For example, if I am working with a Ethernet packet of size 16, and I embed data in the first 12 bytes of the packet, and set the last 4 bytes to zero, I assume the kernel will generate and embed a frame check sequence (FCS) in those last 4 empty remaining bytes. Is this assumption correct?
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This should answer your question: [Is ethernet checksum exposed via AF\_PACKET?](https://stackoverflow.com/questions/15651651/is-ethernet-checksum-exposed-via-af-packet) TL;DR: no need to checksum, send data without padding, checksum is done by hardware. – Marco Bonelli Oct 19 '21 at 20:07
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Modern ethernet interfaces generate and check the FCS in hardware. Frames with a bad FCS are dropped by the interface, never reaching the network stack. – Ron Maupin Oct 19 '21 at 20:44