diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
index bf84a008b441..3fee4705eab2 100644
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -9578,6 +9578,13 @@
   mirror: always
 #endif
 
+# Whether to allow a bypass flag to be set on httpChannel that will
+# prevent proxies from being used for that specific request.
+- name: network.proxy.allow_bypass
+  type: bool
+  value: true
+  mirror: always
+
 - name: network.proxy.parse_pac_on_socket_process
   type: RelaxedAtomicBool
   value: false
diff --git a/netwerk/protocol/http/HttpBaseChannel.cpp b/netwerk/protocol/http/HttpBaseChannel.cpp
index 90e571fe6576..1dd3a22054cc 100644
--- a/netwerk/protocol/http/HttpBaseChannel.cpp
+++ b/netwerk/protocol/http/HttpBaseChannel.cpp
@@ -3355,17 +3355,26 @@ HttpBaseChannel::SetBeConservative(bool aBeConservative) {
   return NS_OK;
 }
 
+bool HttpBaseChannel::BypassProxy() {
+  return StaticPrefs::network_proxy_allow_bypass() && LoadBypassProxy();
+}
+
 NS_IMETHODIMP
 HttpBaseChannel::GetBypassProxy(bool* aBypassProxy) {
   NS_ENSURE_ARG_POINTER(aBypassProxy);
 
-  *aBypassProxy = LoadBypassProxy();
+  *aBypassProxy = BypassProxy();
   return NS_OK;
 }
 
 NS_IMETHODIMP
 HttpBaseChannel::SetBypassProxy(bool aBypassProxy) {
-  StoreBypassProxy(aBypassProxy);
+  if (StaticPrefs::network_proxy_allow_bypass()) {
+    StoreBypassProxy(aBypassProxy);
+  } else {
+    NS_WARNING("bypassProxy set but network.proxy.bypass is disabled");
+    return NS_ERROR_FAILURE;
+  }
   return NS_OK;
 }
 
diff --git a/netwerk/protocol/http/HttpBaseChannel.h b/netwerk/protocol/http/HttpBaseChannel.h
index 849b63cf5e40..fb403afe911a 100644
--- a/netwerk/protocol/http/HttpBaseChannel.h
+++ b/netwerk/protocol/http/HttpBaseChannel.h
@@ -274,6 +274,8 @@ class HttpBaseChannel : public nsHashPropertyBag,
   NS_IMETHOD SetBeConservative(bool aBeConservative) override;
   NS_IMETHOD GetBypassProxy(bool* aBypassProxy) override;
   NS_IMETHOD SetBypassProxy(bool aBypassProxy) override;
+  bool BypassProxy();
+
   NS_IMETHOD GetIsTRRServiceChannel(bool* aTRR) override;
   NS_IMETHOD SetIsTRRServiceChannel(bool aTRR) override;
   NS_IMETHOD GetIsResolvedByTRR(bool* aResolvedByTRR) override;
diff --git a/netwerk/protocol/http/HttpChannelChild.cpp b/netwerk/protocol/http/HttpChannelChild.cpp
index c793e39da2ea..d9c0fa69b22b 100644
--- a/netwerk/protocol/http/HttpChannelChild.cpp
+++ b/netwerk/protocol/http/HttpChannelChild.cpp
@@ -2151,7 +2151,7 @@ nsresult HttpChannelChild::ContinueAsyncOpen() {
   openArgs.allowHttp3() = LoadAllowHttp3();
   openArgs.allowAltSvc() = LoadAllowAltSvc();
   openArgs.beConservative() = LoadBeConservative();
-  openArgs.bypassProxy() = LoadBypassProxy();
+  openArgs.bypassProxy() = BypassProxy();
   openArgs.tlsFlags() = mTlsFlags;
   openArgs.initialRwin() = mInitialRwin;
 
