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https://github.com/tailscale/tailscale.git
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66efa10134
Instead of using a tun device, use AF_XDP to read/write a veth device. Works, but currently slower than tun. :(
286 lines
8.2 KiB
Go
286 lines
8.2 KiB
Go
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tstun
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import (
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"errors"
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"fmt"
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"io"
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"net"
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"os"
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"os/exec"
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"strconv"
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"sync"
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"github.com/asavie/xdp"
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"golang.org/x/sys/unix"
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"golang.zx2c4.com/wireguard/tun"
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"gvisor.dev/gvisor/pkg/tcpip/link/rawfile"
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)
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// This file borrows a lot of values from tap_linux.go, e.g. ourMAC.
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func init() { createVETH = createVETHLinux }
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const queueID = 0 // TODO explore alternatives
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// TODO: do better
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var dstMAC = net.HardwareAddr{0x30, 0x2D, 0x66, 0xEC, 0x7A, 0x94}
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func createVETHLinux(vethName string) (device tun.Device, err error) {
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defer func() {
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if err != nil {
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err = fmt.Errorf("tstun: veth: %w", err)
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}
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}()
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vethBEName := vethName + "be"
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cmd := exec.Command("ip", "link", "add", vethName, "type", "veth", "peer", "name", vethBEName)
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if b, err := cmd.CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ip link add %s: %v: %s", vethName, err, b)
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}
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if b, err := exec.Command("ip", "link", "set", "dev", vethName, "arp", "off").CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ip link up %s: %v: %s", vethName, err, b)
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}
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// TODO why do we need to set the MTU here?
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if b, err := exec.Command("ip", "link", "set", "dev", vethName, "mtu", strconv.Itoa(DefaultMTU)).CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ip link mtu %s: %v: %s", vethName, err, b)
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}
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if b, err := exec.Command("ip", "link", "set", "dev", vethName, "up").CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ip link up %s: %v: %s", vethName, err, b)
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}
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if b, err := exec.Command("ip", "link", "set", "dev", vethBEName, "up").CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ip link up %s: %v: %s", vethBEName, err, b)
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}
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ourMACStr := fmt.Sprintf("%x:%x:%x:%x:%x:%x", ourMAC[0], ourMAC[1], ourMAC[2], ourMAC[3], ourMAC[4], ourMAC[5])
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if b, err := exec.Command("ip", "link", "set", "dev", vethBEName, "address", ourMACStr).CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ifconfig %s hw ether: %v: %s", vethBEName, err, b)
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}
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dstMACStr := fmt.Sprintf("%x:%x:%x:%x:%x:%x", dstMAC[0], dstMAC[1], dstMAC[2], dstMAC[3], dstMAC[4], dstMAC[5])
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if b, err := exec.Command("ip", "link", "set", "dev", vethName, "address", dstMACStr).CombinedOutput(); err != nil {
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return nil, fmt.Errorf("ifconfig %s hw ether: %v: %s", vethBEName, err, b)
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}
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// TODO ubuntu does not ship with ethtool by default.
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// If we don't have ethtool we can calculate checksums ourselves, see wrap.go.
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// I took a quick look at the strace and it's mysterious.
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if b, err := exec.Command("ethtool", "-K", vethName, "tx", "off", "rx", "off").CombinedOutput(); err != nil {
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return nil, fmt.Errorf("checksum offloading: %v: %s", err, b)
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}
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ifaces, err := net.Interfaces()
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if err != nil {
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return nil, fmt.Errorf("net.Interfaces: %v", err)
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}
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ifBEIndex := -1
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for _, iface := range ifaces {
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if iface.Name == vethBEName {
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ifBEIndex = iface.Index
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break
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}
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}
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if ifBEIndex == -1 {
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return nil, errors.New("could not find veth index")
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}
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program, err := xdp.NewProgram(queueID + 1)
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if err != nil {
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return nil, fmt.Errorf("xdp.NewProgram: %w", err)
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}
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if err := program.Attach(ifBEIndex); err != nil {
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return nil, fmt.Errorf("xdp program failed to attach: %w", err)
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}
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xsk, err := xdp.NewSocket(ifBEIndex, queueID, nil)
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if err != nil {
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return nil, fmt.Errorf("xdp failed to create socket: %w", err)
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}
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if err := program.Register(queueID, xsk.FD()); err != nil {
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return nil, fmt.Errorf("xdp failed to register socket: %w", err)
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}
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//ip link add ve_A type veth peer name ve_B
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d := &vethDevice{
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name: vethName,
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events: make(chan tun.Event, 1),
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program: program,
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ifBEIndex: ifBEIndex,
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xsk: xsk,
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}
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fmt.Printf("createVETHLinux: NumFreeFillSlots=%d\n", d.xsk.NumFreeFillSlots())
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fmt.Printf("createVETHLinux: NumFreeTxSlots=%d\n", d.xsk.NumFreeTxSlots())
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return d, nil
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}
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// vethDevice implements tun.Device, using a virtual ethernet pair and AF_XDP.
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type vethDevice struct {
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name string
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events chan tun.Event
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program *xdp.Program
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ifBEIndex int
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xsk *xdp.Socket
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pollEvent rawfile.PollEvent
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rxMu sync.Mutex // guards rxDescs
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rxDescs []xdp.Desc
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txMu sync.Mutex // guards txDescs, txCur
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txDescs []xdp.Desc
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txNext int
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}
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// File implements tun.Device.File.
