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(See also `ext-data-at-start'.)
Report of message "Unexpected response to shell/command request: packet type 91" - seems to be correlated with seeing "Opening forwarded connection" before "Allocated pty" in Event log. Sounds to me like the connection setup code is insufficiently able to cope with asynchrony. PuTTY certainly shouldn't be sending CHANNEL_OPEN then being offended by the resulting CHANNEL_OPEN_CONFIRMATION. ref <email@example.com> and prior in thread. Excerpts from bug reports: ---------- 2003-06-05 00:21:20 Looking up host "server.example.com" 2003-06-05 00:21:20 Connecting to X.Y.Z.W port 22 2003-06-05 00:21:20 Server version: SSH-2.0-OpenSSH_3.4p1 2003-06-05 00:21:20 We claim version: SSH-2.0-PuTTY-Snapshot-2003-06-04 2003-06-05 00:21:20 Using SSH protocol version 2 2003-06-05 00:21:21 Doing Diffie-Hellman group exchange 2003-06-05 00:21:21 Doing Diffie-Hellman key exchange 2003-06-05 00:21:30 Host key fingerprint is: 2003-06-05 00:21:30 ssh-dss 1024 XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX 2003-06-05 00:21:30 Initialised AES-256 client->server encryption 2003-06-05 00:21:30 Initialised AES-256 server->client encryption 2003-06-05 00:21:30 Initialised zlib (RFC1950) compression 2003-06-05 00:21:30 Initialised zlib (RFC1950) decompression 2003-06-05 00:21:31 Reading private key file "C:\some\path\to\key.PPK" 2003-06-05 00:21:31 Offered public key 2003-06-05 00:21:31 Offer of public key accepted 2003-06-05 00:21:32 Access granted 2003-06-05 00:21:32 Opened channel for session 2003-06-05 00:21:32 Requesting X11 forwarding 2003-06-05 00:21:32 X11 forwarding enabled 2003-06-05 00:21:32 Local port 10119 forwarding to news.example.com:119 2003-06-05 00:21:32 Local port 8080 forwarding to proxy.example.com:8080 2003-06-05 00:21:32 Opening forwarded connection to news.example.com:119 2003-06-05 00:21:32 Allocated pty 2003-06-05 00:21:32 Unexpected response to shell/command request: packet type 91 And a bit more verbose (another run with the same behaviour): Event Log: Offered public key Incoming packet type 60 / 0x3c (SSH2_MSG_USERAUTH_PK_OK) Event Log: Offer of public key accepted Outgoing packet type 50 / 0x32 (SSH2_MSG_USERAUTH_REQUEST) Incoming packet type 52 / 0x34 (SSH2_MSG_USERAUTH_SUCCESS) Event Log: Access granted Outgoing packet type 90 / 0x5a (SSH2_MSG_CHANNEL_OPEN) Incoming packet type 91 / 0x5b (SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) Event Log: Opened channel for session Event Log: Requesting X11 forwarding Outgoing packet type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST) Incoming packet type 99 / 0x63 (SSH2_MSG_CHANNEL_SUCCESS) Event Log: X11 forwarding enabled Event Log: Local port 10119 forwarding to news.example.com:119 Event Log: Local port 8080 forwarding to proxy.example.com:8080 Outgoing packet type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST) Event Log: Opening forwarded connection to news.example.com:119 Outgoing packet type 90 / 0x5a (SSH2_MSG_CHANNEL_OPEN) Incoming packet type 99 / 0x63 (SSH2_MSG_CHANNEL_SUCCESS) Event Log: Allocated pty Outgoing packet type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST) Incoming packet type 91 / 0x5b (SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) Event Log: Unexpected response to shell/command request: packet type 91 Reproduced using netcat: "nc -vvvvvv localhost 10119" runned many times while PuTTY is connecting. ---------- Previous report: ---------- PuTTY Release 0.53b Windows 95 B SSH2 Server version: SSH-2.0-OpenSSH_3.4p1 The problem/symptom: PuTTY shows a message box with "Unexpected response to shell/command request: packet type 91" and goes into inactive mode where port forwarding isn't possible (I guess it's line 5236 in ssh.c). How to reproduce: Have PuTTY forward a local port to a machine on the other end. Try to use the forwarded port while starting PuTTY and connecting to the remote host. I have the problem with an internal news server on my university which I read through an SSH forwarded port using Forte Agent that I tell to fetch news before PuTTY is connected. Forte Agent waits 1 second between retries. [...] It seems PuTTY sends an SSH2_MSG_CHANNEL_OPEN interleaved with other packets and then gets confused when it sees the reply SSH2_MSG_CHANNEL_OPEN_CONFIRMATION. I should probably also note that the problem is periodic, and whenever I have seen the problem and the event log (5 times or so) it has had "Opening forwarded connection to news.example.com:119" just before "Allocated pty". Also I have found netcat better to provoke the error by trying "nc -vvv localhost 10119" just before running "C:\Programmer\putty\putty.exe -load ask" in another prompt. ----------
SGT, 2004-11-27: I've rearchitected the SSH back end somewhat, so that it's now a hybrid of coroutine-based sequential code and random dispatch-table handling of incoming packets. This ought to solve this problem, although I'm unable to immediately test it.
Audit trail for this bug.