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Re: why polipo?

On 02/15/2010 12:09 PM, Michael Gomboc wrote:
> Why is polipo used and no longer privoxy?

The first question is, "why a http proxy at all?"

The answer is, because Firefox SOCKS layer has hard-coded timeouts, and
other issues, https://bugzilla.mozilla.org/show_bug.cgi?id=280661.
Personally, I don't use an http proxy, I simply let my browser talk to
tor via socks directly.  The user experience sucks, because you'll
receive untold numbers of "The connection has timed out" warnings,
because firefox won't wait for Tor to build a circuit.  Chrome, Safari,
and Arora (amongst others) don't have this problem.

Once Firefox fixes bug 280661, we don't need a http proxy at all.
However, given the current pace of progress on 280661, we may switch to
Chrome before the fix occurs.

The second question is, "why switch from privoxy to polipo?"

Privoxy is fine filtering software that works well for what is it
intended to do.  However, it's user experience is lacking due to it
lacking a few features, namely, http 1.1 pipelining, caching most
requested objects, and it needs to see the entire page to parse it,
before sending it on to the browser.  Lack of these three features is
the reason we switched from privoxy to polipo.

We've received plenty of feedback that browsing with polipo in place of
privoxy "feels faster".  The feedback indicates that because polipo
streams the content to the browser for rendering nearly as fast as it
receives it from Tor, the user understands what's going on and will
start to read the web page as it loads.  Privoxy, necesarily, will load
the entire page, parse it for items to be filtered, and then send the
page on to the browser.  The user experience, especially on a slow
circuit, is that nothing happens, the browser activity icon spins
forever, and suddenly a page appears many, many seconds later.

If Tor was vastly faster, privoxy's mode of operation wouldn't matter.
We're working on making Tor faster.  However, purposely showing the user
how slow tor can be with privoxy was a huge point of complaint, and not
what we intended to do.

Does polipo have some bugs?  Sure.  Chrisd primarily, among others, is
working on fixing them.  At the current rate of progress on firefox bug
280661, we'll have polipo fixed before mozilla releases the SOCKS layer
fix.  Chrisd even wrote Mozilla a patch and submitted it on the bug.

The final point is that this is all free software.  You are in control.
 If you don't like polipo, but do like privoxy, then don't install
polipo and use privoxy.

The power of choice is yours.

Andrew Lewman
The Tor Project
pgp 0x31B0974B

Website: https://torproject.org/
Blog: https://blog.torproject.org/
Identi.ca: torproject
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