Allow server sockets to rebind to same port if there is nothing actively listening on that port.

net/socket/tcp_server_socket_libevent.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/socket/tcp_server_socket_libevent.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <sys/socket.h>
@@ skipping 45 matching lines @@
     PLOG(ERROR) << "socket() returned an error";
     return MapSystemError(errno);
   }
 
   if (SetNonBlocking(socket_)) {
     int result = MapSystemError(errno);
     Close();
     return result;
   }
 
+  int result = SetSocketOptions();
+  if (result < 0) {
+    return result;
+  }
+
   SockaddrStorage storage;
   if (!address.ToSockAddr(storage.addr, &storage.addr_len))
     return ERR_INVALID_ARGUMENT;
 
-  int result = bind(socket_, storage.addr, storage.addr_len);
+  result = bind(socket_, storage.addr, storage.addr_len);
   if (result < 0) {
     PLOG(ERROR) << "bind() returned an error";
     result = MapSystemError(errno);
     Close();
     return result;
   }
 
   result = listen(socket_, backlog);
   if (result < 0) {
     PLOG(ERROR) << "listen() returned an error";
@@ skipping 102 matching lines @@
     CompletionCallback callback = accept_callback_;
     accept_callback_.Reset();
     callback.Run(result);
   }
 }
 
 void TCPServerSocketLibevent::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }
 
+void TCPServerSocketLibevent::AllowAddressReuse() {
+  DCHECK(CalledOnValidThread());
+  DCHECK_EQ(socket_, kInvalidSocket);
+
+  socket_options_ |= SOCKET_OPTION_REUSE_ADDRESS;
+}
+
+int TCPServerSocketLibevent::SetSocketOptions() {
+  int true_value = 1;
+  if (socket_options_ & SOCKET_OPTION_REUSE_ADDRESS) {
+    int rv = setsockopt(socket_, SOL_SOCKET, SO_REUSEADDR, &true_value,
+                        sizeof(true_value));
+    if (rv < 0)
+      return MapSystemError(errno);
+  }
+  return OK;
+}
+
 }  // namespace net