Hi all,

Contrary to IHAVE, for which the 436 response code can be sent to defer
an article (retry later), TAKETHIS does not have such a response code.

From RFC 4644:

Responses
239 message-id Article transferred OK
439 message-id Transfer rejected; do not retry

The server MUST return either a 239 response,
indicating that the article was successfully transferred, or a 439
response, indicating that the article was rejected. If the server
encounters a temporary error that prevents it from processing the
article but does not want to reject the article, it MUST reply with a
400 response to the client and close the connection.



Yet, RFC 3977 defines a generic response code (403) for temporary
internal problems, as we can see in the example:

Example of a temporary failure:

[C] GROUP archive.local
[S] 403 Archive server temporarily offline


Is the generic code 403 really not allowed for temporary errors in
TAKETHIS? (It seems to be the case when reading that explicit behaviour
to use the 400 generic code.)

Seems like a vestige from RFC 2980 which defined the following responses
for TAKETHIS:

239 article transferred ok
400 not accepting articles
439 article transfer failed
480 Transfer permission denied
500 Command not understood




As far as INN is concerned, it currently returns 403 after TAKETHIS only
in 2 cases: when innd can't store the article (empty token) or can't
write the history file.

Do you think a generic code could be possible in these cases (and then
it would be an erratum to RFC 4644 so as to add the possibility to use
the new 403 generic code introduced with RFC 3977) or should the
connection really be terminated as it was the case with obsolete RFC 2980?


FWIW, one of the case that can trigger the "can't store article" in innd
is when INT_MAX is reached. The 403 (or 400) code should really be 439
in this specific case because it is not a temporary failure. Same thing
for IHAVE which should answer 437 (reject) instead of defer (436) in
this case. We would otherwise end up with an infinite loop where the
article is stuck and kept being proposed even though the maximum article
number has been reached and INN won't be able to store more articles in
the newsgroup. (A log is also present in news.notice.)

--
Julien ÉLIE

« Il faut mépriser l'argent, surtout la petite monnaie. »

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* Origin: fsxNet Usenet Gateway (21:1/5)

Julien ÉLIE <iulius@nom-de-mon-site.com.invalid> writes:

Contrary to IHAVE, for which the 436 response code can be sent to defer an article (retry later), TAKETHIS does not have such a response code.

From RFC 4644:

Responses
239 message-id Article transferred OK
439 message-id Transfer rejected; do not retry

The server MUST return either a 239 response,
indicating that the article was successfully transferred, or a 439
response, indicating that the article was rejected. If the server
encounters a temporary error that prevents it from processing the
article but does not want to reject the article, it MUST reply with a
400 response to the client and close the connection.

Yet, RFC 3977 defines a generic response code (403) for temporary internal problems, as we can see in the example:

Example of a temporary failure:

[C] GROUP archive.local
[S] 403 Archive server temporarily offline

Is the generic code 403 really not allowed for temporary errors in
TAKETHIS? (It seems to be the case when reading that explicit behaviour
to use the 400 generic code.)

Yeah, I think that's the intent. I don't remember why, though. I wonder
if someone tested with 403 and found it didn't work or something.

At the time, we probably couldn't imagine a situation where storing the
article fails but storing the next article is likely to succeed, so 400
and closing the connection felt pretty reasonable.

FWIW, one of the case that can trigger the "can't store article" in innd
is when INT_MAX is reached. The 403 (or 400) code should really be 439
in this specific case because it is not a temporary failure.

Yes, and indeed I think 403 or 400 would be wrong here, because the peer
would be entitled to just keep resending the same article, and it's never
going to succeed.

Same thing for IHAVE which should answer 437 (reject) instead of defer
(436) in this case. We would otherwise end up with an infinite loop
where the article is stuck and kept being proposed even though the
maximum article number has been reached and INN won't be able to store
more articles in the newsgroup. (A log is also present in news.notice.)

Yup, exactly.

--
Russ Allbery (eagle@eyrie.org) <https://www.eyrie.org/~eagle/>

Please post questions rather than mailing me directly.
<https://www.eyrie.org/~eagle/faqs/questions.html> explains why.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Julien ÉLIE <iulius@nom-de-mon-site.com.invalid> writes:

Incidentally, though TAKETHIS does not have a response code for a "retry later" in both RFC 2980 and 4644, I've just checked what Diablo does
with TAKETHIS (which is to use 431 - the "retry later" of CHECK). And previously to the implementation of NNTP Version 2 in INN, it was using
436 (the "retry later" of IHAVE) - that I (wrongly) changed to 403. I'll
fix it.

My recollection of the history of a lot of this is that the expectation is
that you use CHECK first, and servers really shouldn't be saying yes to
the CHECK and then deferring the article on TAKETHIS. Usually deferrals
are used because another peer has already sent CHECK for the same article
and therefore we'll *probably* get the article from them, but we might
not, so try again later just in case. After a TAKETHIS, well, you *have*
the article, so why defer it? You're not going to save any bandwidth; you
have already paid the transit cost and you have the whole article, so just
do whatever you're going to do, accept it or reject it, don't put it off.

I think the problem with this logic is that it was insufficiently
imaginative about why deferrals might happen. It was thinking of the case where you're proactively deduplicating feeds so that you don't consume
more bandwidth than you need to, but not thinking about cases where, say,
the news server is consulting some external spam classification oracle
that's malfunctioning and thus wants you to send the message again later.

That said, one could also make an argument that news servers should be
prepared to spool those articles locally, rather than telling peers to
spool articles for them, if the article has already been sent. Deferring
after TAKETHIS runs the risk of multiplying the bandwidth consumed by that article unnecessarily, so I think that's the logic behind reserving it for really serious problems like "my disk went away and I can't store any
articles and I'm about to explode" sorts of things like 400. Short of
that, well, you have the article now, so I think the idea is that you
should put it somewhere and deal with your problems locally rather than
asking your peer to send it yet again.

