Traditional tftp file access control:
 read access:
  tftpd(8) - tftpd will allow only publicly readable files to be accessed.
 write access:
  tftpd(8) - files may be written only if they already exist and are publicly writable.

Test condition: files may be written only if they are publicly writable (i.e. mode ??2).

Summary, libexec/tftpd write access:
 absolute filenames:
  all modes (??0 ??2 ??4) - correct.
 relative filenames:
  mode ??0 - incorrect 6.1 (RELEASE-p2 tested)
  mode ??2 - incorrect 4.11 (RELEASE-p9 tested)
  mode ??4 - incorrect both - 4.11 and 6.1

Fix: 1) 6.1-RELEASE-p2: diff -up libexec/tftpd/tftpd.c.orig libexec/tftpd/tftpd.c
2) 4.11-RELEASE-p9: diff -up libexec/tftpd/tftpd.c.orig libexec/tftpd/tftpd.c
How-To-Repeat: 
for example:

~# grep '^tftp' /etc/inetd.conf
tftp	dgram	udp	wait	root	/usr/libexec/tftpd	tftpd -l -s /spool/tftp

~# touch a
~# touch /spool/tftp/a
~# chown nobody:nogroup /spool/tftp/a


1) mode ??0
~# chmod 640 /spool/tftp/a
~# tftp localhost

1a) 6.1-RELEASE-p2
tftp| put a /a
Error code 2: Access violation
  ! error - correct
tftp| put a a
  ! no error - incorrect

1b) 4.11-RELEASE-p9
tftp| put a /a
Error code 2: Access violation
  ! error - correct
tftp| put a a
Error code 2: Access violation
  ! error - correct



2) mode ??2
~# chmod 642 /spool/tftp/a
~# tftp localhost

2a) 6.1-RELEASE-p2
tftp| put a /a
  ! no error - correct
tftp| put a a
  ! no error - correct

2b) 4.11-RELEASE-p9
tftp| put a /a
  ! no error - correct
tftp| put a a
Error code 2: Access violation
  ! error - incorrect



3) mode ??4
~# chmod 644 /spool/tftp/a
~# tftp localhost

3a) 6.1-RELEASE-p2
tftp| put a /a
Error code 2: Access violation
  ! error - correct
tftp| put a a
  ! no error - incorrect

3b) 4.11-RELEASE-p9
tftp| put a /a
Error code 2: Access violation
  ! error - correct
tftp| put a a
  ! no error - incorrect