This patch adds a generic next header compression layer interface. There
exists various methods to do a header compression after 6LoWPAN header
to save payload. This introduce a generic nhc header which allow a
simple adding of a new header compression format instead of a static
implementation inside the 6LoWPAN header compression and uncompression
function.
Signed-off-by: Alexander Aring <alex.aring@xxxxxxxxx>
Cc: Jukka Rissanen <jukka.rissanen@xxxxxxxxxxxxxxx>
Cc: Martin Townsend <mtownsend1973@xxxxxxxxx>
---
net/6lowpan/Makefile | 2 +-
net/6lowpan/nhc.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++
net/6lowpan/nhc.h | 142 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 283 insertions(+), 1 deletion(-)
create mode 100644 net/6lowpan/nhc.c
create mode 100644 net/6lowpan/nhc.h
diff --git a/net/6lowpan/Makefile b/net/6lowpan/Makefile
index 415886b..4215602 100644
--- a/net/6lowpan/Makefile
+++ b/net/6lowpan/Makefile
@@ -1,3 +1,3 @@
obj-$(CONFIG_6LOWPAN) := 6lowpan.o
-6lowpan-y := iphc.o
+6lowpan-y := iphc.o nhc.o
diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
new file mode 100644
index 0000000..8c4438c
--- /dev/null
+++ b/net/6lowpan/nhc.c
@@ -0,0 +1,140 @@
+/*
+ * 6LoWPAN next header compression
+ *
+ *
+ * Authors:
+ * Alexander Aring <aar@xxxxxxxxxxxxxx>
+ *
+ * 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 <linux/netdevice.h>
+
+#include <net/ipv6.h>
+
+#include "nhc.h"
+
+static struct rb_root rb_root = RB_ROOT;
+static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
+
+static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
+{
+ struct rb_node **new = &rb_root.rb_node, *parent = NULL;
+
+ /* Figure out where to put new node */
+ while (*new) {
+ struct lowpan_nhc *this = container_of(*new, struct lowpan_nhc,
+ node);
+ int result, len_dif, len;
+
+ len_dif = nhc->idlen - this->idlen;
+
+ if (nhc->idlen < this->idlen)
+ len = nhc->idlen;
+ else
+ len = this->idlen;
+
+ 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);
+}
+
+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 = container_of(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
+ return nhc;
+ }
+
+ return NULL;
+}
+
+struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr)
+{
+ return lowpan_nexthdr_nhcs[nexthdr];
+}
+
+int lowpan_nhc_add(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 %d.\n",
+ nhc->idlen);
+
+ nhc->idsetup(nhc);
+
+ rtnl_lock();
+ if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
+ ret = -EEXIST;
+ goto out;
+ }
+
+ ret = lowpan_nhc_insert(nhc);
+ if (ret < 0)
+ goto out;
+
+ lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
+out:
+ rtnl_unlock();
+ return ret;
+}
+EXPORT_SYMBOL(lowpan_nhc_add);
+
+void lowpan_nhc_del(struct lowpan_nhc *nhc)
+{
+ rtnl_lock();
+ lowpan_nhc_remove(nhc);
+ lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
+
+ synchronize_net();
+ rtnl_unlock();
+}
+EXPORT_SYMBOL(lowpan_nhc_del);
diff --git a/net/6lowpan/nhc.h b/net/6lowpan/nhc.h
new file mode 100644
index 0000000..7141b94
--- /dev/null
+++ b/net/6lowpan/nhc.h
@@ -0,0 +1,142 @@
+#ifndef __6LOWPAN_NHC_H
+#define __6LOWPAN_NHC_H
+
+#include <linux/skbuff.h>
+#include <linux/rbtree.h>
+#include <linux/module.h>
+
+#include <net/6lowpan.h>
+#include <net/ipv6.h>
+
+#define LOWPAN_NHC_MAX_ID_LEN 1
+
+/**
+ * LOWPAN_NHC - helper macro to generate nh id fields and lowpan_nhc struct
+ *
+ * @__nhc: variable name of the lowpan_nhc struct.
+ * @_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.
+ * @_uncompress: callback for uncompression call.
+ * @_compress: callback for compression call.
+ */
+#define LOWPAN_NHC(__nhc, _name, _nexthdr, \
+ _hdrlen, _idsetup, _idlen, \
+ _uncompress, _compress) \
+static u8 __nhc##_val[_idlen]; \
+static u8 __nhc##_mask[_idlen]; \
+static struct lowpan_nhc __nhc = { \
+ .name = _name, \
+ .nexthdr = _nexthdr, \
+ .nexthdrlen = _hdrlen, \
+ .id = __nhc##_val, \
+ .idmask = __nhc##_mask, \
+ .idlen = _idlen, \
+ .idsetup = _idsetup, \
+ .uncompress = _uncompress, \
+ .compress = _compress, \
+}
+
+#define module_lowpan_nhc(__nhc) \
+static int __init __nhc##_init(void) \
+{ \
+ return lowpan_nhc_add(&(__nhc)); \
+} \
+module_init(__nhc##_init); \
+static void __exit __nhc##_exit(void) \
+{ \
+ lowpan_nhc_del(&(__nhc)); \
+} \
+module_exit(__nhc##_exit);
+
+/**
+ * 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.
+ * @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;
+
+ void (*idsetup)(struct lowpan_nhc *nhc);
+ int (*uncompress)(struct sk_buff *skb, size_t needed);
+ int (*compress)(struct sk_buff *skb, u8 **hc_ptr);
+};
+
+/**
+ * lowpan_nhc_by_nhcid - returns the 6lowpan nhc by nhcid
+ *
+ * @skb: skb with skb->data which is pointed to 6lowpan nhc id.
+ */
+struct lowpan_nhc *lowpan_nhc_by_nhcid(const struct sk_buff *skb);
+
+/**
+ * lowpan_nhc_by_nexthdr - return the 6lowpan nhc by ipv6 nexthdr.
+ *
+ * @nexthdr: ipv6 nexthdr value.
+ */
+struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr);
+
+/**
+ * lowpan_nhc_do_compression - calling compress callback for nhc
+ *
+ * @nhc: 6LoWPAN nhc context, get by lowpan_nhc_by_ functions.
+ * @skb: skb of 6LoWPAN header to read nhc and replace header.
+ * @hc_ptr: pointer for 6LoWPAN header which should increment at the end of
+ * replaced header.
+ */
+static inline int
+lowpan_nhc_do_compression(struct lowpan_nhc *nhc, struct sk_buff *skb,
+ u8 **hc_ptr)
+{
+ return nhc->compress(skb, hc_ptr);
+}
+
+/**
+ * lowpan_nhc_do_uncompression - calling uncompress callback for nhc
+ *
+ * @nhc: 6LoWPAN nhc context, get by lowpan_nhc_by_ functions.
+ * @skb: skb of 6LoWPAN header, skb->data should be pointed to nhc id value.
+ */
+static inline int
+lowpan_nhc_do_uncompression(struct lowpan_nhc *nhc, struct sk_buff *skb)
+{
+ return nhc->uncompress(skb, sizeof(struct ipv6hdr) + nhc->nexthdrlen);
+}
+
+/**
+ * lowpan_nhc_add - register a next header compression to framework
+ *
+ * @nhc: nhc which should be add.
+ */
+int lowpan_nhc_add(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);
+
+/**
+ * lowpan_nhc_init - adding all default nhcs
+ */
+void lowpan_nhc_init(void);
+
+#endif /* __6LOWPAN_NHC_H */
--
2.1.3
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