diff --git a/netwerk/protocol/http/nsHttpChannel.cpp b/netwerk/protocol/http/nsHttpChannel.cpp
index 21cc66fe979f..eabf365bd07b 100644
--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -5925,7 +5925,7 @@ void nsHttpChannel::MaybeResolveProxyAndBeginConnect() {
   // settings if we are never going to make a network connection.
   if (!mProxyInfo &&
       !(mLoadFlags & (LOAD_ONLY_FROM_CACHE | LOAD_NO_NETWORK_IO)) &&
-      !LoadBypassProxy() && NS_SUCCEEDED(ResolveProxy())) {
+      !BypassProxy() && NS_SUCCEEDED(ResolveProxy())) {
     return;
   }
 
diff --git a/toolkit/components/telemetry/Events.yaml b/toolkit/components/telemetry/Events.yaml
index d80bac50b109..d47b61f94e81 100644
--- a/toolkit/components/telemetry/Events.yaml
+++ b/toolkit/components/telemetry/Events.yaml
@@ -3013,3 +3013,24 @@ memory_watcher:
     bug_numbers: [1715858]
     notification_emails:
       - tkikuchi@mozilla.com
+
+service_request:
+  bypass:
+    description: >
+      This event is recorded by a small set of services when a proxy failure
+      causes a service to re-request with a proxy bypass.  It records some
+      basic information such as the type of proxy configuration, and the source
+      of the proxy configuration.  The value of the event is the name of the
+      service that triggers the event (e.g. telemetry, remote-settings).
+    methods: ["bypass"]
+    objects: ["proxy_info"]
+    release_channel_collection: opt-out
+    expiry_version: never
+    record_in_processes: ["main"]
+    products: ["firefox"]
+    bug_numbers: [1732792, 1732793, 1733481, 1733994, 1732388]
+    notification_emails:
+      - scaraveo@mozilla.com
+    extra_keys:
+      source: the source of the proxy configuration.  e.g. policy, prefs or extension_id
+      type: the type for the proxy configuration source.  e.g. api or string version of nsIProtocolProxyService.proxyConfigType
diff --git a/toolkit/components/telemetry/app/TelemetrySend.jsm b/toolkit/components/telemetry/app/TelemetrySend.jsm
index 56c830aef210..38774c9fc6f3 100644
--- a/toolkit/components/telemetry/app/TelemetrySend.jsm
+++ b/toolkit/components/telemetry/app/TelemetrySend.jsm
@@ -1308,6 +1308,73 @@ var TelemetrySendImpl = {
     return "/submit/telemetry/" + slug;
   },
 
+  _doPingRequest(ping, id, url, options, errorHandler, onloadHandler) {
+    // Don't send cookies with these requests.
+    let request = new ServiceRequest({ mozAnon: true });
+    request.mozBackgroundRequest = true;
+    request.timeout = Policy.pingSubmissionTimeout();
+
+    request.open("POST", url, options);
+    request.overrideMimeType("text/plain");
+    request.setRequestHeader("Content-Type", "application/json; charset=UTF-8");
+    request.setRequestHeader("Date", Policy.now().toUTCString());
+    request.setRequestHeader("Content-Encoding", "gzip");
+    request.onerror = errorHandler;
+    request.ontimeout = errorHandler;
+    request.onabort = errorHandler;
+    request.onload = onloadHandler;
+    this._pendingPingRequests.set(id, request);
+
+    let startTime = Utils.monotonicNow();
+
+    // If that's a legacy ping format, just send its payload.
+    let networkPayload = isV4PingFormat(ping) ? ping : ping.payload;
+    let converter = Cc[
+      "@mozilla.org/intl/scriptableunicodeconverter"
+    ].createInstance(Ci.nsIScriptableUnicodeConverter);
+    converter.charset = "UTF-8";
+    let utf8Payload = converter.ConvertFromUnicode(
+      JSON.stringify(networkPayload)
+    );
+    utf8Payload += converter.Finish();
+    Services.telemetry
+      .getHistogramById("TELEMETRY_STRINGIFY")
+      .add(Utils.monotonicNow() - startTime);
+
+    let payloadStream = Cc[
+      "@mozilla.org/io/string-input-stream;1"
+    ].createInstance(Ci.nsIStringInputStream);
+    startTime = Utils.monotonicNow();
+    payloadStream.data = Policy.gzipCompressString(utf8Payload);
+
+    // Check the size and drop pings which are too big.
+    const compressedPingSizeBytes = payloadStream.data.length;
+    if (compressedPingSizeBytes > TelemetryStorage.MAXIMUM_PING_SIZE) {
+      this._log.error(
+        "_doPing - submitted ping exceeds the size limit, size: " +
+          compressedPingSizeBytes
+      );
+      Services.telemetry
+        .getHistogramById("TELEMETRY_PING_SIZE_EXCEEDED_SEND")
+        .add();
+      Services.telemetry
+        .getHistogramById("TELEMETRY_DISCARDED_SEND_PINGS_SIZE_MB")
+        .add(Math.floor(compressedPingSizeBytes / 1024 / 1024));
+      // We don't need to call |request.abort()| as it was not sent yet.
+      this._pendingPingRequests.delete(id);
+
+      TelemetryHealthPing.recordDiscardedPing(ping.type);
+      return { promise: TelemetryStorage.removePendingPing(id) };
+    }
+
+    Services.telemetry
+      .getHistogramById("TELEMETRY_COMPRESS")
+      .add(Utils.monotonicNow() - startTime);
+    request.sendInputStream(payloadStream);
+
+    return { payloadStream };
+  },
+
   _doPing(ping, id, isPersisted) {
     if (!this.sendingEnabled(ping)) {
       // We can't send the pings to the server, so don't try to.
@@ -1338,18 +1405,6 @@ var TelemetrySendImpl = {
 
