Opened 18 years ago

Last modified 10 years ago

#971 closed Bug report

Filezilla Hangs in SFTP+ClientAliveInterval

Reported by: seelie Owned by: Alexander Schuch
Priority: normal Component: FileZilla Client
Keywords: Cc: seelie, Alexander Schuch
Component version: Operating system type:
Operating system version:


SFTP using SSH2 works fine with the default
(server-side) sshd_config setting, "ClientAliveInterval 0"

However, Filezilla is stuck in this infinite loop:
"SftpControlSocket.cpp(2423): ResetOperation(1)"
"SftpControlSocket.cpp(2596): OnReceive(0)"
"SftpControlSocket.cpp(2596): OnReceive(0)"
"SftpControlSocket.cpp(2596): OnReceive(0)"
causing 100% CPU load, if you set:
"ClientAliveInterval 15 (or any non-zero value)"
--i.e. if sshd sends a message through the encrypted
channel to request a response from the client--,
and when
(ClientAliveInterval * ClientAliveCountMax)
seconds have passed.

Always reproducible on FileZilla 2.2.17
on my Windows 2000 Pro SP4.

This problem happens both for "KeepAlive yes/no" in
but in my test, Filezilla does:
SftpControlSocket.cpp(289): List(FALSE,0,"","",0)
many times when KeepAlive no, while doing it only once
when KeepAlive yes. (This pert may be unrelated to the
above problem.)

debug.log ("Trace messages from the FTP engine") attached.
This log was taken when sshd_config was:
KeepAlive no
ClientAliveInterval 15
ClientAliveCountMax 3
And the problem seems to have happened 45 seconds
after the session becomes idle.

Quote from man sshd_config
If ClientAliveInterval (above) is set to 15, and
ClientAliveCountMax is left at the default,
unresponsive ssh clients
will be disconnected after approximately 45 seconds.

Attachments (1)

debug.log (41.7 KB ) - added by seelie 18 years ago.
Trace messages from the FTP engine

Download all attachments as: .zip

Change History (7)

by seelie, 18 years ago

Attachment: debug.log added

Trace messages from the FTP engine

comment:1 by Alexander Schuch, 17 years ago

Can you please try the most recent version of FileZilla 2 or preferable even FileZilla 3 beta?

SFTP is handled by the PuTTY suite and lots of changed had been done there already which were merged into the FileZilla source. Chances are that this issue has been fixed already.

comment:2 by Alexander Schuch, 17 years ago

Related but already closed (as duplicate) bug:
[ 1455727 ] Remote file list hangs after a while

comment:3 by Alexander Schuch, 17 years ago

Maybe the following bug is related to this one as well:
[ 1447224 ] Loops at 100% CPU after SFTP upload

comment:4 by Alexander Schuch, 17 years ago

Maybe related to the following one as well:
[ 1442770 ] Processor usage when connection times out

comment:5 by Alexander Schuch, 17 years ago

Related (but closed as duplicate) bug:
[ 1183119 ] 2.2.29 fzsftp tacks CPU to 100%

comment:6 by sf-robot, 17 years ago

This Tracker item was closed automatically by the system. It was
previously set to a Pending status, and the original submitter
did not respond within 14 days (the time period specified by
the administrator of this Tracker).

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