Implement nonblocking IO in IPC server

Added client write buffer and handler for writable status on client
socket.

sway/ipc-server.c

@@ -40,11 +40,15 @@ static const char ipc_magic[] = {'i', '3', '-', 'i', 'p', 'c'};
 
 struct ipc_client {
 	struct wlc_event_source *event_source;
+	struct wlc_event_source *writable_event_source;
 	int fd;
 	uint32_t payload_length;
 	uint32_t security_policy;
 	enum ipc_command_type current_command;
 	enum ipc_command_type subscribed_events;
+	size_t write_buffer_len;
+	size_t write_buffer_size;
+	char *write_buffer;
 };
 
 static list_t *ipc_get_pixel_requests = NULL;
@@ -58,6 +62,7 @@ struct get_pixels_request {
 struct sockaddr_un *ipc_user_sockaddr(void);
 int ipc_handle_connection(int fd, uint32_t mask, void *data);
 int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data);
+int ipc_client_handle_writable(int client_fd, uint32_t mask, void *data);
 void ipc_client_disconnect(struct ipc_client *client);
 void ipc_client_handle_command(struct ipc_client *client);
 bool ipc_send_reply(struct ipc_client *client, const char *payload, uint32_t payload_length);
@@ -168,6 +173,12 @@ int ipc_handle_connection(int fd, uint32_t mask, void *data) {
 		close(client_fd);
 		return 0;
 	}
+	if ((flags = fcntl(client_fd, F_GETFL)) == -1
+			|| fcntl(client_fd, F_SETFL, flags|O_NONBLOCK) == -1) {
+		sway_log_errno(L_ERROR, "Unable to set NONBLOCK on IPC client socket");
+		close(client_fd);
+		return 0;
+	}
 
 	struct ipc_client* client = malloc(sizeof(struct ipc_client));
 	if (!client) {
@@ -179,10 +190,22 @@ int ipc_handle_connection(int fd, uint32_t mask, void *data) {
 	client->fd = client_fd;
 	client->subscribed_events = 0;
 	client->event_source = wlc_event_loop_add_fd(client_fd, WLC_EVENT_READABLE, ipc_client_handle_readable, client);
+	client->writable_event_source = NULL;
+
+	client->write_buffer_size = 128;
+	client->write_buffer_len = 0;
+	client->write_buffer = malloc(client->write_buffer_size);
+	if (!client->write_buffer) {
+		sway_log(L_ERROR, "Unable to allocate ipc client write buffer");
+		close(client_fd);
+		return 0;
+	}
 
 	pid_t pid = get_client_pid(client->fd);
 	client->security_policy = get_ipc_policy_mask(pid);
 
+	sway_log(L_DEBUG, "New client: fd %d, pid %d", client_fd, pid);
+
 	list_add(ipc_client_list, client);
 
 	return 0;
@@ -205,6 +228,8 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 		return 0;
 	}
 
+	sway_log(L_DEBUG, "Client %d readable", client->fd);
+
 	int read_available;
 	if (ioctl(client_fd, FIONREAD, &read_available) == -1) {
 		sway_log_errno(L_INFO, "Unable to read IPC socket buffer size");
@@ -226,6 +251,7 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 
 	uint8_t buf[ipc_header_size];
 	uint32_t *buf32 = (uint32_t*)(buf + sizeof(ipc_magic));
+	// Should be fully available, because read_available >= ipc_header_size
 	ssize_t received = recv(client_fd, buf, ipc_header_size, 0);
 	if (received == -1) {
 		sway_log_errno(L_INFO, "Unable to receive header from IPC client");
@@ -249,6 +275,48 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 	return 0;
 }
 
