Looking for an Iperf utility that does packet validation (compare the CRC at the receiving and signal errors)

Hi guys

I need to do stress testing in a complicated scenario which requires me to compare the payload of the packets sent and received. It has to work like Iperf but should allow me to craft the payload (which Iperf can do) but I need to be able to compare the packets (I guess any variation in the TCP checksum will do it)

Any recommendations ?