doc: add state diagrams

doc/hamnet70.adoc

@@ -524,6 +524,75 @@ msc {
 }
 ....
 
+=== State Diagrams
+
+This section documents state diagrams for the digipeater and the clients.
+They are only informational; different implementations are possible and allowed as long as the procedures defined by the <<_message_sequence_charts,message sequence charts>> are obeyed.
+However, the state diagrams shown here reflect the reference implementation.
+
+==== Connection State Diagram
+
+[graphviz,format=svg,svg-type=interactive,scale=1.0]
+.Connection state diagram
+....
+digraph connection {
+	uninitd [label="Uninitialized"];
+	connecting [label="Connecting"];
+	wait_client [label="Wait for\nclient"];
+	estab [label="Two-way communication\nestablished"];
+	closed [label="Closed"];
+
+	uninitd -> connecting [label="Connection request\nsent [client]"];
+	uninitd -> wait_client [label="Connection request\nreceived [digipeater]"];
+
+	connecting -> estab [label="Connection\nacknowledgement sent"];
+	wait_client -> estab [label="Connection\nacknowledged"];
+
+	connecting -> closed [label="Timeout"];
+	wait_client -> closed [label="Timeout"];
+
+	estab -> closed [label="Disconnect/Timeout"];
+	closed -> uninitd [label="State erased"];
+}
+....
+
+==== Digipeater Connection Multiplexing
+
+[graphviz,layout=neato,format=svg,svg-type=interactive,scale=1.0]
+.Handling of multiple connections at the digipeater
+....
+digraph multiclient {
+	overlap=false;
+
+	idle [label="Idle"];
+	send_beacon [label="Send Beacon"];
+	accept_new [label="Check for\nnew clients"];
+	check_conn [label="Check connection timers"];
+	send_to_client [label="Send queued packets\nto client"];
+	receive_from_client [label="Receive packets\nfrom client"];
+	check_timeout [label="Check connection\ntimeout"];
+	reset_timeout [label="Reset connection\ntimeout"];
+	close_conn [label="Close\nconnection"];
+
+	idle -> send_beacon [label="Beacon timeout\nexpired"];
+	send_beacon -> accept_new;
+	accept_new -> idle;
+
+	idle -> check_conn [label="Any contact\ntimer expired"];
+	check_conn -> send_to_client [label="Contact timer\nexpired"];
+	send_to_client -> receive_from_client;
+	receive_from_client -> reset_timeout [label="Packets received"];
+	reset_timeout -> check_conn;
+
+	receive_from_client -> check_timeout [label="Nothing received"];
+	check_timeout -> check_conn [label="No timeout yet"];
+	check_timeout -> close_conn [label="Timed out"];
+	close_conn -> check_conn;
+
+	check_conn -> idle [label="All expired\nconnections handled"];
+}
+....
+
 == Higher Layer Protocols
 
 [appendix]