github.com/zhouyu0/docker-note@v0.0.0-20190722021225-b8d3825084db/daemon/listeners/listeners_linux.go (about)

     1  package listeners // import "github.com/docker/docker/daemon/listeners"
     2  
     3  import (
     4  	"crypto/tls"
     5  	"fmt"
     6  	"net"
     7  	"os"
     8  	"strconv"
     9  
    10  	"github.com/coreos/go-systemd/activation"
    11  	"github.com/docker/go-connections/sockets"
    12  	"github.com/sirupsen/logrus"
    13  )
    14  
    15  // Init creates new listeners for the server.
    16  // TODO: Clean up the fact that socketGroup and tlsConfig aren't always used.
    17  func Init(proto, addr, socketGroup string, tlsConfig *tls.Config) ([]net.Listener, error) {
    18  	ls := []net.Listener{}
    19  
    20  	switch proto {
    21  	case "fd":
    22  		fds, err := listenFD(addr, tlsConfig)
    23  		if err != nil {
    24  			return nil, err
    25  		}
    26  		ls = append(ls, fds...)
    27  	case "tcp":
    28  		l, err := sockets.NewTCPSocket(addr, tlsConfig)
    29  		if err != nil {
    30  			return nil, err
    31  		}
    32  		ls = append(ls, l)
    33  	case "unix":
    34  		// 查找group的gid从/etc/group中，默认是docker用户的gid
    35  		gid, err := lookupGID(socketGroup)
    36  		if err != nil {
    37  			if socketGroup != "" {
    38  				if socketGroup != defaultSocketGroup {
    39  					return nil, err
    40  				}
    41  				logrus.Warnf("could not change group %s to %s: %v", addr, defaultSocketGroup, err)
    42  			}
    43  			gid = os.Getgid()
    44  		}
    45  		// 创建unix socket对象
    46  		l, err := sockets.NewUnixSocket(addr, gid)
    47  		if err != nil {
    48  			return nil, fmt.Errorf("can't create unix socket %s: %v", addr, err)
    49  		}
    50  		ls = append(ls, l)
    51  	default:
    52  		return nil, fmt.Errorf("invalid protocol format: %q", proto)
    53  	}
    54  
    55  	return ls, nil
    56  }
    57  
    58  // listenFD returns the specified socket activated files as a slice of
    59  // net.Listeners or all of the activated files if "*" is given.
    60  func listenFD(addr string, tlsConfig *tls.Config) ([]net.Listener, error) {
    61  	var (
    62  		err       error
    63  		listeners []net.Listener
    64  	)
    65  	// socket activation
    66  	if tlsConfig != nil {
    67  		listeners, err = activation.TLSListeners(tlsConfig)
    68  	} else {
    69  		listeners, err = activation.Listeners()
    70  	}
    71  	if err != nil {
    72  		return nil, err
    73  	}
    74  
    75  	if len(listeners) == 0 {
    76  		return nil, fmt.Errorf("no sockets found via socket activation: make sure the service was started by systemd")
    77  	}
    78  
    79  	// default to all fds just like unix:// and tcp://
    80  	if addr == "" || addr == "*" {
    81  		return listeners, nil
    82  	}
    83  
    84  	fdNum, err := strconv.Atoi(addr)
    85  	if err != nil {
    86  		return nil, fmt.Errorf("failed to parse systemd fd address: should be a number: %v", addr)
    87  	}
    88  	fdOffset := fdNum - 3
    89  	if len(listeners) < fdOffset+1 {
    90  		return nil, fmt.Errorf("too few socket activated files passed in by systemd")
    91  	}
    92  	if listeners[fdOffset] == nil {
    93  		return nil, fmt.Errorf("failed to listen on systemd activated file: fd %d", fdOffset+3)
    94  	}
    95  	for i, ls := range listeners {
    96  		if i == fdOffset || ls == nil {
    97  			continue
    98  		}
    99  		if err := ls.Close(); err != nil {
   100  			return nil, fmt.Errorf("failed to close systemd activated file: fd %d: %v", fdOffset+3, err)
   101  		}
   102  	}
   103  	return []net.Listener{listeners[fdOffset]}, nil
   104  }