netutil: extract socket activation helpers from daemon package.

1 files changed, 85 insertions, 0 deletions

diff --git a/netutil/activation.go b/netutil/activation.go
new file mode 100644
index 0000000000..48f1205b70
--- /dev/null
+++ b/netutil/activation.go
@@ -0,0 +1,85 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2015-2019 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package netutil
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"runtime"
+	unix "syscall"
+
+	"github.com/coreos/go-systemd/activation"
+
+	"github.com/snapcore/snapd/logger"
+)
+
+// GetListener tries to get a listener for the given socket path from
+// the listener map, and if it fails it tries to set it up directly.
+func GetListener(socketPath string, listenerMap map[string]net.Listener) (net.Listener, error) {
+	if listener, ok := listenerMap[socketPath]; ok {
+	return listener, nil
+	}
+
+	if c, err := net.Dial("unix", socketPath); err == nil {
+	c.Close()
+	return nil, fmt.Errorf("socket %q already in use", socketPath)
+	}
+
+	if err := os.Remove(socketPath); err != nil && !os.IsNotExist(err) {
+	return nil, err
+	}
+
+	address, err := net.ResolveUnixAddr("unix", socketPath)
+	if err != nil {
+	return nil, err
+	}
+
+	runtime.LockOSThread()
+	oldmask := unix.Umask(0111)
+	listener, err := net.ListenUnix("unix", address)
+	unix.Umask(oldmask)
+	runtime.UnlockOSThread()
+	if err != nil {
+	return nil, err
+	}
+
+	logger.Debugf("socket %q was not activated; listening", socketPath)
+
+	return listener, nil
+}
+
+// ActivationListeners builds a map of addresses to listeners that were passed
+// during systemd activation
+func ActivationListeners() (lns map[string]net.Listener, err error) {
+	// pass false to keep LISTEN_* environment variables passed by systemd
+	files := activation.Files(false)
+	lns = make(map[string]net.Listener, len(files))
+
+	for _, f := range files {
+	ln, err := net.FileListener(f)
+	if err != nil {
+	return nil, err
+	}
+	addr := ln.Addr().String()
+	lns[addr] = ln
+	}
+	return lns, nil
+}