Merge tag 'ieee802154-for-net-next-2022-06-09' of git://git.kernel.org/pub/scm/linux/kernel/git/sschmidt/wpan-next

Stefan Schmidt says:

====================
pull-request: ieee802154-next 2022-06-09

This is a separate pull request for 6lowpan changes. We agreed with the
bluetooth maintainers to switch the trees these changing are going into
from bluetooth to ieee802154.

Jukka Rissanen stepped down as a co-maintainer of 6lowpan (Thanks for the
work!). Alexander is staying as maintainer.

Alexander reworked the nhc_id lookup in 6lowpan to be way simpler.
Moved the data structure from rb to an array, which is all we need in this
case.

* tag 'ieee802154-for-net-next-2022-06-09' of git://git.kernel.org/pub/scm/linux/kernel/git/sschmidt/wpan-next:
MAINTAINERS: Remove Jukka Rissanen as 6lowpan maintainer
net: 6lowpan: constify lowpan_nhc structures
net: 6lowpan: use array for find nhc id
net: 6lowpan: remove const from scalars
====================

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

MAINTAINERS

···
 
 6LOWPAN GENERIC (BTLE/IEEE 802.15.4)
 M:	Alexander Aring <[e-mail]>
-M:	Jukka Rissanen <[e-mail]>
 L:	[e-mail]
 L:	[e-mail]
 S:	Maintained

net/6lowpan/nhc.c

···
 
 #include "nhc.h"
 
-static struct rb_root rb_root = RB_ROOT;
-static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
+static const struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
 static DEFINE_SPINLOCK(lowpan_nhc_lock);
 
-static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
+static const struct lowpan_nhc *lowpan_nhc_by_nhcid(struct sk_buff *skb)
 {
-	struct rb_node **new = &rb_root.rb_node, *parent = NULL;
+	const struct lowpan_nhc *nhc;
+	int i;
+	u8 id;
 
-	/* Figure out where to put new node */
-	while (*new) {
-		struct lowpan_nhc *this = rb_entry(*new, struct lowpan_nhc,
-						   node);
-		int result, len_dif, len;
+	if (!pskb_may_pull(skb, 1))
+		return NULL;
 
-		len_dif = nhc->idlen - this->idlen;
+	id = *skb->data;
 
-		if (nhc->idlen < this->idlen)
-			len = nhc->idlen;
-		else
-			len = this->idlen;
+	for (i = 0; i < NEXTHDR_MAX + 1; i++) {
+		nhc = lowpan_nexthdr_nhcs[i];
+		if (!nhc)
+			continue;
 
-		result = memcmp(nhc->id, this->id, len);
-		if (!result)
-			result = len_dif;
-
-		parent = *new;
-		if (result < 0)
-			new = &((*new)->rb_left);
-		else if (result > 0)
-			new = &((*new)->rb_right);
-		else
-			return -EEXIST;
-	}
-
-	/* Add new node and rebalance tree. */
-	rb_link_node(&nhc->node, parent, new);
-	rb_insert_color(&nhc->node, &rb_root);
-
-	return 0;
-}
-
-static void lowpan_nhc_remove(struct lowpan_nhc *nhc)
-{
-	rb_erase(&nhc->node, &rb_root);
-}
-
-static struct lowpan_nhc *lowpan_nhc_by_nhcid(const struct sk_buff *skb)
-{
-	struct rb_node *node = rb_root.rb_node;
-	const u8 *nhcid_skb_ptr = skb->data;
-
-	while (node) {
-		struct lowpan_nhc *nhc = rb_entry(node, struct lowpan_nhc,
-						  node);
-		u8 nhcid_skb_ptr_masked[LOWPAN_NHC_MAX_ID_LEN];
-		int result, i;
-
-		if (nhcid_skb_ptr + nhc->idlen > skb->data + skb->len)
-			return NULL;
-
-		/* copy and mask afterwards the nhid value from skb */
-		memcpy(nhcid_skb_ptr_masked, nhcid_skb_ptr, nhc->idlen);
-		for (i = 0; i < nhc->idlen; i++)
-			nhcid_skb_ptr_masked[i] &= nhc->idmask[i];
-
-		result = memcmp(nhcid_skb_ptr_masked, nhc->id, nhc->idlen);
-		if (result < 0)
-			node = node->rb_left;
-		else if (result > 0)
-			node = node->rb_right;
-		else
+		if ((id & nhc->idmask) == nhc->id)
 			return nhc;
 	}
 
