Hello there,
Is there any way to make Net::OpenSSH not use multiple sessions ?
I'm trying to connect to some legacy router (therefore I have some restrictions on kex/ciphers). I try to run the following 
  my $ssh = Net::OpenSSH->new($ip,user=>$LOGIN,password=>$PASSWD,
                          ssh_cmd=>'/opt/openssh/bin/ssh',
                          master_opts => [-o => "StrictHostKeyChecking
+=no",
                                          -o => "UserKnownHostsFile=/d
+ev/null",
                                          -o => "NumberOfPasswordPromp
+ts=1",
                                          -o => "KexAlgorithms=diffie-
+hellman-group1-sha1",
                                          -o => "HostKeyAlgorithms=ssh
+-dss",
                                          -o => "Ciphers=3des-cbc,blow
+fish-cbc",
                                          -o => "PreferredAuthenticati
+ons=keyboard-interactive,password",
                                          -o => "LogLevel=DEBUG3"]);

  $ssh->error and die "Can't ssh to $ip: " . $t->error;
  print STDERR 'Trying open2pty'."\n";
  my ($fh,$pid) = $ssh->open2pty({ stderr_to_stdout => 1 });
  print STDERR 'opening Telnet'."\n";
  my $teln = Net::Telnet->new(Fhopen => $fh,
                              ErrMode=>'die',
                              timeout=>30,
                              Dump_Log => '/tmp/telnet.log', 
                              prompt => '/(.*#)/');
  $teln->login($LOGIN, $PASSWD);

[download]
Initial setup seems to follow legacy kex method. 
 debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-dss
debug2: ciphers ctos: 3des-cbc,blowfish-cbc,twofish-cbc
debug2: ciphers stoc: 3des-cbc,blowfish-cbc,twofish-cbc
debug2: MACs ctos: hmac-sha1,hmac-sha1-96,hmac-md5
debug2: MACs stoc: hmac-sha1,hmac-sha1-96,hmac-md5

[download]
Initial sessions get open but additional sessions after open2pty fail 
debug3: channel 2: status: The following connections are open:
  #1 client-session (t3 r-1 i0/0 o0/0 fd 6/7 cc -1)
  #2 mux-control (t16 r-1 i3/0 o3/0 fd 9/9 cc -1)

Trying open2pty
opening Telnet
debug1: multiplexing control connection
debug2: fd 9 setting O_NONBLOCK
debug3: fd 9 is O_NONBLOCK
debug1: channel 2: new [mux-control]
debug3: channel_post_mux_listener: new mux channel 2 fd 9
debug3: mux_master_read_cb: channel 2: hello sent
debug3: mux_master_read_cb: channel 2 packet type 0x00000001 len 4
debug2: process_mux_master_hello: channel 2 slave version 4
debug3: mux_master_read_cb: channel 2 packet type 0x10000004 len 4
debug2: process_mux_alive_check: channel 2: alive check
debug3: mux_master_read_cb: channel 2 packet type 0x10000002 len 69
debug2: process_mux_new_session: channel 2: request tty 1, X 0, agent 
+0, subsys 0, term "xterm-256color", cmd "", env 1
debug3: process_mux_new_session: got fds stdin 10, stdout 11, stderr 1
+2
debug1: channel 3: new [client-session]
debug2: process_mux_new_session: channel_new: 3 linked to control chan
+nel 2
debug2: channel 3: send open
debug3: send packet: type 90
debug3: receive packet: type 91
debug2: channel 1: open confirm rwindow 12288 rmax 512
debug3: receive packet: type 1
Received disconnect from 10.10.3.6 port 22:2: Disconnect Protocol erro
+r
Disconnected from 10.10.3.6 port 22

[download]
Remote peer states that there is no common kex method. Shouldn't OpenSSH use only diffie-hellman-group1-sha1 here ? 
WARNING 02/15/2018 22:59:00 UTC/GMT ssh: no supported key exchange met
+hod (curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp25
+6,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange
+-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,d
+iffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffi
+e-hellman-group14-sha1,ext-info-c)
DEBUG 02/15/2018 22:59:00 UTC/GMT ssh: sent msg type 1, 48 bytes

[download]
When I try cli openssh client it opens only one channel and there is no problem.
I appreciate any clue how to workaround this issue. The one that comes to my mind is to use Expect and cli ssh client but I would like to avoid it if possible.
Forgive me this little too long post.
Regards,
Pawel

In reply to Net::OpenSSH multiple sessions and legacy KEX problem by pwlodawi

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