ieee802154: add definitions for link-layer security and header functions

When dealing with 802.15.4, one often has to know the maximum payload
size for a given packet. This depends on many factors, one of which is
whether or not a security header is present in the frame. These
definitions and functions provide an easy way for any upper layer to
calculate the maximum payload size for a packet. The first obvious user
for this is 6lowpan, which duplicates this calculation and gets it
partially wrong because it ignores security headers.

Signed-off-by: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 0 deletions

diff --git a/include/net/ieee802154_netdev.h b/include/net/ieee802154_netdev.h
index 5a719ca892f4..6e4d3e1071b5 100644
--- a/include/net/ieee802154_netdev.h
+++ b/include/net/ieee802154_netdev.h
@@ -27,6 +27,7 @@
 #ifndef IEEE802154_NETDEVICE_H
 #define IEEE802154_NETDEVICE_H
 
+#include <net/ieee802154.h>
 #include <net/af_ieee802154.h>
 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
@@ -114,6 +115,34 @@ int ieee802154_hdr_pull(struct sk_buff *skb, struct ieee802154_hdr *hdr);
 int ieee802154_hdr_peek_addrs(const struct sk_buff *skb,
 			      struct ieee802154_hdr *hdr);
 
+/* parses the full 802.15.4 header a given skb and stores them into hdr,
+ * performing pan id decompression and length checks to be suitable for use in
+ * header_ops.parse
+ */
+int ieee802154_hdr_peek(const struct sk_buff *skb, struct ieee802154_hdr *hdr);
+
+int ieee802154_max_payload(const struct ieee802154_hdr *hdr);
+
+static inline int
+ieee802154_sechdr_authtag_len(const struct ieee802154_sechdr *sec)
+{
+	switch (sec->level) {
+	case IEEE802154_SCF_SECLEVEL_MIC32:
+	case IEEE802154_SCF_SECLEVEL_ENC_MIC32:
+		return 4;
+	case IEEE802154_SCF_SECLEVEL_MIC64:
+	case IEEE802154_SCF_SECLEVEL_ENC_MIC64:
+		return 8;
+	case IEEE802154_SCF_SECLEVEL_MIC128:
+	case IEEE802154_SCF_SECLEVEL_ENC_MIC128:
+		return 16;
+	case IEEE802154_SCF_SECLEVEL_NONE:
+	case IEEE802154_SCF_SECLEVEL_ENC:
+	default:
+		return 0;
+	}
+}
+
 static inline int ieee802154_hdr_length(struct sk_buff *skb)
 {
 	struct ieee802154_hdr hdr;