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cli: add tailscale dns query (#13368)
Updates tailscale/tailscale#13326 Adds a CLI subcommand to perform DNS queries using the internal DNS forwarder and observe its internals (namely, which upstream resolvers are being used). Signed-off-by: Andrea Gottardo <andrea@gottardo.me>
This commit is contained in:
Andrea Gottardo
@@ -128,7 +128,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
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tailscale.com/tsweb from tailscale.com/cmd/derper
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tailscale.com/tsweb/promvarz from tailscale.com/tsweb
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tailscale.com/tsweb/varz from tailscale.com/tsweb+
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tailscale.com/types/dnstype from tailscale.com/tailcfg
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tailscale.com/types/dnstype from tailscale.com/tailcfg+
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tailscale.com/types/empty from tailscale.com/ipn
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tailscale.com/types/ipproto from tailscale.com/tailcfg+
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tailscale.com/types/key from tailscale.com/client/tailscale+
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@@ -91,7 +91,7 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
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golang.org/x/crypto/nacl/secretbox from golang.org/x/crypto/nacl/box
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golang.org/x/crypto/salsa20/salsa from golang.org/x/crypto/nacl/box+
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golang.org/x/crypto/sha3 from crypto/internal/mlkem768+
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golang.org/x/net/dns/dnsmessage from net
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golang.org/x/net/dns/dnsmessage from net+
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golang.org/x/net/http/httpguts from net/http
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golang.org/x/net/http/httpproxy from net/http
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golang.org/x/net/http2/hpack from net/http
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163
cmd/tailscale/cli/dns-query.go
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163
cmd/tailscale/cli/dns-query.go
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@@ -0,0 +1,163 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package cli
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import (
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"context"
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"flag"
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"fmt"
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"net/netip"
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"os"
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"text/tabwriter"
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"golang.org/x/net/dns/dnsmessage"
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"tailscale.com/types/dnstype"
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)
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func runDNSQuery(ctx context.Context, args []string) error {
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if len(args) < 1 {
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return flag.ErrHelp
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}
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name := args[0]
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queryType := "A"
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if len(args) >= 2 {
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queryType = args[1]
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}
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fmt.Printf("DNS query for %q (%s) using internal resolver:\n", name, queryType)
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fmt.Println()
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bytes, resolvers, err := localClient.QueryDNS(ctx, name, queryType)
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if err != nil {
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fmt.Printf("failed to query DNS: %v\n", err)
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return nil
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}
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if len(resolvers) == 1 {
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fmt.Printf("Forwarding to resolver: %v\n", makeResolverString(*resolvers[0]))
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} else {
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fmt.Println("Multiple resolvers available:")
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for _, r := range resolvers {
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fmt.Printf(" - %v\n", makeResolverString(*r))
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}
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}
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fmt.Println()
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var p dnsmessage.Parser
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header, err := p.Start(bytes)
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if err != nil {
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fmt.Printf("failed to parse DNS response: %v\n", err)
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return err
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}
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fmt.Printf("Response code: %v\n", header.RCode.String())
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fmt.Println()
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p.SkipAllQuestions()
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if header.RCode != dnsmessage.RCodeSuccess {
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fmt.Println("No answers were returned.")
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return nil
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}
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answers, err := p.AllAnswers()
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if err != nil {
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fmt.Printf("failed to parse DNS answers: %v\n", err)
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return err
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}
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if len(answers) == 0 {
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fmt.Println(" (no answers found)")
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}
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w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
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fmt.Fprintln(w, "Name\tTTL\tClass\tType\tBody")
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fmt.Fprintln(w, "----\t---\t-----\t----\t----")
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for _, a := range answers {
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fmt.Fprintf(w, "%s\t%d\t%s\t%s\t%s\n", a.Header.Name.String(), a.Header.TTL, a.Header.Class.String(), a.Header.Type.String(), makeAnswerBody(a))
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}
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w.Flush()
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fmt.Println()
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return nil
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}
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// makeAnswerBody returns a string with the DNS answer body in a human-readable format.
