DockerCLI/cli-plugins/socket/socket.go

73 lines
1.8 KiB
Go

package socket
import (
"errors"
"io"
"net"
"os"
"github.com/docker/distribution/uuid"
)
// EnvKey represents the well-known environment variable used to pass the plugin being
// executed the socket name it should listen on to coordinate with the host CLI.
const EnvKey = "DOCKER_CLI_PLUGIN_SOCKET"
// SetupConn sets up a Unix socket listener, establishes a goroutine to handle connections
// and update the conn pointer, and returns the environment variable to pass to the plugin.
func SetupConn(conn **net.UnixConn) (string, error) {
listener, err := listen("docker_cli_" + uuid.Generate().String())
if err != nil {
return "", err
}
accept(listener, conn)
return EnvKey + "=" + listener.Addr().String(), nil
}
func accept(listener *net.UnixListener, conn **net.UnixConn) {
defer listener.Close()
go func() {
for {
// ignore error here, if we failed to accept a connection,
// conn is nil and we fallback to previous behavior
*conn, _ = listener.AcceptUnix()
// perform any platform-specific actions on accept (e.g. unlink non-abstract sockets)
onAccept(*conn, listener)
}
}()
}
// ConnectAndWait connects to the socket passed via well-known env var,
// if present, and attempts to read from it until it receives an EOF, at which
// point cb is called.
func ConnectAndWait(cb func()) {
socketAddr, ok := os.LookupEnv(EnvKey)
if !ok {
// if a plugin compiled against a more recent version of docker/cli
// is executed by an older CLI binary, ignore missing environment
// variable and behave as usual
return
}
addr, err := net.ResolveUnixAddr("unix", socketAddr)
if err != nil {
return
}
conn, err := net.DialUnix("unix", nil, addr)
if err != nil {
return
}
go func() {
b := make([]byte, 1)
for {
_, err := conn.Read(b)
if errors.Is(err, io.EOF) {
cb()
}
}
}()
}