Re: Semantics: clarify handling of invalid or unsatisfiable range requests

Wait, what? I feel like I'm speaking out-of-turn here nowadays. But if, to satisfy some edge cases, PUT would now have the semantics of PATCH then maybe we need a new method, let's call it PLACE, that absolutely reflects the save-file-to-disk user intent, specifically disallowing any sort of range request. Thought this was settled ages ago.



-Eric






---- On Wed, 02 Mar 2022 18:07:25 -0800 Roy T. Fielding <fielding@gbiv.com> wrote ----



A very late request was received for some editorial clarification 
around invalid or unsatisfiable range requests. 
 
 https://github.com/httpwg/http-core/issues/1011 
 
I have proposed a patch that may (or may not) be too late to apply, 
but could use some review in any case. 
 
 https://github.com/httpwg/http-core/pull/1012 
 
and pasted below. I don't think it has any effect on the protocol 
itself, but may make it easier to implement the edge cases. 
 
....Roy 
 
 
index bbf438d4..885a3c5e 100644 
--- draft-ietf-httpbis-semantics-latest.xml 
+++ draft-ietf-httpbis-semantics-latest.xml 
@@ -7717,6 +7717,8 @@ If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT 
 </t> 
 
 <section title="Range Specifiers" anchor="range.specifiers"> 
+  <iref primary="true" item="satisfiable"/> 
+  <iref primary="true" item="unsatisfiable"/> 
 <t> 
 Ranges are expressed in terms of a range unit paired with a set of range 
 specifiers. The range unit name determines what kinds of range-spec 
@@ -7781,6 +7783,18 @@ If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT 
 <x:ref>other-range</x:ref>   = 1*( %x21-2B / %x2D-7E ) 
 ; 1*(VCHAR excluding comma) 
 </sourcecode> 
+<t> 
+   A <x:ref>ranges-specifier</x:ref> is invalid if it contains any 
+   <x:ref>range-spec</x:ref> that is invalid or undefined for the indicated 
+   <x:ref>range-unit</x:ref>. 
+</t> 
+<t anchor="satisfiable"> 
+   A valid <x:ref>ranges-specifier</x:ref> is <x:dfn>satisfiable</x:dfn> 
+   if it contains at least one <x:ref>range-spec</x:ref> that is 
+   satisfiable, as defined by the indicated <x:ref>range-unit</x:ref>. 
+   Otherwise, the <x:ref>ranges-specifier</x:ref> is 
+   <x:dfn>unsatisfiable</x:dfn>. 
+</t> 
 </section> 
 
 <section title="Byte Ranges" anchor="byte.ranges"> 
@@ -7867,13 +7881,15 @@ bytes=500-700,601-999 
 </li> 
 </ul> 
 <t> 
-   If a valid bytes <x:ref>range-set</x:ref> includes at least one 
-   <x:ref>range-spec</x:ref> with a <x:ref>first-pos</x:ref> that is 
-   less than the current length of the representation, or at least one 
-   <x:ref>suffix-range</x:ref> with a non-zero <x:ref>suffix-length</x:ref>, 
-   then the bytes <x:ref>range-set</x:ref> is satisfiable. Otherwise, 
-   the bytes <x:ref>range-set</x:ref> is unsatisfiable. 
+   A valid bytes <x:ref>range-spec</x:ref> is satisfiable if it is either: 
 </t> 
+<ul> 
+   <li><t>an <x:ref>int-range</x:ref> with a <x:ref>first-pos</x:ref> that 
+       is less than the current length of the selected representation; 
+       or,</t></li> 
+   <li><t>a <x:ref>suffix-range</x:ref> with a non-zero 
+       <x:ref>suffix-length</x:ref>.</t></li> 
+</ul> 
 <t> 
 If the selected representation has zero length, the only satisfiable form of 
 <x:ref>range-spec</x:ref> is a <x:ref>suffix-range</x:ref> with a non-zero 
@@ -7957,11 +7973,14 @@ bytes=500-700,601-999 
 </t> 
 <t> 
 If all of the preconditions are true, the server supports the Range header 
-   field for the target resource, and the specified range(s) are valid and 
-   satisfiable (as defined in <xref target="byte.ranges"/>), the 
-   server &SHOULD; send a <x:ref>206 (Partial Content)</x:ref> response with a 
-   content containing one or more partial representations that correspond to 
-   the satisfiable ranges requested. 
+   field for the target resource, the received Range field-value contains a 
+   valid <x:ref>ranges-specifier</x:ref> (<xref target="range.specifiers"/>) 
+   with a <x:ref>range-unit</x:ref> supported for that target resource, 
+   and that <x:ref>ranges-specifier</x:ref> is satisfiable with respect to 
+   the selected representation, 
+   the server &SHOULD; send a <x:ref>206 (Partial Content)</x:ref> response 
+   with content containing one or more partial representations 
+   that correspond to the satisfiable <x:ref>range-spec</x:ref>(s) requested. 
 </t> 
 <t> 
 The above does not imply that a server will send all requested ranges. 
@@ -7972,8 +7991,17 @@ bytes=500-700,601-999 
 </t> 
 <t> 
 If all of the preconditions are true, the server supports the Range header 
-   field for the target resource, and the specified range(s) are invalid or 
-   unsatisfiable, the server &SHOULD; send a 
+   field for the target resource, and the received Range field-value contains 
+   an invalid <x:ref>ranges-specifier</x:ref>, 
+   the server &SHOULD; send a <x:ref>400 (Bad Request)</x:ref> response. 
+</t> 
+<t> 
+   If all of the preconditions are true, the server supports the Range header 
+   field for the target resource, the received Range field-value contains a 
+   valid <x:ref>ranges-specifier</x:ref>, and either the 
+   <x:ref>range-unit</x:ref> is not supported for that target resource or 
+   the <x:ref>ranges-specifier</x:ref> is unsatisfiable with respect to 
+   the selected representation, the server &SHOULD; send a 
 <x:ref>416 (Range Not Satisfiable)</x:ref> response. 
 </t> 
 </section>