ieee802154: add header structs with endiannes and operations

This patch provides a set of structures to represent 802.15.4 MAC
headers, and a set of operations to push/pull/peek these structs from
skbs. We cannot simply pointer-cast the skb MAC header pointer to these
structs, because 802.15.4 headers are wildly variable - depending on the
first three bytes, virtually all other fields of the header may be
present or not, and be present with different lengths.

The new header creation/parsing routines also support 802.15.4 security
headers, which are currently not supported by the mac802154
implementation of the protocol.
Signed-off-by: NPhoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/ieee802154.h

@@ -42,22 +42,42 @@
 	    (((x) << IEEE802154_FC_TYPE_SHIFT) & IEEE802154_FC_TYPE_MASK)); \
 	} while (0)
 
-#define IEEE802154_FC_SECEN		(1 << 3)
-#define IEEE802154_FC_FRPEND		(1 << 4)
-#define IEEE802154_FC_ACK_REQ		(1 << 5)
-#define IEEE802154_FC_INTRA_PAN		(1 << 6)
+#define IEEE802154_FC_SECEN_SHIFT	3
+#define IEEE802154_FC_SECEN		(1 << IEEE802154_FC_SECEN_SHIFT)
+#define IEEE802154_FC_FRPEND_SHIFT	4
+#define IEEE802154_FC_FRPEND		(1 << IEEE802154_FC_FRPEND_SHIFT)
+#define IEEE802154_FC_ACK_REQ_SHIFT	5
+#define IEEE802154_FC_ACK_REQ		(1 << IEEE802154_FC_ACK_REQ_SHIFT)
+#define IEEE802154_FC_INTRA_PAN_SHIFT	6
+#define IEEE802154_FC_INTRA_PAN		(1 << IEEE802154_FC_INTRA_PAN_SHIFT)
 
 #define IEEE802154_FC_SAMODE_SHIFT	14
 #define IEEE802154_FC_SAMODE_MASK	(3 << IEEE802154_FC_SAMODE_SHIFT)
 #define IEEE802154_FC_DAMODE_SHIFT	10
 #define IEEE802154_FC_DAMODE_MASK	(3 << IEEE802154_FC_DAMODE_SHIFT)
 
+#define IEEE802154_FC_VERSION_SHIFT	12
+#define IEEE802154_FC_VERSION_MASK	(3 << IEEE802154_FC_VERSION_SHIFT)
+#define IEEE802154_FC_VERSION(x)	((x & IEEE802154_FC_VERSION_MASK) >> IEEE802154_FC_VERSION_SHIFT)
+
 #define IEEE802154_FC_SAMODE(x)		\
 	(((x) & IEEE802154_FC_SAMODE_MASK) >> IEEE802154_FC_SAMODE_SHIFT)
 
 #define IEEE802154_FC_DAMODE(x)		\
 	(((x) & IEEE802154_FC_DAMODE_MASK) >> IEEE802154_FC_DAMODE_SHIFT)
 
+#define IEEE802154_SCF_SECLEVEL_MASK		7
+#define IEEE802154_SCF_SECLEVEL_SHIFT		0
+#define IEEE802154_SCF_SECLEVEL(x)		(x & IEEE802154_SCF_SECLEVEL_MASK)
+#define IEEE802154_SCF_KEY_ID_MODE_SHIFT	3
+#define IEEE802154_SCF_KEY_ID_MODE_MASK		(3 << IEEE802154_SCF_KEY_ID_MODE_SHIFT)
+#define IEEE802154_SCF_KEY_ID_MODE(x)		\
+	((x & IEEE802154_SCF_KEY_ID_MODE_MASK) >> IEEE802154_SCF_KEY_ID_MODE_SHIFT)
+
+#define IEEE802154_SCF_KEY_IMPLICIT		0
+#define IEEE802154_SCF_KEY_INDEX		1
+#define IEEE802154_SCF_KEY_SHORT_INDEX		2
+#define IEEE802154_SCF_KEY_HW_INDEX		3
 
