valgrind introduce protocol init and destroy user callbacks

To get a clean bill of health from valgrind, we have to have a way to
inform the user code that we're going down and it should free everything
it is holding that was malloc'd.

This patch introduces LWS_CALLBACK_PROTOCOL_DESTROY which each protocol
gets when the context is being destroyed and no more activity will come
after that call.  They can get rid of everything there.

To match it, LWS_CALLBACK_PROTOCOL_INIT is introduced which would allow
one-time init per protocol too.

Signed-off-by: Andy Green <andy.green@linaro.org>

changelog

@@ -21,6 +21,12 @@ User api additions
 	can enable it by setting a non-zero timeout (in seconds) at the new
 	ka_time member at context creation time.
 
+ - Two new optional user callbacks added, LWS_CALLBACK_PROTOCOL_DESTROY which
+ 	is called one-time per protocol as the context is being destroyed, and
+	LWS_CALLBACK_PROTOCOL_INIT which is called when the context is created
+	and the protocols are added, again it's a one-time affair.
+	This lets you manage per-protocol allocations properly including
+	cleaning up after yourself when the server goes down.
 
 User api changes
 ----------------

lib/libwebsockets.c

@@ -1041,6 +1041,7 @@ libwebsocket_context_destroy(struct libwebsocket_context *context)
 	int n;
 	int m;
 	struct libwebsocket_extension *ext;
+	struct libwebsocket_protocols *protocol = context->protocols;
 
 #ifdef LWS_LATENCY
 	if (context->worst_latency_info[0])
@@ -1067,6 +1068,18 @@ libwebsocket_context_destroy(struct libwebsocket_context *context)
 		ext->callback(context, ext, NULL, (enum libwebsocket_extension_callback_reasons)m, NULL, NULL, 0);
 		ext++;
 	}
+
+	/*
+	 * inform all the protocols that they are done and will have no more
+	 * callbacks
+	 */
+
+	while (protocol->callback) {
+		protocol->callback(context, NULL, LWS_CALLBACK_PROTOCOL_DESTROY,
+				NULL, NULL, 0);
+		protocol++;
+	}
+
 #endif
 
 #ifdef WIN32
@@ -2023,6 +2036,13 @@ libwebsocket_create_context(struct lws_context_creation_info *info)
 									context;
 		info->protocols[context->count_protocols].protocol_index =
 						       context->count_protocols;
+
+		/*
+		 * inform all the protocols that they are doing their one-time
+		 * initialization if they want to
+		 */
+		info->protocols[context->count_protocols].callback(context,
+			       NULL, LWS_CALLBACK_PROTOCOL_INIT, NULL, NULL, 0);
 	}
 
 #ifndef LWS_NO_EXTENSIONS

lib/libwebsockets.h

@@ -142,6 +142,8 @@ enum libwebsocket_callback_reasons {
 	LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER,
 	LWS_CALLBACK_CONFIRM_EXTENSION_OKAY,
 	LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED,
+	LWS_CALLBACK_PROTOCOL_INIT,
+	LWS_CALLBACK_PROTOCOL_DESTROY,
 	/* external poll() management support */
 	LWS_CALLBACK_ADD_POLL_FD,
 	LWS_CALLBACK_DEL_POLL_FD,
@@ -534,6 +536,14 @@ struct libwebsocket_extension;
  *		support included in the header to the server.  Notice this
  *		callback comes to protocols[0].
  *
+ *	LWS_CALLBACK_PROTOCOL_INIT:	One-time call per protocol so it can
+ *		do initial setup / allocations etc
+ *
+ *	LWS_CALLBACK_PROTOCOL_DESTROY:	One-time call per protocol indicating
+ *		this protocol won't get used at all after this callback, the
+ *		context is getting destroyed.  Take the opportunity to
+ *		deallocate everything that was allocated by the protocol.
+ *
  *	The next four reasons are optional and only need taking care of if you
  * 	will be integrating libwebsockets sockets into an external polling
  * 	array.

libwebsockets-api-doc.html

@@ -752,6 +752,18 @@ claim to support that extension by returning non-zero.  If
 unhandled, by default 0 will be returned and the extension
 support included in the header to the server.  Notice this
 callback comes to protocols[0].
+</blockquote>
+<h3>LWS_CALLBACK_PROTOCOL_INIT</h3>
+<blockquote>
+One-time call per protocol so it can
+do initial setup / allocations etc
+</blockquote>
+<h3>LWS_CALLBACK_PROTOCOL_DESTROY</h3>
+<blockquote>
+One-time call per protocol indicating
+this protocol won't get used at all after this callback, the
+context is getting destroyed.  Take the opportunity to
+deallocate everything that was allocated by the protocol.
 <p>
 The next four reasons are optional and only need taking care of if you
 will be integrating libwebsockets sockets into an external polling

test-server/test-server.c

@@ -356,6 +356,13 @@ callback_lws_mirror(struct libwebsocket_context *context,
 		pss->wsi = wsi;
 		break;
 
+	case LWS_CALLBACK_PROTOCOL_DESTROY:
+		lwsl_notice("mirror protocol cleaning up\n");
+		for (n = 0; n < sizeof ringbuffer / sizeof ringbuffer[0]; n++)
+			if (ringbuffer[n].payload)
+				free(ringbuffer[n].payload);
+		break;
+
 	case LWS_CALLBACK_SERVER_WRITEABLE:
 		if (close_testing)
 			break;