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>

1 files changed, 60 insertions, 0 deletions

diff --git a/vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/udp/udp.go b/vendor/github.com/rootless-containers/rootlesskit/pkg/port/builtin/parent/udp/udp.go
new file mode 100644
index 000000000..d8f646b5d
--- /dev/null
+++ b/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
+}