Empty TCP payload caused by tx-scatter-gather in ixgbevf

[PLauw]

We noticed that the TCP payload of some packets was empty (all zero) when transmitted by a virtual machine using SR-IOV an the ixgbevf driver.

This happens rarely, but when it happens, all retransmitted packets suffer from the same problem.

When we disable tx-scatter-gather on the sender, the problem never occurs.

ethtool -K eth0 sg off

In the following captures the transmitter is at the right side and the receiver at the left side. The receiving side is actually captured using a port mirror on the switch and an intermediate host to make the capture.

The TCP checksum at the transmitter is incorrect, but that's because of tx checksum offloading. The TCP checksum at the left (receiver) is what you would expect if the TCP payload would have been correct.

The TCP payload at the left only contains zeros.

In another capture, we noticed that the corrupt TCP payload appeared to contain references to kernel objects. This made us believe the issue was caused by pointing to the wrong location in memory.

System information:

Server HP ProLiant BL460c Gen8 with 32 GB RAM

Dual Intel(R) Xeon(R) CPU E5-2658 0 @ 2.10GHz

NIC: HP 560FLB based on Intel 82599

OS: CentOS release 6.8

Drivers ixgbe: 4.2.1-k and ixgbevf 2.12.1-k

The same issue was noticed on several servers including a ProLiant DL360p Gen8 with HP 2-port 561FLR-T based on Intel X540.

[idata]

Hi PieterLauwers,

Thank you for posting in Wired Ethernet community.Based on the provided information, you may want to try outthe updated driver - ixgbe 4.4 and ixgbevf 3.2.2 for your HP 560FLB to check if it help in your issue. Please refer to the HP website link for the drivers. Kindly take note Intel doesn't guaranteethe content of the site below. http://h20566.www2.hpe.com/hpsc/swd/public/readIndex?sp4ts.oid=5274096&swLangOid=8&swEnvOid=4095I'd also suggest contacting HP support for further assistance since our 82599 and X540 were integrated to their adapter, there might have customization to better fit into their product.regards,Vince