diff --git a/metropolis/pkg/freeport/freeport.go b/metropolis/pkg/freeport/freeport.go
new file mode 100644
index 0000000..bd047b5
--- /dev/null
+++ b/metropolis/pkg/freeport/freeport.go
@@ -0,0 +1,51 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package freeport
+
+import (
+	"io"
+	"net"
+)
+
+// AllocateTCPPort allocates a TCP port on the looopback address, and starts a temporary listener on it. That listener
+// is returned to the caller alongside with the allocated port number. The listener must be closed right before
+// the port is used by the caller. This naturally still leaves a race condition window where that port number
+// might be snatched up by some other process, but there doesn't seem to be a better way to do this.
+func AllocateTCPPort() (uint16, io.Closer, error) {
+	addr, err := net.ResolveTCPAddr("tcp", "127.0.0.1:0")
+	if err != nil {
+		return 0, nil, err
+	}
+
+	l, err := net.ListenTCP("tcp", addr)
+	if err != nil {
+		return 0, nil, err
+	}
+	return uint16(l.Addr().(*net.TCPAddr).Port), l, nil
+}
+
+// MustConsume takes the result of AllocateTCPPort, closes the listener and returns the allocated port.
+// If anything goes wrong (port could not be allocated or closed) it will panic.
+func MustConsume(port uint16, lis io.Closer, err error) int {
+	if err != nil {
+		panic(err)
+	}
+	if err := lis.Close(); err != nil {
+		panic(err)
+	}
+	return int(port)
+}