AW: sftp_write waits infinitely

[Jakob Kohl | nowcast GmbH <jkohl@xxxxxxxxxx>]

Hello Andreas,

I just tried with the current master from git -> same problem. Program will hang infinitely in poll function, when network cable gets unplugged for some minutes. It will still hang, when network cable is plugged again.

Then I changed some code parts, so that the poll function is called with the user timeout and the ssh_poll function returns -1 if it runs into the timeout.
Now when I unplug the target machine during a long running sftp file upload, the upload fails. My code then tries to reconnect the ssh session, that also fails as long as the cable is unplugged. When plugging the cable the connection is established and file transfer starts again. Just like I would expect.

Could you (or some other libssh developer) please check my diff: Are there any side-effects of my change? Why is ssh_handle_packets_termination always called with SSH_TIMEOUT_DEFAULT in the current git master?

Thanks in advance!

Jakob Kohl



My diff:
diff --git a/src/channels.c b/src/channels.c
index ffcb1d5..c0ca4ca 100644
--- a/src/channels.c
+++ b/src/channels.c
@@ -2617,7 +2617,7 @@ static int ssh_channel_read_termination(void *s){
  */
 int ssh_channel_read(ssh_channel channel, void *dest, uint32_t count, int is_stderr)
 {
-    return ssh_channel_read_timeout(channel, dest, count, is_stderr, -1);
+    return ssh_channel_read_timeout(channel, dest, count, is_stderr, SSH_TIMEOUT_USER);
 }
 
 /**
@@ -2697,9 +2697,9 @@ int ssh_channel_read_timeout(ssh_channel channel,
   ctx.buffer = stdbuf;
   ctx.count = 1;
 
-  if (timeout < 0) {
-      timeout = SSH_TIMEOUT_DEFAULT;
-  }
+//  if (timeout < 0) {
+//      timeout = SSH_TIMEOUT_DEFAULT;
+//  }
 
   rc = ssh_handle_packets_termination(session,
                                       timeout,
diff --git a/src/poll.c b/src/poll.c
index 807b0a5..2266fe9 100644
--- a/src/poll.c
+++ b/src/poll.c
@@ -95,7 +95,10 @@ void ssh_poll_cleanup(void) {
 }
 
 int ssh_poll(ssh_pollfd_t *fds, nfds_t nfds, int timeout) {
-  return poll((struct pollfd *) fds, nfds, timeout);
+  int rc = poll((struct pollfd *) fds, nfds, timeout);
+  if (rc <= 0)
+      return -1;
+  return rc;
 }
 
 #else /* HAVE_POLL */