What will a host do when it receives a packet with an invalid TCP checksum?

TCP uses a checksum field in its header to verify data integrity. If the checksum computed by the receiver does not match the value in the header, the packet is corrupted and must be dropped immediately. The sender's retransmission timer will eventually trigger a resend of the segment without any explicit notification from the receiver.

TCP has no 'hold and wait for rebroadcast' mechanism - corrupted packets are discarded and retransmission is handled by the sender's own timer, not by a receiver request.

ICMP redirect messages are used by routers to inform hosts of a better route to a destination, not to signal TCP-layer checksum errors.

A TCP RST is sent to abruptly terminate an existing connection or reject an unexpected connection attempt, not as a response to a checksum failure.