···
 int lowpan_nhc_check_compression(struct sk_buff *skb,
 				 const struct ipv6hdr *hdr, u8 **hc_ptr)
 {
-	struct lowpan_nhc *nhc;
+	const struct lowpan_nhc *nhc;
 	int ret = 0;
 
 	spin_lock_bh(&lowpan_nhc_lock);
···
 			      u8 **hc_ptr)
 {
 	int ret;
-	struct lowpan_nhc *nhc;
+	const struct lowpan_nhc *nhc;
 
 	spin_lock_bh(&lowpan_nhc_lock);
 
···
 				const struct net_device *dev,
 				struct ipv6hdr *hdr)
 {
-	struct lowpan_nhc *nhc;
+	const struct lowpan_nhc *nhc;
 	int ret;
 
 	spin_lock_bh(&lowpan_nhc_lock);
···
 	return 0;
 }
 
-int lowpan_nhc_add(struct lowpan_nhc *nhc)
+int lowpan_nhc_add(const struct lowpan_nhc *nhc)
 {
-	int ret;
-
-	if (!nhc->idlen || !nhc->idsetup)
-		return -EINVAL;
-
-	WARN_ONCE(nhc->idlen > LOWPAN_NHC_MAX_ID_LEN,
-		  "LOWPAN_NHC_MAX_ID_LEN should be updated to %zd.\n",
-		  nhc->idlen);
-
-	nhc->idsetup(nhc);
+	int ret = 0;
 
 	spin_lock_bh(&lowpan_nhc_lock);
 
···
 		goto out;
 	}
 
-	ret = lowpan_nhc_insert(nhc);
-	if (ret < 0)
-		goto out;
-
 	lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
 out:
 	spin_unlock_bh(&lowpan_nhc_lock);
···
 }
 EXPORT_SYMBOL(lowpan_nhc_add);
 
-void lowpan_nhc_del(struct lowpan_nhc *nhc)
+void lowpan_nhc_del(const struct lowpan_nhc *nhc)
 {
 	spin_lock_bh(&lowpan_nhc_lock);
 
-	lowpan_nhc_remove(nhc);
 	lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
 
 	spin_unlock_bh(&lowpan_nhc_lock);

net/6lowpan/nhc.h

···
  * @_name: const char * of common header compression name.
  * @_nexthdr: ipv6 nexthdr field for the header compression.
  * @_nexthdrlen: ipv6 nexthdr len for the reserved space.
- * @_idsetup: callback to setup id and mask values.
- * @_idlen: len for the next header id and mask, should be always the same.
+ * @_id: one byte nhc id value.
+ * @_idmask: one byte nhc id mask value.
  * @_uncompress: callback for uncompression call.
  * @_compress: callback for compression call.
  */
 #define LOWPAN_NHC(__nhc, _name, _nexthdr,	\
-		   _hdrlen, _idsetup, _idlen,	\
+		   _hdrlen, _id, _idmask,	\
 		   _uncompress, _compress)	\
-static u8 __nhc##_val[_idlen];			\
-static u8 __nhc##_mask[_idlen];			\
-static struct lowpan_nhc __nhc = {		\
+static const struct lowpan_nhc __nhc = {	\
 	.name		= _name,		\
 	.nexthdr	= _nexthdr,		\
 	.nexthdrlen	= _hdrlen,		\
-	.id		= __nhc##_val,		\
-	.idmask		= __nhc##_mask,		\
-	.idlen		= _idlen,		\
-	.idsetup	= _idsetup,		\
+	.id		= _id,			\
+	.idmask		= _idmask,		\
 	.uncompress	= _uncompress,		\
 	.compress	= _compress,		\
 }
···
 /**
  * struct lowpan_nhc - hold 6lowpan next hdr compression ifnformation
  *
- * @node: holder for the rbtree.
  * @name: name of the specific next header compression
  * @nexthdr: next header value of the protocol which should be compressed.
  * @nexthdrlen: ipv6 nexthdr len for the reserved space.
- * @id: array for nhc id. Note this need to be in network byteorder.
- * @mask: array for nhc id mask. Note this need to be in network byteorder.
- * @len: the length of the next header id and mask.
- * @setup: callback to setup fill the next header id value and mask.
+ * @id: one byte nhc id value.
+ * @idmask: one byte nhc id mask value.
  * @compress: callback to do the header compression.
  * @uncompress: callback to do the header uncompression.
  */
 struct lowpan_nhc {
-	struct rb_node	node;
 	const char	*name;
-	const u8	nexthdr;
-	const size_t	nexthdrlen;
-	u8		*id;
-	u8		*idmask;
-	const size_t	idlen;
+	u8		nexthdr;
+	size_t		nexthdrlen;
+	u8		id;
+	u8		idmask;
 
