Allows QUIC connections to remain established even though the peer's

net/quic/quic_connection.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/quic/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 #include <algorithm>
 #include <iterator>
@@ skipping 186 matching lines @@
                                uint32 max_flow_control_receive_window_bytes)
     : framer_(supported_versions, helper->GetClock()->ApproximateNow(),
               is_server),
       helper_(helper),
       writer_(writer),
       encryption_level_(ENCRYPTION_NONE),
       clock_(helper->GetClock()),
       random_generator_(helper->GetRandomGenerator()),
       connection_id_(connection_id),
       peer_address_(address),
+      migrating_peer_port_(0),
       last_packet_revived_(false),
       last_size_(0),
       last_decrypted_packet_level_(ENCRYPTION_NONE),
       largest_seen_packet_with_ack_(0),
       largest_seen_packet_with_stop_waiting_(0),
       pending_version_negotiation_packet_(false),
       received_packet_manager_(kTCP, &stats_),
       ack_queued_(false),
       stop_waiting_count_(0),
       ack_alarm_(helper->CreateAlarm(new AckAlarm(this))),
@@ skipping 10 matching lines @@
       overall_connection_timeout_(QuicTime::Delta::Infinite()),
       time_of_last_received_packet_(clock_->ApproximateNow()),
       time_of_last_sent_new_packet_(clock_->ApproximateNow()),
       sequence_number_of_last_sent_packet_(0),
       sent_packet_manager_(
           is_server, clock_, &stats_, kTCP,
           FLAGS_quic_use_time_loss_detection ? kTime : kNack),
       version_negotiation_state_(START_NEGOTIATION),
       is_server_(is_server),
       connected_(true),
-      address_migrating_(false),
+      peer_ip_changed_(false),
+      peer_port_changed_(false),
+      self_ip_changed_(false),
+      self_port_changed_(false),
       max_flow_control_receive_window_bytes_(
           max_flow_control_receive_window_bytes) {
   if (max_flow_control_receive_window_bytes_ < kDefaultFlowControlSendWindow) {
     DLOG(ERROR) << "Initial receive window ("
                 << max_flow_control_receive_window_bytes_
                 << ") cannot be set lower than default ("
                 << kDefaultFlowControlSendWindow << ").";
     max_flow_control_receive_window_bytes_ = kDefaultFlowControlSendWindow;
   }
 
@@ skipping 850 matching lines @@
                                       const QuicEncryptedPacket& packet) {
   if (!connected_) {
     return;
   }
   if (debug_visitor_) {
     debug_visitor_->OnPacketReceived(self_address, peer_address, packet);
   }
   last_packet_revived_ = false;
   last_size_ = packet.length();
 
-  address_migrating_ = false;
-
-  if (peer_address_.address().empty()) {
-    peer_address_ = peer_address;
-  }
-  if (self_address_.address().empty()) {
-    self_address_ = self_address;
-  }
-
-  if (!(peer_address == peer_address_ && self_address == self_address_)) {
-    address_migrating_ = true;
-  }
+  CheckForAddressMigration(self_address, peer_address);
 
   stats_.bytes_received += packet.length();
   ++stats_.packets_received;
 
   if (!framer_.ProcessPacket(packet)) {
     // If we are unable to decrypt this packet, it might be
     // because the CHLO or SHLO packet was lost.
     if (encryption_level_ != ENCRYPTION_FORWARD_SECURE &&
         framer_.error() == QUIC_DECRYPTION_FAILURE &&
         undecryptable_packets_.size() < kMaxUndecryptablePackets) {
       QueueUndecryptablePacket(packet);
     }
     DVLOG(1) << ENDPOINT << "Unable to process packet.  Last packet processed: "
              << last_header_.packet_sequence_number;
     return;
   }
 
   ++stats_.packets_processed;
   MaybeProcessUndecryptablePackets();
   MaybeProcessRevivedPacket();
   MaybeSendInResponseToPacket();
   SetPingAlarm();
 }
 
