rootless: use RootlessKit port forwarder

RootlessKit port forwarder has a lot of advantages over the slirp4netns port forwarder:

* Very high throughput.
  Benchmark result on Travis: socat: 5.2 Gbps, slirp4netns: 8.3 Gbps, RootlessKit: 27.3 Gbps
  (https://travis-ci.org/rootless-containers/rootlesskit/builds/597056377)

* Connections from the host are treated as 127.0.0.1 rather than 10.0.2.2 in the namespace.
  No UDP issue (#4586)

* No tcp_rmem issue (#4537)

* Probably works with IPv6. Even if not, it is trivial to support IPv6.  (#4311)

* Easily extensible for future support of SCTP

* Easily extensible for future support of `lxc-user-nic` SUID network

RootlessKit port forwarder has been already adopted as the default port forwarder by Rootless Docker/Moby,
and no issue has been reported AFAIK.

As the port forwarder is imported as a Go package, no `rootlesskit` binary is required for Podman.

Fix #4586
May-fix #4559
Fix #4537
May-fix #4311

See https://github.com/rootless-containers/rootlesskit/blob/v0.7.0/pkg/port/builtin/builtin.go

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/builtin.go

@@ -0,0 +1,14 @@
+package builtin
+
+import (
+	"io"
+
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/child"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent"
+)
+
+var (
+	NewParentDriver func(logWriter io.Writer, stateDir string) (port.ParentDriver, error) = parent.NewDriver
+	NewChildDriver  func(logWriter io.Writer) port.ChildDriver                            = child.NewDriver
+)

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/child/child.go

@@ -0,0 +1,134 @@
+package child
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+
+	"github.com/rootless-containers/rootlesskit/pkg/msgutil"
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/msg"
+	opaquepkg "github.com/rootless-containers/rootlesskit/pkg/port/builtin/opaque"
+)
+
+func NewDriver(logWriter io.Writer) port.ChildDriver {
+	return &childDriver{
+		logWriter: logWriter,
+	}
+}
+
+type childDriver struct {
+	logWriter io.Writer
+}
+
+func (d *childDriver) RunChildDriver(opaque map[string]string, quit <-chan struct{}) error {
+	socketPath := opaque[opaquepkg.SocketPath]
+	if socketPath == "" {
+		return errors.New("socket path not set")
+	}
+	childReadyPipePath := opaque[opaquepkg.ChildReadyPipePath]
+	if childReadyPipePath == "" {
+		return errors.New("child ready pipe path not set")
+	}
+	childReadyPipeW, err := os.OpenFile(childReadyPipePath, os.O_WRONLY, os.ModeNamedPipe)
+	if err != nil {
+		return err
+	}
+	ln, err := net.ListenUnix("unix", &net.UnixAddr{
+		Name: socketPath,
+		Net:  "unix",
+	})
+	if err != nil {
+		return err
+	}
+	// write nothing, just close
+	if err = childReadyPipeW.Close(); err != nil {
+		return err
+	}
+	stopAccept := make(chan struct{}, 1)
+	go func() {
+		<-quit
+		stopAccept <- struct{}{}
+		ln.Close()
+	}()
+	for {
+		c, err := ln.AcceptUnix()
+		if err != nil {
+			select {
+			case <-stopAccept:
+				return nil
+			default:
+			}
+			return err
+		}
+		go func() {
+			if rerr := d.routine(c); rerr != nil {
+				rep := msg.Reply{
+					Error: rerr.Error(),
+				}
+				msgutil.MarshalToWriter(c, &rep)
+			}
+			c.Close()
+		}()
+	}
+	return nil
+}
+
+func (d *childDriver) routine(c *net.UnixConn) error {
+	var req msg.Request
+	if _, err := msgutil.UnmarshalFromReader(c, &req); err != nil {
+		return err
+	}
+	switch req.Type {
+	case msg.RequestTypeInit:
+		return d.handleConnectInit(c, &req)
+	case msg.RequestTypeConnect:
+		return d.handleConnectRequest(c, &req)
+	default:
+		return errors.Errorf("unknown request type %q", req.Type)
+	}
+}
+
+func (d *childDriver) handleConnectInit(c *net.UnixConn, req *msg.Request) error {
+	_, err := msgutil.MarshalToWriter(c, nil)
+	return err
+}
+
+func (d *childDriver) handleConnectRequest(c *net.UnixConn, req *msg.Request) error {
+	switch req.Proto {
+	case "tcp":
+	case "udp":
+	default:
+		return errors.Errorf("unknown proto: %q", req.Proto)
+	}
+	var dialer net.Dialer
+	targetConn, err := dialer.Dial(req.Proto, fmt.Sprintf("127.0.0.1:%d", req.Port))
+	if err != nil {
+		return err
+	}
+	defer targetConn.Close() // no effect on duplicated FD
+	targetConnFiler, ok := targetConn.(filer)
+	if !ok {
+		return errors.Errorf("unknown target connection: %+v", targetConn)
+	}
+	targetConnFile, err := targetConnFiler.File()
+	if err != nil {
+		return err
+	}
+	oob := unix.UnixRights(int(targetConnFile.Fd()))
+	f, err := c.File()
+	if err != nil {
+		return err
+	}
+	err = unix.Sendmsg(int(f.Fd()), []byte("dummy"), oob, nil, 0)
+	return err
+}
+
+// filer is implemented by *net.TCPConn and *net.UDPConn
+type filer interface {
+	File() (f *os.File, err error)
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/msg/msg.go

