Remove the flag which disables non NAT address migration.

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>
@@ skipping 1346 matching lines @@
   }
 }
 
 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;
   }
 
-  PeerAddressChangeType type = NO_CHANGE;
-  if (peer_ip_changed_ || peer_port_changed_) {
-    type = DeterminePeerAddressChangeType();
-    if (FLAGS_quic_disable_non_nat_address_migration && type != PORT_CHANGE &&
-        type != IPV4_SUBNET_CHANGE) {
-      SendConnectionCloseWithDetails(QUIC_ERROR_MIGRATING_ADDRESS,
-                                     "Invalid peer address migration.");
-      return false;
-    }
-  }
-
   if (!Near(header.packet_number, last_header_.packet_number)) {
     DVLOG(1) << ENDPOINT << "Packet " << header.packet_number
              << " out of bounds.  Discarding";
     SendConnectionCloseWithDetails(QUIC_INVALID_PACKET_HEADER,
                                    "packet number out of bounds");
     return false;
   }
 
   // If this packet has already been seen, or the sender has told us that it
   // will not be retransmitted, then stop processing the packet.
@@ skipping 34 matching lines @@
       visitor_->OnSuccessfulVersionNegotiation(version());
       if (debug_visitor_ != nullptr) {
         debug_visitor_->OnSuccessfulVersionNegotiation(version());
       }
     }
   }
 
   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();
@@ skipping 1012 matching lines @@
 void QuicConnection::OnPathClosed(QuicPathId path_id) {
   // Stop receiving packets on this path.
   framer_.OnPathClosed(path_id);
 }
 
 bool QuicConnection::ack_frame_updated() const {
   return received_packet_manager_.ack_frame_updated();
 }
 
 }  // namespace net