net/Kconfig: IP forwarding no long depends on only IPv6. Also update Kconfig comments.

net/Kconfig

@@ -288,24 +288,18 @@ source "net/sixlowpan/Kconfig"
 config NET_IPFORWARD
 	bool "Enable L2 forwarding"
 	default n
-	depends on NET_IPv6
 	---help---
-		Enable forwarding of IPv6 packets.  Packets received with IPv6
-		addresses which are not supported by this platform will be forwarded
-		to the appropriate network device.  Routing table support may be
-		required.
-
-		NOTE: L2 forwarding only supported for IPv6.  There is no technical
-		reason why IPv4 forwarding has not been implemented, it just has
-		not yet been done.
+		Enable forwarding of packets.  Packets received with IP addresses
+		that are not supported by this platform will be forwarded to the
+		appropriate network device.  Routing table support may be required.
 
 config NET_IPFORWARD_NSTRUCT
 	int "Number of pre-allocated forwarding structures"
 	default 4
 	depends on NET_IPFORWARD && CONFIG_NETDEV_MULTINIC
 	---help---
-		When packets are forward from on device to another, a structure must
-		be allocated to hold the state of forwarding across several
+		When packets are forwarded from on device to another, a structure
+		must be allocated to hold the state of forwarding across several
 		asynchronous events.  Those structures are pre-allocated for
 		minimal, deterministic performance and to prevent hogging of memory
 		(of course, that means that this value must be carefully selected
@@ -314,7 +308,8 @@ config NET_IPFORWARD_NSTRUCT
 
 		NOTE: This setting effectively puts a maximum on the number of
 		packets that may be waiting to be forwarded from one network device
-		to another.
+		to another.  CONFIG_IOB_NBUFFERS also limits the forward because the
+		payload of the packet (up to the MSS) is retain in IOBs.
 
 endmenu # Internet Protocol Selection