 /* MAC footer size */
 #define IEEE802154_MFR_SIZE	2 /* 2 octets */

include/net/ieee802154_netdev.h

@@ -28,6 +28,28 @@
 #define IEEE802154_NETDEVICE_H
 
 #include <net/af_ieee802154.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+
+struct ieee802154_sechdr {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	u8 level:3,
+	   key_id_mode:2,
+	   reserved:3;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	u8 reserved:3,
+	   key_id_mode:2,
+	   level:3;
+#else
+#error	"Please fix <asm/byteorder.h>"
+#endif
+	u8 key_id;
+	__le32 frame_counter;
+	union {
+		__le32 short_src;
+		__le64 extended_src;
+	};
+};
 
 struct ieee802154_addr {
 	u8 mode;
@@ -38,6 +60,71 @@ struct ieee802154_addr {
 	};
 };
 
+struct ieee802154_hdr_fc {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	u16 type:3,
+	    security_enabled:1,
+	    frame_pending:1,
+	    ack_request:1,
+	    intra_pan:1,
+	    reserved:3,
+	    dest_addr_mode:2,
+	    version:2,
+	    source_addr_mode:2;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	u16 reserved:1,
+	    intra_pan:1,
+	    ack_request:1,
+	    frame_pending:1,
+	    security_enabled:1,
+	    type:3,
+	    source_addr_mode:2,
+	    version:2,
+	    dest_addr_mode:2,
+	    reserved2:2;
+#else
+#error	"Please fix <asm/byteorder.h>"
+#endif
+};
+
+struct ieee802154_hdr {
+	struct ieee802154_hdr_fc fc;
+	u8 seq;
+	struct ieee802154_addr source;
+	struct ieee802154_addr dest;
+	struct ieee802154_sechdr sec;
+};
+
+/* pushes hdr onto the skb. fields of hdr->fc that can be calculated from
+ * the contents of hdr will be, and the actual value of those bits in
+ * hdr->fc will be ignored. this includes the INTRA_PAN bit and the frame
+ * version, if SECEN is set.
+ */
+int ieee802154_hdr_push(struct sk_buff *skb, const struct ieee802154_hdr *hdr);
+
+/* pulls the entire 802.15.4 header off of the skb, including the security
+ * header, and performs pan id decompression
+ */
+int ieee802154_hdr_pull(struct sk_buff *skb, struct ieee802154_hdr *hdr);
+
+/* parses the frame control, sequence number of address fields in 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_addrs(const struct sk_buff *skb,
+			      struct ieee802154_hdr *hdr);
+
+static inline int ieee802154_hdr_length(struct sk_buff *skb)
+{
+	struct ieee802154_hdr hdr;
+	int len = ieee802154_hdr_pull(skb, &hdr);
+
+	if (len > 0)
+		skb_push(skb, len);
+
+	return len;
+}
+
 static inline bool ieee802154_addr_equal(const struct ieee802154_addr *a1,
 					 const struct ieee802154_addr *a2)
 {

include/net/mac802154.h

@@ -20,6 +20,7 @@
 #define NET_MAC802154_H
 
 #include <net/af_ieee802154.h>
+#include <linux/skbuff.h>
 
 /* General MAC frame format:
  *  2 bytes: Frame Control

net/ieee802154/Makefile

@@ -3,7 +3,8 @@ obj-$(CONFIG_IEEE802154_6LOWPAN) += 6lowpan.o
 obj-$(CONFIG_6LOWPAN_IPHC) += 6lowpan_iphc.o
 
 6lowpan-y := 6lowpan_rtnl.o reassembly.o
-ieee802154-y := netlink.o nl-mac.o nl-phy.o nl_policy.o wpan-class.o
+ieee802154-y := netlink.o nl-mac.o nl-phy.o nl_policy.o wpan-class.o \
+                header_ops.o
 af_802154-y := af_ieee802154.o raw.o dgram.o
 
