Improve local DNS server on darwin
We mistakenly believed that `libresolv`'s `search` function worked correctly in NetworkExtension, but it seems only `getaddrinfo` does. This commit changes the behavior of the `local` DNS server in NetworkExtension to prefer DHCP, falling back to `getaddrinfo` if DHCP servers are unavailable. It's worth noting that `prefer_go` does not disable DHCP since it respects Dial Fields, but `getaddrinfo` does the opposite. The new behavior only applies to NetworkExtension, not to all scenarios (primarily command-line binaries) as it did previously. In addition, this commit also improves the DHCP DNS server to use the same robust query logic as `local`.
This commit is contained in:
世界
@@ -1,28 +1,27 @@
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//go:build !darwin
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package local
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import (
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"context"
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"errors"
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"math/rand"
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"syscall"
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"time"
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"github.com/sagernet/sing-box/adapter"
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C "github.com/sagernet/sing-box/constant"
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"github.com/sagernet/sing-box/dns"
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"github.com/sagernet/sing-box/dns/transport"
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"github.com/sagernet/sing-box/dns/transport/hosts"
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"github.com/sagernet/sing-box/log"
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"github.com/sagernet/sing-box/option"
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"github.com/sagernet/sing/common/buf"
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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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mDNS "github.com/miekg/dns"
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)
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func RegisterTransport(registry *dns.TransportRegistry) {
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dns.RegisterTransport[option.LocalDNSServerOptions](registry, C.DNSTypeLocal, NewTransport)
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}
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var _ adapter.DNSTransport = (*Transport)(nil)
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type Transport struct {
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@@ -31,6 +30,7 @@ type Transport struct {
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logger logger.ContextLogger
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hosts *hosts.File
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dialer N.Dialer
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preferGo bool
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resolved ResolvedResolver
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}
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@@ -45,19 +45,22 @@ func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, opt
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logger: logger,
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hosts: hosts.NewFile(hosts.DefaultPath),
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dialer: transportDialer,
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preferGo: options.PreferGo,
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}, nil
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}
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func (t *Transport) Start(stage adapter.StartStage) error {
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switch stage {
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case adapter.StartStateInitialize:
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resolvedResolver, err := NewResolvedResolver(t.ctx, t.logger)
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if err == nil {
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err = resolvedResolver.Start()
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if !t.preferGo {
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resolvedResolver, err := NewResolvedResolver(t.ctx, t.logger)
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if err == nil {
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t.resolved = resolvedResolver
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} else {
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t.logger.Warn(E.Cause(err, "initialize resolved resolver"))
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err = resolvedResolver.Start()
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if err == nil {
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t.resolved = resolvedResolver
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} else {
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t.logger.Warn(E.Cause(err, "initialize resolved resolver"))
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}
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}
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}
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}
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@@ -85,174 +88,5 @@ func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg,
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return dns.FixedResponse(message.Id, question, addresses, C.DefaultDNSTTL), nil
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}
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}
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systemConfig := getSystemDNSConfig(t.ctx)
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if systemConfig.singleRequest || !(message.Question[0].Qtype == mDNS.TypeA || message.Question[0].Qtype == mDNS.TypeAAAA) {
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return t.exchangeSingleRequest(ctx, systemConfig, message, question.Name)
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} else {
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return t.exchangeParallel(ctx, systemConfig, message, question.Name)
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}
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}
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func (t *Transport) exchangeSingleRequest(ctx context.Context, systemConfig *dnsConfig, message *mDNS.Msg, domain string) (*mDNS.Msg, error) {
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var lastErr error
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for _, fqdn := range systemConfig.nameList(domain) {
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response, err := t.tryOneName(ctx, systemConfig, fqdn, message)
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if err != nil {
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lastErr = err
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continue
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}
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return response, nil
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}
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return nil, lastErr
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}
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func (t *Transport) exchangeParallel(ctx context.Context, systemConfig *dnsConfig, message *mDNS.Msg, domain string) (*mDNS.Msg, error) {
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returned := make(chan struct{})
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defer close(returned)
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type queryResult struct {
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response *mDNS.Msg
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err error
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}
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results := make(chan queryResult)
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startRacer := func(ctx context.Context, fqdn string) {
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response, err := t.tryOneName(ctx, systemConfig, fqdn, message)
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if err == nil {
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if response.Rcode != mDNS.RcodeSuccess {
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err = dns.RcodeError(response.Rcode)
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} else if len(dns.MessageToAddresses(response)) == 0 {
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err = dns.RcodeSuccess
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}
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}
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select {
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case results <- queryResult{response, err}:
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case <-returned:
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}
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}
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queryCtx, queryCancel := context.WithCancel(ctx)
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defer queryCancel()
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var nameCount int
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for _, fqdn := range systemConfig.nameList(domain) {
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nameCount++
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go startRacer(queryCtx, fqdn)
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}
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var errors []error
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for {
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select {
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case <-ctx.Done():
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return nil, ctx.Err()
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case result := <-results:
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if result.err == nil {
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return result.response, nil
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}
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errors = append(errors, result.err)
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if len(errors) == nameCount {
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return nil, E.Errors(errors...)
