Cookies are packed using protocol buffers to reduce their size.

src/ipc.proto

@@ -24,7 +24,6 @@ message auth_cookie_request_msg
 message auth_reply_msg
 {
 	required AUTH_REP reply = 1;
-	optional bytes cookie = 2;
 	optional bytes session_id = 3;
 	optional string vname = 4;
 	optional string user_name = 5;
@@ -160,3 +159,14 @@ message sec_op_msg
 	optional uint32 key_idx = 1;
 	required bytes data = 2;
 }
+
+/* Not a real message, but a cookie */
+message cookie
+{
+	required string username = 1;
+	required string groupname = 2;
+	required string hostname = 3;
+	required bytes session_id = 5;
+	required uint32 expiration = 6;
+	required uint32 ipv4_seed = 7;
+}