handle channel and tty read on closed socket

1. when read returns 0, it means remotes has closed socket, for
normal TCP connections.
2. when read returns -ENOTCONN for vsock, it means remote has closed the
socket.

We should be able to just handle case 1) if we patch vsock kernel
implementation to match normal TCP connection behavior.

Signed-off-by: Peng Tao <bergwolf@gmail.com>

Author: bergwolf

src/init.c

@@ -1044,7 +1044,18 @@ static int hyper_ttyfd_read(struct hyper_event *he, int efd, int events)
 	if (buf->get < STREAM_HEADER_SIZE) {
 		size = hyper_channel_read(he, efd, STREAM_HEADER_SIZE - buf->get, events);
 		if (size < 0) {
+			/* vsock returns -ENOTCONN upon reading closed socket... */
+			if (size == -ENOTCONN) {
+				fprintf(stderr, "ttyfd read failed on %p fd %d with err %d\n", he, he->fd, size);
+				hyper_modify_event(efd, he, he->flag & ~EPOLLIN);
+				size = 0;
+			}
 			return size;
+		} else if (size == 0) {
+			/* remote closes connection */
+			fprintf(stderr, "remote closes connection on %p fd %d\n", he, he->fd);
+			hyper_modify_event(efd, he, he->flag & ~EPOLLIN);
+			return 0;
 		}
 
 		buf->get += size;
@@ -1192,7 +1203,18 @@ static int hyper_ctlfd_read(struct hyper_event *he, int efd, int events)
 	if (buf->get < CONTROL_HEADER_SIZE) {
 		size = hyper_channel_read(he, efd, CONTROL_HEADER_SIZE - buf->get, events);
 		if (size < 0) {
+			/* vsock returns -ENOTCONN upon reading closed socket... */
+			if (size == -ENOTCONN) {
+				fprintf(stderr, "ttyfd read failed on %p fd %d with err %d\n", he, he->fd, size);
+				hyper_modify_event(efd, he, he->flag & ~EPOLLIN);
+				size = 0;
+			}
 			return size;
+		} else if (size == 0) {
+			/* remote closes connection */
+			fprintf(stderr, "remote closes connection on %p fd %d\n", he, he->fd);
+			hyper_modify_event(efd, he, he->flag & ~EPOLLIN);
+			return 0;
 		}
 		if (size > 0) {
 			uint8_t *data = malloc(4);

src/util.c

@@ -714,7 +714,7 @@ ssize_t nonblock_read(int fd, void *buf, size_t count)
 		len += ret;
 	}
 
-	return len > 0 ? len : ret;
+	return len > 0 ? len : -errno;
 }
 
 int hyper_mount_nfs(char *server, char *mountpoint)