vpnkit: Add a config to specify the socket

arch/sim/Kconfig

@@ -142,6 +142,11 @@ endchoice
 
 endif
 
+config SIM_NETDEV_VPNKIT_PATH
+	string "Unix domain socket to communicate with VPNKit"
+	default "/tmp/vpnkit-nuttx"
+	depends on SIM_NETDEV_VPNKIT
+
 if HOST_LINUX
 choice
 	prompt "Simulation Network Type"

arch/sim/src/Makefile

@@ -175,6 +175,7 @@ else # HOSTOS != Cygwin
 endif # HOSTOS != Cygwin
 else ifeq ($(CONFIG_SIM_NETDEV_VPNKIT),y)
   CSRCS += up_netdriver.c
+  HOSTCFLAGS += -DCONFIG_SIM_NETDEV_VPNKIT_PATH=\"$(CONFIG_SIM_NETDEV_VPNKIT_PATH)\"
   HOSTSRCS += up_vpnkit.c
   VPATH += :sim/vpnkit
   HOSTSRCS += protocol.c negotiate.c

arch/sim/src/sim/up_vpnkit.c

@@ -55,7 +55,7 @@
  * Private Data
  ****************************************************************************/
 
-static const char *g_vpnkit_socket_path = "/tmp/vpnkit-nuttx"; /* XXX config */
+static const char *g_vpnkit_socket_path = CONFIG_SIM_NETDEV_VPNKIT_PATH;
 static struct vif_info g_vifinfo;
 static int g_vpnkit_fd = -1;
 static bool g_connect_warned;

boards/sim/sim/sim/NETWORK-VPNKIT.txt

@@ -11,6 +11,7 @@ Configuration
     CONFIG_SIM_NETDEV=y
     CONFIG_SIM_NETDEV_TAP is not set
     CONFIG_SIM_NETDEV_VPNKIT=y
+    CONFIG_SIM_NETDEV_VPNKIT_PATH="/tmp/vpnkit-nuttx"
 
 You can use the sim:vpnkit configuration, which includes the above
 settings.
@@ -35,5 +36,5 @@ You can use it as the following:
     % vpnkit --ethernet /tmp/vpnkit-nuttx &
     % ./nuttx
 
-NOTE: The unix domain socket path (/tmp/vpnkit-nuttx) is
-currently hardcoded in the code.
+NuttX's CONFIG_SIM_NETDEV_VPNKIT_PATH should match vpnkit's
+--ethernet option.