@@ -0,0 +1,129 @@
+package msg
+
+import (
+	"net"
+	"time"
+
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+
+	"github.com/rootless-containers/rootlesskit/pkg/msgutil"
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+)
+
+const (
+	RequestTypeInit    = "init"
+	RequestTypeConnect = "connect"
+)
+
+// Request and Response are encoded as JSON with uint32le length header.
+type Request struct {
+	Type  string // "init" or "connect"
+	Proto string // "tcp" or "udp"
+	Port  int
+}
+
+// Reply may contain FD as OOB
+type Reply struct {
+	Error string
+}
+
+// Initiate sends "init" request to the child UNIX socket.
+func Initiate(c *net.UnixConn) error {
+	req := Request{
+		Type: RequestTypeInit,
+	}
+	if _, err := msgutil.MarshalToWriter(c, &req); err != nil {
+		return err
+	}
+	if err := c.CloseWrite(); err != nil {
+		return err
+	}
+	var rep Reply
+	if _, err := msgutil.UnmarshalFromReader(c, &rep); err != nil {
+		return err
+	}
+	return c.CloseRead()
+}
+
+// ConnectToChild connects to the child UNIX socket, and obtains TCP or UDP socket FD
+// that corresponds to the port spec.
+func ConnectToChild(c *net.UnixConn, spec port.Spec) (int, error) {
+	req := Request{
+		Type:  RequestTypeConnect,
+		Proto: spec.Proto,
+		Port:  spec.ChildPort,
+	}
+	if _, err := msgutil.MarshalToWriter(c, &req); err != nil {
+		return 0, err
+	}
+	if err := c.CloseWrite(); err != nil {
+		return 0, err
+	}
+	oobSpace := unix.CmsgSpace(4)
+	oob := make([]byte, oobSpace)
+	_, oobN, _, _, err := c.ReadMsgUnix(nil, oob)
+	if err != nil {
+		return 0, err
+	}
+	if oobN != oobSpace {
+		return 0, errors.Errorf("expected OOB space %d, got %d", oobSpace, oobN)
+	}
+	oob = oob[:oobN]
+	fd, err := parseFDFromOOB(oob)
+	if err != nil {
+		return 0, err
+	}
+	if err := c.CloseRead(); err != nil {
+		return 0, err
+	}
+	return fd, nil
+}
+
+// ConnectToChildWithSocketPath wraps ConnectToChild
+func ConnectToChildWithSocketPath(socketPath string, spec port.Spec) (int, error) {
+	var dialer net.Dialer
+	conn, err := dialer.Dial("unix", socketPath)
+	if err != nil {
+		return 0, err
+	}
+	defer conn.Close()
+	c := conn.(*net.UnixConn)
+	return ConnectToChild(c, spec)
+}
+
+// ConnectToChildWithRetry retries ConnectToChild every (i*5) milliseconds.
+func ConnectToChildWithRetry(socketPath string, spec port.Spec, retries int) (int, error) {
+	for i := 0; i < retries; i++ {
+		fd, err := ConnectToChildWithSocketPath(socketPath, spec)
+		if i == retries-1 && err != nil {
+			return 0, err
+		}
+		if err == nil {
+			return fd, err
+		}
+		// TODO: backoff
+		time.Sleep(time.Duration(i*5) * time.Millisecond)
+	}
+	// NOT REACHED
+	return 0, errors.New("reached max retry")
+}
+
+func parseFDFromOOB(oob []byte) (int, error) {
+	scms, err := unix.ParseSocketControlMessage(oob)
+	if err != nil {
+		return 0, err
+	}
+	if len(scms) != 1 {
+		return 0, errors.Errorf("unexpected scms: %v", scms)
+	}
+	scm := scms[0]
+	fds, err := unix.ParseUnixRights(&scm)
+	if err != nil {
+		return 0, err
+	}
+	if len(fds) != 1 {
+		return 0, errors.Errorf("unexpected fds: %v", fds)
+	}
+	return fds[0], nil
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/opaque/opaque.go

