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tailscale/cmd/stunstamp/stunstamp_linux.go

318 lines
8.4 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package main
import (
"bytes"
"context"
"encoding/binary"
"errors"
"fmt"
"io"
"math"
"math/rand/v2"
"net/netip"
"syscall"
"time"
"github.com/mdlayher/socket"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
"tailscale.com/net/stun"
)
const (
timestampingFlags = unix.SOF_TIMESTAMPING_TX_SOFTWARE | // tx timestamp generation in device driver
unix.SOF_TIMESTAMPING_RX_SOFTWARE | // rx timestamp generation in the kernel
unix.SOF_TIMESTAMPING_SOFTWARE // report software timestamps
)
func getUDPConnKernelTimestamp() (io.ReadWriteCloser, error) {
sconn, err := socket.Socket(unix.AF_INET6, unix.SOCK_DGRAM, unix.IPPROTO_UDP, "udp", nil)
if err != nil {
return nil, err
}
sa := unix.SockaddrInet6{}
err = sconn.Bind(&sa)
if err != nil {
return nil, err
}
err = sconn.SetsockoptInt(unix.SOL_SOCKET, unix.SO_TIMESTAMPING_NEW, timestampingFlags)
if err != nil {
return nil, err
}
return sconn, nil
}
func parseTimestampFromCmsgs(oob []byte) (time.Time, error) {
msgs, err := unix.ParseSocketControlMessage(oob)
if err != nil {
return time.Time{}, fmt.Errorf("error parsing oob as cmsgs: %w", err)
}
for _, msg := range msgs {
if msg.Header.Level == unix.SOL_SOCKET && msg.Header.Type == unix.SO_TIMESTAMPING_NEW && len(msg.Data) >= 16 {
sec := int64(binary.NativeEndian.Uint64(msg.Data[:8]))
ns := int64(binary.NativeEndian.Uint64(msg.Data[8:16]))
return time.Unix(sec, ns), nil
}
}
return time.Time{}, errors.New("failed to parse timestamp from cmsgs")
}
func mkICMPMeasureFn(source timestampSource) measureFn {
return func(conn io.ReadWriteCloser, hostname string, dst netip.AddrPort) (rtt time.Duration, err error) {
return measureICMPRTT(source, conn, hostname, dst)
}
}
func measureICMPRTT(source timestampSource, conn io.ReadWriteCloser, _ string, dst netip.AddrPort) (rtt time.Duration, err error) {
sconn, ok := conn.(*socket.Conn)
if !ok {
return 0, fmt.Errorf("conn of unexpected type: %T", conn)
}
txBody := &icmp.Echo{
// The kernel overrides this and routes appropriately so there is no
// point in setting or verifying.
ID: 0,
// Make this sufficiently random so that we do not account a late
// arriving reply in a future probe window.
Seq: int(rand.Int32N(math.MaxUint16)),
// Fingerprint ourselves.
Data: []byte("stunstamp"),
}
txMsg := icmp.Message{
Body: txBody,
}
var to unix.Sockaddr
if dst.Addr().Is4() {
txMsg.Type = ipv4.ICMPTypeEcho
to = &unix.SockaddrInet4{}
copy(to.(*unix.SockaddrInet4).Addr[:], dst.Addr().AsSlice())
} else {
txMsg.Type = ipv6.ICMPTypeEchoRequest
to = &unix.SockaddrInet6{}
copy(to.(*unix.SockaddrInet6).Addr[:], dst.Addr().AsSlice())
}
txBuf, err := txMsg.Marshal(nil)
if err != nil {
return 0, err
}
txAt := time.Now()
err = sconn.Sendto(context.Background(), txBuf, 0, to)
if err != nil {
return 0, fmt.Errorf("sendto error: %v", err)
}
if source == timestampSourceKernel {
txCtx, txCancel := context.WithTimeout(context.Background(), txRxTimeout)
defer txCancel()
buf := make([]byte, 1024)
oob := make([]byte, 1024)
for {
n, oobn, _, _, err := sconn.Recvmsg(txCtx, buf, oob, unix.MSG_ERRQUEUE)
if err != nil {
return 0, fmt.Errorf("recvmsg (MSG_ERRQUEUE) error: %v", err) // don't wrap
}
buf = buf[:n]
// Spin until we find the message we sent. We get the full packet
// looped including eth header so match against the tail.