 ccflags-y += -D__CHECK_ENDIAN__

net/ieee802154/header_ops.c

+/*
+ * Copyright (C) 2014 Fraunhofer ITWM
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Written by:
+ * Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
+ */
+
+#include <net/mac802154.h>
+#include <net/ieee802154.h>
+#include <net/ieee802154_netdev.h>
+
+static int
+ieee802154_hdr_push_addr(u8 *buf, const struct ieee802154_addr *addr,
+			 bool omit_pan)
+{
+	int pos = 0;
+
+	if (addr->mode == IEEE802154_ADDR_NONE)
+		return 0;
+
+	if (!omit_pan) {
+		memcpy(buf + pos, &addr->pan_id, 2);
+		pos += 2;
+	}
+
+	switch (addr->mode) {
+	case IEEE802154_ADDR_SHORT:
+		memcpy(buf + pos, &addr->short_addr, 2);
+		pos += 2;
+		break;
+
+	case IEEE802154_ADDR_LONG:
+		memcpy(buf + pos, &addr->extended_addr, IEEE802154_ADDR_LEN);
+		pos += IEEE802154_ADDR_LEN;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return pos;
+}
+
+static int
+ieee802154_hdr_push_sechdr(u8 *buf, const struct ieee802154_sechdr *hdr)
+{
+	int pos = 5;
+
+	memcpy(buf, hdr, 1);
+	memcpy(buf + 1, &hdr->frame_counter, 4);
+
+	switch (hdr->key_id_mode) {
+	case IEEE802154_SCF_KEY_IMPLICIT:
+		return pos;
+
+	case IEEE802154_SCF_KEY_INDEX:
+		break;
+
+	case IEEE802154_SCF_KEY_SHORT_INDEX:
+		memcpy(buf + pos, &hdr->short_src, 4);
+		pos += 4;
+		break;
+
+	case IEEE802154_SCF_KEY_HW_INDEX:
+		memcpy(buf + pos, &hdr->extended_src, IEEE802154_ADDR_LEN);
+		pos += IEEE802154_ADDR_LEN;
+		break;
+	}
+
+	buf[pos++] = hdr->key_id;
+
+	return pos;
+}
+
+int
+ieee802154_hdr_push(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
+{
+	u8 buf[MAC802154_FRAME_HARD_HEADER_LEN];
+	int pos = 2;
+	int rc;
+	struct ieee802154_hdr_fc fc = hdr->fc;
+
+	buf[pos++] = hdr->seq;
+
+	fc.dest_addr_mode = hdr->dest.mode;
+
+	rc = ieee802154_hdr_push_addr(buf + pos, &hdr->dest, false);
+	if (rc < 0)
+		return -EINVAL;
+	pos += rc;
+
+	fc.source_addr_mode = hdr->source.mode;
+
+	if (hdr->source.pan_id == hdr->dest.pan_id &&
+	    hdr->dest.mode != IEEE802154_ADDR_NONE)
+		fc.intra_pan = true;
+
+	rc = ieee802154_hdr_push_addr(buf + pos, &hdr->source, fc.intra_pan);
+	if (rc < 0)
+		return -EINVAL;
+	pos += rc;
+
+	if (fc.security_enabled) {
+		fc.version = 1;
+
+		rc = ieee802154_hdr_push_sechdr(buf + pos, &hdr->sec);
+		if (rc < 0)
+			return -EINVAL;
+
+		pos += rc;
+	}
+
+	memcpy(buf, &fc, 2);
+
+	memcpy(skb_push(skb, pos), buf, pos);
+
+	return pos;
+}
+EXPORT_SYMBOL_GPL(ieee802154_hdr_push);
+
+static int
+ieee802154_hdr_get_addr(const u8 *buf, int mode, bool omit_pan,
+			struct ieee802154_addr *addr)
+{
+	int pos = 0;
+
+	addr->mode = mode;
+
+	if (mode == IEEE802154_ADDR_NONE)
+		return 0;
+
+	if (!omit_pan) {
+		memcpy(&addr->pan_id, buf + pos, 2);
+		pos += 2;
+	}
+
+	if (mode == IEEE802154_ADDR_SHORT) {
+		memcpy(&addr->short_addr, buf + pos, 2);
+		return pos + 2;
+	} else {
+		memcpy(&addr->extended_addr, buf + pos, IEEE802154_ADDR_LEN);