     const url = this._buildSubmissionURL(ping);
 
-    // Don't send cookies with these requests.
-    let request = new ServiceRequest({ mozAnon: true });
-    request.mozBackgroundRequest = true;
-    request.timeout = Policy.pingSubmissionTimeout();
-
-    request.open("POST", url, true);
-    request.overrideMimeType("text/plain");
-    request.setRequestHeader("Content-Type", "application/json; charset=UTF-8");
-    request.setRequestHeader("Date", Policy.now().toUTCString());
-
-    this._pendingPingRequests.set(id, request);
-
     const monotonicStartTime = Utils.monotonicNow();
     let deferred = PromiseUtils.defer();
 
@@ -1379,7 +1434,36 @@ var TelemetrySendImpl = {
       );
     };
 
-    let errorhandler = event => {
+    let retryRequest = request => {
+      if (
+        !request.bypassProxyEnabled ||
+        this._tooLateToSend ||
+        request.bypassProxy ||
+        !request.isProxied
+      ) {
+        return false;
+      }
+      ServiceRequest.logProxySource(request.channel, "telemetry.send");
+      // If the request failed, and it's using a proxy, automatically
+      // attempt without proxy.
+      let { payloadStream } = this._doPingRequest(
+        ping,
+        id,
+        url,
+        { bypassProxy: true },
+        errorHandler,
+        onloadHandler
+      );
+      this.payloadStream = payloadStream;
+      return true;
+    };
+
+    let errorHandler = event => {
+      let request = event.target;
+      if (retryRequest(request)) {
+        return;
+      }
+
       let failure = event.type;
       if (failure === "error") {
         failure = XHR_ERROR_TYPE[request.errorCode];
@@ -1387,23 +1471,6 @@ var TelemetrySendImpl = {
 
       TelemetryHealthPing.recordSendFailure(failure);
 
-      if (this.fallbackHttp) {
-        // only one attempt
-        this.fallbackHttp = false;
-
-        request.channel.securityInfo
-          .QueryInterface(Ci.nsITransportSecurityInfo)
-          .QueryInterface(Ci.nsISerializable);
-        if (request.channel.securityInfo.errorCodeString.startsWith("SEC_")) {
-          // re-open the request with the HTTP version of the URL
-          let fallbackUrl = new URL(url);
-          fallbackUrl.protocol = "http:";
-          // TODO encrypt payload
-          request.open("POST", fallbackUrl, true);
-          request.sendInputStream(this.payloadStream);
-        }
-      }
-
       Services.telemetry
         .getHistogramById("TELEMETRY_SEND_FAILURE_TYPE")
         .add(failure);
@@ -1416,11 +1483,9 @@ var TelemetrySendImpl = {
       );
       onRequestFinished(false, event);
     };
-    request.onerror = errorhandler;
-    request.ontimeout = errorhandler;
-    request.onabort = errorhandler;
 
