[anti-censorship-team] Deployed experimental Turbo Tunnel Snowflake bridge

[David Fifield]

Today I deployed the turbotunnel branch to the Snowflake public bridge.
It's a triple-mode bridge, compatible with current Snowflake clients,
Turbo Tunnel with KCP, and Turbo Tunnel with QUIC.
https://bugs.torproject.org/33336#comment:8

To go with it there are special builds of Tor Browser that use
turbotunnel-kcp and turbotunnel-quic respectively. To try these, just
select "Configure", then "Tor is censored in my country", then "Select a
built-in bridge", then choose snowflake. Alternatively, enable snowflake
at about:preferences#tor.
https://people.torproject.org/~dcf/pt-bundle/tor-browser-snowflake-turbotunnel-kcp-9.5a5-20200215/
https://people.torproject.org/~dcf/pt-bundle/tor-browser-snowflake-turbotunnel-quic-9.5a5-20200215/

The purpose of having two bundles is so we can evaluate both KCP and
QUIC and see if either offers a compelling advantage over the other. My
thinking is that after this experimental phase, we'll choose one of the
two and deploy only that one. The experimental bundles will stop working
after 2020-04-15, when they will be liable to self-update to an ordinary
alpha and lose their Turbo Tunnel nature.

Here are tips on running the experimental bundles simultaneously and
alongside your normal Tor Browser. You just have to change some port
numbers to avoid conflicts.
https://trac.torproject.org/projects/tor/wiki/doc/TorBrowser/Hacking#LaunchingTorwithanAlternateSOCKSandControlport
	tar xf tor-browser-snowflake-turbotunnel-kcp-9.5a5-20200215/tor-browser-linux64-9.5a5_en-US.tar.xz
	mv tor-browser_en-US tor-browser_en-US_kcp
	cd tor-browser_en-US_kcp
	export TOR_SOCKS_PORT=9250
	export TOR_CONTROL_PORT=9251
	sed -i -e 's/Port 915/Port 925/' ./Browser/TorBrowser/Data/Tor/torrc-defaults
	./start-tor-browser.desktop

	tar xf tor-browser-snowflake-turbotunnel-quic-9.5a5-20200215/tor-browser-linux64-9.5a5_en-US.tar.xz
	mv tor-browser_en-US tor-browser_en-US_quic
	cd tor-browser_en-US_quic
	export TOR_SOCKS_PORT=9350
	export TOR_CONTROL_PORT=9351
	sed -i -e 's/Port 915/Port 935/' ./Browser/TorBrowser/Data/Tor/torrc-defaults
	./start-tor-browser.desktop
You may also want to go to the Customize... menu and choose different
themes (default/light/dark) to help distinguish the browsers.

One thing I didn't think about is enabling client logging by default. If
you need a log for debugging, you'll have to manually add
"-log snowflake-client.log" to the "ClientTransportPlugin snowflake"
line in Browser/TorBrowser/Data/Tor/torrc-defaults.

The Turbo Tunnel browsers are meant to keep working even after you've
left them idle for a long time, and even if your Snowflake proxy dies.
When a proxy dies, your connection will hang for at least 30 s--maybe
longer if a replacement isn't immediately available. Occasional hangs
are expected (at least until #25723 is done), but it should always
recover within a few minutes at the outmost.