Re: #1416
Russ Allbery <rra@stanford.edu> Sun, 03 August 2008 23:43 UTC
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To: ietf-usefor@imc.org
Subject: Re: #1416
In-Reply-To: <K4rLJJ.31q@clerew.man.ac.uk> (Charles Lindsey's message of "Tue\, 29 Jul 2008 11\:06\:55 GMT")
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From: Russ Allbery <rra@stanford.edu>
Organization: The Eyrie
Date: Sun, 03 Aug 2008 16:37:43 -0700
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"Charles Lindsey" <chl@clerew.man.ac.uk> writes: > That left just one small worry. I wanted (version IC) Injection Agents > to _always_ insert an Injection-Date (except when it was already > present, of course). Russ argued (version IR) that this would sometimes > cause existing implementations to behave oddly, and proposed a > less-intuitive rule for when Injection Agents should insert it. I think there's also a remaining point of disagreement over whether injection agents SHOULD reject articles with a stale Date. I just submitted draft-ietf-usefor-usepro-10 including the (I believe non-controversial) new history section and corresponding rewordings in the duties of a relaying and serving agent. Below is the remaining diff for my solution for #1416. Please note if any of the below is uncontroversial so that I can commit those sections and reduce the diff to only the disputed portion. --- usepro.xml 2008-08-03 16:12:51.000000000 -0700 +++ usepro-1416.xml 2008-08-03 16:34:50.000000000 -0700 @@ -18,6 +18,8 @@ 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2822.xml'> <!ENTITY rfc3629 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3629.xml'> + <!ENTITY rfc3798 PUBLIC '' + 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3798.xml'> <!ENTITY rfc3977 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3977.xml'> <!ENTITY rfc4234 PUBLIC '' @@ -165,8 +167,9 @@ <t>"Injecting" an article is the processing of a proto-article by an injecting agent. Normally this action is done once and only - once for a given article. "Reinjecting" an article is passing an - already-injected article to an injection agent.</t> + once for a given article. "Multiple injection" is passing the + same article to multiple injecting agents, either serially or in + parallel, by one or several posting agents.</t> <t>A "gateway" is software which receives news articles and converts them to messages of some other kind (such as <xref @@ -519,9 +522,34 @@ <t>Posting agents SHOULD ensure that proto-articles they create are valid according to <xref target="USEFOR" /> and any other - applicable policies. They MUST NOT create any Injection-Date or - Injection-Info header fields; these headers will be added by the - injecting agent.</t> + applicable policies. They MUST NOT create any Injection-Info + header field; this header field may only be added by the injecting + agent.</t> + + <t>If the proto-article already contains both Message-ID and Date + header fields, posting agents MAY add an Injection-Date header + field to that proto-article immediately before passing that + proto-article to an injection agent. They SHOULD do so if the + Date header field (representing the composition time of the + proto-article) is more than a day in the past at the time of + injection. They MUST do so if the proto-article is being + submitted to more than one injecting agent; see <xref + target="multi-injection" />.</t> + + <t>The Injection-Date header field is new in this revision of the + Netnews protocol and is designed to allow the Date header field to + hold the composition date (as recommended in section 3.6.1 of + <xref target="RFC2822" />), even if the proto-article is not to be + injected for some time after its composition. However, note that + all implementations predating this specification ignore the + Injection-Date header field and use the Date header field in its + stead for rejecting articles older than their cutoff (see <xref + target="history" />), and injecting agents predating this + specification do not add an Injection-Date header. Articles with + a Date header field substantially in the past will still be + rejected by implementations predating this specification, + regardless of the Injection-Date header field, and hence may + suffer poorer propagation.</t> <t>Contrary to <xref target="RFC2822" />, which implies that the mailbox or mailboxes in the From header field should be that of @@ -544,48 +572,75 @@ agent.</t> <t>A proto-article has the same format as a normal article - except that the Injection-Date, Injection-Info, and Xref header - fields MUST NOT be present; the Path header field MUST NOT - contain a "POSTED" <diag-keyword>; and any of the following - mandatory header fields MAY be omitted: Message-ID, Date, and - Path. In all other respects, a proto-article MUST be a valid - Netnews article. In particular, the header fields which may be - omitted MUST NOT be present with invalid content.