reverse server should also timeout when -K is set

[Salatiel Filho]

Hi matt, would it be possible to you make the server also times out
when it looses connection with the client that requested a reverse
tunnel ?

Current version: Dropbear 2016.74


Scenario:

1 ) Client 1 connects to the server passing -K 5 option and -R
7777:localhost:22 , after this, if i go to server and type ssh
localhost:7777, i will get a reverse ssh connection to the client. (
works as expected )
2 ) Server disconnects and reconnects using a new public ip.
3)  Client 1 will time out after 5 seconds
4) client 1 try to recreate the tunnel connecting to the new ip
address. It will fail because there is already a 7777 address bound to
dropbear by the old connection.

It would be nice if the previous connection timed out on the server too.






[]'s
Salatiel