vixie@palo-alto.DEC.COM (Paul Vixie) (07/19/88)
(Andrew Macpherson writes:) # You have brought up a nasty. In fact you are highlighting two # of them. Firstly '%' as an address character. IT IS NOT LEGAL RFC822. # It remains around for historical compatibility (RFC7?? --- read the # first page of 822 if you really want to know which). (Rick Adams writes:) # The fact that you are mucking with the LOCAL-PART, which you are supposed # to leave totally alone, is the cause of the problem. (which I agree with, but then Rick says:) # Anyone who gives % precedence over ! should fix their mailer. # % is NOT a synonym for @. It is a valid part of the local-part # of the address and should not be interpreted my any site save # the destination machine. I agree that % is not a defined pseudonym for @ and that anyone who tries to say it is can be ignored. It is, indeed, part of the "local part", and there is no written standard that says it has to be processed one way or another. But, um, has anybody got users on their systems with "%" as part of the user identifier? Probably a few, but vastly: no. "%" _is_ intepreted by most large sites, after all standard address characters have been processed, stripped off, and yet the message is still unresolved. The usual processing of "%" is: locate the rightmost % change it to an @ go back and do what @ requires This is a _HACK_. But it's widely implemented. It has the same level of "pseudo standardization" that "!" has, though the two characters evolved on different planets. So when Rick said: # Anyone who gives % precedence over ! should fix their mailer. I say: uh-uh, nothing's wrong with my mailer. If I'm to interpret % at all, I'll be doing it mostly by the seat of my pants -- since there's no standard for it, it's in the local-part after all. It has a common meaning, which is very similar to the meaning of "@" -- the thing to the right of it is a host or domain or something, and the thing to the left of it is an address or a route or some such that the thing to the right of it can be halfway depended upon to understand. I'll say again: % is just another character if there's an @ anywhere in an address. @ is spoken of in RFC822, % is not. % should be treated like "a" or "b" or "c" if there's an @ anywhere in the address (really route-addr but you know what I mean). The UUCP "!" is in the same state -- it's just another character if there's an @ anywhere to be found. So, shall I fix my mailer to send back mail that gets here looking like "xyzzy!bar" or "bar%xyzzy" after I've stripped off the "@dec.com"? I'd rather not just bounce things, since there is something of a standard for what these LOCAL-PART characters mean. I give ! precedence over %, because I've already got a character that does what % does -- that is, @. % begins to have great value as a low-precedence @ that will be treated as an @ once all @'s and !'s have been stripped out. (Andrew Macpherson continues:) # Having got that off my chest, here is the associated nasty: mcvax # uses it as a 'local-part' operator, and hands on addresses of the form # a!b!u%l, which any Internetted (and probably any JANET) host will treat # as send to 'l' for uucp forwarding. Bleah. Seriously. If I want it to go to "l" first, I can use "@l". If I say "%l", it probably means that I want to do something that @ can't do -- namely, not be evaluated until it reaches "b". # This is not usually a problem but occasionally we recieve US mail which # has hopped to the arpanet and been strangely delt with... "Strangely"? Our conventions are different, that's true. John Diamant @HP once sent me an unfinished RFC that dealt with this issue, but like him, I could never figure out quite how to resolve everything into one neat little package. But I do think that after the one, Crocker-given symbol has been processed and we are down to our nitty-gritties trying to hand off a piece of mail based on the local-part, that ! usefully precedes % in what little decoding is possible. # Now the other point... Mixed addresses. If you live in the uucp world only # you have no trouble. If in 822 land likewise. I understand the JNETters # allow % as a source-routing so they also have a consistent rule-set. All 3 # have a route specification method, therefore there is neither need nor # justification for mixed-mode addressing. [...] The only safe and reasonable # course to take is to provide the destination address in the format required # by the network you are using. I agree completely. The rules I use for local-part precedence are worst-case, and properly generated mail messages don't get that far into the bowels of my mailers. If something comes to me over UUCP, the envelope recipients can easily be coded, each and every one, in pure !