NetBSD ftpd on-the-fly conversions incompatible with curl

[Daniel Feenberg <feenberg%nber.org@localhost>]

I have been using the NetBSD ftpd server for some time specifically 
because of the on-the-fly conversion capability. Usually that is for 
gunziping files before transmission, but I have a more critical need - I 
use it to process data for anonymous users.

However, it seems that curl inquires about the size of the file before 
"get"ing it, and ftpd replies "550 <filename> not a plain file" when a 
file is subject to conversion, which is apparently treated as a fatal 
error by curl, and curl does not attempt to "get" the file. Here is a 
portion of the --verbose output from curl:

  > TYPE I
  < 200 Type set to I.
  > SIZE NBERStostad.txm35
  < 550 NBERStostad.txm35: not a plain file.
  * The file does not exist

According to this post (https://curl.se/mail/lib-2004-10/0035.html), if 
the SIZE command did not exist, curl would still work. It appears that 
existing and providing a specific error message is the getting in the way. 
I am not sure why curl bothers to issue the SIZE command when the 
--max-filesize option is left unspecified. It seems unnecessary.

Is there any way around this? The conversion feature is the primary reason 
for my using NetBSD.

Daniel Feenberg
http://taxsim.nber.org/