Int 2F Fn 1121  CU - Network Redirector - Seek From End Of Remote File     [N]

   AX = 1121h
   CX:DX = offset (in bytes) from end
   ES:DI -> SFT
       SFT DPB field -> DPB of drive with file
   SS = DOS DS

Return: CF set on error
       AL = DOS error code (see #1366 at INT 21/AH=59h/BX=0000h)
   CF clear if successful
       DX:AX = new file position

Note:  this function is called by the DOS 3.1+ kernel, but only when seeking
     from the end of a file opened with sharing modes set in such a
     manner that another process is able to change the size of the file
     while it is already open

See Also: AX=1228h,INT 21/AH=42h