-	void		(*idsetup)(struct lowpan_nhc *nhc);
 	int		(*uncompress)(struct sk_buff *skb, size_t needed);
 	int		(*compress)(struct sk_buff *skb, u8 **hc_ptr);
 };
···
  *
  * @nhc: nhc which should be add.
  */
-int lowpan_nhc_add(struct lowpan_nhc *nhc);
+int lowpan_nhc_add(const struct lowpan_nhc *nhc);
 
 /**
  * lowpan_nhc_del - delete a next header compression from framework
  *
  * @nhc: nhc which should be delete.
  */
-void lowpan_nhc_del(struct lowpan_nhc *nhc);
+void lowpan_nhc_del(const struct lowpan_nhc *nhc);
 
 /**
  * lowpan_nhc_init - adding all default nhcs

net/6lowpan/nhc_dest.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_NHC_DEST_IDLEN	1
 #define LOWPAN_NHC_DEST_ID_0	0xe6
 #define LOWPAN_NHC_DEST_MASK_0	0xfe
 
-static void dest_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_DEST_ID_0;
-	nhc->idmask[0] = LOWPAN_NHC_DEST_MASK_0;
-}
-
 LOWPAN_NHC(nhc_dest, "RFC6282 Destination Options", NEXTHDR_DEST, 0,
-	   dest_nhid_setup, LOWPAN_NHC_DEST_IDLEN, NULL, NULL);
+	   LOWPAN_NHC_DEST_ID_0, LOWPAN_NHC_DEST_MASK_0,  NULL, NULL);
 
 module_lowpan_nhc(nhc_dest);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 Destination Options compression");

net/6lowpan/nhc_fragment.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_NHC_FRAGMENT_IDLEN	1
 #define LOWPAN_NHC_FRAGMENT_ID_0	0xe4
 #define LOWPAN_NHC_FRAGMENT_MASK_0	0xfe
 
-static void fragment_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_FRAGMENT_ID_0;
-	nhc->idmask[0] = LOWPAN_NHC_FRAGMENT_MASK_0;
-}
-
 LOWPAN_NHC(nhc_fragment, "RFC6282 Fragment", NEXTHDR_FRAGMENT, 0,
-	   fragment_nhid_setup, LOWPAN_NHC_FRAGMENT_IDLEN, NULL, NULL);
+	   LOWPAN_NHC_FRAGMENT_ID_0, LOWPAN_NHC_FRAGMENT_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(nhc_fragment);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 Fragment compression");

net/6lowpan/nhc_ghc_ext_dest.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_GHC_EXT_DEST_IDLEN	1
 #define LOWPAN_GHC_EXT_DEST_ID_0	0xb6
 #define LOWPAN_GHC_EXT_DEST_MASK_0	0xfe
 
-static void dest_ghid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_GHC_EXT_DEST_ID_0;
-	nhc->idmask[0] = LOWPAN_GHC_EXT_DEST_MASK_0;
-}
-
 LOWPAN_NHC(ghc_ext_dest, "RFC7400 Destination Extension Header", NEXTHDR_DEST,
-	   0, dest_ghid_setup, LOWPAN_GHC_EXT_DEST_IDLEN, NULL, NULL);
+	   0, LOWPAN_GHC_EXT_DEST_ID_0, LOWPAN_GHC_EXT_DEST_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(ghc_ext_dest);
 MODULE_DESCRIPTION("6LoWPAN generic header destination extension compression");

net/6lowpan/nhc_ghc_ext_frag.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_GHC_EXT_FRAG_IDLEN	1
 #define LOWPAN_GHC_EXT_FRAG_ID_0	0xb4
 #define LOWPAN_GHC_EXT_FRAG_MASK_0	0xfe
 
