Bug#814681: QNAP TS-219P II: Network transmit data corruption caused by mv643xx_eth TCP segmentation offload

["Robert Schlabbach" <Robert.Schlabbach@gmx.net>]

Package: linux-image-4.3.0-0.bpo.1-kirkwood
Version: 4.3.3-7~bpo8+1

This one seems to be a repeat offender (see #764162):

When running a samba server under Debian with the "sendfile = yes" option,
I observe corruption during file transfers from the Debian server to a
Windows 7 PC. Inspection of the corruption reveals that every now and then,
a sequence of 4 bytes is replaced with the destination MAC address.

Sample (Offset: Original Mismatch; M1 through M4 are the first four bytes
of the MAC address of my Windows 7 PC):

0C402D48: 2F M1
0C402D49: C2 M2
0C402D4A: 18 M3
0C402D4B: 3C M4
107ABBDC: 9D M1
107ABBDD: A6 M2
107ABBDE: 97 M3
107ABBDF: 5B M4
1102D860: 7B M1
1102D861: DF M2
1102D862: 5A M3
1102D863: CE M4
17682D48: DA M1
17682D49: 9A M2
17682D4A: 44 M3
17682D4B: 7C M4
1B8AE3C8: 33 M1
1B8AE3C9: FF M2
1B8AE3CA: D2 M3
1B8AE3CB: 17 M4
1CAAD860: 18 M1
1CAAD861: 20 M2
1CAAD862: C7 M3
1CAAD863: 23 M4
1F76CCF8: 76 M1
1F76CCF9: 9E M2
1F76CCFA: 44 M3
1F76CCFB: 79 M4
20EEE3C8: AB M1
20EEE3C9: 40 M2
20EEE3CA: A4 M3
20EEE3CB: A2 M4

The offsets change each time the file is transferred, but the incorrect
values remain the same, it's always the first 4 bytes of my Windows 7 PC
MAC address.

The command suggested in #764162:

sudo ethtool -K eth0 tso off

*fixes* the problem, and the command:

sudo ethtool -K eth0 tso on

makes it reappear most of the time, but sometimes not...?!?

Driver information:

~$ sudo ethtool -i eth0
driver: mv643xx_eth
version: 1.4
firmware-version: N/A
bus-info: platform
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no

Initial offload settings (with the problem observed):

Features for eth0:
rx-checksumming: on
tx-checksumming: on
        tx-checksum-ipv4: on
scatter-gather: on
        tx-scatter-gather: on
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
generic-segmentation-offload: on
generic-receive-offload: on
tx-nocache-copy: off


Best Regards,
Robert Schlabbach