(That being said, I don't think any news server actually *does* that.)

--
Russ Allbery (eagle@eyrie.org) <https://www.eyrie.org/~eagle/>

Please post questions rather than mailing me directly.
<https://www.eyrie.org/~eagle/faqs/questions.html> explains why.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Hi Russ,

Is the generic code 403 really not allowed for temporary errors in
TAKETHIS? (It seems to be the case when reading that explicit behaviour
to use the 400 generic code.)

Yeah, I think that's the intent. I don't remember why, though. I wonder
if someone tested with 403 and found it didn't work or something.

OK, I see the point. It is a bit similar to 501 (syntax error) and
other generic responses that are sometimes not understood by the remote
peer which will consider that the article should be proposed again and
again whereas it is a permanent error.

At the time, we probably couldn't imagine a situation where storing the article fails but storing the next article is likely to succeed, so 400
and closing the connection felt pretty reasonable.

Yes that makes totally sense.

FWIW, one of the case that can trigger the "can't store article" in innd
is when INT_MAX is reached. The 403 (or 400) code should really be 439
in this specific case because it is not a temporary failure.

Yes, and indeed I think 403 or 400 would be wrong here, because the peer would be entitled to just keep resending the same article, and it's never going to succeed.

I'll have a look to fix it, and use the expected 400 response code with
a connection closure.


Incidentally, though TAKETHIS does not have a response code for a "retry
later" in both RFC 2980 and 4644, I've just checked what Diablo does
with TAKETHIS (which is to use 431 - the "retry later" of CHECK). And previously to the implementation of NNTP Version 2 in INN, it was using
436 (the "retry later" of IHAVE) - that I (wrongly) changed to 403.
I'll fix it.

--
Julien ÉLIE

« A program should always respond to the user in the way that astonishes
him least. » (Plauger's Law of Least Astonishment)

--- SoupGate-Win32 v1.05
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Hi Russ,

After a TAKETHIS, well, you *have* the article, so why defer it?
You're not going to save any bandwidth; you have already paid the
transit cost and you have the whole article, so just do whatever
you're going to do, accept it or reject it, don't put it off.

[...]

not thinking about cases where, say, the news server is consulting
some external spam classification oracle that's malfunctioning and
thus wants you to send the message again later.

[...]> Short of that, well, you have the article now, so I think the idea is

that you should put it somewhere and deal with your problems locally
rather than asking your peer to send it yet again.

(That being said, I don't think any news server actually *does* that.)

All very wise thoughts, thanks for sharing them!

--
Julien ÉLIE

« Mais pourquoi courent-ils si vite ? Pour gagner du temps ! Comme le
temps, c'est de l'argent… plus ils courent vite, plus ils en
gagnent. » (Raymond Devos)

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Responding to myself:

FWIW, one of the case that can trigger the "can't store article" in
innd is when INT_MAX is reached.

I do not manage to reproduce it on my current VPS...
A few years ago, with an older hardware and OS, I had "436 can't store article".

Now, on my set up, INN is happily accepting articles > 2^31. No storage
error, and article numbers > 2^31 are present in NNTP responses.

LIST ACTIVE returns large article numbers for all the storage methods:

trigofacile.test.maxartnum.cnfs 2147483649 2147483646 y trigofacile.test.maxartnum.timecaf 2147483648 2147483646 y trigofacile.test.maxartnum.timehash 2147483651 2147483646 y trigofacile.test.maxartnum.trash 2147483648 2147483646 y trigofacile.test.maxartnum.tradspool 2147483650 2147483646 y

Articles are stored in disk, and accessible via ARTICLE <mid> requests
(not by article numbers though).

The overall behaviour depends on the overview method used.



With tradindexed, article numbers > 2^31 are not returned in LISTGROUP,
OVER and like commands because they are not present in the index
("cannot write index record for 18446744071562067968" - seems like
article number wraps to -1 and then is written 2^64 as unsigned long in
the log).


buffindexed returns the articles but not with the right numbers:

LISTGROUP
211 3 2147483646 18446744071562067969 trigofacile.test.maxartnum.timehash 2147483647
2147483648
18446744071562067969
.

though the last one correctly has:

Xref: news.trigofacile.com trigofacile.test.maxartnum.timehash:2147483649






ovdb returns the right article numbers except for the reported high
water mark:

LISTGROUP
211 3 2147483646 18446744071562067969 trigofacile.test.maxartnum.timehash 2147483647
2147483648
2147483649
.

but OVER responses report negative article numbers starting from -2^31: -2147483648, -2147483647, etc.




ovsqlite has a different and strange behaviour as the low and high water
marks are inverted, and article numbers are also returned in reverse order:

LISTGROUP
211 4 18446744071562067968 2147483647 trigofacile.test.maxartnum.timehash 18446744071562067968
18446744071562067969
18446744071562067970
2147483647
.



It was just a quick testing of overview methods. (Expiry and other
programs not tested.)
So there's a bit of work and testing afterwards to make INN compatible
with 2^64 article numbers. At least the good news is that the storage
methods cope with a bit more than 2^31 (maybe 2^32 and beyond) but there
will be a problem with numbers > 10^10 because of the format of the
active file.


For the time being, I'll have a look to prevent postings of new articles
in newsgroups which have reached 2^31-1 articles, with the correct
rejection code (and not deferral).
It will fix the "can't store article" error I once had (which certainly
still happens for some people), and otherwise these wrong article
numbers returned if the article is accepted.

--
Julien ÉLIE

« On appelle ça une insula. C'est une maison où les gens habitent les
uns au-dessus des autres… » (Astérix)

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