capstan/netlisten_unix.go

// +build !windows

package capstan

import (
	"encoding/json"
	"fmt"
	"net"
	"os"
	"os/signal"

	syscall "golang.org/x/sys/unix"
)

func InitNetwork() (err error, errc chan error, close chan struct{}) {
	var env *fdenv

	fds = newfdmap()
	errc = make(chan error, 1)
	close = make(chan struct{}, 1)

	enc := os.Getenv("CAPSTAN_SOCKETS")
	if enc != "" {
		err = json.Unmarshal([]byte(enc), &env)
		if err != nil {
			// Do error.
		}

		parentPID = env.ParentPID
		for _, socket := range env.Sockets {
			fds.addDescriptor(socket.Name, socket.FD)
		}

		for k, v := range env.Addrs {
			fds.addAddrMap(k, v)
		}

		if parentPID != 0 {
			if err = syscall.Kill(parentPID, syscall.SIGUSR1); err != nil {
				return
			}
			// TODO: We should check the state of the parent process to ensure
			// it actually has terminated.
			parentPID = 0
		}
	}

	go func() {
		hup := make(chan os.Signal, 1)
		signal.Notify(hup, syscall.SIGHUP)

		usr1 := make(chan os.Signal, 1)
		signal.Notify(usr1, syscall.SIGUSR1)

		interrupt := make(chan os.Signal, 1)
		signal.Notify(interrupt, os.Interrupt)
		signal.Notify(interrupt, syscall.SIGTERM)

		// TODO: Replace fragile signalling infrastructure with pipes.
		for {
			select {
			case <-hup:
				go func() {
					if err := prelaunchFunc(); err != nil {
						errc <- err
						return
					}
					err := Relaunch()
					if err != nil {
						errc <- err
					}
				}()
				if err != nil {
					errc <- err
				}
			case <-usr1:
				if parentPID == 0 {
					close <- struct{}{}
				} else {
					parentPID = 0
				}
			case <-interrupt:
				for name, listener := range fds.sockets {
					if _, ok := listener.(*net.UnixListener); ok {
						stat, err := os.Stat(name)
						if os.IsNotExist(err) {
							continue
						}
						if stat.Mode()&os.ModeSocket == os.ModeSocket {
							os.Remove(name)
						}
					}
				}
				close <- struct{}{}
			}
		}
	}()

	return
}

func Listen(network, addr string) (net.Listener, error) {
	if fd, ok := fds.getDescriptor(network, addr); ok {
		listener, err := resumeListener(network, addr, fd)
		if err != nil {
			return nil, err
		}
		if _, ok := listener.(Listener); ok {
			fds.addListener(listener.(Listener), network, addr)
			return listener, nil
		}
	}

	listener, err := net.Listen(network, addr)
	if err != nil {
		return nil, err
	}

	if network == "unix" {
		ln, _ := listener.(*net.UnixListener)
		ln.SetUnlinkOnClose(false)
	}

	if _, ok := listener.(Listener); !ok {
		return nil, fmt.Errorf("listener does not implement the appropriate interface")
	}

	if err := fds.addListener(listener.(Listener), network, addr); err != nil {
		return nil, err
	}
	return listener, nil
}

func StopListening(listener net.Listener) error {
	fds.removeListener(listener)
	return listener.Close()
}