+		return pos + IEEE802154_ADDR_LEN;
+	}
+}
+
+static int ieee802154_hdr_addr_len(int mode, bool omit_pan)
+{
+	int pan_len = omit_pan ? 0 : 2;
+
+	switch (mode) {
+	case IEEE802154_ADDR_NONE: return 0;
+	case IEEE802154_ADDR_SHORT: return 2 + pan_len;
+	case IEEE802154_ADDR_LONG: return IEEE802154_ADDR_LEN + pan_len;
+	default: return -EINVAL;
+	}
+}
+
+static int
+ieee802154_hdr_get_sechdr(const u8 *buf, struct ieee802154_sechdr *hdr)
+{
+	int pos = 5;
+
+	memcpy(hdr, buf, 1);
+	memcpy(&hdr->frame_counter, buf + 1, 4);
+
+	switch (hdr->key_id_mode) {
+	case IEEE802154_SCF_KEY_IMPLICIT:
+		return pos;
+
+	case IEEE802154_SCF_KEY_INDEX:
+		break;
+
+	case IEEE802154_SCF_KEY_SHORT_INDEX:
+		memcpy(&hdr->short_src, buf + pos, 4);
+		pos += 4;
+		break;
+
+	case IEEE802154_SCF_KEY_HW_INDEX:
+		memcpy(&hdr->extended_src, buf + pos, IEEE802154_ADDR_LEN);
+		pos += IEEE802154_ADDR_LEN;
+		break;
+	}
+
+	hdr->key_id = buf[pos++];
+
+	return pos;
+}
+
+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;
+	}
+}
+
+static int ieee802154_hdr_minlen(const struct ieee802154_hdr *hdr)
+{
+	int dlen, slen;
+
+	dlen = ieee802154_hdr_addr_len(hdr->fc.dest_addr_mode, false);
+	slen = ieee802154_hdr_addr_len(hdr->fc.source_addr_mode,
+				       hdr->fc.intra_pan);
+
+	if (slen < 0 || dlen < 0)
+		return -EINVAL;
+
+	return 3 + dlen + slen + hdr->fc.security_enabled;
+}
+
+static int
+ieee802154_hdr_get_addrs(const u8 *buf, struct ieee802154_hdr *hdr)
+{
+	int pos = 0;
+
+	pos += ieee802154_hdr_get_addr(buf + pos, hdr->fc.dest_addr_mode,
+				       false, &hdr->dest);
+	pos += ieee802154_hdr_get_addr(buf + pos, hdr->fc.source_addr_mode,
+				       hdr->fc.intra_pan, &hdr->source);
+
+	if (hdr->fc.intra_pan)
+		hdr->source.pan_id = hdr->dest.pan_id;
+
+	return pos;
+}
+
+int
+ieee802154_hdr_pull(struct sk_buff *skb, struct ieee802154_hdr *hdr)
+{
+	int pos = 3, rc;
+
+	if (!pskb_may_pull(skb, 3))
+		return -EINVAL;
+
+	memcpy(hdr, skb->data, 3);
+
+	rc = ieee802154_hdr_minlen(hdr);
+	if (rc < 0 || !pskb_may_pull(skb, rc))
+		return -EINVAL;
+
+	pos += ieee802154_hdr_get_addrs(skb->data + pos, hdr);
+
+	if (hdr->fc.security_enabled) {
+		int want = pos + ieee802154_hdr_sechdr_len(skb->data[pos]);
+
+		if (!pskb_may_pull(skb, want))
+			return -EINVAL;
+
+		pos += ieee802154_hdr_get_sechdr(skb->data + pos, &hdr->sec);
+	}
+
+	skb_pull(skb, pos);
+	return pos;
+}
+EXPORT_SYMBOL_GPL(ieee802154_hdr_pull);
+
+int
+ieee802154_hdr_peek_addrs(const struct sk_buff *skb, struct ieee802154_hdr *hdr)
+{
+	const u8 *buf = skb_mac_header(skb);
+	int pos = 3, rc;
+
+	if (buf + 3 > skb_tail_pointer(skb))
+		return -EINVAL;
+
+	memcpy(hdr, buf, 3);
+
+	rc = ieee802154_hdr_minlen(hdr);
+	if (rc < 0 || buf + rc > skb_tail_pointer(skb))
+		return -EINVAL;
+
+	pos += ieee802154_hdr_get_addrs(buf + pos, hdr);
+	return pos;
+}
+EXPORT_SYMBOL_GPL(ieee802154_hdr_peek_addrs);