-static void frag_ghid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_GHC_EXT_FRAG_ID_0;
-	nhc->idmask[0] = LOWPAN_GHC_EXT_FRAG_MASK_0;
-}
-
 LOWPAN_NHC(ghc_ext_frag, "RFC7400 Fragmentation Extension Header",
-	   NEXTHDR_FRAGMENT, 0, frag_ghid_setup,
-	   LOWPAN_GHC_EXT_FRAG_IDLEN, NULL, NULL);
+	   NEXTHDR_FRAGMENT, 0, LOWPAN_GHC_EXT_FRAG_ID_0,
+	   LOWPAN_GHC_EXT_FRAG_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(ghc_ext_frag);
 MODULE_DESCRIPTION("6LoWPAN generic header fragmentation extension compression");

net/6lowpan/nhc_ghc_ext_hop.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_GHC_EXT_HOP_IDLEN	1
 #define LOWPAN_GHC_EXT_HOP_ID_0		0xb0
 #define LOWPAN_GHC_EXT_HOP_MASK_0	0xfe
 
-static void hop_ghid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_GHC_EXT_HOP_ID_0;
-	nhc->idmask[0] = LOWPAN_GHC_EXT_HOP_MASK_0;
-}
-
 LOWPAN_NHC(ghc_ext_hop, "RFC7400 Hop-by-Hop Extension Header", NEXTHDR_HOP, 0,
-	   hop_ghid_setup, LOWPAN_GHC_EXT_HOP_IDLEN, NULL, NULL);
+	   LOWPAN_GHC_EXT_HOP_ID_0, LOWPAN_GHC_EXT_HOP_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(ghc_ext_hop);
 MODULE_DESCRIPTION("6LoWPAN generic header hop-by-hop extension compression");

net/6lowpan/nhc_ghc_ext_route.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_GHC_EXT_ROUTE_IDLEN	1
 #define LOWPAN_GHC_EXT_ROUTE_ID_0	0xb2
 #define LOWPAN_GHC_EXT_ROUTE_MASK_0	0xfe
 
-static void route_ghid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_GHC_EXT_ROUTE_ID_0;
-	nhc->idmask[0] = LOWPAN_GHC_EXT_ROUTE_MASK_0;
-}
-
 LOWPAN_NHC(ghc_ext_route, "RFC7400 Routing Extension Header", NEXTHDR_ROUTING,
-	   0, route_ghid_setup, LOWPAN_GHC_EXT_ROUTE_IDLEN, NULL, NULL);
+	   0, LOWPAN_GHC_EXT_ROUTE_ID_0, LOWPAN_GHC_EXT_ROUTE_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(ghc_ext_route);
 MODULE_DESCRIPTION("6LoWPAN generic header routing extension compression");

net/6lowpan/nhc_ghc_icmpv6.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_GHC_ICMPV6_IDLEN		1
 #define LOWPAN_GHC_ICMPV6_ID_0		0xdf
 #define LOWPAN_GHC_ICMPV6_MASK_0	0xff
 
-static void icmpv6_ghid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_GHC_ICMPV6_ID_0;
-	nhc->idmask[0] = LOWPAN_GHC_ICMPV6_MASK_0;
-}
-
 LOWPAN_NHC(ghc_icmpv6, "RFC7400 ICMPv6", NEXTHDR_ICMP, 0,
-	   icmpv6_ghid_setup, LOWPAN_GHC_ICMPV6_IDLEN, NULL, NULL);
+	   LOWPAN_GHC_ICMPV6_ID_0, LOWPAN_GHC_ICMPV6_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(ghc_icmpv6);
 MODULE_DESCRIPTION("6LoWPAN generic header ICMPv6 compression");

net/6lowpan/nhc_ghc_udp.c

···
 
 #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);
+	   LOWPAN_GHC_UDP_ID_0, LOWPAN_GHC_UDP_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(ghc_udp);
 MODULE_DESCRIPTION("6LoWPAN generic header UDP compression");

net/6lowpan/nhc_hop.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_NHC_HOP_IDLEN	1
 #define LOWPAN_NHC_HOP_ID_0	0xe0
 #define LOWPAN_NHC_HOP_MASK_0	0xfe
 
