Roberto Deandrea created SSHD-1292:
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Summary: Connection problem with Rebex Buru SFTP Server
Key: SSHD-1292
URL: https://issues.apache.org/jira/browse/SSHD-1292
Project: MINA SSHD
Issue Type: Question
Affects Versions: 2.8.0
Reporter: Roberto Deandrea
Hi Thomas,
I have connection problems with a Microsoft SFTP server called Rebex SFTP
Server
([https://www.rebex.net/buru-sftp-server/).|https://www.rebex.net/buru-sftp-server/)]
This is a NEW connection setup for our SFTP client/server product.
I have SFTP client based on Apache SSHD 2.8.0. The client is configured for
pushing files to the Rebex SFTP server.
Description of the problem :
Sometimes the SFTP client is unable to push files on this remote SFTP Server,
the SSH handshake fails during SSH handshake for an authentication timeout set
to 60 secs that expires.
The exception is the following :
{quote}Caused by: org.apache.sshd.common.SshException:
DefaultAuthFuture[ssh-connection]: Failed to get operation result within
specified timeout: 60000
at
org.apache.sshd.common.future.AbstractSshFuture$$Lambda$284/0000000000000000.apply(Unknown
Source)
at
org.apache.sshd.common.future.AbstractSshFuture.formatExceptionMessage(AbstractSshFuture.java:185)
at
org.apache.sshd.common.future.AbstractSshFuture.verifyResult(AbstractSshFuture.java:111)
at
org.apache.sshd.client.future.DefaultAuthFuture.verify(DefaultAuthFuture.java:39)
at
org.apache.sshd.client.future.DefaultAuthFuture.verify(DefaultAuthFuture.java:32)
at
org.apache.sshd.common.future.VerifiableFuture.verify(VerifiableFuture.java:56)
at com.primeur.sshd.client.SSHDClient.connect(SSHDClient.java:157)
{quote}
When the connection fails, looking through the verbose logs of the client I
sometimes found :
[8/23/22 6:35:52:064 EDT] 0000bfcb id=00000000
org.apache.sshd.common.channel.ChannelAsyncOutputStream 1 doWriteIfPossible
doWriteIfPossible([SftpChannelSubsystem[id=0,
recipient=0]-ClientSessionImpl[StateStreet@/127.0.0.1:40787][sftp]]
cmd=SSH_MSG_CHANNEL_DATA) *delaying write until space is available in the
remote window*
This trace seems to evidence some issues writing data on socket according to
SSH protocol....
I've managed to handle this warning "delaying write until space is available in
the remote window{*}"{*} setting the system property
*-Dorg.apache.sshd.config.sftp-chunk-if-window-less-than-packet=true* without
any improvement.
The authentication timeout expires because the SSH messages related to client
authentication are not sent and received between client and server.
+Q. What do you think about this log ?+
[8/23/22 6:35:52:285 EDT] 0000bfcf id=00000000
common.session.helpers.ReservedSessionMessagesHandlerAdapter 1
handleIgnoreMessage
handleIgnoreMessage(ClientSessionImpl[StateStreet@/127.0.0.1:40787])
*SSH_MSG_IGNORE*
The receiving of some *SSH_MSG_IGNORE* messages from SFTP remote server could
mean that the socket connection is in idle state and no data flow on the socket.
+Q. Can you confirm ?+
Q. Do you think that this issue is caused by external factor (i.e network
latency/load, firewalls, balancers etc..... or is caused by some tricky SSH
implementation details or interoperability issues with this SFTP server (less
likely...) ?
Thank you in advance for your cooperation.
Regards, Roberto.
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