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Define preconnect and dns-prefetch with CSP #1620

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Define preconnect and dns-prefetch with CSP #1620

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Define preconnect and dns-prefetch with CSP
noamr Mar 19, 2023
daab9c1
Update fetch.bs
noamr Mar 20, 2023
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Update fetch.bs
noamr Apr 24, 2023
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Update fetch.bs
noamr Apr 24, 2023
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PR nits
noamr Apr 24, 2023
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should
noamr Apr 24, 2023
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A few editorial nits
noamr May 7, 2023
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Use boolean for algo
noamr May 8, 2023
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noamr Sep 28, 2023
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Update fetch.bs
noamr Sep 28, 2023
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95 changes: 85 additions & 10 deletions fetch.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -2850,16 +2850,7 @@ steps:
<a>connection</a>.
</ol>

<li>
<p>Let <var>proxies</var> be the result of finding proxies for <var>url</var> in an
<a>implementation-defined</a> manner. If there are no proxies, let <var>proxies</var> be
« "<code>DIRECT</code>" ».

<p class=note>This is where non-standard technology such as
<a href="https://en.wikipedia.org/wiki/Web_Proxy_Auto-Discovery_Protocol">Web Proxy Auto-Discovery Protocol (WPAD)</a>
and <a href="https://en.wikipedia.org/wiki/Proxy_auto-config">proxy auto-config (PAC)</a> come
into play. The "<code>DIRECT</code>" value means to not use a proxy for this particular
<var>url</var>.
<li><p>Let <var>proxies</var> be the result of calling <a>resolve proxies</a> given <var>url</var>.

<li><p>Let <var>timingInfo</var> be a new <a for=/>connection timing info</a>.

Expand Down Expand Up @@ -2916,6 +2907,20 @@ reused across <a>connections</a> whose <a for=connection>credentials</a> are fal

<hr>

<div algorithm>
<p>To <dfn>resolve proxies</dfn> given a <a for=/>URL</a> <var>url</var>, return the result of
finding proxies for <var>url</var> in an <a>implementation-defined</a> manner. If there are no
proxies, return « "<code>DIRECT</code>" ».

<p class=note>This is where non-standard technology such as
<a href="https://en.wikipedia.org/wiki/Web_Proxy_Auto-Discovery_Protocol">Web Proxy Auto-Discovery Protocol (WPAD)</a>
and <a href="https://en.wikipedia.org/wiki/Proxy_auto-config">proxy auto-config (PAC)</a> come
into play. The "<code>DIRECT</code>" value means to not use a proxy for this particular
<var>url</var>.
</div>

<hr>

<div algorithm>
<p>To <dfn>create a connection</dfn>, given a <a for=/>network partition key</a> <var>key</var>,
<a for=/>origin</a> <var>origin</var>, boolean <var>credentials</var>, string <var>proxy</var>,
Expand Down Expand Up @@ -3027,6 +3032,76 @@ details of reused connections are not exposed and time values are coarsened.
</div>


<h3 id=preemptive-connections>Preemptive connections</h3>

<div algorithm>
<p>To <dfn export>preemptively obtain a connection</dfn>, given an
<a>environment settings object</a> <var>environment</var>, a <a for=/>URL</a> <var>url</var>, and a
boolean <var>credentials</var>, run these steps:

<ol>
<li><p>Let <var>key</var> be the result of <a for=/>determining the network partition key</a> given
<var>environment</var>.

<li>
<p>Run <a>determine if Content Security Policy allows connection</a> with
<var>environment</var> and <var>url</var>. If that returns true,
<a>obtain a connection</a> with <var>key</var>, <var>url</var>, and <var>credentials</var>.

<p class=note>This connection is obtained but not used directly. It will remain in the
<a>connection pool</a> for subsequent use.

<p class=note>The user agent can attempt to initiate a preconnect and perform the full
connection handshake (DNS+TCP for HTTP, and DNS+TCP+TLS for HTTPS origins) whenever possible, but
is allowed to elect to perform a partial handshake (DNS only for HTTP, and DNS or DNS+TCP for
HTTPS origins), or skip it entirely, due to resource constraints or other reasons.</p>

<p class=note>The optimal number of connections per origin is dependent on the negotiated
protocol, users current connectivity profile, available device resources, global connection
limits, and other context specific variables. As a result, the decision for how many connections
should be opened is deferred to the user agent.</p>
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These notes feel like normative material. One even contains "should"! In the step above where we obtain the connection perhaps we should have a "with these caveats" ending that then leads into some bullet points?

</ol>
</div>

<div algorithm>
<p>To <dfn export>preemptively resolve an origin</dfn>, given an
<a>environment settings object</a> <var>environment</var> and a <a for=/>URL</a> <var>url</var>, run
these steps:

<ol>
<li><p>Let <var>key</var> be the result of <a for=/>determining the network partition key</a> given
<var>environment</var>.

<li>Run <p><a>determine if Content Security Policy allows connection</a> with
<var>environment</var> and <var>url</var>. If that returns false, return.
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<li><p>Let <var>proxies</var> be the result of calling <a>resolve proxies</a>.

<li>
<p>If <var>proxies</var> <a for=list>contains</a> "<code>DIRECT</code>", then
<a>resolve an origin</a> given <var>key</var> and <var>url</var>'s <a for=url>origin</a>.

<p class=note>As the results of this algorithm can be cached, future fetches could be faster.
</ol>
</div>

<div algorithm>
<p>To <dfn>determine if Content Security Policy allows connection</dfn>, given an
<a>environment settings object</a> <var>environment</var>, and a <a for=/>URL</a> <var>url</var>:

<ol>
<li><p>Let <var>request</var> be a <a for=/>request</a> whose <a for=request>URL</a> is
<var>url</var>, <a for=request>initiator</a> is "<code>prefetch</code>", and whose
<a for=request>client</a> is <var>environment</var>.

<li><p>Let <var>result</var> be the result of running
<a>should request be blocked by Content Security Policy?</a> given <var>request</var>.

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<li><p>Return true if <var>result</var> is <b>allowed</b>, otherwise false.
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</ol>
</div>


<h3 id=network-partition-keys>Network partition keys</h3>

<p>A <dfn>network partition key</dfn> is a tuple consisting of a <a for=/>site</a> and null or
Expand Down