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func (d *vethDevice) File() *os.File { panic("no file for veth/xdp") }
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func (d *vethDevice) blockingPoll(events pollEvent) (numReceived, numCompleted int, err error) {
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//return d.xsk.Poll(-1)
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d.pollEvent = rawfile.PollEvent{
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FD: int32(d.xsk.FD()),
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Events: int16(events),
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}
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/*if d.xsk.NumFilled() > 0 {
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d.pollEvent.Events |= unix.POLLIN
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}
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/*if d.xsk.NumTransmitted() > 0 {
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d.pollEvent.Events |= unix.POLLOUT
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}*/
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if d.pollEvent.Events == 0 {
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return
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}
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for err = unix.EINTR; err == unix.EINTR; {
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_, errNo := rawfile.BlockingPoll(&d.pollEvent, 1, nil)
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if errNo == 0 {
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err = nil
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} else {
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err = errNo
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}
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}
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if err != nil {
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fmt.Printf("blockingPoll err=%v (%d)", err, err)
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return 0, 0, err
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}
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numReceived = d.xsk.NumReceived()
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numCompleted = d.xsk.NumCompleted()
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if numCompleted > 0 {
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d.xsk.Complete(numCompleted)
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}
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return numReceived, numCompleted, err
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}
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// Read implements tun.Device.Read.
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// read a packet from the device (without any additional headers)
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func (d *vethDevice) Read(b []byte, off int) (int, error) {
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d.rxMu.Lock()
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defer d.rxMu.Unlock()
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for len(d.rxDescs) == 0 {
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if n := d.xsk.NumFreeFillSlots(); n > 0 {
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d.xsk.Fill(d.xsk.GetDescs(n, true))
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}
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numRx, _, err := d.blockingPoll(pollRx)
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if err != nil {
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return 0, fmt.Errorf("veth: %w", err)
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}
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d.rxDescs = d.xsk.Receive(numRx)
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//fmt.Printf("vethDevice.Read numRx=%d, len(d.rxDescs)=%d\n", numRx, len(d.rxDescs))
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//fmt.Printf("--- vethDevice.Read: NumFreeFillSlots: %d numRx: %d, len(rxDescs): %d\n", n, numRx, len(d.rxDescs))
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}
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if len(d.rxDescs) == 0 {
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return 0, fmt.Errorf("veth: %w", io.EOF) // TODO: what error?
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}
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data := d.xsk.GetFrame(d.rxDescs[0])
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n := copy(b[off:], data)
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//fmt.Printf("--- vethDevice.Read: frame data len=%d (n=%d): %x\n", len(data), n, data)
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d.rxDescs = d.rxDescs[1:]
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return n, nil
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}
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// Write implements tun.Device.Write.
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// writes a packet to the device (without any additional headers)
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func (d *vethDevice) Write(b []byte, off int) (int, error) {
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d.txMu.Lock()
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defer d.txMu.Unlock()
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for len(d.txDescs) == 0 {
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if numCompleted := d.xsk.NumCompleted(); numCompleted > 0 {
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d.xsk.Complete(numCompleted)
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}
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d.txNext = 0
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d.txDescs = d.xsk.GetDescs(d.xsk.NumFreeTxSlots(), false)
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if len(d.txDescs) == 0 {
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_, _, err := d.blockingPoll(pollTx)
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if err != nil {
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return 0, fmt.Errorf("veth: Write: %w", io.EOF)
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}
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}
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//fmt.Printf("veth.Write len(txDescs)=%d\n", len(d.txDescs))
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}
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n := copy(d.xsk.GetFrame(d.txDescs[d.txNext]), b[off:])
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d.txDescs[d.txNext].Len = uint32(n)
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d.txNext++
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if d.txNext == len(d.txDescs) {
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return len(b), d.flushTxLocked()
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}
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return len(b), nil
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}
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// Flush implements tun.Device.Flush.
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// flush all previous writes to the device
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func (d *vethDevice) Flush() error {
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d.txMu.Lock()
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defer d.txMu.Unlock()
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return d.flushTxLocked()
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}
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func (d *vethDevice) flushTxLocked() error {
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if d.txNext == 0 {
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return nil
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}
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if d.xsk.Transmit(d.txDescs[:d.txNext]) > 0 {
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if numCompleted := d.xsk.NumCompleted(); numCompleted > 0 {
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d.xsk.Complete(numCompleted)
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}
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}
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// We pick up the transmission using the blocking poll in Write.
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d.txDescs = nil
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d.txNext = 0
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return nil
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}
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type pollEvent int
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const (
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pollRx = pollEvent(unix.POLLIN)
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pollTx = pollEvent(unix.POLLOUT)
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)
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// MTU implements tun.Device.MTU.
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func (d *vethDevice) MTU() (int, error) { return DefaultMTU, nil } // TODO
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// Name implements tun.Device.Name.
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func (d *vethDevice) Name() (string, error) { return d.name, nil }
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// Events implements tun.Device.Events.
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// returns a constant channel of events related to the device
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func (d *vethDevice) Events() chan tun.Event {
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d.events <- tun.EventUp
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// TODO EventDown, EventMTUUpdate
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return d.events
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}
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// Close implements tun.Device.Close.
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// stops the device and closes the event channel
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func (d *vethDevice) Close() error {
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close(d.events)
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d.program.Unregister(queueID)
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d.xsk.Close()
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d.program.Detach(d.ifBEIndex)
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d.program.Close()
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return nil
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}
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