nsh: add GSO support

Add a new nsh/ directory. It currently holds only GSO functions but more
will come: in particular, code shared by openvswitch and tc to manipulate
NSH headers.

For now, assume there's no hardware support for NSH segmentation. We can
always introduce netdev->nsh_features later.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/nsh/Kconfig b/net/nsh/Kconfig
new file mode 100644
index 0000000..bafc3dd
--- /dev/null
+++ b/net/nsh/Kconfig
@@ -0,0 +1,9 @@
+menuconfig NET_NSH
+	tristate "Network Service Header (NSH) protocol"
+	default n
+	---help---
+	  Network Service Header is an implementation of Service Function
+	  Chaining (RFC 7665). The current implementation in Linux supports
+	  only MD type 1 and only with the openvswitch module.
+
+	  If unsure, say N.