hardware.nix ]; };
+
+    b = { config, pkgs, ... }: {
+      imports = [ ../nixos-modules/hardware.nix ];
+      networking.interfaces.eth1.genode.stack = null;
+      genode.init.children.ping = {
+        inputs = with pkgs.genodePackages; [ ping ];
+        configFile = let
+          ip = builtins.head config.networking.interfaces.eth1.ipv4.addresses;
+        in pkgs.writeText "ping.dhall" ''
+          let Genode = env:DHALL_GENODE
+
+          let Init = Genode.Init
+
+          let Child = Init.Child
+
+          in  Child.flat
+                Child.Attributes::{
+                , binary = "ping"
+                , resources = Init.Resources::{ ram = Genode.units.MiB 8 }
+                , routes = [ Init.ServiceRoute.child "Nic" "eth1.driver" ]
+                , config = Init.Config::{
+                  , attributes = toMap
+                      { interface = "${ip.address}/${toString ip.prefixLength}"
+                      , dst_ip = "192.168.1.1"
+                      , period_sec = "1"
+                      , count = "10"
+                      , verbose = "yes"
+                      }
+                  }
+                }
+        '';
+      };
+    };
+
+  };
+  testScript = ''
+    start_all()
+    b.wait_until_serial_output('child "ping" exited with exit value 0')
+  '';
+}