if n < len(txBuf) {
continue
}
txLoopedMsg, err := icmp.ParseMessage(txMsg.Type.Protocol(), buf[len(buf)-len(txBuf):])
if err != nil {
continue
}
txLoopedBody, ok := txLoopedMsg.Body.(*icmp.Echo)
if !ok || txLoopedBody.Seq != txBody.Seq || txLoopedMsg.Code != txMsg.Code ||
txLoopedMsg.Type != txLoopedMsg.Type || !bytes.Equal(txLoopedBody.Data, txBody.Data) {
continue
}
txAt, err = parseTimestampFromCmsgs(oob[:oobn])
if err != nil {
return 0, fmt.Errorf("failed to get tx timestamp: %v", err) // don't wrap
}
break
}
}
rxCtx, rxCancel := context.WithTimeout(context.Background(), txRxTimeout)
defer rxCancel()
rxBuf := make([]byte, 1024)
oob := make([]byte, 1024)
for {
n, oobn, _, _, err := sconn.Recvmsg(rxCtx, rxBuf, oob, 0)
if err != nil {
return 0, fmt.Errorf("recvmsg error: %w", err)
}
rxAt := time.Now()
rxMsg, err := icmp.ParseMessage(txMsg.Type.Protocol(), rxBuf[:n])
if err != nil {
continue
}
if txMsg.Type == ipv4.ICMPTypeEcho {
if rxMsg.Type != ipv4.ICMPTypeEchoReply {
continue
}
} else {
if rxMsg.Type != ipv6.ICMPTypeEchoReply {
continue
}
}
if rxMsg.Code != txMsg.Code {
continue
}
rxBody, ok := rxMsg.Body.(*icmp.Echo)
if !ok || rxBody.Seq != txBody.Seq || !bytes.Equal(rxBody.Data, txBody.Data) {
continue
}
if source == timestampSourceKernel {
rxAt, err = parseTimestampFromCmsgs(oob[:oobn])
if err != nil {
return 0, fmt.Errorf("failed to get rx timestamp: %v", err)
}
}
return rxAt.Sub(txAt), nil
}
}
func measureSTUNRTTKernel(conn io.ReadWriteCloser, _ string, dst netip.AddrPort) (rtt time.Duration, err error) {
sconn, ok := conn.(*socket.Conn)
if !ok {
return 0, fmt.Errorf("conn of unexpected type: %T", conn)
}
var to unix.Sockaddr
if dst.Addr().Is4() {
to = &unix.SockaddrInet4{
Port: int(dst.Port()),
}
copy(to.(*unix.SockaddrInet4).Addr[:], dst.Addr().AsSlice())
} else {
to = &unix.SockaddrInet6{
Port: int(dst.Port()),
}
copy(to.(*unix.SockaddrInet6).Addr[:], dst.Addr().AsSlice())
}
txID := stun.NewTxID()
req := stun.Request(txID)
err = sconn.Sendto(context.Background(), req, 0, to)
if err != nil {
return 0, fmt.Errorf("sendto error: %v", err) // don't wrap
}
txCtx, txCancel := context.WithTimeout(context.Background(), txRxTimeout)
defer txCancel()
buf := make([]byte, 1024)
oob := make([]byte, 1024)
var txAt time.Time
for {
n, oobn, _, _, err := sconn.Recvmsg(txCtx, buf, oob, unix.MSG_ERRQUEUE)
if err != nil {
return 0, fmt.Errorf("recvmsg (MSG_ERRQUEUE) error: %v", err) // don't wrap
}
buf = buf[:n]
if n < len(req) || !bytes.Equal(req, buf[len(buf)-len(req):]) {
// Spin until we find the message we sent. We get the full packet
// looped including eth header so match against the tail.
continue
}
txAt, err = parseTimestampFromCmsgs(oob[:oobn])
if err != nil {
return 0, fmt.Errorf("failed to get tx timestamp: %v", err) // don't wrap
}
break
}
rxCtx, rxCancel := context.WithTimeout(context.Background(), txRxTimeout)
defer rxCancel()
for {
n, oobn, _, _, err := sconn.Recvmsg(rxCtx, buf, oob, 0)
if err != nil {
return 0, fmt.Errorf("recvmsg error: %w", err) // wrap for timeout-related error unwrapping
}
gotTxID, _, err := stun.ParseResponse(buf[:n])
if err != nil || gotTxID != txID {
// Spin until we find the txID we sent. We may end up reading
// extremely late arriving responses from previous intervals. As
// such, we can't be certain if we're parsing the "current"
// response, so spin for parse errors too.
continue
}
rxAt, err := parseTimestampFromCmsgs(oob[:oobn])
if err != nil {
return 0, fmt.Errorf("failed to get rx timestamp: %v", err) // don't wrap
}
return rxAt.Sub(txAt), nil
}
}
func getICMPConn(forDst netip.Addr, source timestampSource) (io.ReadWriteCloser, error) {
domain := unix.AF_INET
proto := unix.IPPROTO_ICMP
if forDst.Is6() {
domain = unix.AF_INET6
proto = unix.IPPROTO_ICMPV6
}
conn, err := socket.Socket(domain, unix.SOCK_DGRAM, proto, "icmp", nil)
if err != nil {
return nil, err
}
if source == timestampSourceKernel {
err = conn.SetsockoptInt(unix.SOL_SOCKET, unix.SO_TIMESTAMPING_NEW, timestampingFlags)
}
return conn, err
}
func getProtocolSupportInfo(p protocol) protocolSupportInfo {
switch p {
case protocolSTUN:
return protocolSupportInfo{
kernelTS: true,
userspaceTS: true,
stableConn: true,
}
case protocolHTTPS:
return protocolSupportInfo{
kernelTS: false,
userspaceTS: true,
stableConn: true,
}
case protocolTCP:
return protocolSupportInfo{
kernelTS: true,
userspaceTS: false,
stableConn: true,
}
case protocolICMP:
return protocolSupportInfo{
kernelTS: true,
userspaceTS: true,
stableConn: false,
}
}
return protocolSupportInfo{}
}
func setSOReuseAddr(fd uintptr) error {
// we may restart faster than TIME_WAIT can clear
return syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
}