Only record fallback metrics on successful requests.

net/http/http_network_transaction.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/http/http_network_transaction.h"
 
 #include <set>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 768 matching lines @@
           "424359 HttpNetworkTransaction::DoCreateStreamComplete"));
 
   // If |result| is ERR_HTTPS_PROXY_TUNNEL_RESPONSE, then
   // DoCreateStreamComplete is being called from OnHttpsProxyTunnelResponse,
   // which resets the stream request first. Therefore, we have to grab the
   // connection attempts in *that* function instead of here in that case.
   if (result != ERR_HTTPS_PROXY_TUNNEL_RESPONSE)
     CopyConnectionAttemptsFromStreamRequest();
 
   if (result == OK) {
+    if (request_->url.SchemeIs("https"))

[Ryan Sleevi, 2015/05/01 23:57:55]

BUG: Why not WSS? Why not SchemeIsCryptographic?

[davidben, 2015/05/02 00:22:09]

Done.

+      RecordSSLFallbackMetrics();
     next_state_ = STATE_INIT_STREAM;
     DCHECK(stream_.get());
   } else if (result == ERR_SSL_CLIENT_AUTH_CERT_NEEDED) {
     result = HandleCertificateRequest(result);
   } else if (result == ERR_HTTPS_PROXY_TUNNEL_RESPONSE) {
     // Return OK and let the caller read the proxy's error page
     next_state_ = STATE_NONE;
     return OK;
   } else if (result == ERR_HTTP_1_1_REQUIRED ||
              result == ERR_PROXY_HTTP_1_1_REQUIRED) {
@@ skipping 724 matching lines @@
 
   pending_auth_target_ = HttpAuth::AUTH_NONE;
   read_buf_ = NULL;
   read_buf_len_ = 0;
   headers_valid_ = false;
   request_headers_.Clear();
   response_ = HttpResponseInfo();
   establishing_tunnel_ = false;
 }
 
+void HttpNetworkTransaction::RecordSSLFallbackMetrics() {
+  enum FallbackVersion {
+    FALLBACK_NONE = 0,    // SSL version fallback did not occur.
+    FALLBACK_SSL3 = 1,    // Fell back to SSL 3.0.
+    FALLBACK_TLS1 = 2,    // Fell back to TLS 1.0.
+    FALLBACK_TLS1_1 = 3,  // Fell back to TLS 1.1.
+    FALLBACK_MAX,
+  };

[Ryan Sleevi, 2015/05/01 23:57:55]

Do you need to document the (hopefully obvious, but not intrinisically) fact
that this is used for UMA and must remain stable?

[davidben, 2015/05/02 00:22:09]

Done.

+
+  FallbackVersion fallback = FALLBACK_NONE;
+  if (server_ssl_config_.version_fallback) {
+    switch (server_ssl_config_.version_max) {
+      case SSL_PROTOCOL_VERSION_SSL3:
+        fallback = FALLBACK_SSL3;
+        break;
+      case SSL_PROTOCOL_VERSION_TLS1:
+        fallback = FALLBACK_TLS1;
+        break;
+      case SSL_PROTOCOL_VERSION_TLS1_1:
+        fallback = FALLBACK_TLS1_1;
+        break;
+      default:
+        NOTREACHED();
+    }
+  }
+  UMA_HISTOGRAM_ENUMERATION("Net.ConnectionUsedSSLVersionFallback2", fallback,
+                            FALLBACK_MAX);
+
+  // We also wish to measure the amount of fallback connections for a host that
+  // we know implements TLS up to 1.2. Ideally there would be no fallback here
+  // but high numbers of SSLv3 would suggest that SSLv3 fallback is being
+  // caused by network middleware rather than buggy HTTPS servers.
+  const std::string& host = request_->url.host();
+  if (EndsWith(host, "google.com", true) &&
+      (host.size() == 10 || host[host.size() - 11] == '.')) {
+    UMA_HISTOGRAM_ENUMERATION("Net.GoogleConnectionUsedSSLVersionFallback2",
+                              fallback, FALLBACK_MAX);
+  }

[Ryan Sleevi, 2015/05/01 23:57:55]

Is this even worthwhile with the fallback SCSV? We should never succeed to such
a host. Can't this be removed now?

[davidben, 2015/05/02 00:22:08]

I'm actually especially interested in a fixed version of these metrics now that
FALLBACK_SCSV exists. :-) With this fix, these metrics will never see a spurious
fallback on Google servers, so we get to find out how many TLS-intolerant MITM
proxies there are[*].

[*] It'll still be an overestimate because there may exist spurious fallbacks on
tolerant MITMs that don't implement FALLBACK_SCSV.

+
+  UMA_HISTOGRAM_BOOLEAN("Net.ConnectionUsedSSLDeprecatedCipherFallback2",
+                        server_ssl_config_.enable_deprecated_cipher_suites);
+}
+
 HttpResponseHeaders* HttpNetworkTransaction::GetResponseHeaders() const {
   return response_.headers.get();
 }
 
 bool HttpNetworkTransaction::ShouldResendRequest() const {
   bool connection_is_proven = stream_->IsConnectionReused();
   bool has_received_headers = GetResponseHeaders() != NULL;
 
   // NOTE: we resend a request only if we reused a keep-alive connection.
   // This automatically prevents an infinite resend loop because we'll run
@@ skipping 134 matching lines @@
   DCHECK(stream_request_);
 
   // Since the transaction can restart with auth credentials, it may create a
   // stream more than once. Accumulate all of the connection attempts across
   // those streams by appending them to the vector:
   for (const auto& attempt : stream_request_->connection_attempts())
     connection_attempts_.push_back(attempt);
 }
 
 }  // namespace net