-    request.onload = event => {
+    let onloadHandler = event => {
+      let request = event.target;
       let status = request.status;
       let statusClass = status - (status % 100);
       let success = false;
@@ -1464,57 +1529,24 @@ var TelemetrySendImpl = {
             event.type
         );
       }
+      if (!success && retryRequest(request)) {
+        return;
+      }
 
       onRequestFinished(success, event);
     };
 
-    // If that's a legacy ping format, just send its payload.
-    let networkPayload = isV4PingFormat(ping) ? ping : ping.payload;
-    request.setRequestHeader("Content-Encoding", "gzip");
-    let converter = Cc[
-      "@mozilla.org/intl/scriptableunicodeconverter"
-    ].createInstance(Ci.nsIScriptableUnicodeConverter);
-    converter.charset = "UTF-8";
-    let startTime = Utils.monotonicNow();
-    let utf8Payload = converter.ConvertFromUnicode(
-      JSON.stringify(networkPayload)
+    let { payloadStream, promise } = this._doPingRequest(
+      ping,
+      id,
+      url,
+      {},
+      errorHandler,
+      onloadHandler
     );
-    utf8Payload += converter.Finish();
-    Services.telemetry
-      .getHistogramById("TELEMETRY_STRINGIFY")
-      .add(Utils.monotonicNow() - startTime);
-
-    let payloadStream = Cc[
-      "@mozilla.org/io/string-input-stream;1"
-    ].createInstance(Ci.nsIStringInputStream);
-    startTime = Utils.monotonicNow();
-    payloadStream.data = Policy.gzipCompressString(utf8Payload);
-
-    // Check the size and drop pings which are too big.
-    const compressedPingSizeBytes = payloadStream.data.length;
-    if (compressedPingSizeBytes > TelemetryStorage.MAXIMUM_PING_SIZE) {
-      this._log.error(
-        "_doPing - submitted ping exceeds the size limit, size: " +
-          compressedPingSizeBytes
-      );
-      Services.telemetry
-        .getHistogramById("TELEMETRY_PING_SIZE_EXCEEDED_SEND")
-        .add();
-      Services.telemetry
-        .getHistogramById("TELEMETRY_DISCARDED_SEND_PINGS_SIZE_MB")
-        .add(Math.floor(compressedPingSizeBytes / 1024 / 1024));
-      // We don't need to call |request.abort()| as it was not sent yet.
-      this._pendingPingRequests.delete(id);
-
-      TelemetryHealthPing.recordDiscardedPing(ping.type);
-      return TelemetryStorage.removePendingPing(id);
+    if (promise) {
+      return promise;
     }
-
-    Services.telemetry
-      .getHistogramById("TELEMETRY_COMPRESS")
-      .add(Utils.monotonicNow() - startTime);
-    request.sendInputStream(payloadStream);
-
     this.payloadStream = payloadStream;
 
     return deferred.promise;
diff --git a/toolkit/components/telemetry/tests/unit/head.js b/toolkit/components/telemetry/tests/unit/head.js
index 5f70841e0f9d..6c2e14fa64e5 100644
--- a/toolkit/components/telemetry/tests/unit/head.js
+++ b/toolkit/components/telemetry/tests/unit/head.js
@@ -52,6 +52,10 @@ const PingServer = {
     return this._httpServer.identity.primaryPort;
   },
 
