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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses.
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

longgang <zhlonggang@aliyun.com> changed:

What |Removed |Added
----------------------------------------------------------------------------
Summary|sshd process had became |sshd process had became
|<defunct> and could not |into a defunct process and
|accept requests any more |could not accept requests
|after many count sftp |any more after many count
|accesses. |sftp accesses.

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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses. [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

Darren Tucker <dtucker@dtucker.net> changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |dtucker@dtucker.net

--- Comment #1 from Darren Tucker <dtucker@dtucker.net> ---
A <defunct> process is a child process that has exited but has not yet
had its parent wait() for it yet. There is a (usually) brief period
between when the process exits and its parent retrieves its exit
status. Having a very small number of them appearing briefly is not
necessarily a problem. Having the same pid appearing for any
significant time (say, more than a second) is probably a problem.

I had a look at the log, but did not see anything that would explain
what you're describing.

If you increase MaxStartups does the behaviour change? The default is
10:30:100 so I'd suggest trying "100:30:1000"

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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses. [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

--- Comment #2 from longgang <zhlonggang@aliyun.com> ---
Darren Tucker, thanks for your sugestion, I`ll have a try today and
give my test result here.

I uploaded the last 500 lines log when the problem occured and the
sshd_config files used. I hope some useful infomation you can find.

I also has run following tests:

1. I run openssh-5.3p1 with the same sshd_config file which I has
uploaded except that the macs, kexalgorithoms, ciphers were commented.
The same java client programe has already run more then 24 hours so
far, everything is ok, the problem do not occur.

2. I run openssh-7.9p1 with the same sshd_config file which I has
uploaded. The same java client programe has already run for 10 hours so
far, everything is also ok, the problem also do not occur.

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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses. [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

--- Comment #3 from longgang <zhlonggang@aliyun.com> ---
Created attachment 3406
--> https://bugzilla.mindrot.org/attachment.cgi?id=3406&action=edit
the last 500 lines log

the last 500 lines log

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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses. [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

--- Comment #4 from longgang <zhlonggang@aliyun.com> ---
Created attachment 3407
--> https://bugzilla.mindrot.org/attachment.cgi?id=3407&action=edit
sshd_config file used

sshd_config file used

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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses. [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

--- Comment #5 from Darren Tucker <dtucker@dtucker.net> ---
One possibility is the SA_RESTART signal change.
It's worth trying 8.3p1 both as is and with "./configure
--with-cflags=-DNO_SA_RESTART" (NO_SA_RESTART wasn't added until 8.3p1,
so it won't do anything on 8.2p1).

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[Bug 3177] sshd process had became into a defunct process and could not accept requests any more after many count sftp accesses. [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=3177

--- Comment #6 from longgang <zhlonggang@aliyun.com> ---
Darren Tucker, I have run the test on last weekend. The following is
the test result.

1. The openssh-8.3p1 complied with or without NO_SA_RESTART flags
defined, both had run into the problem as openssh-8.2p1. After a few
hours later, the java client program failed with the following
exception:

"Session.connect: java.net.SocketTimeoutException: Read timed out".

The sshd process became into defunct status.

[root@bjm7-9-10 ~]# ps -ef|grep sshd
root 1118 1 0 2019 ? 00:02:24 /usr/sbin/sshd
root 14170 16380 0 16:28 ? 00:00:00 [sshd] <defunct>
root 16380 1 0 08:57 ? 00:00:26 sshd:
/usr/local/openssh-8.3p1/sbin/sshd -p 99 -f
/etc/ssh/sshd_config_sftp.bad [listener] 0 of 10-100 startups


2. I also have run the openssh-8.1p1, the sshd process was normal and
did not become into defunct status, but the java client program failed
occasionally with the following exeption:

"java.io.IOException: inputstream is closed".

If the java client program catch the exception and ignore the error, it
will success next time.

3. My test with openssh-7.9p1 has already run 3 days so far,
everything is also ok, the problem also do not occur, and the java
client program has no errors as openssh-8.1p1.

I seems like openssh-7.9p1 is my best choice.

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