ieee802154: add ieee802154_skb_src_pan helper

This patch adds ieee802154_skb_src_pan function to get the pointer
address of the source pan id at skb mac pointer.
Signed-off-by: Alexander Aring <aar@pengutronix.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/linux/ieee802154.h

@@ -50,6 +50,7 @@
 
 #define IEEE802154_EXTENDED_ADDR_LEN	8
 #define IEEE802154_SHORT_ADDR_LEN	2
+#define IEEE802154_PAN_ID_LEN		2
 
 #define IEEE802154_LIFS_PERIOD		40
 #define IEEE802154_SIFS_PERIOD		12
@@ -224,12 +225,15 @@ enum {
 #define IEEE802154_FCTL_SECEN		0x0004
 #define IEEE802154_FCTL_INTRA_PAN	0x0040
 #define IEEE802154_FCTL_DADDR		0x0c00
+#define IEEE802154_FCTL_SADDR		0xc000
 
 #define IEEE802154_FTYPE_DATA		0x0001
 
 #define IEEE802154_FCTL_ADDR_NONE	0x0000
 #define IEEE802154_FCTL_DADDR_SHORT	0x0800
 #define IEEE802154_FCTL_DADDR_EXTENDED	0x0c00
+#define IEEE802154_FCTL_SADDR_SHORT	0x8000
+#define IEEE802154_FCTL_SADDR_EXTENDED	0xc000
 
 /*
  * ieee802154_is_data - check if type is IEEE802154_FTYPE_DATA
@@ -277,6 +281,15 @@ static inline __le16 ieee802154_daddr_mode(__le16 fc)
 	return fc & cpu_to_le16(IEEE802154_FCTL_DADDR);
 }
 
+/*
+ * ieee802154_saddr_mode - get saddr mode from fc
+ * @fc: frame control bytes in little-endian byteorder
+ */
+static inline __le16 ieee802154_saddr_mode(__le16 fc)
+{
+	return fc & cpu_to_le16(IEEE802154_FCTL_SADDR);
+}
+
 /**
  * ieee802154_is_valid_psdu_len - check if psdu len is valid
  * available lengths:

include/net/mac802154.h

@@ -286,6 +286,65 @@ static inline unsigned char *ieee802154_skb_dst_pan(__le16 fc,
 	return dst_pan;
 }
 
+/**
+ * ieee802154_skb_src_pan - get the pointer to source pan field
+ * @fc: mac header frame control field
+ * @skb: skb where the source pan pointer will be get from
+ */
+static inline unsigned char *ieee802154_skb_src_pan(__le16 fc,
+						    const struct sk_buff *skb)
+{
+	unsigned char *src_pan;
+
+	switch (ieee802154_saddr_mode(fc)) {
+	case cpu_to_le16(IEEE802154_FCTL_ADDR_NONE):
+		src_pan = NULL;
+		break;
+	case cpu_to_le16(IEEE802154_FCTL_SADDR_SHORT):
+	case cpu_to_le16(IEEE802154_FCTL_SADDR_EXTENDED):
+		/* if intra-pan and source addr mode is non none,
+		 * then source pan id is equal destination pan id.
+		 */
+		if (ieee802154_is_intra_pan(fc)) {
+			src_pan = ieee802154_skb_dst_pan(fc, skb);
+			break;
+		}
+
+		switch (ieee802154_daddr_mode(fc)) {
+		case cpu_to_le16(IEEE802154_FCTL_ADDR_NONE):
+			src_pan = skb_mac_header(skb) +
+				  IEEE802154_FC_LEN +
+				  IEEE802154_SEQ_LEN;
+			break;
+		case cpu_to_le16(IEEE802154_FCTL_DADDR_SHORT):
+			src_pan = skb_mac_header(skb) +
+				  IEEE802154_FC_LEN +
+				  IEEE802154_SEQ_LEN +
+				  IEEE802154_PAN_ID_LEN +
+				  IEEE802154_SHORT_ADDR_LEN;
+			break;
+		case cpu_to_le16(IEEE802154_FCTL_DADDR_EXTENDED):
+			src_pan = skb_mac_header(skb) +
+				  IEEE802154_FC_LEN +
+				  IEEE802154_SEQ_LEN +
+				  IEEE802154_PAN_ID_LEN +
+				  IEEE802154_EXTENDED_ADDR_LEN;
+			break;
+		default:
+			WARN_ONCE(1, "invalid addr mode detected");
+			src_pan = NULL;
+			break;
+		}
+		break;
+	default:
+		WARN_ONCE(1, "invalid addr mode detected");
+		src_pan = NULL;
+		break;
+	}
+
+	return src_pan;
+}
+
 /**
  * ieee802154_be64_to_le64 - copies and convert be64 to le64
  * @le64_dst: le64 destination pointer