Re: sftp_write waits infinitely

[Andreas Schneider <asn@xxxxxxxxxxxxxx>]

On Thursday 18 February 2016 12:09:38 Jakob Kohl | nowcast GmbH wrote:
> 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?

Hi Jakob,

I think the patch looks ok, just needs some cleanup. Aris what do you think?


	-- andreas

> 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 */

-- 
Andreas Schneider                   GPG-ID: CC014E3D
www.cryptomilk.org                asn@xxxxxxxxxxxxxx