Checksum offload, recalculating a bad checksum after corrupting the data, is really insidious.

Shows that trust in TCP can be badly misplaced -- in this case the trouble was cache coherency, but lack of ECC RAM or other electrical gremlins could easily corrupt packets too (and NIC buffer RAM is never ECC afaik), and blindly trusting TCP checksums would eat your data every time.

(Side note, doesn't 'zfs send' blindly trust TCP checksums?)

Props to Rsync and SSH and Wireguard and everything else that went beyond the call of duty to keep your data safe, with varying levels of alertness.