+  get host() {
+    return this._httpServer.identity.primaryHost;
+  },
+
   get started() {
     return this._started;
   },
diff --git a/toolkit/components/telemetry/tests/unit/test_failover_retry.js b/toolkit/components/telemetry/tests/unit/test_failover_retry.js
new file mode 100644
index 000000000000..eef6929e6b68
--- /dev/null
+++ b/toolkit/components/telemetry/tests/unit/test_failover_retry.js
@@ -0,0 +1,258 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+const { HttpServer } = ChromeUtils.import("resource://testing-common/httpd.js");
+
+const { TelemetryUtils } = ChromeUtils.import(
+  "resource://gre/modules/TelemetryUtils.jsm"
+);
+
+Services.prefs.setBoolPref("network.dns.native-is-localhost", true);
+const TELEMETRY_HOST = "telemetry.mochi.test";
+
+// Trigger a proper telemetry init.
+do_get_profile(true);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+// setup and configure a proxy server that will just deny connections.
+const proxy = AddonTestUtils.createHttpServer();
+proxy.registerPrefixHandler("/", (request, response) => {
+  response.setStatusLine(request.httpVersion, 504, "hello proxy user");
+  response.write("ok!");
+});
+
+// Register a proxy to be used by TCPSocket connections later.
+let proxy_info;
+
+function getBadProxyPort() {
+  let server = new HttpServer();
+  server.start(-1);
+  const badPort = server.identity.primaryPort;
+  server.stop();
+  return badPort;
+}
+
+function registerProxy() {
+  let pps = Cc["@mozilla.org/network/protocol-proxy-service;1"].getService(
+    Ci.nsIProtocolProxyService
+  );
+
+  const proxyFilter = {
+    applyFilter(uri, defaultProxyInfo, callback) {
+      if (
+        proxy_info &&
+        uri.host == PingServer.host &&
+        uri.port == PingServer.port
+      ) {
+        let proxyInfo = pps.newProxyInfo(
+          proxy_info.type,
+          proxy_info.host,
+          proxy_info.port,
+          "",
+          "",
+          0,
+          4096,
+          null
+        );
+        proxyInfo.sourceId = proxy_info.sourceId;
+        callback.onProxyFilterResult(proxyInfo);
+      } else {
+        callback.onProxyFilterResult(defaultProxyInfo);
+      }
+    },
+  };
+
+  pps.registerFilter(proxyFilter, 0);
+  registerCleanupFunction(() => {
+    pps.unregisterFilter(proxyFilter);
+  });
+}
+
+add_task(async function setup() {
+  fakeIntlReady();
+
+  // Make sure we don't generate unexpected pings due to pref changes.
+  await setEmptyPrefWatchlist();
+  Services.prefs.setBoolPref(
+    TelemetryUtils.Preferences.HealthPingEnabled,
+    false
+  );
+  TelemetryStopwatch.setTestModeEnabled(true);
+
+  registerProxy();
+
+  PingServer.start();
+
+  // accept proxy connections for PingServer
+  proxy.identity.add("http", PingServer.host, PingServer.port);
+
+  await TelemetrySend.setup(true);
+  TelemetrySend.setTestModeEnabled(true);
+  TelemetrySend.setServer(`http://localhost:${PingServer.port}`);
+});
+
+function checkEvent() {
+  // ServiceRequest should have recorded an event for this.
+  let expected = [
+    "service_request",
+    "bypass",
+    "proxy_info",
+    "telemetry.send",
+    {
+      source: proxy_info.sourceId,
+      type: "api",
+    },
+  ];
+  let snapshot = Telemetry.snapshotEvents(
+    Ci.nsITelemetry.DATASET_ALL_CHANNELS,
+    false
+  );
+
+  let received = snapshot.parent[0];
+  received.shift();
+  Assert.deepEqual(
+    expected,
+    received,
+    `retry telemetry data matched ${JSON.stringify(received)}`
+  );
+  Telemetry.clearEvents();
+}
+
+async function submitPingWithDate(date, expected) {
+  fakeNow(new Date(date));
+  let pingId = await TelemetryController.submitExternalPing(
+    "test-send-date-header",
+    {}
+  );
+  let req = await PingServer.promiseNextRequest();
+  let ping = decodeRequestPayload(req);
+  Assert.equal(
+    req.getHeader("Date"),
+    expected,
+    "Telemetry should send the correct Date header with requests."