@@ -0,0 +1,6 @@
+package opaque
+
+const (
+	SocketPath         = "builtin.socketpath"
+	ChildReadyPipePath = "builtin.readypipepath"
+)

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/parent.go

@@ -0,0 +1,145 @@
+package parent
+
+import (
+	"context"
+	"io"
+	"io/ioutil"
+	"net"
+	"os"
+	"path/filepath"
+	"sync"
+	"syscall"
+
+	"github.com/pkg/errors"
+
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/msg"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/opaque"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/tcp"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/udp"
+	"github.com/rootless-containers/rootlesskit/pkg/port/portutil"
+)
+
+// NewDriver for builtin driver.
+func NewDriver(logWriter io.Writer, stateDir string) (port.ParentDriver, error) {
+	// TODO: consider using socketpair FD instead of socket file
+	socketPath := filepath.Join(stateDir, ".bp.sock")
+	childReadyPipePath := filepath.Join(stateDir, ".bp-ready.pipe")
+	// remove the path just in case the previous rootlesskit instance crashed
+	if err := os.RemoveAll(childReadyPipePath); err != nil {
+		return nil, errors.Wrapf(err, "cannot remove %s", childReadyPipePath)
+	}
+	if err := syscall.Mkfifo(childReadyPipePath, 0600); err != nil {
+		return nil, errors.Wrapf(err, "cannot mkfifo %s", childReadyPipePath)
+	}
+	d := driver{
+		logWriter:          logWriter,
+		socketPath:         socketPath,
+		childReadyPipePath: childReadyPipePath,
+		ports:              make(map[int]*port.Status, 0),
+		stoppers:           make(map[int]func() error, 0),
+		nextID:             1,
+	}
+	return &d, nil
+}
+
+type driver struct {
+	logWriter          io.Writer
+	socketPath         string
+	childReadyPipePath string
+	mu                 sync.Mutex
+	ports              map[int]*port.Status
+	stoppers           map[int]func() error
+	nextID             int
+}
+
+func (d *driver) OpaqueForChild() map[string]string {
+	return map[string]string{
+		opaque.SocketPath:         d.socketPath,
+		opaque.ChildReadyPipePath: d.childReadyPipePath,
+	}
+}
+
+func (d *driver) RunParentDriver(initComplete chan struct{}, quit <-chan struct{}, _ *port.ChildContext) error {
+	childReadyPipeR, err := os.OpenFile(d.childReadyPipePath, os.O_RDONLY, os.ModeNamedPipe)
+	if err != nil {
+		return err
+	}
+	if _, err = ioutil.ReadAll(childReadyPipeR); err != nil {
+		return err
+	}
+	childReadyPipeR.Close()
+	var dialer net.Dialer
+	conn, err := dialer.Dial("unix", d.socketPath)
+	if err != nil {
+		return err
+	}
+	err = msg.Initiate(conn.(*net.UnixConn))
+	conn.Close()
+	if err != nil {
+		return err
+	}
+	initComplete <- struct{}{}
+	<-quit
+	return nil
+}
+
+func (d *driver) AddPort(ctx context.Context, spec port.Spec) (*port.Status, error) {
+	d.mu.Lock()
+	err := portutil.ValidatePortSpec(spec, d.ports)
+	d.mu.Unlock()
+	if err != nil {
+		return nil, err
+	}
+	routineStopCh := make(chan struct{})
+	routineStop := func() error {
+		close(routineStopCh)
+		return nil // FIXME
+	}
+	switch spec.Proto {
+	case "tcp":
+		err = tcp.Run(d.socketPath, spec, routineStopCh, d.logWriter)
+	case "udp":
+		err = udp.Run(d.socketPath, spec, routineStopCh, d.logWriter)
+	default:
+		// NOTREACHED
+		return nil, errors.New("spec was not validated?")
+	}
+	if err != nil {
+		return nil, err
+	}
+	d.mu.Lock()
+	id := d.nextID
+	st := port.Status{
+		ID:   id,
+		Spec: spec,
+	}
+	d.ports[id] = &st
+	d.stoppers[id] = routineStop
+	d.nextID++
+	d.mu.Unlock()
+	return &st, nil
+}
+
+func (d *driver) ListPorts(ctx context.Context) ([]port.Status, error) {
+	var ports []port.Status
+	d.mu.Lock()
+	for _, p := range d.ports {
+		ports = append(ports, *p)
+	}
+	d.mu.Unlock()
+	return ports, nil
+}
+
+func (d *driver) RemovePort(ctx context.Context, id int) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	stop, ok := d.stoppers[id]
+	if !ok {
+		return errors.Errorf("unknown id: %d", id)
+	}
+	err := stop()
+	delete(d.stoppers, id)
+	delete(d.ports, id)
+	return err
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/tcp/tcp.go