</t> + except that the Injection-Info and Xref header fields MUST NOT + be present; the Path header field MUST NOT contain a "POSTED" + <diag-keyword>; and any of the following mandatory header + fields MAY be omitted: Message-ID, Date, and Path. In all other + respects, a proto-article MUST be a valid Netnews article. In + particular, the header fields which may be omitted MUST NOT be + present with invalid content.</t> <t>If a posting agent intends to offer the same proto-article to - multiple injecting agents, the header fields Message-ID and Date - MUST be present and identical in all copies of the - proto-article.</t> + multiple injecting agents, the header fields Message-ID, Date, + and Injection-Date MUST be present and identical in all copies + of the proto-article. See <xref target="multi-injection" />.</t> </section> - <section anchor="reinjection" title="Reinjection of Articles"> - <t>A given article SHOULD be processed by an injecting agent - once and only once. The Injection-Date or Injection-Info - header fields are added by an injecting agent and are not - permitted in a proto-article. Their presence (or the presence - of other unstandardized or obsolete trace headers such as - NNTP-Posting-Host, NNTP-Posting-Date, or X-Trace) indicates - that the proto-article is instead an article and has already - been processed by an injecting agent. A posting agent SHOULD - normally reject such articles.</t> - - <t>In the exceptional case that an article needs to be - reinjected for some reason (such as transferring an article from - one Netnews to another where those networks have no relaying - agreement), the posting agent doing the reinjection MUST convert - the article back into a proto-article before passing it to an - injecting agent (such as by renaming the Injection-Info and - Injection-Date header fields and removing any Xref header field) - and MUST perform the date checks on the existing Injection-Date - or Date header fields that would otherwise be done by the - injecting agent.</t> - - <t>Reinjecting articles may cause loops, loss of trace - information, and other problems and should only be done with - care and when there is no available alternative. A posting - agent that does reinjection is a limited type of gateway and as - such is subject to all of the requirements of an incoming - gateway in addition to the requirements of a posting agent.</t> + <section anchor="multi-injection" + title="Multiple Injection of Articles"> + <t>Under some circumstances (posting to multiple disjoint + networks, injecting agents with spotty connectivity, or for + redundancy, for example), a posting agent may wish to offer the + same article to multiple injecting agents. In this unusual + case, the goal is to not create multiple independent articles + but rather to inject the same article at multiple points and let + the normal duplicate suppression facility of Netnews (see <xref + target="history" />) ensure that any given agent accepts the + article only once, even if supposedly disjoint networks have + unexpected links.</t> + + <t>Whenever possible, multiple injection SHOULD be done by + offering the same proto-article to multiple injecting agents. + The posting agent MUST supply the Message-ID, Date, and + Injection-Date header fields, and the proto-article as offered + to each injecting agent MUST be identical.</t> + + <t>In some cases, offering the same proto-article to all + injecting agents may not be possible (such as when gatewaying, + after the fact, articles found on one Netnews network to + another, supposedly unconnected one). In this case, the posting + agent MUST convert the article back into a proto-article before + passing it to another injecting agent, but it MUST retain + unmodified the Message-ID, Date, and Injection-Date header + fields. It MUST NOT add an Injection-Date header field if it is + missing from the existing article. It MUST remove any Xref + header field and either rename or remove any Injection-Info + header field and other trace fields. + <list style="empty"> + <t>NOTE: Multiple injection inherently risks duplicating + articles. Multiple injection after the fact, by converting + an article back to a proto-article and injecting it again, + additionally risks loops, loss of trace information, + unintended repeat injection into the same network, and other + problems. It should be done with care and only when there + is no alternative. The requirement to retain Message-ID, + Date, and Injection-Date header fields minimizes the + possibility of a loop and ensures that the newly injected + article is not treated as a new, separate article.</t> + </list> + </t> + + <t>Multiple injection of an article listing one or more + moderated newsgroups in its Newsgroups header field SHOULD only + be done by a moderator and MUST only be done after the + proto-article has been approved for all moderated groups to + which it is to be posted and has an Approved header field (see + <xref target="moderator" />). Multiple injection of an + unapproved article intended for moderated newsgroups will + normally only result in the moderator receiving multiple copies, + and if the newsgroup status is not consistent across all + injecting agents, may result in duplication of the article or + other problems.