+  );
+  Assert.equal(ping.id, pingId, "Should have received the correct ping id.");
+}
+
+// While there is no specific indiction, this test causes the
+// telemetrySend doPing onload handler to be invoked.
+add_task(async function test_failed_server() {
+  proxy_info = {
+    type: "http",
+    host: proxy.identity.primaryHost,
+    port: proxy.identity.primaryPort,
+    sourceId: "failed_server_test",
+  };
+
+  await TelemetrySend.reset();
+  await submitPingWithDate(
+    Date.UTC(2011, 1, 1, 11, 0, 0),
+    "Tue, 01 Feb 2011 11:00:00 GMT"
+  );
+  checkEvent();
+});
+
+// While there is no specific indiction, this test causes the
+// telemetrySend doPing error handler to be invoked.
+add_task(async function test_no_server() {
+  // Make sure the underlying proxy failover is disabled to easily force
+  // telemetry to retry the request.
+  Services.prefs.setBoolPref("network.proxy.failover_direct", false);
+
+  proxy_info = {
+    type: "http",
+    host: "localhost",
+    port: getBadProxyPort(),
+    sourceId: "no_server_test",
+  };
+
+  await TelemetrySend.reset();
+  await submitPingWithDate(
+    Date.UTC(2012, 1, 1, 11, 0, 0),
+    "Wed, 01 Feb 2012 11:00:00 GMT"
+  );
+  checkEvent();
+});
+
+// Mock out the send timer activity.
+function waitForTimer() {
+  return new Promise(resolve => {
+    fakePingSendTimer(
+      (callback, timeout) => {
+        resolve([callback, timeout]);
+      },
+      () => {}
+    );
+  });
+}
+
+add_task(async function test_no_bypass() {
+  // Make sure the underlying proxy failover is disabled to easily force
+  // telemetry to retry the request.
+  Services.prefs.setBoolPref("network.proxy.failover_direct", false);
+  // Disable the retry and submit again.
+  Services.prefs.setBoolPref("network.proxy.allow_bypass", false);
+
+  proxy_info = {
+    type: "http",
+    host: "localhost",
+    port: getBadProxyPort(),
+    sourceId: "no_server_test",
+  };
+
+  await TelemetrySend.reset();
+
+  fakeNow(new Date(Date.UTC(2013, 1, 1, 11, 0, 0)));
+
+  let timerPromise = waitForTimer();
+  let pingId = await TelemetryController.submitExternalPing(
+    "test-send-date-header",
+    {}
+  );
+  let [pingSendTimerCallback] = await timerPromise;
+  Assert.ok(!!pingSendTimerCallback, "Should have a timer callback");
+
+  Assert.equal(
+    TelemetrySend.pendingPingCount,
+    1,
+    "Should have correct pending ping count"
+  );
+
+  // Reset the proxy, trigger the next tick - we should receive the ping.
+  proxy_info = null;
+  pingSendTimerCallback();
+  let req = await PingServer.promiseNextRequest();
+  let ping = decodeRequestPayload(req);
+
+  // PingServer finished before telemetry, so make sure it's done.
+  await TelemetrySend.testWaitOnOutgoingPings();
+
+  Assert.equal(
+    req.getHeader("Date"),
+    "Fri, 01 Feb 2013 11:00:00 GMT",
+    "Telemetry should send the correct Date header with requests."
+  );
+  Assert.equal(ping.id, pingId, "Should have received the correct ping id.");
+
+  // reset to save any pending pings
+  Assert.equal(
+    TelemetrySend.pendingPingCount,
+    0,
+    "Should not have any pending pings"
+  );
+
+  await TelemetrySend.reset();
+  PingServer.stop();
+});
diff --git a/toolkit/components/telemetry/tests/unit/xpcshell.ini b/toolkit/components/telemetry/tests/unit/xpcshell.ini
index 43f1344d3eb7..6d52aa74a4c8 100644
--- a/toolkit/components/telemetry/tests/unit/xpcshell.ini
+++ b/toolkit/components/telemetry/tests/unit/xpcshell.ini
@@ -106,3 +106,4 @@ tags = coverage
 [test_bug1555798.js]
 [test_UninstallPing.js]
 run-if = os == 'win'
+[test_failover_retry.js]
diff --git a/toolkit/modules/ServiceRequest.jsm b/toolkit/modules/ServiceRequest.jsm
index fa07d60a0dd5..56fab9c8d623 100644
--- a/toolkit/modules/ServiceRequest.jsm
+++ b/toolkit/modules/ServiceRequest.jsm
@@ -9,17 +9,94 @@
  * can be set, Telemetry collected, etc. in a central place.
  */
 
