[webkit-gtk] dns prefetching knob

Marco Peereboom slash at peereboom.us
Wed Mar 9 06:28:23 PST 2011

On Wed, Mar 09, 2011 at 09:10:16AM -0500, Dan Winship wrote:
> On 03/09/2011 07:55 AM, Marco Peereboom wrote:
> > For some reason
> > people are still attached to this relic of the modem era.  DNS prefetch
> > is optional in the HTTP spec and the time has come to admit that it no
> > longer serves a purpose.  Back in the day when modems were king and DNS
> > lookups were expensive you could save some time when a user clicked on a
> > link.  Times have changes and the web has evolved.
> Prefetch isn't mentioned in the HTTP spec at all. And I don't think
> anyone was doing it back in the modem age. AFAIK, Google started doing
> it with Chrome, and other people followed.

I am sorry I meant the optional "dns-prefetch" and
"x-dns-prefetch-control" webkit looks for and does magic with.

> It *does* help in some cases. Lots of sites have lame slow DNS servers
> (and lots of ISPs have lame slow recursive resolvers). We just don't
> want to try to pre-resolve every single link on the page.

Hence the knobbing part.  Some people have legitimate use for it which
is of course fine.  I want it for performance reasons but also to
prevent DNS tracking.  Between DNS prefetching, link hovering and the
empty DNS lookups webkit generates one can get near pixel resolution on
how the user moves his mouse.  This comes in handy for "Online
Behavioral Tracking".  Being a practical paranoid I'd like to prevent

And this knob exists in 1.3.12 as well.  My patch just adds it to the
current stable branch and exposes it in GTK.

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