Postpone checking peer address change after the packet is successfully

net/quic/quic_connection.cc

Index: net/quic/quic_connection.cc
diff --git a/net/quic/quic_connection.cc b/net/quic/quic_connection.cc
index a59eaa23ea6498fe5d08a2af1475754fa1cbeaae..6c6a1f27757805f2ee97a6f632e77c07c2fb4881 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -21,6 +21,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
+#include "net/base/address_family.h"
 #include "net/base/net_errors.h"
 #include "net/quic/crypto/crypto_protocol.h"
 #include "net/quic/crypto/quic_decrypter.h"
@@ -79,6 +80,11 @@ bool Near(QuicPacketNumber a, QuicPacketNumber b) {
   return delta <= kMaxPacketGap;
 }
 
+bool IsInitializedIPEndPoint(const IPEndPoint& address) {
+  return net::GetAddressFamily(address.address().bytes()) !=
+         net::ADDRESS_FAMILY_UNSPECIFIED;
+}
+
 // An alarm that is scheduled to send an ack if a timeout occurs.
 class AckAlarm : public QuicAlarm::Delegate {
  public:
@@ -665,6 +671,8 @@ bool QuicConnection::OnPacketHeader(const QuicPacketHeader& header) {
     return false;
   }
 
+  MaybeMigrateConnectionToNewPeerAddress();
+
   --stats_.packets_dropped;
   DVLOG(1) << ENDPOINT << "Received packet header: " << header;
   last_header_ = header;
@@ -1259,7 +1267,18 @@ void QuicConnection::ProcessUdpPacket(const IPEndPoint& self_address,
   }
   last_size_ = packet.length();
 
-  CheckForAddressMigration(self_address, peer_address);
+  if (FLAGS_check_peer_address_change_after_decryption) {
+    last_packet_destination_address_ = self_address;
+    last_packet_source_address_ = peer_address;
+    if (!IsInitializedIPEndPoint(self_address_)) {
+      self_address_ = last_packet_destination_address_;
+    }
+    if (!IsInitializedIPEndPoint(peer_address_)) {
+      peer_address_ = last_packet_source_address_;
+    }
+  } else {
+    CheckForAddressMigration(self_address, peer_address);
+  }
 
   stats_.bytes_received += packet.length();
   ++stats_.packets_received;
@@ -1314,14 +1333,6 @@ void QuicConnection::CheckForAddressMigration(const IPEndPoint& self_address,
     self_ip_changed_ = (self_address.address() != self_address_.address());
     self_port_changed_ = (self_address.port() != self_address_.port());
   }
-
-  // TODO(vasilvv): reset maximum packet size on connection migration. Whenever
-  // the connection is migrated, it usually ends up being on a different path,
-  // with possibly smaller MTU.  This means the max packet size has to be reset
-  // and MTU discovery mechanism re-initialized.  The main reason the code does
-  // not do it now is that the retransmission code currently cannot deal with
-  // the case when it needs to resend a packet created with larger MTU (see
-  // b/22172803).
 }
 
 void QuicConnection::OnCanWrite() {
@@ -1362,10 +1373,22 @@ void QuicConnection::WriteIfNotBlocked() {
 }
 
 bool QuicConnection::ProcessValidatedPacket(const QuicPacketHeader& header) {
-  if (self_ip_changed_ || self_port_changed_) {
-    SendConnectionCloseWithDetails(QUIC_ERROR_MIGRATING_ADDRESS,
-                                   "Self address migration is not supported.");
-    return false;
+  if (FLAGS_check_peer_address_change_after_decryption) {
+    if (IsInitializedIPEndPoint(self_address_) &&
+        IsInitializedIPEndPoint(last_packet_destination_address_) &&
+        (!(self_address_ == last_packet_destination_address_))) {
+      SendConnectionCloseWithDetails(
+          QUIC_ERROR_MIGRATING_ADDRESS,
+          "Self address migration is not supported.");
+      return false;
+    }
+  } else {
+    if (self_ip_changed_ || self_port_changed_) {
+      SendConnectionCloseWithDetails(
+          QUIC_ERROR_MIGRATING_ADDRESS,
+          "Self address migration is not supported.");
+      return false;
+    }
   }
 
   if (!Near(header.packet_number, last_header_.packet_number)) {
@@ -1421,22 +1444,6 @@ bool QuicConnection::ProcessValidatedPacket(const QuicPacketHeader& header) {
 
   DCHECK_EQ(NEGOTIATED_VERSION, version_negotiation_state_);
 
