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Commit c3a6114f authored by Phoebe Buckheister's avatar Phoebe Buckheister Committed by David S. Miller
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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: default avatarPhoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9dbccc30

include/net/ieee802154.h

+9 −0
Original line number Diff line number Diff line
@@ -79,6 +79,15 @@ 
#define IEEE802154_SCF_KEY_SHORT_INDEX		2

#define IEEE802154_SCF_KEY_HW_INDEX		3



#define IEEE802154_SCF_SECLEVEL_NONE		0

#define IEEE802154_SCF_SECLEVEL_MIC32		1

#define IEEE802154_SCF_SECLEVEL_MIC64		2

#define IEEE802154_SCF_SECLEVEL_MIC128		3

#define IEEE802154_SCF_SECLEVEL_ENC		4

#define IEEE802154_SCF_SECLEVEL_ENC_MIC32	5

#define IEEE802154_SCF_SECLEVEL_ENC_MIC64	6

#define IEEE802154_SCF_SECLEVEL_ENC_MIC128	7



/* MAC footer size */

#define IEEE802154_MFR_SIZE	2 /* 2 octets */

include/net/ieee802154_netdev.h

+29 −0
Original line number Diff line number Diff line
@@ -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;

net/ieee802154/header_ops.c

+45 −7
Original line number Diff line number Diff line
@@ -195,15 +195,16 @@ ieee802154_hdr_get_sechdr(const u8 *buf, struct ieee802154_sechdr *hdr) 
	return pos;

}



static int ieee802154_sechdr_lengths[4] = {

	[IEEE802154_SCF_KEY_IMPLICIT] = 5,

	[IEEE802154_SCF_KEY_INDEX] = 6,

	[IEEE802154_SCF_KEY_SHORT_INDEX] = 10,

	[IEEE802154_SCF_KEY_HW_INDEX] = 14,

};



static int ieee802154_hdr_sechdr_len(u8 sc)

{

	switch (IEEE802154_SCF_KEY_ID_MODE(sc)) {

	case IEEE802154_SCF_KEY_IMPLICIT: return 5;

	case IEEE802154_SCF_KEY_INDEX: return 6;

	case IEEE802154_SCF_KEY_SHORT_INDEX: return 10;

	case IEEE802154_SCF_KEY_HW_INDEX: return 14;

	default: return -EINVAL;

	}

	return ieee802154_sechdr_lengths[IEEE802154_SCF_KEY_ID_MODE(sc)];

}



static int ieee802154_hdr_minlen(const struct ieee802154_hdr *hdr)
@@ -285,3 +286,40 @@ ieee802154_hdr_peek_addrs(const struct sk_buff *skb, struct ieee802154_hdr *hdr) 
	return pos;

}

EXPORT_SYMBOL_GPL(ieee802154_hdr_peek_addrs);



int

ieee802154_hdr_peek(const struct sk_buff *skb, struct ieee802154_hdr *hdr)

{

	const u8 *buf = skb_mac_header(skb);

	int pos;



	pos = ieee802154_hdr_peek_addrs(skb, hdr);

	if (pos < 0)

		return -EINVAL;



	if (hdr->fc.security_enabled) {

		u8 key_id_mode = IEEE802154_SCF_KEY_ID_MODE(*(buf + pos));

		int want = pos + ieee802154_sechdr_lengths[key_id_mode];



		if (buf + want > skb_tail_pointer(skb))

			return -EINVAL;



		pos += ieee802154_hdr_get_sechdr(buf + pos, &hdr->sec);

	}



	return pos;

}

EXPORT_SYMBOL_GPL(ieee802154_hdr_peek);



int ieee802154_max_payload(const struct ieee802154_hdr *hdr)

{

	int hlen = ieee802154_hdr_minlen(hdr);



	if (hdr->fc.security_enabled) {

		hlen += ieee802154_sechdr_lengths[hdr->sec.key_id_mode] - 1;

		hlen += ieee802154_sechdr_authtag_len(&hdr->sec);

	}



	return IEEE802154_MTU - hlen - IEEE802154_MFR_SIZE;

}

EXPORT_SYMBOL_GPL(ieee802154_max_payload);