better error handling

pixelflut.c

@@ -231,15 +231,21 @@ static void *worker_main(void *arg)
 				/* Transient back-pressure. Back off briefly so the queue
 				 * drains (rather than spinning on failing syscalls), then
 				 * resend the same batch - no need to repaint. */
-				usleep(200);
+				usleep(100);
 				continue;
 			case ECONNREFUSED:
 				break; /* stale ICMP on connected UDP; repaint and retry */
+			case EHOSTUNREACH: /* display down / IPv6 ND unresolved */
+			case ENETUNREACH:
+			case EHOSTDOWN:
+			case ENETDOWN:
+				usleep(100000);
+				break;
 			default:
 				perror("sendmmsg");
 				break;
 			}
-			break; /* ECONNREFUSED / unexpected: stop, repaint, retry */
+			break;
 		}
 	}