net/: Permit net/neighbor to build when IPv6 is defined, but not Ethernet. Needs more work to support 6loWPAN. Also included, some minor configuration updates for 6loWPAN.

net/Kconfig

@@ -123,8 +123,7 @@ config NET_USER_DEVFMT
 
 config NET_ETHERNET
 	bool "Ethernet support"
-	default y if !NET_SLIP
-	default n if NET_SLIP
+	default y
 	select NETDEV_MULTINIC if NET_6LOWPAN || NET_LOOPBACK || NET_SLIP || NET_TUN
 	select NET_MULTILINK if NET_6LOWPAN || NET_LOOPBACK || NET_SLIP || NET_TUN
 	---help---
@@ -132,6 +131,16 @@ config NET_ETHERNET
 		no need to define anything special in the configuration file to use
 		Ethernet -- it is the default).
 
+menuconfig NET_6LOWPAN
+	bool "IEEE 802.15.4 6LoWPAN support"
+	default n
+	select NETDEV_MULTINIC if NET_ETHERNET || NET_LOOPBACK || NET_SLIP || NET_TUN
+	select NET_MULTILINK if NET_ETHERNET || NET_LOOPBACK || NET_SLIP || NET_TUN
+	depends on EXPERIMENTAL && NET_IPv6
+	---help---
+		Enable support for IEEE 802.15.4 Low power Wireless Personal Area
+		Networking (6LoWPAN).
+
 config NET_LOOPBACK
 	bool "Local loopback"
 	default n

net/neighbor/Make.defs

@@ -39,7 +39,16 @@ ifeq ($(CONFIG_NET_IPv6),y)
 
 NET_CSRCS += neighbor_initialize.c neighbor_add.c neighbor_lookup.c
 NET_CSRCS += neighbor_update.c neighbor_periodic.c neighbor_findentry.c
-NET_CSRCS += neighbor_out.c
+
+# Link layer specific support
+
+ifeq ($(CONFIG_NET_ETHERNET),y)
+NET_CSRCS += neighbor_ethernet_out.c
+endif
+
+ifeq ($(CONFIG_NET_6LOWPAN),y)
+# NET_CSRCS += neighbor_6lowpan_out.c
+endif
 
 # Include utility build support
 

net/neighbor/neighbor_ethernet_out.c

@@ -1,7 +1,7 @@
 /****************************************************************************
- * net/neighbor/neighbor_out.c
+ * net/neighbor/neighbor_ethernet_out.c
  *
- *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2015, 2017 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without

net/sixlowpan/Kconfig

@@ -3,14 +3,6 @@
 # see the file kconfig-language.txt in the NuttX tools repository.
 #
 
-menuconfig NET_6LOWPAN
-	bool "IEEE 802.15.4 6LoWPAN support"
-	default n
-	depends on EXPERIMENTAL && NET_IPv6
-	---help---
-		Enable support for IEEE 802.15.4 Low power Wireless Personal Area
-		Networking (6LoWPAN).
-
 if NET_6LOWPAN
 
 config NET_6LOWPAN_FRAG