+int ipc_client_handle_writable(int client_fd, uint32_t mask, void *data) {
+	struct ipc_client *client = data;
+
+	if (mask & WLC_EVENT_ERROR) {
+		sway_log(L_ERROR, "IPC Client socket error, removing client");
+		ipc_client_disconnect(client);
+		return 0;
+	}
+
+	if (mask & WLC_EVENT_HANGUP) {
+		sway_log(L_DEBUG, "Client %d hung up", client->fd);
+		ipc_client_disconnect(client);
+		return 0;
+	}
+
+	if (client->write_buffer_len <= 0) {
+		return 0;
+	}
+
+	sway_log(L_DEBUG, "Client %d writable", client->fd);
+
+	ssize_t written = write(client->fd, client->write_buffer, client->write_buffer_len);
+
+	if (written == -1 && errno == EAGAIN) {
+		return 0;
+	} else if (written == -1) {
+		sway_log_errno(L_INFO, "Unable to send data from queue to IPC client");
+		ipc_client_disconnect(client);
+		return 0;
+	}
+
+	memmove(client->write_buffer, client->write_buffer + written, client->write_buffer_len - written);
+	client->write_buffer_len -= written;
+
+	if (client->write_buffer_len == 0 && client->writable_event_source) {
+		wlc_event_source_remove(client->writable_event_source);
+		client->writable_event_source = NULL;
+	}
+
+	return 0;
+}
+
 void ipc_client_disconnect(struct ipc_client *client) {
 	if (!sway_assert(client != NULL, "client != NULL")) {
 		return;
@@ -260,9 +328,13 @@ void ipc_client_disconnect(struct ipc_client *client) {
 
 	sway_log(L_INFO, "IPC Client %d disconnected", client->fd);
 	wlc_event_source_remove(client->event_source);
+	if (client->writable_event_source) {
+		wlc_event_source_remove(client->writable_event_source);
+	}
 	int i = 0;
 	while (i < ipc_client_list->length && ipc_client_list->items[i] != client) i++;
 	list_del(ipc_client_list, i);
+	free(client->write_buffer);
 	close(client->fd);
 	free(client);
 }
@@ -334,6 +406,7 @@ void ipc_client_handle_command(struct ipc_client *client) {
 		return;
 	}
 	if (client->payload_length > 0) {
+		// Payload should be fully available
 		ssize_t received = recv(client->fd, buf, client->payload_length, 0);
 		if (received == -1)
 		{
@@ -590,17 +663,35 @@ bool ipc_send_reply(struct ipc_client *client, const char *payload, uint32_t pay
 	data32[0] = payload_length;
 	data32[1] = client->current_command;
 
-	if (write(client->fd, data, ipc_header_size) == -1) {
+	while (client->write_buffer_len + ipc_header_size + payload_length >=
-		sway_log_errno(L_INFO, "Unable to send header to IPC client");
+				 client->write_buffer_size) {
+		client->write_buffer_size *= 2;
+	}
+
+	if (client->write_buffer_size > (1 << 22)) { // 4 MB
+		sway_log(L_ERROR, "Client write buffer too big, disconnecting client");
+		ipc_client_disconnect(client);
 		return false;
 	}
 
-	if (write(client->fd, payload, payload_length) == -1) {
+	char *new_buffer = realloc(client->write_buffer, client->write_buffer_size);
-		sway_log_errno(L_INFO, "Unable to send payload to IPC client");
+	if (!new_buffer) {
+		sway_log(L_ERROR, "Unable to reallocate ipc client write buffer");
+		ipc_client_disconnect(client);
 		return false;
 	}
+	client->write_buffer = new_buffer;
+
+	memcpy(client->write_buffer + client->write_buffer_len, data, ipc_header_size);
+	client->write_buffer_len += ipc_header_size;
+	memcpy(client->write_buffer + client->write_buffer_len, payload, payload_length);
+	client->write_buffer_len += payload_length;
+
+	if (!client->writable_event_source) {
+		client->writable_event_source = wlc_event_loop_add_fd(client->fd, WLC_EVENT_WRITABLE, ipc_client_handle_writable, client);
+	}
 
-	sway_log(L_DEBUG, "Send IPC reply: %s", payload);
+	sway_log(L_DEBUG, "Added IPC reply to client %d queue: %s", client->fd, payload);
 
 	return true;
 }