+void QuicConnection::CheckForAddressMigration(
+    const IPEndPoint& self_address, const IPEndPoint& peer_address) {
+  peer_ip_changed_ = false;
+  peer_port_changed_ = false;
+  self_ip_changed_ = false;
+  self_port_changed_ = false;
+
+  if (peer_address_.address().empty()) {
+    peer_address_ = peer_address;
+  }
+  if (self_address_.address().empty()) {
+    self_address_ = self_address;
+  }
+
+  if (!peer_address.address().empty() && !peer_address_.address().empty()) {
+    peer_ip_changed_ = (peer_address.address() != peer_address_.address());
+    peer_port_changed_ = (peer_address.port() != peer_address_.port());
+
+    // Store in case we want to migrate connection in ProcessValidatedPacket.
+    migrating_peer_port_ = peer_address.port();
+  }
+
+  if (!self_address.address().empty() && !self_address_.address().empty()) {
+    self_ip_changed_ = (self_address.address() != self_address_.address());
+    self_port_changed_ = (self_address.port() != self_address_.port());
+  }
+}
+
 void QuicConnection::OnCanWrite() {
   DCHECK(!writer_->IsWriteBlocked());
 
   WriteQueuedPackets();
   WritePendingRetransmissions();
 
   IsHandshake pending_handshake = visitor_->HasPendingHandshake() ?
       IS_HANDSHAKE : NOT_HANDSHAKE;
   // Sending queued packets may have caused the socket to become write blocked,
   // or the congestion manager to prohibit sending.  If we've sent everything
@@ skipping 24 matching lines @@
   }
 }
 
 void QuicConnection::WriteIfNotBlocked() {
   if (!writer_->IsWriteBlocked()) {
     OnCanWrite();
   }
 }
 
 bool QuicConnection::ProcessValidatedPacket() {
-  if (address_migrating_) {
+  if ((!FLAGS_quic_allow_port_migration && peer_port_changed_) ||
+      peer_ip_changed_ || self_ip_changed_ || self_port_changed_) {
     SendConnectionCloseWithDetails(
         QUIC_ERROR_MIGRATING_ADDRESS,
-        "Address migration is not yet a supported feature");
+        "IP or port migration is not yet a supported feature");

[wtc, 2014/05/13 16:37:15]

I think this error message is wrong. At least, it contradicts the comment on
line 1217 that port migration is supported.

One possible solution is to use different error messages:

  if (!FLAGS_quic_allow_port_migration && peer_port_changed_) {
    SendConnectionCloseWithDetails(
        QUIC_ERROR_MIGRATING_ADDRESS, "Port migration is not allowed");
    return false;
  }
  if (peer_ip_changed_ || self_ip_changed_ || self_port_changed_) {
    SendConnectionCloseWithDetails(
        QUIC_ERROR_MIGRATING_ADDRESS,
        "IP migration is not yet a supported feature");
    return false;
  }

The second error message is still not correct for the self_port_changed_ case
though.

[Robbie Shade, 2014/05/13 21:31:21]

How about:

"Neither IP address migration, nor server port migration are supported."

[wtc, 2014/05/13 23:20:41]

This sounds good. Did you mean "server port" or "self port"?

Also, do you think we should use a different error message for the
!FLAGS_quic_allow_port_migration && peer_port_changed_) case?

[Robbie Shade, 2014/05/13 23:30:11]

Yep "self port" is correct, although in practice "server port" is also right as
the only expected use case for this is a client behind a NAT.
Not worth changing I don't think - the flag will be removed in a few weeks once
it's been verified as safe.

[ramant (doing other things), 2014/05/14 05:30:23]

Done.
Acknowledged.

[ramant (doing other things), 2014/05/14 05:30:23]

Made this change in
https://codereview.chromium.org/286693003/diff/1/net/quic/quic_connection.cc

Done.

     return false;
   }
+
+  // Port migration is supported, do it now if port has changed.
+  if (FLAGS_quic_allow_port_migration &&
+      peer_port_changed_) {
+    DVLOG(1) << ENDPOINT << "Peer's port changed from "
+             << peer_address_.port() << " to " << migrating_peer_port_
+             << ", migrating connection.";
+    peer_address_ = IPEndPoint(peer_address_.address(), migrating_peer_port_);
+  }
+
   time_of_last_received_packet_ = clock_->Now();
   DVLOG(1) << ENDPOINT << "time of last received packet: "
            << time_of_last_received_packet_.ToDebuggingValue();
 
   if (is_server_ && encryption_level_ == ENCRYPTION_NONE &&
       last_size_ > options()->max_packet_length) {
     options()->max_packet_length = last_size_;
   }
   return true;
 }
@@ skipping 762 matching lines @@
   // If we changed the generator's batch state, restore original batch state.
   if (!already_in_batch_mode_) {
     DVLOG(1) << "Leaving Batch Mode.";
     connection_->packet_generator_.FinishBatchOperations();
   }
   DCHECK_EQ(already_in_batch_mode_,
             connection_->packet_generator_.InBatchMode());
 }
 
 }  // namespace net