-static void hop_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_HOP_ID_0;
-	nhc->idmask[0] = LOWPAN_NHC_HOP_MASK_0;
-}
-
 LOWPAN_NHC(nhc_hop, "RFC6282 Hop-by-Hop Options", NEXTHDR_HOP, 0,
-	   hop_nhid_setup, LOWPAN_NHC_HOP_IDLEN, NULL, NULL);
+	   LOWPAN_NHC_HOP_ID_0, LOWPAN_NHC_HOP_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(nhc_hop);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 Hop-by-Hop Options compression");

net/6lowpan/nhc_ipv6.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_NHC_IPV6_IDLEN	1
 #define LOWPAN_NHC_IPV6_ID_0	0xee
 #define LOWPAN_NHC_IPV6_MASK_0	0xfe
 
-static void ipv6_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_IPV6_ID_0;
-	nhc->idmask[0] = LOWPAN_NHC_IPV6_MASK_0;
-}
-
-LOWPAN_NHC(nhc_ipv6, "RFC6282 IPv6", NEXTHDR_IPV6, 0, ipv6_nhid_setup,
-	   LOWPAN_NHC_IPV6_IDLEN, NULL, NULL);
+LOWPAN_NHC(nhc_ipv6, "RFC6282 IPv6", NEXTHDR_IPV6, 0, LOWPAN_NHC_IPV6_ID_0,
+	   LOWPAN_NHC_IPV6_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(nhc_ipv6);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 IPv6 compression");

net/6lowpan/nhc_mobility.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_NHC_MOBILITY_IDLEN	1
 #define LOWPAN_NHC_MOBILITY_ID_0	0xe8
 #define LOWPAN_NHC_MOBILITY_MASK_0	0xfe
 
-static void mobility_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_MOBILITY_ID_0;
-	nhc->idmask[0] = LOWPAN_NHC_MOBILITY_MASK_0;
-}
-
 LOWPAN_NHC(nhc_mobility, "RFC6282 Mobility", NEXTHDR_MOBILITY, 0,
-	   mobility_nhid_setup, LOWPAN_NHC_MOBILITY_IDLEN, NULL, NULL);
+	   LOWPAN_NHC_MOBILITY_ID_0, LOWPAN_NHC_MOBILITY_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(nhc_mobility);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 Mobility compression");

net/6lowpan/nhc_routing.c

···
 
 #include "nhc.h"
 
-#define LOWPAN_NHC_ROUTING_IDLEN	1
 #define LOWPAN_NHC_ROUTING_ID_0		0xe2
 #define LOWPAN_NHC_ROUTING_MASK_0	0xfe
 
-static void routing_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_ROUTING_ID_0;
-	nhc->idmask[0] = LOWPAN_NHC_ROUTING_MASK_0;
-}
-
 LOWPAN_NHC(nhc_routing, "RFC6282 Routing", NEXTHDR_ROUTING, 0,
-	   routing_nhid_setup, LOWPAN_NHC_ROUTING_IDLEN, NULL, NULL);
+	   LOWPAN_NHC_ROUTING_ID_0, LOWPAN_NHC_ROUTING_MASK_0, NULL, NULL);
 
 module_lowpan_nhc(nhc_routing);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 Routing compression");

net/6lowpan/nhc_udp.c

···
 
 #define LOWPAN_NHC_UDP_MASK		0xF8
 #define LOWPAN_NHC_UDP_ID		0xF0
-#define LOWPAN_NHC_UDP_IDLEN		1
 
 #define LOWPAN_NHC_UDP_4BIT_PORT	0xF0B0
 #define LOWPAN_NHC_UDP_4BIT_MASK	0xFFF0
···
 	return 0;
 }
 
-static void udp_nhid_setup(struct lowpan_nhc *nhc)
-{
-	nhc->id[0] = LOWPAN_NHC_UDP_ID;
-	nhc->idmask[0] = LOWPAN_NHC_UDP_MASK;
-}
-
 LOWPAN_NHC(nhc_udp, "RFC6282 UDP", NEXTHDR_UDP, sizeof(struct udphdr),
-	   udp_nhid_setup, LOWPAN_NHC_UDP_IDLEN, udp_uncompress, udp_compress);
+	   LOWPAN_NHC_UDP_ID, LOWPAN_NHC_UDP_MASK, udp_uncompress, udp_compress);
 
 module_lowpan_nhc(nhc_udp);
 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 UDP compression");