auto-virtserial: Ensure we handle EINTR/EAGAIN on local file descriptors

For the guest and host file send functions, we could get EINTR or EAGAIN
on local file descriptors.  Ensure we handle that.

Also, add a timeout to read() on the local descriptor to ensure we don't
block forever on a guest that gets stuck.

Signed-off-by: Amit Shah <amit.shah@redhat.com>

1 files changed, 30 insertions, 2 deletions

diff --git a/auto-virtserial.c b/auto-virtserial.c
index 03c3090..560a3e4 100644
--- a/auto-virtserial.c
+++ b/auto-virtserial.c
@@ -1097,8 +1097,18 @@ static int test_host_file_send(int nr)
 	guest_cmd_only(&gpkt);
 	/* The guest now is waiting for our data */
 
-	while ((ret = read(fd, buf, BUF_LENGTH)))
+	while (1) {
+		ret = read(fd, buf, BUF_LENGTH);
+		if (ret < 0 && (errno == EINTR || errno == EAGAIN))
+			continue;
+		else if (ret < 0) {
+			fprintf(stderr, "read error %d\n", errno);
+			break;
+		}
+		if (ret == 0)
+			break;
 		write(chardevs[nr].sock, buf, ret);
+	}
 
 	close(fd);
 	/* guest will stop reading only if read() returns 0 */
@@ -1180,6 +1190,7 @@ static int test_guest_file_send(int nr)
 {
 	char buf[BUF_LENGTH];
 	char csum[BUF_LENGTH];
+	struct pollfd pollfds[1];
 	struct guest_packet gpkt;
 	int err, ret, fd, csum_fd;
 
@@ -1210,7 +1221,24 @@ static int test_guest_file_send(int nr)
 	guest_cmd_only(&gpkt);
 	/* The guest now is sending us data */
 
-	while ((ret = read(chardevs[nr].sock, buf, BUF_LENGTH))) {
+	pollfds[0].fd = chardevs[nr].sock;
+	pollfds[0].events = POLLIN;
+	while (1) {
+		/* If no response received for 5s, assume guest is stuck. */
+		ret = poll(pollfds, 1, 5000);
+		if (ret <= 0) {
+			debug("poll returned %d\n", ret);
+			break;
+		}
+		ret = read(chardevs[nr].sock, buf, BUF_LENGTH);
+		if (ret == 0)
+			break;
+		if (ret < 0 && (errno == EINTR || errno == EAGAIN))
+			continue;
+		else if (ret < 0) {
+			fprintf(stderr, "read error %d\n", errno);
+			break;
+		}
 		write(fd, buf, ret);
 		if (ret > 0 && ret < BUF_LENGTH)
 			break;