Add DHCP DNS server support
This commit is contained in:
世界
262
transport/dhcp/server.go
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262
transport/dhcp/server.go
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@@ -0,0 +1,262 @@
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package dhcp
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import (
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"context"
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"net"
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"net/netip"
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"net/url"
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"os"
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"strings"
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"sync"
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"time"
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"github.com/sagernet/sing-box/adapter"
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"github.com/sagernet/sing-box/common/dialer"
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C "github.com/sagernet/sing-box/constant"
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"github.com/sagernet/sing-box/option"
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"github.com/sagernet/sing-dns"
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"github.com/sagernet/sing-tun"
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"github.com/sagernet/sing/common"
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"github.com/sagernet/sing/common/buf"
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"github.com/sagernet/sing/common/control"
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E "github.com/sagernet/sing/common/exceptions"
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"github.com/sagernet/sing/common/logger"
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M "github.com/sagernet/sing/common/metadata"
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N "github.com/sagernet/sing/common/network"
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"github.com/sagernet/sing/common/task"
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"github.com/sagernet/sing/common/x/list"
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"github.com/insomniacslk/dhcp/dhcpv4"
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mDNS "github.com/miekg/dns"
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)
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func init() {
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dns.RegisterTransport([]string{"dhcp"}, NewTransport)
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}
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type Transport struct {
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ctx context.Context
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router adapter.Router
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logger logger.Logger
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interfaceName string
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autoInterface bool
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interfaceCallback *list.Element[tun.DefaultInterfaceUpdateCallback]
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transports []dns.Transport
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updateAccess sync.Mutex
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updatedAt time.Time
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}
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func NewTransport(ctx context.Context, logger logger.ContextLogger, dialer N.Dialer, link string) (dns.Transport, error) {
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linkURL, err := url.Parse(link)
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if err != nil {
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return nil, err
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}
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if linkURL.Host == "" {
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return nil, E.New("missing interface name for DHCP")
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}
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router := adapter.RouterFromContext(ctx)
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if router == nil {
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return nil, E.New("missing router in context")
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}
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transport := &Transport{
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ctx: ctx,
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router: router,
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logger: logger,
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interfaceName: linkURL.Host,
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autoInterface: linkURL.Host == "auto",
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}
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return transport, nil
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}
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func (t *Transport) Start() error {
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err := t.fetchServers()
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if err != nil {
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return err
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}
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if t.autoInterface {
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t.interfaceCallback = t.router.InterfaceMonitor().RegisterCallback(t.interfaceUpdated)
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}
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return nil
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}
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func (t *Transport) Close() error {
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if t.interfaceCallback != nil {
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t.router.InterfaceMonitor().UnregisterCallback(t.interfaceCallback)
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}
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return nil
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}
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func (t *Transport) Raw() bool {
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return true
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}
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func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
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err := t.fetchServers()
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if err != nil {
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return nil, err
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}
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if len(t.transports) == 0 {
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return nil, E.New("dhcp: empty DNS servers from response")
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}
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var response *mDNS.Msg
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for _, transport := range t.transports {
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response, err = transport.Exchange(ctx, message)
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if err == nil {
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return response, nil
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}
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}
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return nil, err
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}
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func (t *Transport) fetchInterface() (*net.Interface, error) {
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interfaceName := t.interfaceName
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if t.autoInterface {
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if t.router.NetworkMonitor() == nil {
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return nil, E.New("missing monitor for auto DHCP, set route.auto_detect_interface")
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}
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interfaceName = t.router.InterfaceMonitor().DefaultInterfaceName(netip.Addr{})
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}
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if interfaceName == "" {
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return nil, E.New("missing default interface")
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}
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return net.InterfaceByName(interfaceName)
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}
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func (t *Transport) fetchServers() error {
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if time.Since(t.updatedAt) < C.DHCPTTL {
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return nil
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}
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t.updateAccess.Lock()
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defer t.updateAccess.Unlock()
