cmd/tailscale/tsdnsjsonv0: extract a new package for tailscale dns --json (#20017)

This patch extracts all the DNS related JSON handling from the
cmd/tailscale/jsonoutput package into a new tsdnsjsonv0 package.

It adds package documentation for tsdnsjsonv0 with a big WARNING that
this is an unstable format with no backwards compatibility guarantees.
When we stabilize this format, we should spin off a new tsdnsjsonv1
package that uses jsonoutput.ResponseEnvelope to declare version 1.

Updates #13326
Updates #18750

Signed-off-by: Simon Law <sfllaw@tailscale.com>

cmd/tailscale/cli/dns-query.go

@@ -16,7 +16,7 @@
 	"github.com/peterbourgon/ff/v3/ffcli"
 	"golang.org/x/net/dns/dnsmessage"
 
-	"tailscale.com/cmd/tailscale/jsonoutput"
+	"tailscale.com/cmd/tailscale/tsdnsjsonv0"
 )
 
 var dnsQueryArgs struct {
@@ -74,7 +74,7 @@ func runDNSQuery(ctx context.Context, args []string) error {
 		return fmt.Errorf("failed to query DNS: %w", err)
 	}
 
-	data := &jsonoutput.DNSQueryResult{
+	data := &tsdnsjsonv0.QueryResponse{
 		Name:      name,
 		QueryType: queryType,
 	}
@@ -97,9 +97,9 @@ func runDNSQuery(ctx context.Context, args []string) error {
 		if err != nil {
 			return fmt.Errorf("failed to parse DNS answers: %w", err)
 		}
-		data.Answers = make([]jsonoutput.DNSAnswer, 0, len(answers))
+		data.Answers = make([]tsdnsjsonv0.Answer, 0, len(answers))
 		for _, a := range answers {
-			data.Answers = append(data.Answers, jsonoutput.DNSAnswer{
+			data.Answers = append(data.Answers, tsdnsjsonv0.Answer{
 				Name:  a.Header.Name.String(),
 				TTL:   a.Header.TTL,
 				Class: a.Header.Class.String(),
@@ -121,7 +121,7 @@ func runDNSQuery(ctx context.Context, args []string) error {
 	return nil
 }
 
-func formatDNSQueryText(data *jsonoutput.DNSQueryResult) string {
+func formatDNSQueryText(data *tsdnsjsonv0.QueryResponse) string {
 	var sb strings.Builder
 
 	fmt.Fprintf(&sb, "DNS query for %q (%s) using internal resolver:\n", data.Name, data.QueryType)
@@ -159,8 +159,8 @@ func formatDNSQueryText(data *jsonoutput.DNSQueryResult) string {
 	return sb.String()
 }
 
-// formatResolverString formats a jsonoutput.DNSResolverInfo for human-readable text output.
-func formatResolverString(r jsonoutput.DNSResolverInfo) string {
+// formatResolverString formats a [tsdnsjsonv0.ResolverInfo] for human-readable text output.
+func formatResolverString(r tsdnsjsonv0.ResolverInfo) string {
 	if len(r.BootstrapResolution) > 0 {
 		return fmt.Sprintf("%s (bootstrap: %v)", r.Addr, r.BootstrapResolution)
 	}

cmd/tailscale/cli/dns-status.go

@@ -14,7 +14,7 @@
 
 	"github.com/peterbourgon/ff/v3/ffcli"
 
-	"tailscale.com/cmd/tailscale/jsonoutput"
+	"tailscale.com/cmd/tailscale/tsdnsjsonv0"
 	"tailscale.com/types/dnstype"
 )
 
@@ -85,9 +85,9 @@
 	json bool
 }
 
-// makeDNSResolverInfo converts a dnstype.Resolver to a jsonoutput.DNSResolverInfo.
-func makeDNSResolverInfo(r *dnstype.Resolver) jsonoutput.DNSResolverInfo {
-	info := jsonoutput.DNSResolverInfo{Addr: r.Addr}
+// makeDNSResolverInfo converts a [dnstype.Resolver] to a [tsdnsjsonv0.ResolverInfo].
+func makeDNSResolverInfo(r *dnstype.Resolver) tsdnsjsonv0.ResolverInfo {
+	info := tsdnsjsonv0.ResolverInfo{Addr: r.Addr}
 	if r.BootstrapResolution != nil {
 		info.BootstrapResolution = make([]string, 0, len(r.BootstrapResolution))
 		for _, a := range r.BootstrapResolution {
@@ -108,12 +108,12 @@ func runDNSStatus(ctx context.Context, args []string) error {
 		return err
 	}
 