</t> </section> <section anchor="followups" title="Followups"> @@ -710,23 +765,27 @@ <t>It MUST reject any proto-article that does not have the proper mandatory header fields for a proto-article; that has - Injection-Date, Injection-Info, or Xref header fields; that - has a Path header field containing the "POSTED" - <diag-keyword>; or that is not syntactically valid as - defined by <xref target="USEFOR" />. It SHOULD reject any - proto-article which contains a header field deprecated for - Netnews. It MAY reject any proto-article that contains trace - header fields indicating that it was already injected by an - injecting agent that did not add Injection-Info or - Injection-Date.</t> - - <t>It SHOULD reject any article whose Date header field is - more than 24 hours into the future (and MAY use a margin less - than 24 hours). It SHOULD reject any article whose Date - header appears to be stale (more than 72 hours into the past, - for example, or too old to still be recorded in the database - of a relaying agent the injecting agent will be using) since - not all news servers support Injection-Date.</t> + Injection-Info or Xref header fields; that has a Path header + field containing the "POSTED" <diag-keyword>; or that is + not syntactically valid as defined by <xref target="USEFOR" + />. It SHOULD reject any proto-article which contains a + header field deprecated for Netnews (see, for example, <xref + target="RFC3798" />). It MAY reject any proto-article that + contains trace header fields (e.g., NNTP-Posting-Host) + indicating that it was already injected by an injecting agent + that did not add Injection-Info or Injection-Date.</t> + + <t>It SHOULD reject any article whose Injection-Date or Date + header field is more than 24 hours into the future (and MAY + use a margin less than 24 hours). It SHOULD reject any + article whose Injection-Date header field is too far in the + past (older than the cutoff interval of a relaying agent the + injecting agent is using, for example). It SHOULD similarly + reject any article whose Date header field is too far in the + past, since not all news servers support Injection-Date and + only the injecting agent can provide a useful error message to + the posting agent. In either case, this interval SHOULD NOT + be any shorter than 72 hours into the past.</t> <t>It SHOULD reject any proto-article whose Newsgroups header field does not contain at least one <newsgroup-name> for a @@ -770,8 +829,14 @@ the source of the article and possibly other trace information as described in Section 3.2.8 of <xref target="USEFOR" />.</t> - <t>The injecting agent MUST then add an Injection-Date header - field containing the current date and time.</t> + <t>If the proto-article already had an Injection-Date header + field, it MUST NOT be modified or replaced. If the + proto-article had both a Message-ID header field and a Date + header field, an Injection-Date header field MUST NOT be + added, since the proto-article may have been multiply injected + by a posting agent that predates this standard. Otherwise, + the injecting agent MUST add an Injection-Date header field + containing the current date and time.</t> <t>Finally, the injecting agent forwards the article to one or more relaying agents, and the injection process is @@ -1068,8 +1133,7 @@ for reasons understood by the moderator (such as delays in the moderation process) in which case they MAY substitute the current date. Any Injection-Date, Injection-Info, or Xref - header fields already present (though there should be none) - MUST be removed.</t> + header fields already present MUST be removed.</t> <t>Any Path header field MUST either be removed or truncated to only those entries following its "POSTED" @@ -2109,6 +2173,7 @@ &rfc1036; &rfc2045; &rfc2606; + &rfc3798; &rfc3977; <reference anchor="USEAGE"> <front> -- Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/>
- Plan to finish draft-ietf-usefor-usepro Lisa Dusseault
- Re: Plan to finish draft-ietf-usefor-usepro Charles Lindsey
- Re: Plan to finish draft-ietf-usefor-usepro Frank Ellermann
- Re: Plan to finish draft-ietf-usefor-usepro Russ Allbery
- #1416 (WAS: Plan to finish ...) Charles Lindsey
- Re: Plan to finish draft-ietf-usefor-usepro Charles Lindsey
- Re: #1416 Russ Allbery
- Re: #1416 Charles Lindsey
- Re: #1416 Harald Alvestrand
- Re: #1416 Russ Allbery
- Re: #1416 Charles Lindsey
- Re: #1416 Forrest J. Cavalier III
- Re: #1416 Dan Schlitt
- Re: #1416 Frank Ellermann
- Re: #1416 Charles Lindsey
- Re: #1416 Frank Ellermann
- Re: #1416 Forrest J. Cavalier III
- Re: #1416 Russ Allbery
- Re: #1416 Frank Ellermann
- Re: #1416 Ralph Babel