batman-adv: don't rely on positions in struct for hashing

The hash functions in the bridge loop avoidance code expects the
VLAN vid to be right after the mac address, but this is not guaranteed.

Fix this by explicitly hashing over the right fields of the struct.

Reported-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

net/batman-adv/hash.h

@@ -81,6 +81,28 @@ static inline void batadv_hash_delete(struct batadv_hashtable *hash,
 	batadv_hash_destroy(hash);
 }
 
+/**
+ *	batadv_hash_bytes - hash some bytes and add them to the previous hash
+ *	@hash: previous hash value
+ *	@data: data to be hashed
+ *	@size: number of bytes to be hashed
+ *
+ *	Returns the new hash value.
+ */
+static inline uint32_t batadv_hash_bytes(uint32_t hash, void *data,
+					 uint32_t size)
+{
+	const unsigned char *key = data;
+	int i;
+
+	for (i = 0; i < size; i++) {
+		hash += key[i];
+		hash += (hash << 10);
+		hash ^= (hash >> 6);
+	}
+	return hash;
+}
+
 /**
  *	batadv_hash_add - adds data to the hashtable
  *	@hash: storage hash table