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Rewrite HTTP cache integration
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In particular:

* Be more specific about terminology
* Detail more clearly how requests are to be modified

Tests: web-platform-tests/wpt#5137.

During review we decided to postpone #144 (poorly implemented if at all) and #307 (also poorly implemented despite security implications).

Fixes #336 and fixes #373.
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@mnot @annevk
mnot authored and annevk committed Mar 23, 2017
1 parent 1d76b02 commit cbca2c2
Showing 1 changed file with 85 additions and 61 deletions.
146 changes: 85 additions & 61 deletions fetch.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,9 @@ url: https://tools.ietf.org/html/rfc7234#section-1.2.1;text:delta-seconds;type:d
"HTTP-CACHING": {
"aliasOf": "RFC7234"
},
"HTTP-RANGE": {
"aliasOf": "RFC7233"
},
"HTTP-AUTH": {
"aliasOf": "RFC7235"
},
Expand Down Expand Up @@ -95,7 +98,6 @@ url: https://tools.ietf.org/html/rfc7234#section-1.2.1;text:delta-seconds;type:d
"href": "https://www.kb.cert.org/vuls/id/150227",
"title": "HTTP proxy default configurations allow arbitrary TCP connections."
}

}
</pre>

Expand Down Expand Up @@ -3140,6 +3142,9 @@ steps:
<p class=note><i>CORS flag</i> is still a bookkeeping detail. As is
<i>authentication-fetch flag</i>.

<p class=note>Some implementations might support caching of partial content, as per <cite>HTTP
Range Requests</cite>. [[HTTP-RANGE]] However, this is not widely supported by browser caches.

<ol>
<li><p>Let <var>httpRequest</var> be null.

Expand Down Expand Up @@ -3364,88 +3369,107 @@ steps:
<var>httpRequest</var>'s
<a for=request>credentials mode</a>.

<li><p>Let <var>response</var> be null.
<li><p>Let <var>response</var> and <var>storedResponse</var> be null.

<li><p>Let the <var>revalidatingFlag</var> be unset.

<li>
<p>If <var>httpRequest</var>'s
<a for=request>cache mode</a> is neither
"<code>no-store</code>" nor "<code>reload</code>", and there is a <em>complete</em>
<a for=/>response</a> in the HTTP cache for
<var>httpRequest</var> run these substeps:
<!-- XXX xref "HTTP cache" -->
<p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is neither "<code>no-store</code>"
nor "<code>reload</code>", run these substeps:

<ol>
<li>
<p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
"<code>force-cache</code>" or "<code>only-if-cached</code>", then set
<var>response</var> to the <a for=/>response</a> in the HTTP cache for
<var>httpRequest</var>.
<p>Set <var>storedResponse</var> to the result of selecting a response from the HTTP cache,
possibly needing validation, as per the
"<a href=https://tools.ietf.org/html/rfc7234#section-4>Constructing Responses from Caches</a>"
chapter of <cite>HTTP Caching</cite> [[!HTTP-CACHING]], if any.

<p class=note>As mandated by HTTP, this still takes the `<code>Vary</code>`
<a>header</a> into account.
<li><p>If <var>storedResponse</var> is null, then abort these substeps.

<li><p>Otherwise, if <var>httpRequest</var>'s
<a for=request>cache mode</a> is "<code>default</code>" and the
<a for=/>response</a> in the HTTP cache for <var>httpRequest</var> does
not require revalidation, then set <var>response</var> to that
<a for=/>response</a>.
<!-- XXX xref "revalidation" -->
<!-- cache hit -->
<li><p>If <var>storedResponse</var> requires validation (i.e., it is not fresh), then set the
<var>revalidatingFlag</var>.

<li><p>Otherwise, if <var>httpRequest</var>'s
<a for=request>cache mode</a> is either "<code>default</code>"
or "<code>no-cache</code>", modify <var>httpRequest</var>'s
<a for=request>header list</a> with revalidation
<a>headers</a>.
<!-- XXX modify, revalidation headers -->
</ol>
<li>
<p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is "<code>force-cache</code>" or
"<code>only-if-cached</code>", then set <var>response</var> to <var>storedResponse</var> and
abort these substeps.

<li><p>Otherwise, if <var>httpRequest</var>'s
<a for=request>cache mode</a> is either
"<code>default</code>" or "<code>force-cache</code>", and there is a
<em>partial</em> <a for=/>response</a> in the HTTP cache for
<var>httpRequest</var>, modify <var>httpRequest</var>'s
<a for=request>header list</a> with resume
<a>headers</a>.
<!-- XXX xref partial, modify, resume headers -->
<p class=note>As mandated by HTTP, this still takes the `<code>Vary</code>` <a>header</a>
into account.