-const { Log } = ChromeUtils.import("resource://gre/modules/Log.jsm");
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 const { XPCOMUtils } = ChromeUtils.import(
   "resource://gre/modules/XPCOMUtils.jsm"
 );
 XPCOMUtils.defineLazyGlobalGetters(this, ["XMLHttpRequest"]);
 
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "ProxyService",
+  "@mozilla.org/network/protocol-proxy-service;1",
+  "nsIProtocolProxyService"
+);
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  ExtensionPreferencesManager:
+    "resource://gre/modules/ExtensionPreferencesManager.jsm",
+});
+
 var EXPORTED_SYMBOLS = ["ServiceRequest"];
 
-const logger = Log.repository.getLogger("ServiceRequest");
-logger.level = Log.Level.Debug;
-logger.addAppender(new Log.ConsoleAppender(new Log.BasicFormatter()));
+const PROXY_CONFIG_TYPES = [
+  "direct",
+  "manual",
+  "pac",
+  "unused", // nsIProtocolProxyService.idl skips index 3.
+  "wpad",
+  "system",
+];
+
+function recordEvent(service, source = {}) {
+  try {
+    Services.telemetry.setEventRecordingEnabled("service_request", true);
+    Services.telemetry.recordEvent(
+      "service_request",
+      "bypass",
+      "proxy_info",
+      service,
+      source
+    );
+  } catch (err) {
+    // If the telemetry throws just log the error so it doesn't break any
+    // functionality.
+    Cu.reportError(err);
+  }
+}
+
+// If proxy.settings is used to change the proxy, an extension will
+// be "in control".  This returns the id of that extension.
+async function getControllingExtension() {
+  if (
+    !WebExtensionPolicy.getActiveExtensions().some(p =>
+      p.permissions.includes("proxy")
+    )
+  ) {
+    return undefined;
+  }
+  // Is this proxied by an extension that set proxy prefs?
+  let setting = await ExtensionPreferencesManager.getSetting("proxy.settings");
+  return setting?.id;
+}
+
+async function getProxySource(proxyInfo) {
+  // sourceId is set when using proxy.onRequest
+  if (proxyInfo.sourceId) {
+    return {
+      source: proxyInfo.sourceId,
+      type: "api",
+    };
+  }
+  let type = PROXY_CONFIG_TYPES[ProxyService.proxyConfigType] || "unknown";
+
+  // If we have a policy it will have set the prefs.
+  if (Services.policies.status === Services.policies.ACTIVE) {
+    let policies = Services.policies.getActivePolicies()?.filter(p => p.Proxy);
+    if (policies?.length) {
+      return {
+        source: "policy",
+        type,
+      };
+    }
+  }
+
+  let source = await getControllingExtension();
+  return {
+    source: source || "prefs",
+    type,
+  };
+}
 
 /**
  * ServiceRequest is intended to be a drop-in replacement for current users
@@ -47,7 +124,30 @@ class ServiceRequest extends XMLHttpRequest {
       // Disable cutting edge features, like TLS 1.3, where middleboxes might brick us
       internal.beConservative = true;
       // Disable use of proxy for this request if necessary.
-      internal.bypassProxy = options?.bypassProxy;
+      if (options?.bypassProxy && this.bypassProxyEnabled) {
+        internal.bypassProxy = this.bypassProxyEnabled;
+      }
+    }
+  }
+
+  get bypassProxy() {
+    let { channel } = this;
+    return channel.QueryInterface(Ci.nsIHttpChannelInternal).bypassProxy;
+  }
+
+  get isProxied() {
+    let { channel } = this;
+    return !!(channel instanceof Ci.nsIProxiedChannel && channel.proxyInfo);
+  }
+
+  get bypassProxyEnabled() {
+    return Services.prefs.getBoolPref("network.proxy.allow_bypass", true);
+  }
+
+  static async logProxySource(channel, service) {
+    if (channel.proxyInfo) {
+      let source = await getProxySource(channel.proxyInfo);
+      recordEvent(service, source);
     }
   }
 }