6lowpan: introduce LOWPAN_IPHC_MAX_HC_BUF_LEN
This patch introduces the LOWPAN_IPHC_MAX_HC_BUF_LEN define which
represent the worst-case supported IPHC buffer length. It's used to
allocate the stack buffer space for creating the IPHC header.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
index 07db532..aa5a823 100644
--- a/include/net/6lowpan.h
+++ b/include/net/6lowpan.h
@@ -64,12 +64,20 @@
#define EUI64_ADDR_LEN 8
#define LOWPAN_NHC_MAX_ID_LEN 1
+/* Maximum next header compression length which we currently support inclusive
+ * possible inline data.
+ */
+#define LOWPAN_NHC_MAX_HDR_LEN (sizeof(struct udphdr))
/* Max IPHC Header len without IPv6 hdr specific inline data.
* Useful for getting the "extra" bytes we need at worst case compression.
*
* LOWPAN_IPHC + CID + LOWPAN_NHC_MAX_ID_LEN
*/
#define LOWPAN_IPHC_MAX_HEADER_LEN (2 + 1 + LOWPAN_NHC_MAX_ID_LEN)
+/* Maximum worst case IPHC header buffer size */
+#define LOWPAN_IPHC_MAX_HC_BUF_LEN (sizeof(struct ipv6hdr) + \
+ LOWPAN_IPHC_MAX_HEADER_LEN + \
+ LOWPAN_NHC_MAX_HDR_LEN)
/*
* ipv6 address based on mac