@@ -0,0 +1,104 @@
+package tcp
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"sync"
+
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/msg"
+)
+
+func Run(socketPath string, spec port.Spec, stopCh <-chan struct{}, logWriter io.Writer) error {
+	ln, err := net.Listen("tcp", fmt.Sprintf("%s:%d", spec.ParentIP, spec.ParentPort))
+	if err != nil {
+		fmt.Fprintf(logWriter, "listen: %v\n", err)
+		return err
+	}
+	newConns := make(chan net.Conn)
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				fmt.Fprintf(logWriter, "accept: %v\n", err)
+				close(newConns)
+				return
+			}
+			newConns <- c
+		}
+	}()
+	go func() {
+		defer ln.Close()
+		for {
+			select {
+			case c, ok := <-newConns:
+				if !ok {
+					return
+				}
+				go func() {
+					if err := copyConnToChild(c, socketPath, spec, stopCh); err != nil {
+						fmt.Fprintf(logWriter, "copyConnToChild: %v\n", err)
+						return
+					}
+				}()
+			case <-stopCh:
+				return
+			}
+		}
+	}()
+	// no wait
+	return nil
+}
+
+func copyConnToChild(c net.Conn, socketPath string, spec port.Spec, stopCh <-chan struct{}) error {
+	defer c.Close()
+	// get fd from the child as an SCM_RIGHTS cmsg
+	fd, err := msg.ConnectToChildWithRetry(socketPath, spec, 10)
+	if err != nil {
+		return err
+	}
+	f := os.NewFile(uintptr(fd), "")
+	defer f.Close()
+	fc, err := net.FileConn(f)
+	if err != nil {
+		return err
+	}
+	defer fc.Close()
+	bicopy(c, fc, stopCh)
+	return nil
+}
+
+// bicopy is based on libnetwork/cmd/proxy/tcp_proxy.go .
+// NOTE: sendfile(2) cannot be used for sockets
+func bicopy(x, y net.Conn, quit <-chan struct{}) {
+	var wg sync.WaitGroup
+	var broker = func(to, from net.Conn) {
+		io.Copy(to, from)
+		if fromTCP, ok := from.(*net.TCPConn); ok {
+			fromTCP.CloseRead()
+		}
+		if toTCP, ok := to.(*net.TCPConn); ok {
+			toTCP.CloseWrite()
+		}
+		wg.Done()
+	}
+
+	wg.Add(2)
+	go broker(x, y)
+	go broker(y, x)
+	finish := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(finish)
+	}()
+
+	select {
+	case <-quit:
+	case <-finish:
+	}
+	x.Close()
+	y.Close()
+	<-finish
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/udp/udp.go

