FTP protocol violations


Benson I. Margulies (Margulies@SCRC-YUKON.ARPA)
Thu, 3 Apr 86 07:29 EST


    Date: Wed, 2 Apr 86 17:06 EST
    From: David C. Plummer <DCP@SCRC-QUABBIN.ARPA>

        Date: Wed, 2 Apr 86 14:15:37 est
        From: romkey@BORAX.LCS.MIT.EDU (John Romkey)

           Date: Wed, 2 Apr 86 09:36 EST
           From: Benson I. Margulies <Margulies@SCRC-YUKON.ARPA>

           If being permissive about what one accepts means accepting this, should
           I make my implementation ignore the second two digits of positive
           responses to simple model commands? I can't see taking too and 250 and
           no other 2xy's.

        That's the way my IBM PC FTP does it. The command state machine is
        just driven by the first digit. The other two digits can be used to
        get more information, but unless I've missed something somewhere,
        you can safely ignore them in deciding whether or not a command
        succeeded, or what to do next.
                                                        - john romkey
                                                          ftp software

    Wait a minute. A spec is a spec. What's the point of the two digits if
    (a) some hosts send the wrong ones, and (b) some hosts don't bother to
    look at them. If the spec said you could be lazy, then it would be OK.
    If the spec doesn't, an implementation is INCORRECT if it sends the
    wrong codes and an implementation is ASKING FOR TROUBLE if it accepts
    more than what the spec says.

I would point out that the general princible: `be precise in what you
send, be forgiving in what you receive' has been stated many times for
the internet protocol set. FTP, however, nowhere says that the
implication of this is to just look at the first digit. What are the
chances of a clarification from on-high?



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