6lowpan: iphc: add support for stateful compression

This patch introduce support for IPHC stateful address compression. It
will offer the context table via one debugfs entry.
This debugfs has and directory for each cid entry for the context table.
Inside each cid directory there exists the following files:

 - "active": If the entry is added or deleted. The context table is
   original a list implementation, this flag will indicate if the
   context is part of list or not.
 - "prefix": The ipv6 prefix.
 - "prefix_length": The prefix length for the prefix.
 - "compression": The compression flag according RFC6775.

This part should be moved into sysfs after some testing time.

Also the debugfs entry contains a "show" file which is a pretty-printout
for the current context table information.

Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <aar@pengutronix.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
index 2f6a3f2233ed..da3a77d25fcb 100644
--- a/include/net/6lowpan.h
+++ b/include/net/6lowpan.h
@@ -75,6 +75,8 @@
 #define LOWPAN_IPHC_MAX_HC_BUF_LEN	(sizeof(struct ipv6hdr) +	\
 					 LOWPAN_IPHC_MAX_HEADER_LEN +	\
 					 LOWPAN_NHC_MAX_HDR_LEN)
+/* SCI/DCI is 4 bit width, so we have maximum 16 entries */
+#define LOWPAN_IPHC_CTX_TABLE_SIZE	(1 << 4)
 
 #define LOWPAN_DISPATCH_IPV6		0x41 /* 01000001 = 65 */
 #define LOWPAN_DISPATCH_IPHC		0x60 /* 011xxxxx = ... */
@@ -98,9 +100,39 @@ enum lowpan_lltypes {
 	LOWPAN_LLTYPE_IEEE802154,
 };
 
+enum lowpan_iphc_ctx_flags {
+	LOWPAN_IPHC_CTX_FLAG_ACTIVE,
+	LOWPAN_IPHC_CTX_FLAG_COMPRESSION,
+};
+
+struct lowpan_iphc_ctx {
+	u8 id;
+	struct in6_addr pfx;
+	u8 plen;
+	unsigned long flags;
+};
+
+struct lowpan_iphc_ctx_table {
+	spinlock_t lock;
+	const struct lowpan_iphc_ctx_ops *ops;
+	struct lowpan_iphc_ctx table[LOWPAN_IPHC_CTX_TABLE_SIZE];
+};
+
+static inline bool lowpan_iphc_ctx_is_active(const struct lowpan_iphc_ctx *ctx)
+{
+	return test_bit(LOWPAN_IPHC_CTX_FLAG_ACTIVE, &ctx->flags);
+}
+
+static inline bool
+lowpan_iphc_ctx_is_compression(const struct lowpan_iphc_ctx *ctx)
+{
+	return test_bit(LOWPAN_IPHC_CTX_FLAG_COMPRESSION, &ctx->flags);
+}
+
 struct lowpan_priv {
 	enum lowpan_lltypes lltype;
 	struct dentry *iface_debugfs;
+	struct lowpan_iphc_ctx_table ctx;
 
 	/* must be last */
 	u8 priv[0] __aligned(sizeof(void *));