Re: channel_write will fail if large amount of data are being written (0.4 branch)

[Aris Adamantiadis <aris@xxxxxxxxxxxx>]

Vic,

Sorry I just realized I did not finish and sent the email in which I 
suggested you to do so. Good thing it resolved your issue.

Regards,

Aris

Vic Lee a écrit :
> Hi Aris,
>
> It seems it's ok after I remove the ssh_set_blocking call. So probably
> we don't need this patch for 0.4.
>
> Thanks,
>
> Vic
>
> On Sat, 2010-01-23 at 01:13 +0800, Vic Lee wrote:
> > Hi Aris,
> >
> > It's the ssh_set_blocking() call in session.c. Maybe I shouldn't use it?
> > If I don't set blocking to false, will there be any impact on
> > channel_read_nonblocking?
> >
> > I also attach a patch which works for me, though I am not very sure if I
> > am doing the right thing here.
> >
> > Thanks,
> >
> > Vic
> >
> > On Thu, 2010-01-21 at 22:22 +0100, Aris Adamantiadis wrote:
> > > Hi Vic,
> > >
> > > Could you try to get a backtrace at this place ?
> > > I wonder why ssh_socket_nonblocking_flush is called. I put a breakpoint 
> > > on this function and was not able to trigger it using samplessh.
> > > Could you also check session->blocking value ? normaly it's set to 1 in 
> > > ssh_new and I could not find any other place where it's changed.
> > >
> > > Thanks,
> > >
> > > Aris
> > >
> > > Vic Lee a écrit :
> > > > Hi,
> > > >
> > > > I found another bug in channel_write() which make it fail to tunnel an
> > > > xterm over SSH.
> > > >
> > > > According to the description, channel_write() is a blocking write until
> > > > all data written or until error. However, in the following call
> > > > sequence:
> > > >
> > > > channel_write -> packet_send -> packet_send2 -> packet_write ->
> > > > packet_flush (at packet.c:456), it uses a non-blocking call:
> > > >
> > > >   rc = packet_flush(session, 0);
> > > >
> > > > which will almost always return SSH_AGAIN if large amount of data are
> > > > being flushed, and SSH_AGAIN will eventually returned by packet_send.
> > > > However, when channel_write calls packet_send it does not check for
> > > > SSH_AGAIN and simply think anything other than SSH_OK is an error.
> > > >
> > > > This bug makes it impossible to tunnel an xterm (it's funny somehow
> > > > xterm has large data transmit). I temporarily change the packet_flush to
> > > > a blocking call fix the issue. But I think a right patch should be on
> > > > channel_write, checking SSH_AGAIN.
> > > >
> > > > Your comments?
> > > >
> > > > Thanks,
> > > >
> > > > Vic