[Pkg-samba-maint] Bug#856843: Bug#856843: smbclient: connection flood to port 445 on mounting cifs volume under kernel 4.9.0
Jelmer Vernooij
jelmer at jelmer.uk
Sun Mar 5 13:36:06 UTC 2017
On Sun, Mar 05, 2017 at 12:30:33PM +0100, nils wrote:
> Package: smbclient
> Version: 2:4.2.14+dfsg-0+deb8u2
> Severity: important
>
> Hello,
> after upgrading my kernel from 4.0.8 to 4.0.9 I am getting connection floods to
> my FreeNAS samba server from my debian machine. I never had this issue with
> 4.0.8
>
> Linux dnet64 4.9.0-0.bpo.1-amd64 #1 SMP Debian 4.9.2-2~bpo8+1 (2017-01-26)
> x86_64 GNU/Linux
> ii smbclient 2:4.2.14+dfsg-0+deb8u2 amd64 command-line
> SMB/CIFS clients for Unix
>
> After mouting the cifs share(s) everything is OK for about 10 minutes, then a
> flood of connections happens. Here is an extract of 'netstat -an' run every
> second. Only one or two connections are shown for every 'netstat -an' run. The
> connections are opening and closing at an incredible speed (nethogs goes to
> 100% and doesn't show anything because it's overwhelmed). gkrellm reports about
> 70k/Sec traffic due to this. See how the source port numbers increase
> increadibly quickly to get an idea of how many connections are really
> happening...
> ....
> tcp 0 1 10.0.2.15:55044 192.168.2.88:445 SYN_SENT
> tcp 0 1 10.0.2.15:55252 192.168.2.88:445 SYN_SENT
> tcp 0 0 10.0.2.15:55288 192.168.2.88:445 ESTABLISHED
> tcp 0 1 10.0.2.15:55314 192.168.2.88:445 SYN_SENT
> tcp 0 1 10.0.2.15:55348 192.168.2.88:445 SYN_SENT
> tcp 0 0 10.0.2.15:55396 192.168.2.88:445 ESTABLISHED
> tcp 0 1 10.0.2.15:55454 192.168.2.88:445 SYN_SENT
> tcp 0 0 10.0.2.15:55500 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:55544 192.168.2.88:445 ESTABLISHED
> tcp 0 42 10.0.2.15:55586 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:55630 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:55676 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:55720 192.168.2.88:445 ESTABLISHED
> tcp 0 1 10.0.2.15:55770 192.168.2.88:445 SYN_SENT
> tcp 1 0 10.0.2.15:55820 192.168.2.88:445 CLOSE_WAIT
> tcp 0 1 10.0.2.15:55868 192.168.2.88:445 SYN_SENT
> tcp 0 0 10.0.2.15:55912 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:55962 192.168.2.88:445 ESTABLISHED
> tcp 1 0 10.0.2.15:56010 192.168.2.88:445 CLOSE_WAIT
> tcp 0 1 10.0.2.15:56058 192.168.2.88:445 SYN_SENT
> tcp 0 0 10.0.2.15:56056 192.168.2.88:445 LAST_ACK
> tcp 0 0 10.0.2.15:56104 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:56162 192.168.2.88:445 ESTABLISHED
> tcp 0 0 10.0.2.15:56202 192.168.2.88:445 ESTABLISHED
> tcp 0 1 10.0.2.15:56246 192.168.2.88:445 SYN_SENT
> tcp 0 0 10.0.2.15:56290 192.168.2.88:445 ESTABLISHED
> ....etc.
>
> Rebooting in 4.0.8 makes the issue go away, and I can have the shares mounted
> as long as I want without a connection flood. Hence I assume that it's a
> smbclient + Kernel 4.0.9 issue
smbclient is a command-line tool, if you're just mounting CIFS shares then this
is an issue in the kernel rather than in smbclient.
Jelmer
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