The main purpose of this is to be able to disable the rx offload that is enabled by default on some NICs. The Intel 810 series NICs in particular seem to have an issue where certain packets cause false positives when using the hardware offloaded rx checksuming which is causing some issues with our monitoring.
vyos@vyos1:~$ show interfaces ethernet eth3
eth3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 98:b7:85:a8:10:e5 brd ff:ff:ff:ff:ff:ff
altname enp1s0f1np1
inet 192.168.1.1/24 brd 192.168.1.255 scope global eth3
valid_lft forever preferred_lft forever
inet6 fe80::9ab7:85ff:fea8:10e5/64 scope link
valid_lft forever preferred_lft forever
RX: bytes packets errors dropped overrun mcast
7515477561315 36559040450 32106 92383 0 1761158
TX: bytes packets errors dropped carrier collisions
7579331854068 15788158922 0 0 0 0
vyos@vyos1:~$ ethtool -S eth3 | grep csum
rx_csum_bad.nic: 32106