From 3c4432e0f2fb8ddf54a2e441063d584b99572a4e Mon Sep 17 00:00:00 2001
From: Mikhail Osipov <mike.osipov@gmail.com>
Date: Thu, 26 Mar 2020 00:29:12 +0300
Subject: add tun socket

---
 pkg/server/socket/tun.go | 133 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 pkg/server/socket/tun.go

(limited to 'pkg/server/socket/tun.go')

diff --git a/pkg/server/socket/tun.go b/pkg/server/socket/tun.go
new file mode 100644
index 0000000..78bdfd4
--- /dev/null
+++ b/pkg/server/socket/tun.go
@@ -0,0 +1,133 @@
+package socket
+
+import (
+	"errors"
+	"fmt"
+	"golang.org/x/sys/unix"
+	"log"
+	"os"
+	"strings"
+	"sync"
+	"tunnel/pkg/pack"
+	"tunnel/pkg/server/env"
+	"tunnel/pkg/server/queue"
+	"unsafe"
+)
+
+const maxTunBufSize = 65535
+
+var errPartialWrite = errors.New("partial write")
+
+type ifReq struct {
+	name  [unix.IFNAMSIZ]uint8
+	flags uint16
+}
+
+type tunSocket struct {
+	name string
+}
+
+type tunChannel struct {
+	name string
+	s    *tunSocket
+	fp   *os.File
+	once sync.Once
+}
+
+func ioctl(fd int, req uintptr, ptr unsafe.Pointer) error {
+	_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), req, uintptr(ptr))
+	if errno != 0 {
+		return errno
+	}
+
+	return nil
+}
+
+func newTunSocket(name string) (S, error) {
+	return &tunSocket{name: name}, nil
+
+}
+
+func (s *tunSocket) String() string {
+	return fmt.Sprintf("tun/%s", s.name)
+}
+
+func (s *tunSocket) Open(env.Env) (Channel, error) {
+	fd, err := unix.Open("/dev/net/tun", unix.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	ifr := &ifReq{}
+	copy(ifr.name[:], s.name)
+	ifr.flags = unix.IFF_TUN | unix.IFF_NO_PI
+
+	if err := ioctl(fd, unix.TUNSETIFF, unsafe.Pointer(ifr)); err != nil {
+		unix.Close(fd)
+		return nil, fmt.Errorf("ioctl TUNSETIFF %s: %w", s.name, err)
+	}
+
+	if err := unix.SetNonblock(fd, true); err != nil {
+		unix.Close(fd)
+		return nil, fmt.Errorf("set nonblock %s: %w", s.name, err)
+	}
+
+	c := &tunChannel{
+		name: strings.Trim(string(ifr.name[:]), "\x00"),
+		fp:   os.NewFile(uintptr(fd), "tun"),
+	}
+
+	return c, nil
+}
+
+func (s *tunSocket) Close() {
+}
+
+func (c *tunChannel) Send(wq queue.Q) error {
+	buf := make([]byte, maxTunBufSize)
+	enc := pack.NewEncoder(wq.Writer())
+
+	for {
+		n, err := c.fp.Read(buf)
+		if err != nil {
+			return err
+		}
+
+		enc.Lps(buf[0:n])
+	}
+}
+
+func (c *tunChannel) Recv(rq queue.Q) error {
+	dec := pack.NewDecoder(rq.Reader())
+
+	for {
+		b, err := dec.Lps()
+		if err != nil {
+			return err
+		}
+
+		n, err := c.fp.Write(b)
+		if err != nil {
+			return err
+		}
+
+		if n != len(b) {
+			return errPartialWrite
+		}
+	}
+}
+
+func (c *tunChannel) String() string {
+	return "tun/" + c.name
+}
+
+func (c *tunChannel) Close() error {
+	err := ErrAlreadyClosed
+
+	c.once.Do(func() {
+		log.Println("close", c)
+		err = c.fp.Close()
+	})
+
+	return err
+}
-- 
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