help with debugging "Close for unknown channel 0" in dropbear-0.53.1

[Matt Johnston]

On Tue, May 08, 2012 at 05:45:50PM +0200, Bodo Meissner wrote:
> With debugging on the PC we found out that the library SSH.NET sometimes sends SSH_MSG_CHANNEL_CLOSE twice for the same channel number.
> This seems to depend on which end first decides to close the channel.
> I filed a bug report for SSH.NET with a description of a possible fix.
> http://sshnet.codeplex.com/workitem/1227
> 
> I don't know if the behaviour is specified in the SSH protocol or how other SSH servers will handle this.
> Would it make sense for dropbear to ignore CHANNEL_CLOSE messages for unknown channels, assuming it has already been closed?

The RFC is fairly clear that there should be only one
SSH_MSG_CHANNEL_CLOSE for a channel. See
https://www.ietf.org/rfc/rfc4254.txt section 5.3.

I'd prefer to avoid workarounds in this case.

Cheers,
Matt