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}
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}
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}
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}
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func (t *Transport) tryOneName(ctx context.Context, config *dnsConfig, fqdn string, message *mDNS.Msg) (*mDNS.Msg, error) {
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serverOffset := config.serverOffset()
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sLen := uint32(len(config.servers))
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var lastErr error
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for i := 0; i < config.attempts; i++ {
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for j := uint32(0); j < sLen; j++ {
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server := config.servers[(serverOffset+j)%sLen]
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question := message.Question[0]
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question.Name = fqdn
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response, err := t.exchangeOne(ctx, M.ParseSocksaddr(server), question, config.timeout, config.useTCP, config.trustAD)
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if err != nil {
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lastErr = err
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continue
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}
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return response, nil
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}
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}
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return nil, E.Cause(lastErr, fqdn)
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}
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func (t *Transport) exchangeOne(ctx context.Context, server M.Socksaddr, question mDNS.Question, timeout time.Duration, useTCP, ad bool) (*mDNS.Msg, error) {
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if server.Port == 0 {
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server.Port = 53
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}
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request := &mDNS.Msg{
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MsgHdr: mDNS.MsgHdr{
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Id: uint16(rand.Uint32()),
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RecursionDesired: true,
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AuthenticatedData: ad,
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},
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Question: []mDNS.Question{question},
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Compress: true,
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}
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request.SetEdns0(buf.UDPBufferSize, false)
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if !useTCP {
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return t.exchangeUDP(ctx, server, request, timeout)
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} else {
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return t.exchangeTCP(ctx, server, request, timeout)
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}
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}
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func (t *Transport) exchangeUDP(ctx context.Context, server M.Socksaddr, request *mDNS.Msg, timeout time.Duration) (*mDNS.Msg, error) {
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conn, err := t.dialer.DialContext(ctx, N.NetworkUDP, server)
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if err != nil {
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return nil, err
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}
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defer conn.Close()
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if deadline, loaded := ctx.Deadline(); loaded && !deadline.IsZero() {
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newDeadline := time.Now().Add(timeout)
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if deadline.After(newDeadline) {
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deadline = newDeadline
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}
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conn.SetDeadline(deadline)
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}
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buffer := buf.Get(buf.UDPBufferSize)
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defer buf.Put(buffer)
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rawMessage, err := request.PackBuffer(buffer)
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if err != nil {
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return nil, E.Cause(err, "pack request")
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}
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_, err = conn.Write(rawMessage)
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if err != nil {
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if errors.Is(err, syscall.EMSGSIZE) {
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return t.exchangeTCP(ctx, server, request, timeout)
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}
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return nil, E.Cause(err, "write request")
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}
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n, err := conn.Read(buffer)
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if err != nil {
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if errors.Is(err, syscall.EMSGSIZE) {
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return t.exchangeTCP(ctx, server, request, timeout)
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}
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return nil, E.Cause(err, "read response")
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}
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var response mDNS.Msg
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err = response.Unpack(buffer[:n])
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if err != nil {
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return nil, E.Cause(err, "unpack response")
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}
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if response.Truncated {
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return t.exchangeTCP(ctx, server, request, timeout)
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}
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return &response, nil
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}
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func (t *Transport) exchangeTCP(ctx context.Context, server M.Socksaddr, request *mDNS.Msg, timeout time.Duration) (*mDNS.Msg, error) {
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conn, err := t.dialer.DialContext(ctx, N.NetworkTCP, server)
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if err != nil {
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return nil, err
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}
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defer conn.Close()
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if deadline, loaded := ctx.Deadline(); loaded && !deadline.IsZero() {
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newDeadline := time.Now().Add(timeout)
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if deadline.After(newDeadline) {
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deadline = newDeadline
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}
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conn.SetDeadline(deadline)
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}
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err = transport.WriteMessage(conn, 0, request)
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if err != nil {
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return nil, err
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}
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return transport.ReadMessage(conn)
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return t.exchange(ctx, message, question.Name)
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}
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