Bug 14577 - copying files to samba triggers unexpected network error on Windows 10 client
Summary: copying files to samba triggers unexpected network error on Windows 10 client
Alias: None
Product: Samba 4.1 and newer
Classification: Unclassified
Component: File services (show other bugs)
Version: 4.12.10
Hardware: All All
: P5 normal (vote)
Target Milestone: ---
Assignee: Samba QA Contact
QA Contact: Samba QA Contact
: 12003 (view as bug list)
Depends on:
Reported: 2020-11-17 20:39 UTC by Björn Jacke
Modified: 2020-11-18 09:23 UTC (History)
2 users (show)

See Also:

sample SMB packet that a Palo Alto deep inspection firewall drops (844 bytes, application/x-pcapng)
2020-11-17 23:17 UTC, Björn Jacke
no flags Details

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Description Björn Jacke 2020-11-17 20:39:47 UTC
testing with the files from the iso image: https://bugzilla.samba.org/attachment.cgi?id=9718

tested with 4.12.10 and Windows 10 as client, trying to copy the files using explorer. The copy process hangs always in "get_file.m", which
*interestingly* is one if the very few filenames, that exist multiple times in
different directories:


Copying those files onto a *Windows* volume works without a problem, also via

Copying it from there on a Samba share triggers an error. Actually copying the
vpm folder alone is enough to trigger the problem. SetInfo
SMB2_FILE_ENDOFFILE_INFO comes from the client, the server replyies with a
successful response, but then the client is unhappy:

Error 0x8007003B: An unexpected network error occurred

Something that smbd sends back seems to be bad here.
Comment 1 Ralph Böhme 2020-11-17 21:06:46 UTC
Can you share a network trace?
Comment 2 Björn Jacke 2020-11-17 23:17:22 UTC
Created attachment 16344 [details]
sample SMB packet that a Palo Alto deep inspection firewall drops

I was trying to make a network sniff using a smbd share on my local machine, where the Windows 10 client is also running. It was not reproducible any more. The error happens if I access a Samba server via VPN though. I thought the latency might make the difference and that might trigger a SMB2/3 client bug in Windows, this is also is what you think of if you read the similar bug #12003 and the related links in that bug report. It seemed like this is not a Samba bug but a Windows client bug that exists since Windows 8.1 and is still around in latest Windows 10 releases. I tried to trigger the "Windows Client VPN bug" by adding artificial latency to my local network interface until I would see the same bug that I saw via VPN. But the bug just didn't pop up.

So I remembered that I had some days of fun with a terribly broken SMB connection some weeks ago that, that was cause by an intelligent Palo Alto device, I now did a network capture on the server AND on the client site and compared both of them. Palo Alto strikes again here. It just drops a SMB3 Create Request of the client, that the server never sees, I'll attach the create request packet here.
Comment 3 Björn Jacke 2020-11-17 23:19:44 UTC
*** Bug 12003 has been marked as a duplicate of this bug. ***
Comment 4 Björn Jacke 2020-11-18 09:23:06 UTC
closing the bug as invalid because it's not a Samba bug.

People using SMB should not use broken DPI Firewalls or ask their IT department to disable those broken features.