-	data := &jsonoutput.DNSStatusResult{
+	data := &tsdnsjsonv0.StatusResponse{
 		TailscaleDNS: prefs.CorpDNS,
 	}
 
 	if s.CurrentTailnet != nil {
-		data.CurrentTailnet = &jsonoutput.DNSTailnetInfo{
+		data.CurrentTailnet = &tsdnsjsonv0.TailnetInfo{
 			MagicDNSEnabled: s.CurrentTailnet.MagicDNSEnabled,
 			MagicDNSSuffix:  s.CurrentTailnet.MagicDNSSuffix,
 			SelfDNSName:     s.Self.DNSName,
@@ -128,7 +128,7 @@ func runDNSStatus(ctx context.Context, args []string) error {
 			data.Resolvers = append(data.Resolvers, makeDNSResolverInfo(r))
 		}
 
-		data.SplitDNSRoutes = make(map[string][]jsonoutput.DNSResolverInfo)
+		data.SplitDNSRoutes = make(map[string][]tsdnsjsonv0.ResolverInfo)
 		for k, v := range dnsConfig.Routes {
 			for _, r := range v {
 				data.SplitDNSRoutes[k] = append(data.SplitDNSRoutes[k], makeDNSResolverInfo(r))
@@ -150,7 +150,7 @@ func runDNSStatus(ctx context.Context, args []string) error {
 		data.CertDomains = dnsConfig.CertDomains
 
 		for _, er := range dnsConfig.ExtraRecords {
-			data.ExtraRecords = append(data.ExtraRecords, jsonoutput.DNSExtraRecord{
+			data.ExtraRecords = append(data.ExtraRecords, tsdnsjsonv0.ExtraRecord{
 				Name:  er.Name,
 				Type:  er.Type,
 				Value: er.Value,
@@ -167,7 +167,7 @@ func runDNSStatus(ctx context.Context, args []string) error {
 				data.SystemDNSError = err.Error()
 			}
 		} else if osCfg != nil {
-			data.SystemDNS = &jsonoutput.DNSSystemConfig{
+			data.SystemDNS = &tsdnsjsonv0.SystemConfig{
 				Nameservers:   osCfg.Nameservers,
 				SearchDomains: osCfg.SearchDomains,
 				MatchDomains:  osCfg.MatchDomains,
@@ -187,7 +187,7 @@ func runDNSStatus(ctx context.Context, args []string) error {
 	return nil
 }
 
-func formatDNSStatusText(data *jsonoutput.DNSStatusResult, all bool) string {
+func formatDNSStatusText(data *tsdnsjsonv0.StatusResponse, all bool) string {
 	var sb strings.Builder
 
 	fmt.Fprintf(&sb, "\n")

cmd/tailscale/depaware.txt

@@ -187,6 +187,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/cmd/tailscale/cli/ffcomplete                   from tailscale.com/cmd/tailscale/cli
         tailscale.com/cmd/tailscale/cli/ffcomplete/internal          from tailscale.com/cmd/tailscale/cli/ffcomplete
         tailscale.com/cmd/tailscale/jsonoutput                       from tailscale.com/cmd/tailscale/cli
+        tailscale.com/cmd/tailscale/tsdnsjsonv0                      from tailscale.com/cmd/tailscale/cli
         tailscale.com/cmd/tailscale/tsroutecheckjsonv0               from tailscale.com/cmd/tailscale/cli
         tailscale.com/control/controlbase                            from tailscale.com/control/controlhttp+
         tailscale.com/control/controlhttp                            from tailscale.com/control/ts2021

cmd/tailscale/tsdnsjsonv0/doc.go

@@ -0,0 +1,14 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package tsdnsjsonv0 provides types for unmarshalling the JSON output of the
+// "tailscale dns --json" command:
+//
+//   - [QueryResponse] will unmarshal the output of "tailscale dns query --json=1"
+//   - [StatusResponse] will unmarshal the output of "tailscale dns status --json=1".
+//
+// # WARNING: unstable
+//
+// Format is "v0" and is subject to change.
+// There is no guarantee of backwards or forwards compatibility.
+package tsdnsjsonv0

cmd/tailscale/tsdnsjsonv0/example_dnsqueryresult_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
-package jsonoutput_test
+package tsdnsjsonv0_test
 
 import (
 	"encoding/json"
@@ -10,10 +10,10 @@
 	"os"
 	"os/exec"
 
-	"tailscale.com/cmd/tailscale/jsonoutput"
+	"tailscale.com/cmd/tailscale/tsdnsjsonv0"
 )
 
-func ExampleDNSQueryResult() {
+func ExampleQueryResponse() {
 	cmd := exec.Command("tailscale", "dns", "query", "--json", "hello.ts.net")
 	out, err := cmd.Output()
 	if err != nil {
@@ -23,9 +23,9 @@ func ExampleDNSQueryResult() {
 		panic(err)
 	}
 
