Re: [patch]: Stop connector socket-to-channel EOF flooding

[Tilo Eckert <tilo.eckert@xxxxxxx>]

Am 08.04.2019 um 20:54 schrieb g4-lisz@xxxxxxxxxxxx:
>> I'm using connectors for a direct-tcp client. So this creates two
>> connectors FD in --> channel out and vice versa.
>>
>> Now when the socket forwarding peer (not the ssh server) closes the
>> connection, i.e. reading on the socket returns 0 = EOF, we end up in
>> some loop with sending EOFs on the channel, until finally the client
>> receives a channel close message.
>>
> I attached some test code to reproduce this.
> 
> Edit line 14 to your needs. It should connect to a service which does
> not dicsonnecet the connenction from its side. I.e. SSH is fine. A
> webserver will not do because it disconnects after answering the request.
> 
> Start a local sshd with 
> 
> shell1>  /usr/sbin/sshd -d -d -p 2222
> 
> shell2> ./fwconnector username localhost 2222
> 
> shell3> ssh admin@localhost -p 2022
> Welcome to Debian...
> ~: exit
> 
> On shell1 you will see the > 20 lines of "channel 0: rcvd eof"

Your callback sends an EOF for every received EOF from the server. If
your server does the same, you end up with EOF ping pong. You might want
to check whether you already sent it before: channel->local_eof != 0

Btw, if you close the channel on your end, an EOF is sent automatically
if one has not been sent, yet.