It's not save to presume any zero page variable to stay intact after using the Ethernet drivers to perform actual network I/O. In example a necessary ARP lookup may require network I/O in not anticipated scenarios. Therefore the tftp_filename is rather to be placed in a normal variable and copied to a zero page variable just-in-time.
- Tab chars were partially used with the unusual width of two blanks. I removed them altogether.
- Line endings were inconsistent even iniside individual files. I normalized them.
- I introduced a consistent coding style regarding comment indenting and blank line usage.
- I removed trailing spaces.
- I removed newlines following unnamed labels.
- ...
