[SSHD-1207] Large file get using WinSCP with Apache SFTP Server is not working

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Sreedhar J
• Created: 04/Aug/21 17:02
• Updated: 24/Jan/22 07:47

Description

We have been using Apache SSHD version 2.5.1 for SFTP Server functionaity and it was working very well with all the sftp clients. Recently we have upgraded 2.7.0 and facing issues with largefile downloads using WinSCP. Entire file is not getting downloaded. Some time with out downloading the entire file WinSCP is showing the transfer as complete. In the Apache SSHD logs, I see many EOF status messages to the client. Not sure why so many EOF messages are exchanged between the client and Server.

04 Aug 2021 21:38:10,841 [sshd-SftpSubsystem-46473-thread-1] DEBUG Nio2Session - writeBuffer(Nio2Session[local=/10.15.102.66:59119, remote=10.84.42.167/10.84.42.167:59334]) writing 16448 bytes
04 Aug 2021 21:38:10,842 [sshd-SftpSubsystem-46473-thread-1] DEBUG SftpSubsystem - process(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334])[length=53, type=SSH_FXP_READ, id=4884997] processing
04 Aug 2021 21:38:10,842 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-1] DEBUG ServerSessionImpl - encode(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334]) packet #149 sending command=94[SSH_MSG_CHANNEL_DATA] len=10734
04 Aug 2021 21:38:10,842 [sshd-SftpSubsystem-46473-thread-1] DEBUG SftpSubsystem - doSendStatus(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334])[id=4884997] SSH_FXP_STATUS (substatus=SSH_FX_EOF, lang=, msg=End of file)
04 Aug 2021 21:38:10,842 [sshd-SftpSubsystem-46473-thread-1] DEBUG SftpSubsystem - process(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334])[length=53, type=SSH_FXP_READ, id=4885253] processing
04 Aug 2021 21:38:10,842 [sshd-SftpSubsystem-46473-thread-1] DEBUG SftpSubsystem - doSendStatus(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334])[id=4885253] SSH_FXP_STATUS (substatus=SSH_FX_EOF, lang=, msg=End of file)
04 Aug 2021 21:38:10,843 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-1] DEBUG Nio2Session - writeBuffer(Nio2Session[local=/10.15.102.66:59119, remote=10.84.42.167/10.84.42.167:59334]) writing 10800 bytes
04 Aug 2021 21:38:10,843 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-1] DEBUG ServerSessionImpl - encode(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334]) packet #150 sending command=94[SSH_MSG_CHANNEL_DATA] len=41
04 Aug 2021 21:38:10,843 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-1] DEBUG Nio2Session - writeBuffer(Nio2Session[local=/10.15.102.66:59119, remote=10.84.42.167/10.84.42.167:59334]) writing 96 bytes
04 Aug 2021 21:38:10,843 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-1] DEBUG ServerSessionImpl - encode(ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334]) packet #151 sending command=94[SSH_MSG_CHANNEL_DATA] len=41
04 Aug 2021 21:38:10,843 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-1] DEBUG Nio2Session - writeBuffer(Nio2Session[local=/10.15.102.66:59119, remote=10.84.42.167/10.84.42.167:59334]) writing 96 bytes
04 Aug 2021 21:38:11,038 [sshd-SshServer[6ad1bbb8](port=59119)-nio2-thread-8] DEBUG ChannelSession - handleData(ChannelSession[id=0, recipient=256]-ServerSessionImpl[testuser1@10.84.42.167/10.84.42.167:59334]) SSH_MSG_CHANNEL_DATA len=57

 

Issue Links

• relates to: SSHD-1123 ChannelAsyncOutputStream breaks downloads of sftp client by not chunking when the remote window is smaller than the packet size
• relates to: SSHD-1196 sendChunkIfRemoteWindowIsSmallerThanPacketSize flag in ChannelAsyncOutputStream constructor configurable from outside using variable/config file