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

net/socket/tcp_server_socket_libevent.cc

Index: net/socket/tcp_server_socket_libevent.cc
diff --git a/net/socket/tcp_server_socket_libevent.cc b/net/socket/tcp_server_socket_libevent.cc
index ef8d1b1bcbef21f851decf142c01181d9c5e1c30..48e65e53d53c8adab2b139feb1face8138a96a43 100644
--- a/net/socket/tcp_server_socket_libevent.cc
+++ b/net/socket/tcp_server_socket_libevent.cc
@@ -63,11 +63,16 @@ int TCPServerSocketLibevent::Listen(const IPEndPoint& address, int backlog) {
     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);
@@ -190,4 +195,22 @@ 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