@@ -0,0 +1,60 @@
+package udp
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+
+	"github.com/pkg/errors"
+
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/msg"
+	"github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/udp/udpproxy"
+)
+
+func Run(socketPath string, spec port.Spec, stopCh <-chan struct{}, logWriter io.Writer) error {
+	addr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", spec.ParentIP, spec.ParentPort))
+	if err != nil {
+		return err
+	}
+	c, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		return err
+	}
+	udpp := &udpproxy.UDPProxy{
+		LogWriter: logWriter,
+		Listener:  c,
+		BackendDial: func() (*net.UDPConn, error) {
+			// get fd from the child as an SCM_RIGHTS cmsg
+			fd, err := msg.ConnectToChildWithRetry(socketPath, spec, 10)
+			if err != nil {
+				return nil, err
+			}
+			f := os.NewFile(uintptr(fd), "")
+			defer f.Close()
+			fc, err := net.FileConn(f)
+			if err != nil {
+				return nil, err
+			}
+			uc, ok := fc.(*net.UDPConn)
+			if !ok {
+				return nil, errors.Errorf("file conn doesn't implement *net.UDPConn: %+v", fc)
+			}
+			return uc, nil
+		},
+	}
+	go udpp.Run()
+	go func() {
+		for {
+			select {
+			case <-stopCh:
+				// udpp.Close closes ln as well
+				udpp.Close()
+				return
+			}
+		}
+	}()
+	// no wait
+	return nil
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/udp/udpproxy/udp_proxy.go

