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>main
Andrea Gottardo
2 years ago
committed by
GitHub
parent
a98f75b783
commit
8a6f48b455
@ -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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