From 256f33f2b395502b0b3a66a821af07dc27c7252a Mon Sep 17 00:00:00 2001
From: Cecylia Bocovich <cohosh@torproject.org>
Date: Thu, 2 Apr 2020 12:20:42 -0400
Subject: [PATCH 1/2] Move proxy datachannel timeout value to config

---
 proxy/config.js    | 3 +++
 proxy/snowflake.js | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/proxy/config.js b/proxy/config.js
index 39c2b15..5b8963a 100644
--- a/proxy/config.js
+++ b/proxy/config.js
@@ -26,6 +26,9 @@ Config.prototype.rateLimitHistory = 5.0;
 
 Config.prototype.defaultBrokerPollInterval = 300.0 * 1000;
 
+// Timeout after sending answer before datachannel is opened
+Config.prototype.datachannelTimeout = 20 * 1000;
+
 Config.prototype.maxNumClients = 1;
 
 Config.prototype.proxyType = "";
diff --git a/proxy/snowflake.js b/proxy/snowflake.js
index 0e9730e..3baddbe 100644
--- a/proxy/snowflake.js
+++ b/proxy/snowflake.js
@@ -76,7 +76,7 @@ class Snowflake {
           log('proxypair datachannel timed out waiting for open');
           return pair.close();
         }
-      }), 20000); // 20 second timeout
+      }), this.config.datachannelTimeout);
     }, function() {
       //on error, close proxy pair
       return pair.close();

From 3d8e04966523f373bd9d7bc09c5712c4c99f36c6 Mon Sep 17 00:00:00 2001
From: Cecylia Bocovich <cohosh@torproject.org>
Date: Thu, 2 Apr 2020 12:53:10 -0400
Subject: [PATCH 2/2] Dynamically adjust proxy poll interval

If the proxy succeeds in opening a datachannel to the client, decrease
the poll interval. If they fail, increase the poll interval. This will
cause less reliable/more restrictive proxies to poll less frequently.
---
 proxy/config.js    |  4 +++-
 proxy/snowflake.js | 23 +++++++++++++++++------
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/proxy/config.js b/proxy/config.js
index 5b8963a..3f632ca 100644
--- a/proxy/config.js
+++ b/proxy/config.js
@@ -24,7 +24,9 @@ Config.prototype.minRateLimit = 10 * 1024;
 
 Config.prototype.rateLimitHistory = 5.0;
 
-Config.prototype.defaultBrokerPollInterval = 300.0 * 1000;
+Config.prototype.defaultBrokerPollInterval = 300.0 * 1000; //1 poll every 5 minutes
+Config.prototype.slowestBrokerPollInterval = 6 * 60 * 60.0 * 1000; //1 poll every 6 hours
+Config.prototype.pollAdjustment = 300.0 * 1000;
 
 // Timeout after sending answer before datachannel is opened
 Config.prototype.datachannelTimeout = 20 * 1000;
diff --git a/proxy/snowflake.js b/proxy/snowflake.js
index 3baddbe..ba96d99 100644
--- a/proxy/snowflake.js
+++ b/proxy/snowflake.js
@@ -22,6 +22,8 @@ class Snowflake {
     this.ui = ui;
     this.broker = broker;
     this.proxyPairs = [];
+    this.failures = 0;
+    this.pollInterval = this.config.defaultBrokerPollInterval;
     if (void 0 === this.config.rateLimitBytes) {
       this.rateLimit = new DummyRateLimit();
     } else {
@@ -43,9 +45,9 @@ class Snowflake {
   // process. |pollBroker| automatically arranges signalling.
   beginWebRTC() {
     this.pollBroker();
-    return this.pollInterval = setInterval((() => {
-      return this.pollBroker();
-    }), this.config.defaultBrokerPollInterval);
+    return this.pollTimeout = setTimeout((() => {
+      return this.beginWebRTC()
+    }), this.pollInterval);
   }
 
   // Regularly poll Broker for clients to serve until this snowflake is
@@ -74,8 +76,18 @@ class Snowflake {
       return setTimeout((() => {
         if (!pair.webrtcIsReady()) {
           log('proxypair datachannel timed out waiting for open');
-          return pair.close();
+          pair.close();
+          // increase poll interval
+          this.pollInterval =
+                Math.min(this.pollInterval + this.config.pollAdjustment,
+                  this.config.slowestBrokerPollInterval);
+        } else {
+          // decrease poll interval
+          this.pollInterval =
+                Math.max(this.pollInterval - this.config.pollAdjustment,
+                  this.config.defaultBrokerPollInterval);
         }
+        return;
       }), this.config.datachannelTimeout);
     }, function() {
       //on error, close proxy pair
@@ -146,7 +158,7 @@ class Snowflake {
   disable() {
     var results;
     log('Disabling Snowflake.');
-    clearInterval(this.pollInterval);
+    clearTimeout(this.pollTimeout);
     results = [];
     while (this.proxyPairs.length > 0) {
       results.push(this.proxyPairs.pop().close());
@@ -158,7 +170,6 @@ class Snowflake {
 
 Snowflake.prototype.relayAddr = null;
 Snowflake.prototype.rateLimit = null;
-Snowflake.prototype.pollInterval = null;
 
 Snowflake.MESSAGE = {
   CONFIRMATION: 'You\'re currently serving a Tor user via Snowflake.'