@@ -0,0 +1,150 @@
+// Package udpproxy is from https://raw.githubusercontent.com/docker/libnetwork/fec6476dfa21380bf8ee4d74048515d968c1ee63/cmd/proxy/udp_proxy.go
+package udpproxy
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"sync"
+	"syscall"
+	"time"
+)
+
+const (
+	// UDPConnTrackTimeout is the timeout used for UDP connection tracking
+	UDPConnTrackTimeout = 90 * time.Second
+	// UDPBufSize is the buffer size for the UDP proxy
+	UDPBufSize = 65507
+)
+
+// A net.Addr where the IP is split into two fields so you can use it as a key
+// in a map:
+type connTrackKey struct {
+	IPHigh uint64
+	IPLow  uint64
+	Port   int
+}
+
+func newConnTrackKey(addr *net.UDPAddr) *connTrackKey {
+	if len(addr.IP) == net.IPv4len {
+		return &connTrackKey{
+			IPHigh: 0,
+			IPLow:  uint64(binary.BigEndian.Uint32(addr.IP)),
+			Port:   addr.Port,
+		}
+	}
+	return &connTrackKey{
+		IPHigh: binary.BigEndian.Uint64(addr.IP[:8]),
+		IPLow:  binary.BigEndian.Uint64(addr.IP[8:]),
+		Port:   addr.Port,
+	}
+}
+
+type connTrackMap map[connTrackKey]*net.UDPConn
+
+// UDPProxy is proxy for which handles UDP datagrams.
+// From libnetwork udp_proxy.go .
+type UDPProxy struct {
+	LogWriter      io.Writer
+	Listener       *net.UDPConn
+	BackendDial    func() (*net.UDPConn, error)
+	connTrackTable connTrackMap
+	connTrackLock  sync.Mutex
+}
+
+func (proxy *UDPProxy) replyLoop(proxyConn *net.UDPConn, clientAddr *net.UDPAddr, clientKey *connTrackKey) {
+	defer func() {
+		proxy.connTrackLock.Lock()
+		delete(proxy.connTrackTable, *clientKey)
+		proxy.connTrackLock.Unlock()
+		proxyConn.Close()
+	}()
+
+	readBuf := make([]byte, UDPBufSize)
+	for {
+		proxyConn.SetReadDeadline(time.Now().Add(UDPConnTrackTimeout))
+	again:
+		read, err := proxyConn.Read(readBuf)
+		if err != nil {
+			if err, ok := err.(*net.OpError); ok && err.Err == syscall.ECONNREFUSED {
+				// This will happen if the last write failed
+				// (e.g: nothing is actually listening on the
+				// proxied port on the container), ignore it
+				// and continue until UDPConnTrackTimeout
+				// expires:
+				goto again
+			}
+			return
+		}
+		for i := 0; i != read; {
+			written, err := proxy.Listener.WriteToUDP(readBuf[i:read], clientAddr)
+			if err != nil {
+				return
+			}
+			i += written
+		}
+	}
+}
+
+// Run starts forwarding the traffic using UDP.
+func (proxy *UDPProxy) Run() {
+	proxy.connTrackTable = make(connTrackMap)
+	readBuf := make([]byte, UDPBufSize)
+	for {
+		read, from, err := proxy.Listener.ReadFromUDP(readBuf)
+		if err != nil {
+			// NOTE: Apparently ReadFrom doesn't return
+			// ECONNREFUSED like Read do (see comment in
+			// UDPProxy.replyLoop)
+			if !isClosedError(err) {
+				fmt.Fprintf(proxy.LogWriter, "Stopping proxy on udp: %v\n", err)
+			}
+			break
+		}
+
+		fromKey := newConnTrackKey(from)
+		proxy.connTrackLock.Lock()
+		proxyConn, hit := proxy.connTrackTable[*fromKey]
+		if !hit {
+			proxyConn, err = proxy.BackendDial()
+			if err != nil {
+				fmt.Fprintf(proxy.LogWriter, "Can't proxy a datagram to udp: %v\n", err)
+				proxy.connTrackLock.Unlock()
+				continue
+			}
+			proxy.connTrackTable[*fromKey] = proxyConn
+			go proxy.replyLoop(proxyConn, from, fromKey)
+		}
+		proxy.connTrackLock.Unlock()
+		for i := 0; i != read; {
+			written, err := proxyConn.Write(readBuf[i:read])
+			if err != nil {
+				fmt.Fprintf(proxy.LogWriter, "Can't proxy a datagram to udp: %v\n", err)
+				break
+			}
+			i += written
+		}
+	}
+}
+
+// Close stops forwarding the traffic.
+func (proxy *UDPProxy) Close() {
+	proxy.Listener.Close()
+	proxy.connTrackLock.Lock()
+	defer proxy.connTrackLock.Unlock()
+	for _, conn := range proxy.connTrackTable {
+		conn.Close()
+	}
+}
+
+func isClosedError(err error) bool {
+	/* This comparison is ugly, but unfortunately, net.go doesn't export errClosing.
+	 * See:
+	 * http://golang.org/src/pkg/net/net.go
+	 * https://code.google.com/p/go/issues/detail?id=4337
+	 * https://groups.google.com/forum/#!msg/golang-nuts/0_aaCvBmOcM/SptmDyX1XJMJ
+	 */
+	return strings.HasSuffix(err.Error(), "use of closed network connection")
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/port.go

