https://bugs.kde.org/show_bug.cgi?id=390452
--- Comment #4 from Caspar Schutijser <cas...@schutijser.com> ---
I looked at the QtWebkit source code and this piece of code caught my
attention:
4729 void Document::initDNSPrefetch()
4730 {
4731 Settings* settings = this->settings();
4732
4733 m_haveExplicitlyDisabledDNSPrefetch = false;
4734 m_isDNSPrefetchEnabled = settings &&
settings->dnsPrefetchingEnabled() && securityOrigin()->protocol() == "http";
4735
4736 // Inherit DNS prefetch opt-out from parent frame
4737 if (Document* parent = parentDocument()) {
4738 if (!parent->isDNSPrefetchEnabled())
4739 m_isDNSPrefetchEnabled = false;
4740 }
4741 }
4742
4743 void Document::parseDNSPrefetchControlHeader(const String&
dnsPrefetchControl)
4744 {
4745 if (equalIgnoringCase(dnsPrefetchControl, "on") &&
!m_haveExplicitlyDisabledDNSPrefetch) {
4746 m_isDNSPrefetchEnabled = true;
4747 return;
4748 }
4749
4750 m_isDNSPrefetchEnabled = false;
4751 m_haveExplicitlyDisabledDNSPrefetch = true;
4752 }
Source:
https://github.com/qt/qtwebkit/blob/5.9/Source/WebCore/dom/Document.cpp#L4729
The way I read the code: when initializing the DNS prefetch code, the settings
regarding DNS prefetching are taken into account (line 4734), but when DNS
prefetching is turned on by the "website", for instance with a header or the
http-equiv meta tag, the settings are ignored and DNS prefetching is turned on
regardless (line 4746).
To verify my assumption, I applied the diff found at the bottom to the QtWebkit
code and observed stdout while running trojita. When opening one of those
emails in Trojita, this is what I see on stdout:
initDNSPrefetch(): DNS prefetching disabled in settings
initDNSPrefetch(): DNS prefetching disabled in settings
Processing HTTP equiv:
parseDNSPrefetchControlHeader(): turning DNS prefetching on
This seems to confirm my understanding of the code. So the way I see it, there
is no easy, straightforward way for us to disable this behavior in (Qt)Webkit.
Do you agree with my analysis?
Index: Source/WebCore/dom/Document.cpp
--- Source/WebCore/dom/Document.cpp.orig
+++ Source/WebCore/dom/Document.cpp
@@ -28,6 +28,8 @@
#include "config.h"
#include "Document.h"
+#include <iostream>
+
#include "AXObjectCache.h"
#include "AnimationController.h"
#include "Attr.h"
@@ -2824,6 +2826,8 @@ void Document::processHttpEquiv(const String& equiv, c
Frame* frame = this->frame();
+ cout << "Processing HTTP equiv:" << endl;
+
if (equalIgnoringCase(equiv, "default-style")) {
// The preferred style set has been overridden as per section
// 14.3.2 of the HTML4.0 specification. We need to update the
@@ -4732,6 +4736,10 @@ void Document::initDNSPrefetch()
m_haveExplicitlyDisabledDNSPrefetch = false;
m_isDNSPrefetchEnabled = settings && settings->dnsPrefetchingEnabled() &&
securityOrigin()->protocol() == "http";
+ if (settings && settings->dnsPrefetchingEnabled())
+ cout << "initDNSPrefetch(): DNS prefetching enabled in settings" <<
endl;
+ else
+ cout << "initDNSPrefetch(): DNS prefetching disabled in settings" <<
endl;
// Inherit DNS prefetch opt-out from parent frame
if (Document* parent = parentDocument()) {
@@ -4743,6 +4751,7 @@ void Document::initDNSPrefetch()
void Document::parseDNSPrefetchControlHeader(const String& dnsPrefetchControl)
{
if (equalIgnoringCase(dnsPrefetchControl, "on") &&
!m_haveExplicitlyDisabledDNSPrefetch) {
+ cout << "parseDNSPrefetchControlHeader(): turning DNS prefetching on"
<< endl;
m_isDNSPrefetchEnabled = true;
return;
}
--
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