ifconfig -m <interface>-m display the capability list and all of the supported media for the specified interface. Check the capabilities= line for offload settings.
Capabilities can be modified with ifconfig as well:
ifconfig <interface> tso4 # Enable tcp(4) segmentation offloading for ip(4) only
ifconfig <interface> -tso4 # Disable tcp(4) segmentation offloading for ip(4) onlyReferences
IFCONFIG(8)