-  if (peer_ip_changed_ || peer_port_changed_) {
-    PeerAddressChangeType type = DeterminePeerAddressChangeType();
-    IPEndPoint old_peer_address = peer_address_;
-    peer_address_ = IPEndPoint(
-        peer_ip_changed_ ? migrating_peer_ip_ : peer_address_.address().bytes(),
-        peer_port_changed_ ? migrating_peer_port_ : peer_address_.port());
-
-    DVLOG(1) << ENDPOINT << "Peer's ip:port changed from "
-             << old_peer_address.ToString() << " to "
-             << peer_address_.ToString() << ", migrating connection.";
-
-    visitor_->OnConnectionMigration();
-    DCHECK_NE(type, NO_CHANGE);
-    sent_packet_manager_.OnConnectionMigration(type);
-  }
-
   time_of_last_received_packet_ = clock_->Now();
   DVLOG(1) << ENDPOINT << "time of last received packet: "
            << time_of_last_received_packet_.ToDebuggingValue();
@@ -1838,10 +1845,6 @@ void QuicConnection::SendOrQueuePacket(SerializedPacket* packet) {
   }
 }
 
-PeerAddressChangeType QuicConnection::DeterminePeerAddressChangeType() {
-  return UNSPECIFIED_CHANGE;
-}
-
 void QuicConnection::OnPingTimeout() {
   if (!retransmission_alarm_->IsSet()) {
     SendPing();
@@ -2446,6 +2449,90 @@ void QuicConnection::DiscoverMtu() {
   DCHECK(!mtu_discovery_alarm_->IsSet());
 }
 
+PeerAddressChangeType QuicConnection::DeterminePeerAddressChangeType() {
+  IPEndPoint last_peer_address;
+  if (FLAGS_check_peer_address_change_after_decryption) {
+    last_peer_address = last_packet_source_address_;
+  } else {
+    last_peer_address = IPEndPoint(
+        peer_ip_changed_ ? migrating_peer_ip_ : peer_address_.address().bytes(),
+        peer_port_changed_ ? migrating_peer_port_ : peer_address_.port());
+  }
+
+  if (!IsInitializedIPEndPoint(peer_address_) ||
+      !IsInitializedIPEndPoint(last_peer_address) ||
+      peer_address_ == last_peer_address) {
+    return NO_CHANGE;
+  }
+
+  if (peer_address_.address() == last_peer_address.address()) {
+    return PORT_CHANGE;
+  }
+
+  bool old_ip_is_ipv4 = peer_address_.address().IsIPv4();
+  bool migrating_ip_is_ipv4 = last_peer_address.address().IsIPv4();
+  if (old_ip_is_ipv4 && !migrating_ip_is_ipv4) {
+    return IPV4_TO_IPV6_CHANGE;
+  }
+
+  if (!old_ip_is_ipv4) {
+    return migrating_ip_is_ipv4 ? IPV6_TO_IPV4_CHANGE : IPV6_TO_IPV6_CHANGE;
+  }
+
+  // TODO(rtenneti): Implement better way to test SubnetMask length of 24 bits.
+  IPAddressNumber peer_address_bytes = peer_address_.address().bytes();
+  IPAddressNumber last_peer_address_bytes = last_peer_address.address().bytes();
+  if (peer_address_bytes[0] == last_peer_address_bytes[0] &&
+      peer_address_bytes[1] == last_peer_address_bytes[1] &&
+      peer_address_bytes[2] == last_peer_address_bytes[2]) {
+    // Subnet part does not change (here, we use /24), which is considered to be
+    // caused by NATs.
+    return IPV4_SUBNET_CHANGE;
+  }
+
+  return UNSPECIFIED_CHANGE;
+}
+
+void QuicConnection::MaybeMigrateConnectionToNewPeerAddress() {
+  PeerAddressChangeType peer_address_change_type =
+      DeterminePeerAddressChangeType();
+  // TODO(fayang): Currently, all peer address change type are allowed. Need to
+  // add a method ShouldAllowPeerAddressChange(PeerAddressChangeType type) to
+  // determine whehter |type| is allowed.
+  if (FLAGS_check_peer_address_change_after_decryption) {
+    if (peer_address_change_type == NO_CHANGE) {
+      return;
+    }
+
+    IPEndPoint old_peer_address = peer_address_;
+    peer_address_ = last_packet_source_address_;
+
+    DVLOG(1) << ENDPOINT << "Peer's ip:port changed from "
+             << old_peer_address.ToString() << " to "
+             << peer_address_.ToString() << ", migrating connection.";
+
+    visitor_->OnConnectionMigration();
+    sent_packet_manager_.OnConnectionMigration(peer_address_change_type);
+
+    return;
+  }
+
+  if (peer_ip_changed_ || peer_port_changed_) {
+    IPEndPoint old_peer_address = peer_address_;
+    peer_address_ = IPEndPoint(
+        peer_ip_changed_ ? migrating_peer_ip_ : peer_address_.address().bytes(),
+        peer_port_changed_ ? migrating_peer_port_ : peer_address_.port());
+
+    DVLOG(1) << ENDPOINT << "Peer's ip:port changed from "
+             << old_peer_address.ToString() << " to "
+             << peer_address_.ToString() << ", migrating connection.";
+
+    visitor_->OnConnectionMigration();
+    DCHECK_NE(peer_address_change_type, NO_CHANGE);
+    sent_packet_manager_.OnConnectionMigration(peer_address_change_type);
+  }
+}
+
 void QuicConnection::OnPathClosed(QuicPathId path_id) {
   // Stop receiving packets on this path.
   framer_.OnPathClosed(path_id);