package plugin
import (
"errors"
"fmt"
"io/ioutil"
"log"
"net"
"os"
"os/signal"
"runtime"
"strconv"
"sync/atomic"
)
// CoreProtocolVersion is the ProtocolVersion of the plugin system itself.
// We will increment this whenever we change any protocol behavior. This
// will invalidate any prior plugins but will at least allow us to iterate
// on the core in a safe way. We will do our best to do this very
// infrequently.
const CoreProtocolVersion = 1
// HandshakeConfig is the configuration used by client and servers to
// handshake before starting a plugin connection. This is embedded by
// both ServeConfig and ClientConfig.
//
// In practice, the plugin host creates a HandshakeConfig that is exported
// and plugins then can easily consume it.
type HandshakeConfig struct {
// ProtocolVersion is the version that clients must match on to
// agree they can communicate. This should match the ProtocolVersion
// set on ClientConfig when using a plugin.
ProtocolVersion uint
// MagicCookieKey and value are used as a very basic verification
// that a plugin is intended to be launched. This is not a security
// measure, just a UX feature. If the magic cookie doesn't match,
// we show human-friendly output.
MagicCookieKey string
MagicCookieValue string
}
// ServeConfig configures what sorts of plugins are served.
type ServeConfig struct {
// HandshakeConfig is the configuration that must match clients.
HandshakeConfig
// Plugins are the plugins that are served.
Plugins map[string]Plugin
}
// Serve serves the plugins given by ServeConfig.
//
// Serve doesn't return until the plugin is done being executed. Any
// errors will be outputted to the log.
//
// This is the method that plugins should call in their main() functions.
func Serve(opts *ServeConfig) {
// Validate the handshake config
if opts.MagicCookieKey == "" || opts.MagicCookieValue == "" {
fmt.Fprintf(os.Stderr,
"Misconfigured ServeConfig given to serve this plugin: no magic cookie\n"+
"key or value was set. Please notify the plugin author and report\n"+
"this as a bug.\n")
os.Exit(1)
}
// First check the cookie
if os.Getenv(opts.MagicCookieKey) != opts.MagicCookieValue {
fmt.Fprintf(os.Stderr,
"This binary is a plugin. These are not meant to be executed directly.\n"+
"Please execute the program that consumes these plugins, which will\n"+
"load any plugins automatically\n")
os.Exit(1)
}
// Logging goes to the original stderr
log.SetOutput(os.Stderr)
// Create our new stdout, stderr files. These will override our built-in
// stdout/stderr so that it works across the stream boundary.
stdout_r, stdout_w, err := os.Pipe()
if err != nil {
fmt.Fprintf(os.Stderr, "Error preparing plugin: %s\n", err)
os.Exit(1)
}
stderr_r, stderr_w, err := os.Pipe()
if err != nil {
fmt.Fprintf(os.Stderr, "Error preparing plugin: %s\n", err)
os.Exit(1)
}
// Register a listener so we can accept a connection
listener, err := serverListener()
if err != nil {
log.Printf("[ERR] plugin: plugin init: %s", err)
return
}
defer listener.Close()
// Create the channel to tell us when we're done
doneCh := make(chan struct{})
// Create the RPC server to dispense
server := &RPCServer{
Plugins: opts.Plugins,
Stdout: stdout_r,
Stderr: stderr_r,
DoneCh: doneCh,
}
// Output the address and service name to stdout so that core can bring it up.
log.Printf("[DEBUG] plugin: plugin address: %s %s\n",
listener.Addr().Network(), listener.Addr().String())
fmt.Printf("%d|%d|%s|%s\n",
CoreProtocolVersion,
opts.ProtocolVersion,
listener.Addr().Network(),
listener.Addr().String())
os.Stdout.Sync()
// Eat the interrupts
ch := make(chan os.Signal, 1)
signal.Notify(ch, os.Interrupt)
go func() {
var count int32 = 0
for {
<-ch
newCount := atomic.AddInt32(&count, 1)
log.Printf(
"[DEBUG] plugin: received interrupt signal (count: %d). Ignoring.",
newCount)
}
}()
// Set our new out, err
os.Stdout = stdout_w
os.Stderr = stderr_w
// Serve
go server.Accept(listener)
// Wait for the graceful exit
<-doneCh
}
func serverListener() (net.Listener, error) {
if runtime.GOOS == "windows" {
return serverListener_tcp()
}
return serverListener_unix()
}
func serverListener_tcp() (net.Listener, error) {
minPort, err := strconv.ParseInt(os.Getenv("PLUGIN_MIN_PORT"), 10, 32)
if err != nil {
return nil, err
}
maxPort, err := strconv.ParseInt(os.Getenv("PLUGIN_MAX_PORT"), 10, 32)
if err != nil {
return nil, err
}
for port := minPort; port <= maxPort; port++ {
address := fmt.Sprintf("127.0.0.1:%d", port)
listener, err := net.Listen("tcp", address)
if err == nil {
return listener, nil
}
}
return nil, errors.New("Couldn't bind plugin TCP listener")
}
func serverListener_unix() (net.Listener, error) {
tf, err := ioutil.TempFile("", "plugin")
if err != nil {
return nil, err
}
path := tf.Name()
// Close the file and remove it because it has to not exist for
// the domain socket.
if err := tf.Close(); err != nil {
return nil, err
}
if err := os.Remove(path); err != nil {
return nil, err
}
l, err := net.Listen("unix", path)
if err != nil {
return nil, err
}
// Wrap the listener in rmListener so that the Unix domain socket file
// is removed on close.
return &rmListener{
Listener: l,
Path: path,
}, nil
}
// rmListener is an implementation of net.Listener that forwards most
// calls to the listener but also removes a file as part of the close. We
// use this to cleanup the unix domain socket on close.
type rmListener struct {
net.Listener
Path string
}
func (l *rmListener) Close() error {
// Close the listener itself
if err := l.Listener.Close(); err != nil {
return err
}
// Remove the file
return os.Remove(l.Path)
}