@@ -0,0 +1,51 @@
+package port
+
+import (
+	"context"
+	"net"
+)
+
+type Spec struct {
+	Proto      string `json:"proto,omitempty"`    // either "tcp" or "udp". in future "sctp" will be supported as well.
+	ParentIP   string `json:"parentIP,omitempty"` // IPv4 address. can be empty (0.0.0.0).
+	ParentPort int    `json:"parentPort,omitempty"`
+	ChildPort  int    `json:"childPort,omitempty"`
+}
+
+type Status struct {
+	ID   int  `json:"id"`
+	Spec Spec `json:"spec"`
+}
+
+// Manager MUST be thread-safe.
+type Manager interface {
+	AddPort(ctx context.Context, spec Spec) (*Status, error)
+	ListPorts(ctx context.Context) ([]Status, error)
+	RemovePort(ctx context.Context, id int) error
+}
+
+// ChildContext is used for RunParentDriver
+type ChildContext struct {
+	// PID of the child, can be used for ns-entering to the child namespaces.
+	PID int
+	// IP of the tap device
+	IP net.IP
+}
+
+// ParentDriver is a driver for the parent process.
+type ParentDriver interface {
+	Manager
+	// OpaqueForChild typically consists of socket path
+	// for controlling child from parent
+	OpaqueForChild() map[string]string
+	// RunParentDriver signals initComplete when ParentDriver is ready to
+	// serve as Manager.
+	// RunParentDriver blocks until quit is signaled.
+	//
+	// ChildContext is optional.
+	RunParentDriver(initComplete chan struct{}, quit <-chan struct{}, cctx *ChildContext) error
+}
+
+type ChildDriver interface {
+	RunChildDriver(opaque map[string]string, quit <-chan struct{}) error
+}

vendor/github.com/rootless-containers/rootlesskit/pkg/port/portutil/portutil.go

@@ -0,0 +1,67 @@
+package portutil
+
+import (
+	"net"
+	"regexp"
+	"strconv"
+
+	"github.com/pkg/errors"
+
+	"github.com/rootless-containers/rootlesskit/pkg/port"
+)
+
+// ParsePortSpec parses a Docker-like representation of PortSpec.
+// e.g. "127.0.0.1:8080:80/tcp"
+func ParsePortSpec(s string) (*port.Spec, error) {
+	r := regexp.MustCompile("^([0-9a-f\\.]+):([0-9]+):([0-9]+)/([a-z]+)$")
+	g := r.FindStringSubmatch(s)
+	if len(g) != 5 {
+		return nil, errors.Errorf("unexpected PortSpec string: %q", s)
+	}
+	parentIP := g[1]
+	parentPort, err := strconv.Atoi(g[2])
+	if err != nil {
+		return nil, errors.Wrapf(err, "unexpected ParentPort in PortSpec string: %q", s)
+	}
+	childPort, err := strconv.Atoi(g[3])
+	if err != nil {
+		return nil, errors.Wrapf(err, "unexpected ChildPort in PortSpec string: %q", s)
+	}
+	proto := g[4]
+	// validation is up to the caller (as json.Unmarshal doesn't validate values)
+	return &port.Spec{
+		Proto:      proto,
+		ParentIP:   parentIP,
+		ParentPort: parentPort,
+		ChildPort:  childPort,
+	}, nil
+}
+
+// ValidatePortSpec validates *port.Spec.
+// existingPorts can be optionally passed for detecting conflicts.
+func ValidatePortSpec(spec port.Spec, existingPorts map[int]*port.Status) error {
+	if spec.Proto != "tcp" && spec.Proto != "udp" {
+		return errors.Errorf("unknown proto: %q", spec.Proto)
+	}
+	if spec.ParentIP != "" {
+		if net.ParseIP(spec.ParentIP) == nil {
+			return errors.Errorf("invalid ParentIP: %q", spec.ParentIP)
+		}
+	}
+	if spec.ParentPort <= 0 || spec.ParentPort > 65535 {
+		return errors.Errorf("invalid ParentPort: %q", spec.ParentPort)
+	}
+	if spec.ChildPort <= 0 || spec.ChildPort > 65535 {
+		return errors.Errorf("invalid ChildPort: %q", spec.ChildPort)
+	}
+	for id, p := range existingPorts {
+		sp := p.Spec
+		sameProto := sp.Proto == spec.Proto
+		sameParent := sp.ParentIP == spec.ParentIP && sp.ParentPort == spec.ParentPort
+		sameChild := sp.ChildPort == spec.ChildPort
+		if sameProto && (sameParent || sameChild) {
+			return errors.Errorf("conflict with ID %d", id)
+		}
+	}
+	return nil
+}