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func makeAnswerBody(a dnsmessage.Resource) string {
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switch a.Header.Type {
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case dnsmessage.TypeA:
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return makeABody(a.Body)
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case dnsmessage.TypeAAAA:
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return makeAAAABody(a.Body)
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case dnsmessage.TypeCNAME:
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return makeCNAMEBody(a.Body)
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case dnsmessage.TypeMX:
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return makeMXBody(a.Body)
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case dnsmessage.TypeNS:
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return makeNSBody(a.Body)
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case dnsmessage.TypeOPT:
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return makeOPTBody(a.Body)
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case dnsmessage.TypePTR:
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return makePTRBody(a.Body)
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case dnsmessage.TypeSRV:
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return makeSRVBody(a.Body)
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case dnsmessage.TypeTXT:
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return makeTXTBody(a.Body)
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default:
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return a.Body.GoString()
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}
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}
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func makeABody(a dnsmessage.ResourceBody) string {
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if a, ok := a.(*dnsmessage.AResource); ok {
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return netip.AddrFrom4(a.A).String()
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}
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return ""
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}
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func makeAAAABody(aaaa dnsmessage.ResourceBody) string {
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if a, ok := aaaa.(*dnsmessage.AAAAResource); ok {
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return netip.AddrFrom16(a.AAAA).String()
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}
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return ""
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}
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func makeCNAMEBody(cname dnsmessage.ResourceBody) string {
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if c, ok := cname.(*dnsmessage.CNAMEResource); ok {
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return c.CNAME.String()
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}
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return ""
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}
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func makeMXBody(mx dnsmessage.ResourceBody) string {
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if m, ok := mx.(*dnsmessage.MXResource); ok {
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return fmt.Sprintf("%s (Priority=%d)", m.MX, m.Pref)
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}
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return ""
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}
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func makeNSBody(ns dnsmessage.ResourceBody) string {
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if n, ok := ns.(*dnsmessage.NSResource); ok {
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return n.NS.String()
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}
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return ""
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}
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func makeOPTBody(opt dnsmessage.ResourceBody) string {
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if o, ok := opt.(*dnsmessage.OPTResource); ok {
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return o.GoString()
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}
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return ""
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}
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func makePTRBody(ptr dnsmessage.ResourceBody) string {
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if p, ok := ptr.(*dnsmessage.PTRResource); ok {
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return p.PTR.String()
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}
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return ""
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}
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func makeSRVBody(srv dnsmessage.ResourceBody) string {
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if s, ok := srv.(*dnsmessage.SRVResource); ok {
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return fmt.Sprintf("Target=%s, Port=%d, Priority=%d, Weight=%d", s.Target.String(), s.Port, s.Priority, s.Weight)
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}
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return ""
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}
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func makeTXTBody(txt dnsmessage.ResourceBody) string {
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if t, ok := txt.(*dnsmessage.TXTResource); ok {
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return fmt.Sprintf("%q", t.TXT)
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}
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return ""
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}
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func makeResolverString(r dnstype.Resolver) string {
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if len(r.BootstrapResolution) > 0 {
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return fmt.Sprintf("%s (bootstrap: %v)", r.Addr, r.BootstrapResolution)
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}
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return fmt.Sprintf("%s", r.Addr)
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}
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@@ -75,7 +75,7 @@ func runDNSStatus(ctx context.Context, args []string) error {
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fmt.Print("\n")
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fmt.Println("Split DNS Routes:")
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if len(dnsConfig.Routes) == 0 {
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fmt.Println(" (no routes configured: split DNS might not be in use)")
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fmt.Println(" (no routes configured: split DNS disabled)")
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}
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for _, k := range slices.Sorted(maps.Keys(dnsConfig.Routes)) {
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v := dnsConfig.Routes[k]
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@@ -28,8 +28,13 @@ var dnsCmd = &ffcli.Command{
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return fs
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})(),
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},
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// TODO: implement `tailscale query` here
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{
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Name: "query",
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ShortUsage: "tailscale dns query <name> [a|aaaa|cname|mx|ns|opt|ptr|srv|txt]",
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Exec: runDNSQuery,
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ShortHelp: "Perform a DNS query",
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LongHelp: "The 'tailscale dns query' subcommand performs a DNS query for the specified name using the internal DNS forwarder (100.100.100.100).\n\nIt also provides information about the resolver(s) used to resolve the query.",
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},
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// TODO: implement `tailscale log` here
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@@ -134,7 +134,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
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tailscale.com/tstime/mono from tailscale.com/tstime/rate
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tailscale.com/tstime/rate from tailscale.com/cmd/tailscale/cli+
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tailscale.com/tsweb/varz from tailscale.com/util/usermetric
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tailscale.com/types/dnstype from tailscale.com/tailcfg
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tailscale.com/types/dnstype from tailscale.com/tailcfg+
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tailscale.com/types/empty from tailscale.com/ipn
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tailscale.com/types/ipproto from tailscale.com/net/flowtrack+
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tailscale.com/types/key from tailscale.com/client/tailscale+
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