6lowpan: add nhc module for GHC UDP detection

Acked-by: Jukka Rissanen <[e-mail]>
Signed-off-by: Stefan Schmidt <[e-mail]>
Signed-off-by: Alexander Aring <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

net/6lowpan/Kconfig

···
 	  6LoWPAN IPv6 Hop-by-Hop option generic header compression according
 	  to RFC7400.
 
+config 6LOWPAN_GHC_UDP
+	tristate "GHC UDP Support"
+	---help---
+	  6LoWPAN IPv6 UDP generic header compression according to RFC7400.
+
 endif

net/6lowpan/Makefile

···
 
 #rfc7400 ghcs
 obj-$(CONFIG_6LOWPAN_GHC_EXT_HDR_HOP) += nhc_ghc_ext_hop.o
+obj-$(CONFIG_6LOWPAN_GHC_UDP) += nhc_ghc_udp.o

net/6lowpan/nhc_ghc_udp.c

···
+/*
+ *	6LoWPAN UDP compression according to RFC7400
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include "nhc.h"
+
+#define LOWPAN_GHC_UDP_IDLEN	1
+#define LOWPAN_GHC_UDP_ID_0	0xd0
+#define LOWPAN_GHC_UDP_MASK_0	0xf8
+
+static void udp_ghid_setup(struct lowpan_nhc *nhc)
+{
+	nhc->id[0] = LOWPAN_GHC_UDP_ID_0;
+	nhc->idmask[0] = LOWPAN_GHC_UDP_MASK_0;
+}
+
+LOWPAN_NHC(ghc_udp, "RFC7400 UDP", NEXTHDR_UDP, 0,
+	   udp_ghid_setup, LOWPAN_GHC_UDP_IDLEN, NULL, NULL);
+
+module_lowpan_nhc(ghc_udp);
+MODULE_DESCRIPTION("6LoWPAN generic header UDP compression");
+MODULE_LICENSE("GPL");