[tor-talk] Invitation to try experimental Snowflake Tor Browser packages

[David Fifield]

The anti-censorship team is looking for people to try Tor Browser
packages built from an experimental branch of Snowflake that is supposed
to make Snowflake more reliable. There are two versions; you can try
either one or both of them. If you have feedback, tell us whether you
are using the "kcp" or "quic" version.

https://people.torproject.org/~dcf/pt-bundle/tor-browser-snowflake-turbotunnel-kcp-9.5a5-20200223/
https://people.torproject.org/~dcf/pt-bundle/tor-browser-snowflake-turbotunnel-quic-9.5a5-20200223/

To enable Snowflake the first time you run the browser:
 * Click "Configure"
 * Click "Tor is censored in my country"
 * Click "Select a built-in bridge"
 * Select "snowflake" from the menu
If the browser is already running:
 * Go to about:preferences#tor (open the Preferences menu then click Tor
   on the left side)
 * Look at the "Bridges" section
 * Click "Use a bridge"
 * Click "Select a built-in bridge"
 * Select "snowflake" from the menu

What's different about these experimental packages? As you may know,
Snowflake is already part of alpha Tor Browser. Snowflake works by
routing your connection through temporary proxies before they reach a
bridge, but until now there wasn't a way to switch to a new proxy when
the one you are using stops working--the connection would just stop
working. These packages solve the problem by putting a session protocol
under the temporary Snowflake layer. (That's why there are two options.
We are testing two session protocols: KCP and QUIC.) If you are curious
about the background:
https://lists.torproject.org/pipermail/anti-censorship-team/2020-February/000074.html
https://bugs.torproject.org/33336
https://github.com/net4people/bbs/issues/9

These special packages are made not to auto-update until 2020-04-23.
After that, they will update and become a normal Tor Browser alpha.

What to expect. You should be able to use these browsers all day without
the connection breaking. The speed of the Snowflake connection depends
on the temporary proxy you get assigned. If you think you have a slow
proxy, try this trick: go to about:preferences#tor, switch to obfs4 for
1 second, then switch back to snowflake. That will restart the pluggable
transport and give you a chance at a different proxy. It takes 30
seconds to detect a failed proxy. So if your proxy dies, it will be at
least 30 seconds before your connection starts working again. It may be
even longer than that, if you happen to be assigned another bad proxy
right away. You can see what's going on by watching the log file:
	linux:   Browser/TorBrowser/Data/Tor/pt_state/snowflake-client.log
	windows: Browser\TorBrowser\Data\Tor\pt_state\snowflake-client.log
	mac: Tor Browser.app/Contents/Resources/TorBrowser/Tor/pt_state/snowflake-client.log

Here's a guide to reading the log file:
Traffic Bytes (in|out): 0 | 972
Traffic Bytes (in|out): 52457 | 7270
	If the number on the left stays at 0, the proxy isn't working.
	If it's nonzero, the proxy is working.
WebRTC: No messages received for 30s -- closing stale connection
redialing on same connection
	This means that your proxy died and the system is switching to a
	new one.

It's possible to run multiple Tor Browsers at the same time, if you want
to run one of these Snowflake browsers alongside your normal Tor
Browser, or run the "kcp" and "quic" versions at the same time. I posted
instructions to https://lists.torproject.org/pipermail/anti-censorship-team/2020-February/000074.html
but the short summary is you have to set a couple of environment
variables:
	TOR_SOCKS_PORT=9250 TOR_CONTROL_PORT=9251 ./start-tor-browser.desktop