lwsgs: update messageboard to avoid back-to-back writes

plugins/generic-sessions/handlers.c

@@ -262,9 +262,10 @@ reply:
 		lwsl_err("_write returned %d from %ld\n", n, (long)(p - start));
 		return -1;
 	}
-	n = lws_write(wsi, (unsigned char *)s, 1, LWS_WRITE_HTTP);
-	if (n != 1)
-		return -1;
+	pss->check_response_value = s[0];
+	pss->check_response = 1;
+
+	lws_callback_on_writable(wsi);
 
 	return 0;
 }

plugins/generic-sessions/private-lwsgs.h

@@ -94,8 +94,10 @@ struct per_session_data__gs {
 	char ip[46];
 	struct lws_process_html_state phs;
 	int spos;
+	char check_response_value;
 
 	unsigned int logging_out:1;
+	unsigned int check_response:1;
 };
 
 /* utils.c */

plugins/generic-sessions/protocol_generic_sessions.c

@@ -420,6 +420,14 @@ callback_generic_sessions(struct lws *wsi, enum lws_callback_reasons reason,
 		}
 		break;
 
+	case LWS_CALLBACK_HTTP_WRITEABLE:
+                if (!pss->check_response)
+                        break;
+		n = lws_write(wsi, (unsigned char *)&pss->check_response_value, 1, LWS_WRITE_HTTP_FINAL);
+		if (n != 1)
+			return -1;
+		goto try_to_reuse;
+
 	case LWS_CALLBACK_HTTP:
 		lwsl_info("LWS_CALLBACK_HTTP: %s\n", (const char *)in);
 
@@ -439,7 +447,8 @@ callback_generic_sessions(struct lws *wsi, enum lws_callback_reasons reason,
 		}
 		if (!strcmp((const char *)in, "/lwsgs-check")) {
 			lwsgs_handler_check(vhd, wsi, pss);
-			goto try_to_reuse;
+			/* second, async part will complete transaction */
+			break;
 		}
 
 		if (!strcmp((const char *)in, "/lwsgs-login"))

plugins/generic-sessions/protocol_lws_messageboard.c

@@ -41,6 +41,7 @@ struct per_session_data__gs_mb {
 	struct lws_spa *spa;
 	unsigned long last_idx;
 	unsigned int our_form:1;
+	char second_http_part;
 };
 
 static const char * const param_names[] = {
@@ -309,6 +310,16 @@ callback_messageboard(struct lws *wsi, enum lws_callback_reasons reason,
 		}
 		break;
 
+	case LWS_CALLBACK_HTTP_WRITEABLE:
+		if (!pss->second_http_part)
+			break;
+		s[0] = '0';
+		n = lws_write(wsi, (unsigned char *)s, 1, LWS_WRITE_HTTP);
+		if (n != 1)
+			return -1;
+
+		goto try_to_reuse;
+
 	case LWS_CALLBACK_HTTP_BODY_COMPLETION:
 		if (!pss->our_form)
 			goto passthru;
@@ -334,12 +345,10 @@ callback_messageboard(struct lws *wsi, enum lws_callback_reasons reason,
 			lwsl_err("_write returned %d from %ld\n", n, (long)(p - start));
 			return -1;
 		}
-		s[0] = '0';
-		n = lws_write(wsi, (unsigned char *)s, 1, LWS_WRITE_HTTP);
-		if (n != 1)
-			return -1;
+		pss->second_http_part = 1;
 
-		goto try_to_reuse;
+		lws_callback_on_writable(wsi);
+		break;
 
 	case LWS_CALLBACK_HTTP_BIND_PROTOCOL:
 		if (!pss || pss->pss_gs)