)In the MITM attack code, the attacker tries to modify the packets from A to B. After intercepting such a packet, the attacker makes a copy of the packet, and then does the following. Why does the attacker have to delete the IP adn TCP checksums?

newpkt= IP(bytes(pkt[IP])

del(newpkt.chksum)

del(newpkt[TCP].chksum)