worker: notify early main on session info

That allows to pass TLS information early, but more importantly
to pass information on the IP of the client (and our listen IP),
to main, which will be provided in turn to the up and down scripts,
as well as occtl.

src/ipc.proto

@@ -17,6 +17,8 @@
    |                      |                      |
    | -----------------AUTH_REP-----------------> |
    |                      |                      |
+   | <------------SESSION_INFO------------------ |
+   |                      |                      |
    |                      | <-- CLI_STATS ------ |
    |                      |            (disconnect)
    | ---SESSION_CLOSE---> |
@@ -140,6 +142,12 @@ message session_info_msg
 	required string user_agent = 3;
 	optional string cstp_compr = 4;
 	optional string dtls_compr = 5;
+	/* these two are of type sockaddr_storage,
+	 * and contain the addresses we got from proxy
+	 * protocol (if any).
+	 */
+	optional bytes our_addr = 6;
+	optional bytes remote_addr = 7;
 }
 
 /* WORKER_BAN_IP: sent from worker to main */