>> [...ftp client vs EPSV vs download.fedora.redhat.com...]
> I'm guessing that they are using vsftpd (at least I believe that the
> vsftpd documentation claims use by RedHat).  You may want to take a
> look at the vsftpd code.  It is in pkgsrc.

I got a reply from Red Hat.  They say they "do not currently support
commands from the epsv command set" and ask me to "[p]lease use
commands from the classical passive command set only".  I sent back a
reply pointing out that their server responds to EPSV with something
that looks like a perfectly good EPSV response, and they may want to
change that if they don't really support EPSV.  No response to that
yet.

They do acknowledge that this "is not a great response", adding "but it
is all we have right now", so there is at least some awareness that the
current situation is..suboptimal.

In any case, it's no particular skin off my nose; by fetching manually,
with epsv4 disabled and passive enabled, I was able to get the files I
actually wanted.  I mentioned it here in case there was any desire to
tweak our FTP client to handle this better somehow.  In view of what
you say about vsftpd, it might be worth doing interop testing of our
client against a vsftpd server, if anyone thinks it's worth the trouble.

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