types/dnstype: delete unused func, move other one to its sole caller

The dnstype package is used by tailcfg, which tries to be light and
leafy. But it brings in dnstype. So dnstype shouldn't bring in
x/net/dns/dnsmessage.

Updates #12614

Change-Id: I043637a7ce7fed097e648001f13ca1927a781def
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/stund/depaware.txt

@@ -97,7 +97,7 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         golang.org/x/crypto/nacl/secretbox                           from golang.org/x/crypto/nacl/box
         golang.org/x/crypto/salsa20/salsa                            from golang.org/x/crypto/nacl/box+
         golang.org/x/exp/constraints                                 from tailscale.com/tsweb/varz
-        golang.org/x/net/dns/dnsmessage                              from net+
+        golang.org/x/net/dns/dnsmessage                              from net
         golang.org/x/net/http/httpguts                               from net/http+
         golang.org/x/net/http/httpproxy                              from net/http
         golang.org/x/net/http2/hpack                                 from net/http+

ipn/localapi/localapi.go

@@ -38,7 +38,6 @@ import (
 	"tailscale.com/net/netutil"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstime"
-	"tailscale.com/types/dnstype"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
@@ -1995,7 +1994,7 @@ func (h *Handler) serveDNSQuery(w http.ResponseWriter, r *http.Request) {
 	queryType := q.Get("type")
 	qt := dnsmessage.TypeA
 	if queryType != "" {
-		t, err := dnstype.DNSMessageTypeForString(queryType)
+		t, err := dnsMessageTypeForString(queryType)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
@@ -2016,6 +2015,43 @@ func (h *Handler) serveDNSQuery(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+// dnsMessageTypeForString returns the dnsmessage.Type for the given string.
+// For example, DNSMessageTypeForString("A") returns dnsmessage.TypeA.
+func dnsMessageTypeForString(s string) (t dnsmessage.Type, err error) {
+	s = strings.TrimSpace(strings.ToUpper(s))
+	switch s {
+	case "AAAA":
+		return dnsmessage.TypeAAAA, nil
+	case "ALL":
+		return dnsmessage.TypeALL, nil
+	case "A":
+		return dnsmessage.TypeA, nil
+	case "CNAME":
+		return dnsmessage.TypeCNAME, nil
+	case "HINFO":
+		return dnsmessage.TypeHINFO, nil
+	case "MINFO":
+		return dnsmessage.TypeMINFO, nil
+	case "MX":
+		return dnsmessage.TypeMX, nil
+	case "NS":
+		return dnsmessage.TypeNS, nil
+	case "OPT":
+		return dnsmessage.TypeOPT, nil
+	case "PTR":
+		return dnsmessage.TypePTR, nil
+	case "SOA":
+		return dnsmessage.TypeSOA, nil
+	case "SRV":
+		return dnsmessage.TypeSRV, nil
+	case "TXT":
+		return dnsmessage.TypeTXT, nil
+	case "WKS":
+		return dnsmessage.TypeWKS, nil
+	}
+	return 0, errors.New("unknown DNS message type: " + s)
+}
+
 // serveSuggestExitNode serves a POST endpoint for returning a suggested exit node.
 func (h *Handler) serveSuggestExitNode(w http.ResponseWriter, r *http.Request) {
 	if r.Method != httpm.GET {

types/dnstype/messagetypes-string.go

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