+/*
+ * miscdevfs packet format:
+ * Octet 0: Type
+ * Octets 1-4: network byte order msg_ctx->counter
+ * Octets 5-N0: Size of struct ecryptfs_message to follow
+ * Octets N0-N1: struct ecryptfs_message (including data)
+ *
+ * Octets 5-N1 not written if the packet type does not include a message
+ */
+#define PKT_TYPE_SIZE 1
+#define PKT_CTR_SIZE 4
+#define MIN_NON_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE)
+#define MIN_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE \
+ + ECRYPTFS_MIN_PKT_LEN_SIZE)
+/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
+#define MAX_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE \
+ + ECRYPTFS_MAX_PKT_LEN_SIZE \
+ + sizeof(struct ecryptfs_message) \
+ + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
+#define PKT_TYPE_OFFSET 0
+#define PKT_CTR_OFFSET PKT_TYPE_SIZE
+#define PKT_LEN_OFFSET (PKT_TYPE_SIZE + PKT_CTR_SIZE)
+