-notation. If I want to submit a message into a UUCP transport system, I can bloody well code up all the envelope recipients in pure !-notation. Likewise, if something comes in over SMTP, the envelope recips can and should be in straight route-addr notation (i.e., @a,@b,@c:u@d, and gosh that sure is ugly, Dave), and I can certainly be expected to submit things in that form. As Diamant (am I spelling that right, John?) points out, though, RFC822 and its friends imply or demand that all domains named in a route-addr be registered with the NIC. This is silly and inconvenient and everybody ignores it. But it does mean that if something comes to you over UUCP with an envelope recip of a!b!c!d and you decide to reach "a" via SMTP and you want to rewrite the envelope recip into route-addr and you rewrite it to be @a,@b:d@c and either "b" or "c" is not registered with the NIC, you've just broken another silly regulation. -- Paul Vixie Digital Equipment Corporation Work: vixie@dec.com Play: paul@vixie.UUCP Western Research Laboratory uunet!decwrl!vixie uunet!vixie!paul Palo Alto, California, USA +1 415 853 6600 +1 415 864 7013
rsalz@bbn.com (Rich Salz) (07/19/88)
>[ Treating % as a delayed @ if there are no other meta-characters in the >address ] has the same level of "pseudo standardization" that "!" has, >though the two characters evolved on different planets. Unh, no. The "!" character for UUCP routing is documented in RFC976. I'd also claim that UUCP and ARPA aren't two different planets, but were at worst two different continents, shared by a few common passageways, navigable only by some very hardy souls. In particular, now-civilized natives of far-off UUCP backwaters fondly remember the great trappers and trackers that would hang around Old Camp Seismo. There's definitely been a shift in the plate tectonics, and these two lands are know merged into one (un)common market. With apologies to Dave Mills for the second paragraph, /rich $alz -- Please send comp.sources.unix-related mail to rsalz@uunet.uu.net.
david@ms.uky.edu (David Herron -- One of the vertebrae) (07/21/88)
Paul,
neither rfc822 nor rfc976 specify that % does what the %-hack do. In fact,
both specify other methods to do routing. That means, both specs expect
the local-part to only be paid attention to by the 'local' machine, not
by machines along the route.
In:
user%a@some.dom.ain
and some!long!path!with!a%percent
the local part *shouldn't* be evaluated until it reaches the destination.
In the '@' case, until it reaches some.dom.ain, and the '!' case until
it reaches 'with'. Whatever either of those places wishes to do with
a local-part like "a%b" is up to them BECAUSE IT IS NOT SPECIFIED BY
EITHER SPEC!
Now, I didn't read your posting very closely and it's possible that you
said exactly that in your posting. But I think I caught a few statements
to the otherwise.
Oh, I suppose the next question is what to do with
some!long!path!a%b@some.dom.ain
RFC976 is the applicable spec. (according to rfc822, the "some!long!path!a%b"
is *all* local part and get's evaluated according to some.dom.ain's rules
for evaluating such things). The rfc recommends first that mailers not
use mixed adresses internally, instead preferring something like
some.dom.ain!some!long!path!a%b
or some!long!path!some.dom.ain!a%b
but if you must, to treat such an address as in rfc822 -- the local part
is the local part and isn't evaluated until it reaches some.dom.ain
(i.e. the "some.dom.ain!some!long!path!a%b" interpretation -- effectively)
It's right there in the specs in black&white (or purple&brown with the
right toner/paper combination ...)
--
<---- David Herron -- The E-Mail guy <david@ms.uky.edu>
<---- ska: David le casse\*' {rutgers,uunet}!ukma!david, david@UKMA.BITNET
<---- A misplaced Kansan trapped in the heart of Kentucky,
<---- the state where it is now illegal to water your lawn on the wrong day.scott@stl.stc.co.uk (Mike Scott) (07/26/88)
In article <3503@palo-alto.DEC.COM> vixie@palo-alto.DEC.COM (Paul Vixie) writes: >But, um, has anybody got users on their systems with "%" as part of the >user identifier? Probably a few, but vastly: no. But it's not just user identifiers... consider a system where mail is being gatewayed on a VMS machine between the un*x world and the DEC foreign mail interface which uses a % character in the address to define the interface - for example, mail from PSS has the address prefix "PSI%", which can wreak some havoc when replied to by the unwary! -- Regards. Mike Scott (scott@stl.stc.co.uk <or> ...uunet!mcvax!ukc!stl!scott) phone +44-279-29531 xtn 3133.