This is a patch for tftpd. It does 2 things:

1. adds an '-u' option for tftpd

With this option I can run tftpd as current user - no switch to user none.
Then I don't need to create world writable dir for tftp write requests.
It is useful for QEMU with the user network stack and redirected ports.
I can exchange files between my host OS and Plan9 guest in QEMU
with tftp client in my host OS. 
I start tftpd in my working dir, send/receive files, kill tftpd.

Example of batch file for starting QEMU in MS-Windows:

set QEMU=C:/Program Files/QEMU
"%QEMU%/qemu.exe" -hda plan9.10G.qcow2 -m 256 -net nic,model=rtl8139 -net user -redir udp:69::69 -redir tcp:567::567 -redir tcp:17010::17010 -L "%QEMU%"

2. it was impossible to send file to tftpd server (write request) due to an error. I corrected it.