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NTP up and running

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soypat
2025-07-12 16:45:20 -03:00
parent 698610242e
commit 2bd056a04c
4 changed files with 255 additions and 81 deletions
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examples/bridge/main.go
+73 -12
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@@ -11,7 +11,6 @@ import (
"net/netip"
"os"
"runtime"
"strconv"
"strings"
"time"
@@ -24,6 +23,7 @@ import (
"github.com/soypat/lneto/internal/ltesto"
"github.com/soypat/lneto/internet"
"github.com/soypat/lneto/internet/pcap"
"github.com/soypat/lneto/ntp"
)
var softRand = time.Now().Unix()
@@ -43,11 +43,13 @@ func run() (err error) {
flagUseHTTP = false
flagHostToResolve = ""
flagRequestedIP = ""
flagDoNTP = false
)
flag.StringVar(&flagInterface, "i", flagInterface, "Interface to use. Either tap* or the name of an existing interface to bridge to.")
flag.BoolVar(&flagUseHTTP, "http", flagUseHTTP, "Use HTTP tap interface.")
flag.StringVar(&flagHostToResolve, "host", flagHostToResolve, "Hostname to resolve via DNS.")
flag.StringVar(&flagRequestedIP, "addr", flagRequestedIP, "IP address to request via DHCP.")
flag.BoolVar(&flagDoNTP, "ntp", flagDoNTP, "Do NTP round and print result time")
flag.Parse()
fmt.Println("softrand", softRand)
_, err = dns.NewName(flagHostToResolve)
@@ -80,34 +82,41 @@ func run() (err error) {
return err
}
brHW := nicHW
brHW[5] += byte(softRand)%128 + 1 // We'll be using a similar HW address but with NIC specific identifier modified.
brHW[4]++
mtu, err := iface.MTU()
if err != nil {
return err
}
nicAddr, err := iface.IPMask()
if err != nil {
return err
}
fmt.Println("NIC hardware address:", net.HardwareAddr(nicHW[:]).String(), "bridgeHW:", net.HardwareAddr(brHW[:]).String(), "mtu:", mtu, "addr:", nicAddr.String())
var stack Stack
err = stack.Reset(brHW, netip.AddrFrom4([4]byte{}), uint16(mtu))
if err != nil {
return err
}
err = stack.BeginDHCPRequest([4]byte{192, 168, 1, 199})
if err != nil {
return err
}
buf := make([]byte, mtu)
lastAction := time.Now()
const (
stateDHCP = iota
stateInitARP
stateDNSNTP
stateNTP
stateDNS
stateDone
)
err = stack.BeginDHCPRequest([4]byte{192, 168, 1, 96})
if err != nil {
return err
}
state := stateDHCP
prevState := state
for {
switch state {
case stateDHCP:
@@ -128,14 +137,46 @@ func run() (err error) {
router := stack.dhcp.RouterAddr()
hw, err := stack.ResultResolveHardwareAddress6(netip.AddrFrom4(router))
if err == nil {
state = stateDNS
stack.link.SetGateway6(hw)
stack.link.SetHardwareAddr6([6]byte{0xd8, 0x5e, 0xd3, 0x43, 0x03, 0xeb})
stack.ip.SetAddr(netip.AddrFrom4([4]byte{192, 168, 1, 53}))
if flagDoNTP {
state = stateDNSNTP
err = stack.StartLookupIP("pool.ntp.org")
} else {
state = stateDNS
err = stack.StartLookupIP(flagHostToResolve)
}
if err != nil {
return err
}
}
case stateDNSNTP:
addrs, done, err := stack.ResultLookupIP()
if err == nil {
state = stateNTP
fmt.Println("START NTP")
err = stack.StartNTP(addrs[0])
} else if !done {
err = nil
}
if err != nil {
return err
}
case stateNTP:
offset, done := stack.ResultNTP()
if done {
relative := "behind"
if offset < 0 {
relative = "ahead"
}
fmt.Println("NTP completed. You are", offset.Abs(), relative, "of the NTP server")
state = stateDNS
err = stack.StartLookupIP(flagHostToResolve)
if err != nil {
return err
}
}
case stateDNS:
addrs, done, err := stack.ResultLookupIP()
if err == nil {
@@ -145,6 +186,10 @@ func run() (err error) {
return err
}
}
if prevState != state {
fmt.Println("STATE CHANGE", prevState, state)
}
prevState = state
clear(buf)
nwrite, err := stack.Encapsulate(buf[:], 0)
@@ -189,6 +234,8 @@ type Stack struct {
dns dns.Client
ednsopt dns.Resource
lookup dns.Message
ntp ntp.Client
sysprec int8 // NTP system precision.
