mirror of https://github.com/tailscale/tailscale/
cli: add `tailscale dns query`
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>angott/dns-cli-stream
Andrea Gottardo
2 months ago
parent
d0a56a8870
commit
7c02dcf93a
@ -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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@ -0,0 +1,84 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package dnstype
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import (
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"errors"
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"strings"
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"golang.org/x/net/dns/dnsmessage"
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)
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// StringForType returns the string representation of a dnsmessage.Type.
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// For example, StringForType(dnsmessage.TypeA) returns "A".
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func StringForDNSMessageType(t dnsmessage.Type) string {
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switch t {
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case dnsmessage.TypeAAAA:
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return "AAAA"
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case dnsmessage.TypeALL:
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return "ALL"
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case dnsmessage.TypeA:
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return "A"
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case dnsmessage.TypeCNAME:
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return "CNAME"
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case dnsmessage.TypeHINFO:
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return "HINFO"
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case dnsmessage.TypeMINFO:
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return "MINFO"
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case dnsmessage.TypeMX:
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return "MX"
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case dnsmessage.TypeNS:
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return "NS"
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case dnsmessage.TypeOPT:
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return "OPT"
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case dnsmessage.TypePTR:
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return "PTR"
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case dnsmessage.TypeSOA:
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return "SOA"
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case dnsmessage.TypeSRV:
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return "SRV"
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case dnsmessage.TypeTXT:
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return "TXT"
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case dnsmessage.TypeWKS:
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return "WKS"
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}
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return "UNKNOWN"
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}
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// DNSMessageTypeForString returns the dnsmessage.Type for the given string.
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// For example, DNSMessageTypeForString("A") returns dnsmessage.TypeA.
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func DNSMessageTypeForString(s string) (t dnsmessage.Type, err error) {
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s = strings.TrimSpace(strings.ToUpper(s))
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switch s {
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case "AAAA":
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return dnsmessage.TypeAAAA, nil
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case "ALL":
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return dnsmessage.TypeALL, nil
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case "A":
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return dnsmessage.TypeA, nil
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case "CNAME":
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return dnsmessage.TypeCNAME, nil
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case "HINFO":
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return dnsmessage.TypeHINFO, nil
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case "MINFO":
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return dnsmessage.TypeMINFO, nil
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case "MX":
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return dnsmessage.TypeMX, nil
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case "NS":
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return dnsmessage.TypeNS, nil
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case "OPT":
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return dnsmessage.TypeOPT, nil
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case "PTR":
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return dnsmessage.TypePTR, nil
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case "SOA":
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return dnsmessage.TypeSOA, nil
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case "SRV":
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return dnsmessage.TypeSRV, nil
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case "TXT":
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return dnsmessage.TypeTXT, nil
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case "WKS":
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return dnsmessage.TypeWKS, nil
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}
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return 0, errors.New("unknown DNS message type: " + s)
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}
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