Configuring checksum offload operations

Some operations can be offloaded to the OSA adapter, thus relieving the burden on the host CPU.

The qeth device driver supports offloading the following checksum operations on both layer 2 and layer 3:
  • Inbound (receive) checksum calculations
  • Outbound (send) checksum calculations
The qeth device driver also supports offloading TSO segmentation, see Enabling and disabling TCP segmentation offload.

VLAN interfaces inherit offload settings from their base interface.

The offload operations can be set with the Linux ethtool command, version 6 or later. See the ethtool man page for details. The following abbreviated example shows some of the offload settings:
# ethtool -k encf500
Features for encf500:
rx-checksumming: on
tx-checksumming: on
	tx-checksum-ipv4: on
	tx-checksum-ip-generic: off [fixed]
	tx-checksum-ipv6: off [fixed]
	tx-checksum-fcoe-crc: off [fixed]
	tx-checksum-sctp: off [fixed]
scatter-gather: on
	tx-scatter-gather: on
	tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
	tx-tcp-segmentation: on
	tx-tcp-ecn-segmentation: off [fixed]
	tx-tcp6-segmentation: off [fixed]
udp-fragmentation-offload: off [fixed]
generic-segmentation-offload: off [requested on]
generic-receive-offload: on
large-receive-offload: off [fixed]
...