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tailscale/cmd/stunstamp/stunstamp_linux.go

127 lines
3.3 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package main
import (
"bytes"
"context"
"encoding/binary"
"errors"
"fmt"
"io"
"net"
"time"
"github.com/mdlayher/socket"
"golang.org/x/sys/unix"
)
const (
flags = 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 getConnKernelTimestamp() (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, flags)
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 measureRTTKernel(conn io.ReadWriteCloser, dst *net.UDPAddr, req []byte) (resp []byte, rtt time.Duration, err error) {
sconn, ok := conn.(*socket.Conn)
if !ok {
return nil, 0, fmt.Errorf("conn of unexpected type: %T", conn)
}
var to unix.Sockaddr
to4 := dst.IP.To4()
if to4 != nil {
to = &unix.SockaddrInet4{
Port: 3478,
}
copy(to.(*unix.SockaddrInet4).Addr[:], to4)
} else {
to = &unix.SockaddrInet6{
Port: 3478,
}
copy(to.(*unix.SockaddrInet6).Addr[:], dst.IP)
}
err = sconn.Sendto(context.Background(), req, 0, to)
if err != nil {
return nil, 0, fmt.Errorf("sendto error: %v", err) // don't wrap
}
txCtx, txCancel := context.WithTimeout(context.Background(), time.Second*2)
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 nil, 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 nil, 0, fmt.Errorf("failed to get tx timestamp: %v", err) // don't wrap
}
break
}
rxCtx, rxCancel := context.WithTimeout(context.Background(), time.Second*2)
defer rxCancel()
n, oobn, _, _, err := sconn.Recvmsg(rxCtx, buf, oob, 0)
if err != nil {
return nil, 0, fmt.Errorf("recvmsg error: %w", err) // wrap for timeout-related error unwrapping
}
rxAt, err := parseTimestampFromCmsgs(oob[:oobn])
if err != nil {
return nil, 0, fmt.Errorf("failed to get rx timestamp: %v", err) // don't wrap
}
return buf[:n], rxAt.Sub(txAt), nil
}
func supportsKernelTS() bool {
return true
}