<li>
<p>If <var>response</var> is null, run these substeps:
<li>
<p>If the <var>revalidatingFlag</var> is set, then:

<ol>
<li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
"<code>only-if-cached</code>", then return a
<a>network error</a>.
<ol>
<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
<a for="header list">contains</a> `<code>ETag</code>`, then <a for="header list">append</a>
`<code>If-None-Match</code>` with its value to <var>httpRequest</var>'s
<a for=request>header list</a>.

<li><p>Set <var>response</var> to the result of making an
<a>HTTP-network fetch</a> using <var>httpRequest</var>
with <i>credentials flag</i> if set.
<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
<a for="header list">contains</a> `<code>Last-Modified</code>`, then
<a for="header list">append</a> `<code>If-Modified-Since</code>` with its value to
<var>httpRequest</var>'s <a for=request>header list</a>.
</ol>

<p class=note>See also the
"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Sending a Validation Request</a>"
chapter of <cite>HTTP Caching</cite> [[!HTTP-CACHING]].

<li><p>Otherwise, if the <var>revalidatingFlag</var> is unset, then set <var>response</var> to
<var>storedResponse</var>.
</ol>

<li>
<p>If <var>response</var>'s <a for=response>status</a> is <code>304</code> and
<var>httpRequest</var>'s <a for=request>cache mode</a> is either
"<code>default</code>" or "<code>no-cache</code>", run these substeps:
<!-- If response is still null, we require a forwarded request. -->
<p>If <var>response</var> is null, then run these substeps:

<ol>
<li><p>Set <var>cachedResponse</var> to the result of selecting a stored
<a for=/>response</a> from the HTTP cache using <var>httpRequest</var>, as
per the
"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Freshening Stored Responses upon Validation</a>"
chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]
<li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
"<code>only-if-cached</code>", then return a <a>network error</a>.

<li><p>If <var>cachedResponse</var> is null (i.e., one cannot be selected), return a
<a>network error</a>.
<li><p>Set <var>forwardResponse</var> to the result of making an <a>HTTP-network fetch</a> using
<var>httpRequest</var> with <i>credentials flag</i> if set.

<li><p>If <var>httpRequest</var>'s <var>method</var> is
<a href=https://tools.ietf.org/html/rfc7231#safe.methods>unsafe</a> and
<var>forwardResponse</var>'s <a for=response>status</a> is in the range <code>200</code> to
<code>399</code>, inclusive, invalidate appropriate stored responses in the HTTP cache, as per
the "<a href=https://tools.ietf.org/html/rfc7234#section-4.4>Invalidation</a>" chapter of
<cite>HTTP Caching</cite>, and set <var>storedResponse</var> to null. [[!HTTP-CACHING]]

<li>
<p>If the <var>revalidatingFlag</var> is set and <var>forwardResponse</var>'s
<a for=response>status</a> is <code>304</code>, then:

<ol>
<li>
<p>Update <var>storedResponse</var>'s <a for=response>header list</a> using
<var>forwardResponse</var>'s <a for=response>header list</a>, as per the
"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Freshening Stored Responses upon Validation</a>"
chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]

<p class="note">This updates the stored response in cache as well.

<li><p>Update <var>cachedResponse</var>'s <a for=response>header list</a>
using <var>response</var>'s <a for=response>header list</a>, as per the
"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Freshening Stored Responses upon Validation</a>"
chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]
<li><p>Set <var>response</var> to <var>storedResponse</var>.

</ol>

<li>
<p>Set <var>response</var> to the <var>cachedResponse</var>.
<p>If <var>response</var> is null, then:

<p class="note no-backref">This changes <var>response</var> entirely, including its
<a for=response>status</a> which is most likely <code>200</code> now.
<ol>
<li><p>Set <var>response</var> to <var>forwardResponse</var>.

<li>
<p>Store <var>httpRequest</var> and <var>forwardResponse</var> in the HTTP cache, as per the
"<a href=https://tools.ietf.org/html/rfc7234#section-3>Storing Responses in Caches</a>"
chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]

<p class=note>If <var>forwardResponse</var> is a <a>network error</a>, this effectively caches
the network error, which is sometimes known as "negative caching".
</ol>
</ol>

<li>
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