Retry upon 421 status code without IP pooling.

net/http/http_network_transaction.cc

Index: net/http/http_network_transaction.cc
diff --git a/net/http/http_network_transaction.cc b/net/http/http_network_transaction.cc
index a5395d758bcc4c9d26ef115ca43da28ce9424a0c..e0105c60396fe3f891916b12114cff7c14da899b 100644
--- a/net/http/http_network_transaction.cc
+++ b/net/http/http_network_transaction.cc
@@ -100,9 +100,9 @@ HttpNetworkTransaction::HttpNetworkTransaction(RequestPriority priority,
       total_sent_bytes_(0),
       next_state_(STATE_NONE),
       establishing_tunnel_(false),
+      enable_ip_based_pooling_(true),
       websocket_handshake_stream_base_create_helper_(NULL),
-      net_error_details_() {
-}
+      net_error_details_() {}
 
 HttpNetworkTransaction::~HttpNetworkTransaction() {
   if (stream_.get()) {
@@ -847,22 +847,13 @@ int HttpNetworkTransaction::DoCreateStream() {
     stream_request_.reset(
         session_->http_stream_factory_for_websocket()
             ->RequestWebSocketHandshakeStream(
-                  *request_,
-                  priority_,
-                  server_ssl_config_,
-                  proxy_ssl_config_,
-                  this,
-                  websocket_handshake_stream_base_create_helper_,
-                  net_log_));
+                *request_, priority_, server_ssl_config_, proxy_ssl_config_,
+                this, websocket_handshake_stream_base_create_helper_,
+                enable_ip_based_pooling_, net_log_));
   } else {
-    stream_request_.reset(
-        session_->http_stream_factory()->RequestStream(
-            *request_,
-            priority_,
-            server_ssl_config_,
-            proxy_ssl_config_,
-            this,
-            net_log_));
+    stream_request_.reset(session_->http_stream_factory()->RequestStream(
+        *request_, priority_, server_ssl_config_, proxy_ssl_config_, this,
+        enable_ip_based_pooling_, net_log_));
   }
   DCHECK(stream_request_.get());
   return ERR_IO_PENDING;
@@ -1292,6 +1283,10 @@ int HttpNetworkTransaction::DoReadHeadersComplete(int result) {
     return OK;
   }
 
+  if (response_.headers->response_code() == 421) {
+    return HandleIOError(ERR_MISDIRECTED_REQUEST);
+  }
+
   if (IsSecureRequest()) {
     session_->http_stream_factory()->ProcessAlternativeServices(
         session_, response_.headers.get(), url::SchemeHostPort(request_->url));
@@ -1546,6 +1541,18 @@ int HttpNetworkTransaction::HandleIOError(int error) {
       ResetConnectionAndRequestForResend();
       error = OK;
       break;
+    case ERR_MISDIRECTED_REQUEST:

[Ryan Hamilton, 2017/03/30 23:51:07]

It's a bit weird that ERR_MISDIRECTED_REQUEST is a new error code which is only
used in a single .cc file. It seems like we could just do the retry inline when
we find the 421 status code. But HTTP_TRANSACTION_RESTART_AFTER_ERROR seems
logical, so adding a new error seems reasonable.

[Bence, 2017/03/31 00:09:33]

Yes, I absolutely agree with you.  I was thinking about inlining, but decided
that introducing a new net error code is worth the clarity we get in NetLog.

+      // If this is the second try, just give up.
+      if (!enable_ip_based_pooling_)
+        return OK;
+      // Otherwise, since the response status was 421 Misdirected Request,
+      // retry the request with IP based pooling disabled.
+      enable_ip_based_pooling_ = false;
+      net_log_.AddEventWithNetErrorCode(
+          NetLogEventType::HTTP_TRANSACTION_RESTART_AFTER_ERROR, error);
+      ResetConnectionAndRequestForResend();
+      error = OK;
+      break;
   }
   return error;
 }