-	var dnsQuery jsonoutput.DNSQueryResult
-	if err := json.Unmarshal(out, &dnsQuery); err != nil {
+	var resp tsdnsjsonv0.QueryResponse
+	if err := json.Unmarshal(out, &resp); err != nil {
 		panic(err)
 	}
-	fmt.Printf("{type: %s, name: %q}\n", dnsQuery.QueryType, dnsQuery.Name)
+	fmt.Printf("{type: %s, name: %q}\n", resp.QueryType, resp.Name)
 }

cmd/tailscale/tsdnsjsonv0/example_dnsstatusresult_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
-package jsonoutput_test
+package tsdnsjsonv0_test
 
 import (
 	"encoding/json"
@@ -10,10 +10,10 @@
 	"os"
 	"os/exec"
 
-	"tailscale.com/cmd/tailscale/jsonoutput"
+	"tailscale.com/cmd/tailscale/tsdnsjsonv0"
 )
 
-func ExampleDNSStatusResult() {
+func ExampleStatusResponse() {
 	cmd := exec.Command("tailscale", "dns", "status", "--json")
 	out, err := cmd.Output()
 	if err != nil {
@@ -23,9 +23,9 @@ func ExampleDNSStatusResult() {
 		panic(err)
 	}
 
-	var dnsStatus jsonoutput.DNSStatusResult
-	if err := json.Unmarshal(out, &dnsStatus); err != nil {
+	var resp tsdnsjsonv0.StatusResponse
+	if err := json.Unmarshal(out, &resp); err != nil {
 		panic(err)
 	}
-	fmt.Printf("{accept-dns: %t, resolvers: %q}\n", dnsStatus.TailscaleDNS, dnsStatus.Resolvers)
+	fmt.Printf("{accept-dns: %t, resolvers: %q}\n", resp.TailscaleDNS, resp.Resolvers)
 }

cmd/tailscale/tsdnsjsonv0/query.go

@@ -0,0 +1,25 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+package tsdnsjsonv0
+
+// Answer is a single DNS resource record from a query response.
+type Answer struct {
+	Name  string
+	TTL   uint32
+	Class string // e.g. "ClassINET"
+	Type  string // e.g. "TypeA", "TypeAAAA"
+	Body  string // human-readable record data
+}
+
+// QueryResponse is the result of a DNS query via the Tailscale
+// internal forwarder (100.100.100.100). It is the output of:
+//
+//	$ tailscale dns query --json NAME
+type QueryResponse struct {
+	Name         string
+	QueryType    string         // e.g. "A", "AAAA"
+	Resolvers    []ResolverInfo `json:",omitzero"`
+	ResponseCode string         // e.g. "RCodeSuccess", "RCodeNameError"
+	Answers      []Answer       `json:",omitzero"`
+}

cmd/tailscale/tsdnsjsonv0/status.go

@@ -1,10 +1,17 @@
 // Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
-package jsonoutput
+package tsdnsjsonv0
 
-// DNSResolverInfo is the JSON form of [tailscale.com/types/dnstype.Resolver].
-type DNSResolverInfo struct {
+// ExtraRecord is the JSON form of [tailscale.com/tailcfg.DNSRecord].
+type ExtraRecord struct {
+	Name  string
+	Type  string `json:",omitempty"` // empty means A or AAAA, depending on Value
+	Value string // typically an IP address
+}
+
+// ResolverInfo is the JSON form of [tailscale.com/types/dnstype.Resolver].
+type ResolverInfo struct {
 	// Addr is a plain IP, IP:port, DoH URL, or HTTP-over-WireGuard URL.
 	Addr string
 
@@ -13,16 +20,9 @@ type DNSResolverInfo struct {
 	BootstrapResolution []string `json:",omitempty"`
 }
 
-// DNSExtraRecord is the JSON form of [tailscale.com/tailcfg.DNSRecord].
-type DNSExtraRecord struct {
-	Name  string
-	Type  string `json:",omitempty"` // empty means A or AAAA, depending on Value
-	Value string // typically an IP address
-}
-
-// DNSSystemConfig is the OS DNS configuration as observed by Tailscale,
+// SystemConfig is the OS DNS configuration as observed by Tailscale,
 // mirroring [tailscale.com/net/dns.OSConfig].
-type DNSSystemConfig struct {
+type SystemConfig struct {
 	Nameservers   []string `json:",omitzero"`
 	SearchDomains []string `json:",omitzero"`
 
@@ -32,10 +32,10 @@ type DNSSystemConfig struct {
 	MatchDomains []string `json:",omitzero"`
 }
 
