Implementation bug with payload modification

[ozawawi]

The README specifies that for payload modification a text file that contains pattern of 0x00000001,0x00000002,0x00000003 should be supplied with the ----payload_file_path option. However, the current method of parsing the file results in an incorrect payload_len in this line of code.

This is caused because the content of the file is parsed byte by byte and casted to char in this line. To get the payload_len, the current method is using strlen which would interpret zeros like the one between the brackets here 0x0000(00)01 as the null character and so payload_len becomes incorrect.

Finally, this line ends up writing only a subset of the payload file to the buffer.

[sshaulnv]

Thanks for your contribution. we made a fix: https://github.com/linux-rdma/perftest/commit/a416f72011da640345ea95f7f3963afbec24ed69