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if time.Since(t.updatedAt) < C.DHCPTTL {
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return nil
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}
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return t.updateServers()
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}
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func (t *Transport) updateServers() error {
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iface, err := t.fetchInterface()
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if err != nil {
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return E.Cause(err, "dhcp: prepare interface")
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}
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t.logger.Info("dhcp: query DNS servers on ", iface.Name)
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fetchCtx, cancel := context.WithTimeout(t.ctx, C.DHCPTimeout)
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err = t.fetchServers0(fetchCtx, iface)
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cancel()
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if err != nil {
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return err
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} else if len(t.transports) == 0 {
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return E.New("dhcp: empty DNS servers response")
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} else {
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t.updatedAt = time.Now()
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return nil
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}
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}
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func (t *Transport) interfaceUpdated(int) error {
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return t.updateServers()
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}
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func (t *Transport) fetchServers0(ctx context.Context, iface *net.Interface) error {
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var listener net.ListenConfig
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listener.Control = control.Append(listener.Control, control.BindToInterfaceFunc(t.router.InterfaceFinder(), func(network string, address string) (interfaceName string, interfaceIndex int) {
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return iface.Name, iface.Index
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}))
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listener.Control = control.Append(listener.Control, control.ReuseAddr())
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packetConn, err := listener.ListenPacket(t.ctx, "udp4", "0.0.0.0:68")
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if err != nil {
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return err
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}
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defer packetConn.Close()
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discovery, err := dhcpv4.NewDiscovery(iface.HardwareAddr, dhcpv4.WithBroadcast(true), dhcpv4.WithRequestedOptions(dhcpv4.OptionDomainNameServer))
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if err != nil {
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return err
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}
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_, err = packetConn.WriteTo(discovery.ToBytes(), &net.UDPAddr{IP: net.IPv4bcast, Port: 67})
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if err != nil {
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return err
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}
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var group task.Group
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group.Append0(func(ctx context.Context) error {
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return t.fetchServersResponse(iface, packetConn, discovery.TransactionID)
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})
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group.Cleanup(func() {
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packetConn.Close()
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})
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return group.Run(ctx)
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}
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func (t *Transport) fetchServersResponse(iface *net.Interface, packetConn net.PacketConn, transactionID dhcpv4.TransactionID) error {
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_buffer := buf.StackNewSize(dhcpv4.MaxMessageSize)
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defer common.KeepAlive(_buffer)
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buffer := common.Dup(_buffer)
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defer buffer.Release()
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for {
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_, _, err := buffer.ReadPacketFrom(packetConn)
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if err != nil {
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return err
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}
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dhcpPacket, err := dhcpv4.FromBytes(buffer.Bytes())
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if err != nil {
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t.logger.Trace("dhcp: parse DHCP response: ", err)
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return err
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}
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if dhcpPacket.MessageType() != dhcpv4.MessageTypeOffer {
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t.logger.Trace("dhcp: expected OFFER response, but got ", dhcpPacket.MessageType())
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continue
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}
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if dhcpPacket.TransactionID != transactionID {
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t.logger.Trace("dhcp: expected transaction ID ", transactionID, ", but got ", dhcpPacket.TransactionID)
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continue
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}
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dns := dhcpPacket.DNS()
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if len(dns) == 0 {
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return nil
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}
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var addrs []netip.Addr
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for _, ip := range dns {
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addr, _ := netip.AddrFromSlice(ip)
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addrs = append(addrs, addr.Unmap())
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}
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return t.recreateServers(iface, addrs)
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}
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}
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func (t *Transport) recreateServers(iface *net.Interface, serverAddrs []netip.Addr) error {
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if len(serverAddrs) > 0 {
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t.logger.Info("dhcp: updated DNS servers from ", iface.Name, ": [", strings.Join(common.Map(serverAddrs, func(it netip.Addr) string {
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return it.String()
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}), ","), "]")
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}
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serverDialer := dialer.NewDefault(t.router, option.DialerOptions{
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BindInterface: iface.Name,
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UDPFragmentDefault: true,
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})
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var transports []dns.Transport
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for _, serverAddr := range serverAddrs {
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serverTransport, err := dns.NewUDPTransport(t.ctx, serverDialer, M.Socksaddr{Addr: serverAddr, Port: 53})
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if err != nil {
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return err
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}
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transports = append(transports, serverTransport)
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}
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t.transports = transports
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return nil
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}
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func (t *Transport) Lookup(ctx context.Context, domain string, strategy dns.DomainStrategy) ([]netip.Addr, error) {
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return nil, os.ErrInvalid
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}
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