Track and report the concurrent connections per client highwater mark

It's possible now for clients to easily exceed the configured max concurrent
connections limit, even though they just get an error 429 page. Let's at least
track and log when a new highwater mark is reached.

src/sbbs3/websrvr.c

@@ -108,6 +108,7 @@ static volatile bool	http_logging_thread_running=false;
 static protected_uint32_t active_clients;
 static protected_uint32_t thread_count;
 static volatile uint32_t client_highwater=0;
+static volatile uint32_t con_conn_highwater=0;
 static volatile bool	terminate_server=false;
 static volatile bool	terminate_js=false;
 static volatile bool	terminate_http_logging_thread=false;
@@ -6793,7 +6794,7 @@ void http_session_thread(void* arg)
 
 	if(startup->login_attempt.throttle
 		&& (login_attempts=loginAttempts(startup->login_attempt_list, &session.addr)) > 1) {
-		lprintf(LOG_DEBUG,"%04d %s Throttling suspicious connection from: %s (%lu login attempts)"
+		lprintf(LOG_DEBUG,"%04d %s [%s] Throttling suspicious connection (%lu login attempts)"
 			,socket, session.client.protocol, session.host_ip, login_attempts);
 		mswait(login_attempts*startup->login_attempt.throttle);
 	}
@@ -6804,13 +6805,18 @@ void http_session_thread(void* arg)
 
 	session.subscan=(subscan_t*)calloc(scfg.total_subs, sizeof(subscan_t));
 
+	uint connections = listCountMatches(&current_connections, session.host_ip, strlen(session.host_ip) + 1);
+	if(connections > con_conn_highwater) {
+		con_conn_highwater = connections;
+		if(con_conn_highwater > 1)
+			lprintf(LOG_NOTICE, "%04d %s [%s] New concurrent connections per client highwater mark: %u"
+				,socket, session.client.protocol, session.host_ip, con_conn_highwater);
+	}
 	if(startup->max_concurrent_connections > 0) {
-		int ip_len = strlen(session.host_ip) + 1;
-		uint connections = listCountMatches(&current_connections, session.host_ip, ip_len);
 		if(connections > startup->max_concurrent_connections
 			&& !is_host_exempt(&scfg, session.host_ip, /* host_name */NULL)) {
-			lprintf(LOG_NOTICE, "%04d [%s] !Maximum concurrent connections (%u) exceeded"
-				,socket, session.host_ip, startup->max_concurrent_connections);
+			lprintf(LOG_NOTICE, "%04d %s [%s] !Maximum concurrent connections (%u) exceeded"
+				,socket, session.client.protocol, session.host_ip, startup->max_concurrent_connections);
 			send_error(&session, __LINE__, error_429);
 		}
 	}