Add support for better pipelining of commands, in order to reduce the number of send() calls.

src/hub.c

@@ -312,9 +312,11 @@ void hub_send_hubinfo(struct hub_info* hub, struct user* u)
 
 void hub_send_handshake(struct hub_info* hub, struct user* u)
 {
+	user_flag_set(u, flag_pipeline);
 	hub_send_support(hub, u);
 	hub_send_sid(hub, u);
 	hub_send_hubinfo(hub, u);
+	route_flush_pipeline(hub, u);
 
 	if (!user_is_disconnecting(u))
 	{

src/route.c

@@ -97,7 +97,7 @@ int route_to_user(struct hub_info* hub, struct user* user, struct adc_message* m
 	free(data);
 #endif
 
-	if (hub_sendq_is_empty(user->net.send_queue))
+	if (hub_sendq_is_empty(user->net.send_queue) && !user_flag_get(user, flag_pipeline))
 	{
 		/* Perform oportunistic write */
 		hub_sendq_add(user->net.send_queue, msg);
@@ -108,12 +108,24 @@ int route_to_user(struct hub_info* hub, struct user* user, struct adc_message* m
 		if (check_send_queue(hub, user, msg) >= 0)
 		{
 			hub_sendq_add(user->net.send_queue, msg);
-			user_net_io_want_write(user);
+			if (!user_flag_get(user, flag_pipeline))
+				user_net_io_want_write(user);
 		}
 	}
 	return 1;
 }
 
+int route_flush_pipeline(struct hub_info* hub, struct user* u)
+{
+	if (hub_sendq_is_empty(u->net.send_queue))
+		return 0;
+
+	handle_net_write(u);
+	user_flag_unset(u, flag_pipeline);
+	return 1;
+}
+
+
 int route_to_all(struct hub_info* hub, struct adc_message* command) /* iterate users */
 {
 	struct user* user = (struct user*) list_get_first(hub->users->list);

src/route.h

@@ -25,6 +25,11 @@
  */
 extern int route_message(struct hub_info* hub, struct user* u, struct adc_message* msg);
 
+/**
+ * Send queued messages.
+ */
+extern int route_flush_pipeline(struct hub_info* hub, struct user* u);
+
 /**
  * Transmit message directly to one user.
  */

src/user.h

@@ -50,7 +50,8 @@ enum user_flags
 	flag_want_read  = 0x08000000, /** Need to read (SSL) */
 	flag_want_write = 0x10000000, /** Need to write (SSL) */
 	flag_user_list  = 0x20000000, /** Send queue bypass (when receiving the send queue) */
-	flag_nat        = 0x40000000, /** nat override enabled */
+	flag_pipeline   = 0x40000000, /** Hub message pipelining */
+	flag_nat        = 0x80000000, /** nat override enabled */
 };
 
 enum user_quit_reason