// Packet capture and top level filtering.
shark pcap.PacketBreakdown
@@ -198,8 +245,9 @@ type Stack struct {
func (s *Stack) Demux(b []byte, _ int) (err error) {
s.aux, err = s.shark.CaptureEthernet(s.aux[:0], b, 0)
topFrame := s.aux[len(s.aux)-1]
isOK := topFrame.Protocol == "DHCPv4" || // Allow DHCP responses.
isOK := topFrame.Protocol == "DHCPv4" || // Allow DHCP, DNS and NTP responses.
topFrame.Protocol == "DNS" ||
topFrame.Protocol == "NTP" ||
topFrame.Protocol == ethernet.TypeARP // Allow ARP responses.
if !isOK {
return nil
@@ -269,6 +317,8 @@ func (s *Stack) Reset(mac [6]byte, addr netip.Addr, mtu uint16) error {
return err
}
s.ip.SetLogger(slog.Default())
var timebuf [32]time.Time
s.sysprec = ntp.CalculateSystemPrecision(time.Now, timebuf[:])
return nil
}
@@ -281,8 +331,6 @@ func (s *Stack) StartLookupIP(host string) error {
if err != nil {
return err
}
s.link.SetHardwareAddr6([6]byte{0xd8, 0x5e, 0xd3, 0x43, 0x03, 0xeb})
s.ip.SetAddr(netip.AddrFrom4([4]byte{192, 168, 1, 53}))
s.ednsopt.SetEDNS0(uint16(s.link.MTU())-100, 0, 0, nil)
err = s.dns.StartResolve(uint16(softRand>>1)+1024, uint16(softRand), dns.ResolveConfig{
Questions: []dns.Question{
@@ -330,6 +378,10 @@ func (s *Stack) ResultLookupIP() ([]netip.Addr, bool, error) {
return addrs, done, nil
}
func (s *Stack) ResultNTP() (time.Duration, bool) {
return s.ntp.Offset(), s.ntp.IsDone()
}
func (s *Stack) BeginDHCPRequest(request [4]byte) error {
var buf [4]byte
rand.Read(buf[:])
@@ -337,7 +389,7 @@ func (s *Stack) BeginDHCPRequest(request [4]byte) error {
err := s.dhcp.BeginRequest(xid, dhcpv4.RequestConfig{
RequestedAddr: request,
ClientHardwareAddr: s.link.HardwareAddr6(),
Hostname: "lneto" + strconv.FormatInt(softRand%100, 16),
Hostname: "lneto",
})
if err != nil {
return err
@@ -351,6 +403,15 @@ func (s *Stack) BeginDHCPRequest(request [4]byte) error {
return err
}
func (s *Stack) StartNTP(addr netip.Addr) error {
s.ntp.Reset(time.Now, s.sysprec)
var u internet.StackUDPPort
addr4 := addr.As4()
u.SetStackNode(&s.ntp, addr4[:], ntp.ServerPort)
err := s.udps.Register(&u)
return err
}
func (s *Stack) StartResolveHardwareAddress6(ip netip.Addr) error {
if !ip.Is4() {
return errors.New("unsupported or invalid IP address")