-// DNSTailnetInfo describes MagicDNS configuration for the tailnet,
+// TailnetInfo describes MagicDNS configuration for the tailnet,
 // combining [tailscale.com/ipn/ipnstate.TailnetStatus]
 // and [tailscale.com/ipn/ipnstate.PeerStatus].
-type DNSTailnetInfo struct {
+type TailnetInfo struct {
 	// MagicDNSEnabled is whether MagicDNS is enabled for the
 	// tailnet. The device may still not use it if
 	// --accept-dns=false.
@@ -50,30 +50,30 @@ type DNSTailnetInfo struct {
 	SelfDNSName string `json:",omitempty"`
 }
 
-// DNSStatusResult is the full DNS status collected from the local
+// StatusResponse is the full DNS status collected from the local
 // Tailscale daemon. It is the output of:
 //
 //	$ tailscale dns status --json
-type DNSStatusResult struct {
+type StatusResponse struct {
 	// TailscaleDNS is whether the Tailscale DNS configuration is
 	// installed on this device (the --accept-dns setting).
 	TailscaleDNS bool
 
 	// CurrentTailnet describes MagicDNS configuration for the tailnet.
-	CurrentTailnet *DNSTailnetInfo `json:",omitzero"` // nil if not connected
+	CurrentTailnet *TailnetInfo `json:",omitzero"` // nil if not connected
 
 	// Resolvers are the DNS resolvers, in preference order. If
 	// empty, the system defaults are used.
-	Resolvers []DNSResolverInfo `json:",omitzero"`
+	Resolvers []ResolverInfo `json:",omitzero"`
 
 	// SplitDNSRoutes maps domain suffixes to dedicated resolvers.
 	// An empty resolver slice means the suffix is handled by
 	// Tailscale's built-in resolver (100.100.100.100).
-	SplitDNSRoutes map[string][]DNSResolverInfo `json:",omitzero"`
+	SplitDNSRoutes map[string][]ResolverInfo `json:",omitzero"`
 
 	// FallbackResolvers are like Resolvers but only used when
 	// split DNS needs explicit default resolvers.
-	FallbackResolvers []DNSResolverInfo `json:",omitzero"`
+	FallbackResolvers []ResolverInfo `json:",omitzero"`
 
 	SearchDomains []string `json:",omitzero"`
 
@@ -87,7 +87,7 @@ type DNSStatusResult struct {
 	CertDomains []string `json:",omitzero"`
 
 	// ExtraRecords contains extra DNS records in the MagicDNS config.
-	ExtraRecords []DNSExtraRecord `json:",omitzero"`
+	ExtraRecords []ExtraRecord `json:",omitzero"`
 
 	// ExitNodeFilteredSet are DNS suffixes this node won't resolve
 	// when acting as an exit node DNS proxy. Period-prefixed
@@ -95,27 +95,6 @@ type DNSStatusResult struct {
 	// lowercase, no trailing dots.
 	ExitNodeFilteredSet []string `json:",omitzero"`
 
-	SystemDNS      *DNSSystemConfig `json:",omitzero"` // nil if unavailable
-	SystemDNSError string           `json:",omitempty"`
-}
-
-// DNSAnswer is a single DNS resource record from a query response.
-type DNSAnswer struct {
-	Name  string
-	TTL   uint32
-	Class string // e.g. "ClassINET"
-	Type  string // e.g. "TypeA", "TypeAAAA"
-	Body  string // human-readable record data
-}
-
-// DNSQueryResult is the result of a DNS query via the Tailscale
-// internal forwarder (100.100.100.100). It is the output of:
-//
-//	$ tailscale dns query --json NAME
-type DNSQueryResult struct {
-	Name         string
-	QueryType    string            // e.g. "A", "AAAA"
-	Resolvers    []DNSResolverInfo `json:",omitzero"`
-	ResponseCode string            // e.g. "RCodeSuccess", "RCodeNameError"
-	Answers      []DNSAnswer       `json:",omitzero"`
+	SystemDNS      *SystemConfig `json:",omitzero"` // nil if unavailable
+	SystemDNSError string        `json:",omitempty"`
 }

cmd/tailscaled/depaware-minbox.txt

@@ -55,7 +55,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/cmd/tailscale/cli                              from tailscale.com/cmd/tailscaled
         tailscale.com/cmd/tailscale/cli/ffcomplete                   from tailscale.com/cmd/tailscale/cli
         tailscale.com/cmd/tailscale/cli/ffcomplete/internal          from tailscale.com/cmd/tailscale/cli/ffcomplete
-        tailscale.com/cmd/tailscale/jsonoutput                       from tailscale.com/cmd/tailscale/cli
+        tailscale.com/cmd/tailscale/tsdnsjsonv0                      from tailscale.com/cmd/tailscale/cli
         tailscale.com/cmd/tailscaled/childproc                       from tailscale.com/cmd/tailscaled
         tailscale.com/control/controlbase                            from tailscale.com/control/controlhttp+
         tailscale.com/control/controlclient                          from tailscale.com/cmd/tailscaled+