github.com/meulengracht/snapd@v0.0.0-20210719210640-8bde69bcc84e/netutil/activation.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2015-2019 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package netutil
    21  
    22  import (
    23  	"fmt"
    24  	"net"
    25  	"os"
    26  	"runtime"
    27  	unix "syscall"
    28  
    29  	"github.com/coreos/go-systemd/activation"
    30  
    31  	"github.com/snapcore/snapd/logger"
    32  )
    33  
    34  // GetListener tries to get a listener for the given socket path from
    35  // the listener map, and if it fails it tries to set it up directly.
    36  func GetListener(socketPath string, listenerMap map[string]net.Listener) (net.Listener, error) {
    37  	if listener, ok := listenerMap[socketPath]; ok {
    38  		return listener, nil
    39  	}
    40  
    41  	if c, err := net.Dial("unix", socketPath); err == nil {
    42  		c.Close()
    43  		return nil, fmt.Errorf("socket %q already in use", socketPath)
    44  	}
    45  
    46  	if err := os.Remove(socketPath); err != nil && !os.IsNotExist(err) {
    47  		return nil, err
    48  	}
    49  
    50  	address, err := net.ResolveUnixAddr("unix", socketPath)
    51  	if err != nil {
    52  		return nil, err
    53  	}
    54  
    55  	runtime.LockOSThread()
    56  	oldmask := unix.Umask(0111)
    57  	listener, err := net.ListenUnix("unix", address)
    58  	unix.Umask(oldmask)
    59  	runtime.UnlockOSThread()
    60  	if err != nil {
    61  		return nil, err
    62  	}
    63  
    64  	logger.Debugf("socket %q was not activated; listening", socketPath)
    65  
    66  	return listener, nil
    67  }
    68  
    69  // ActivationListeners builds a map of addresses to listeners that were passed
    70  // during systemd activation
    71  func ActivationListeners() (lns map[string]net.Listener, err error) {
    72  	// pass false to keep LISTEN_* environment variables passed by systemd
    73  	files := activation.Files(false)
    74  	lns = make(map[string]net.Listener, len(files))
    75  
    76  	for _, f := range files {
    77  		ln, err := net.FileListener(f)
    78  		if err != nil {
    79  			return nil, err
    80  		}
    81  		addr := ln.Addr().String()
    82  		lns[addr] = ln
    83  	}
    84  	return lns, nil
    85  }