all: add UpstreamConfig.VerifyDomain

So the self-check process is only done for ControlD upstream, and can be
distinguished between .com and .dev resolvers.

cmd/ctrld/cli.go

@@ -36,8 +36,6 @@ import (
 	"github.com/Control-D-Inc/ctrld/internal/router"
 )
 
-const selfCheckFQDN = "verify.controld.com"
-
 var (
 	version = "dev"
 	commit  = "none"
@@ -289,6 +287,10 @@ func initCLI() {
 
 			processCDFlags()
 
+			if err := ctrld.ValidateConfig(validator.New(), &cfg); err != nil {
+				mainLog.Fatal().Msgf("invalid config: %v", err)
+			}
+
 			// Explicitly passing config, so on system where home directory could not be obtained,
 			// or sub-process env is different with the parent, we still behave correctly and use
 			// the expected config file.
@@ -320,7 +322,8 @@ func initCLI() {
 					return
 				}
 
-				status = selfCheckStatus(status)
+				domain := cfg.Upstream["0"].VerifyDomain()
+				status = selfCheckStatus(status, domain)
 				switch status {
 				case service.StatusRunning:
 					mainLog.Notice().Msg("Service started")
@@ -855,7 +858,11 @@ func defaultIfaceName() string {
 	return dri
 }
 
-func selfCheckStatus(status service.Status) service.Status {
+func selfCheckStatus(status service.Status, domain string) service.Status {
+	if domain == "" {
+		// Nothing to do, return the status as-is.
+		return status
+	}
 	c := new(dns.Client)
 	bo := backoff.NewBackoff("self-check", logf, 10*time.Second)
 	bo.LogLongerThan = 500 * time.Millisecond
@@ -883,16 +890,16 @@ func selfCheckStatus(status service.Status) service.Status {
 		}
 		mu.Unlock()
 		m := new(dns.Msg)
-		m.SetQuestion(selfCheckFQDN+".", dns.TypeA)
+		m.SetQuestion(domain+".", dns.TypeA)
 		m.RecursionDesired = true
 		r, _, err := c.ExchangeContext(ctx, m, net.JoinHostPort(lc.IP, strconv.Itoa(lc.Port)))
 		if r != nil && r.Rcode == dns.RcodeSuccess && len(r.Answer) > 0 {
-			mainLog.Debug().Msgf("self-check against %q succeeded", selfCheckFQDN)
+			mainLog.Debug().Msgf("self-check against %q succeeded", domain)
 			return status
 		}
 		bo.BackOff(ctx, fmt.Errorf("ExchangeContext: %w", err))
 	}
-	mainLog.Debug().Msgf("self-check against %q failed", selfCheckFQDN)
+	mainLog.Debug().Msgf("self-check against %q failed", domain)
 	return service.StatusUnknown
 }
 

cmd/ctrld/dns_proxy_test.go

@@ -174,7 +174,7 @@ func Test_macFromMsg(t *testing.T) {
 				t.Fatal(err)
 			}
 			m := new(dns.Msg)
-			m.SetQuestion(selfCheckFQDN+".", dns.TypeA)
+			m.SetQuestion("example.com.", dns.TypeA)
 			o := &dns.OPT{Hdr: dns.RR_Header{Name: ".", Rrtype: dns.TypeOPT}}
 			if tc.wantMac {
 				ec1 := &dns.EDNS0_LOCAL{Code: EDNS0_OPTION_MAC, Data: hw}

config.go

@@ -29,9 +29,19 @@ const (
 	IpStackV4    = "v4"
 	IpStackV6    = "v6"
 	IpStackSplit = "split"
+
+	controlDComDomain = "controld.com"
+	controlDNetDomain = "controld.net"
+	controlDDevDomain = "controld.dev"
 )
 
-var controldParentDomains = []string{"controld.com", "controld.net", "controld.dev"}
+var (
+	controldParentDomains  = []string{controlDComDomain, controlDNetDomain, controlDDevDomain}
+	controldVerifiedDomain = map[string]string{
+		controlDComDomain: "verify.controld.com",
+		controlDDevDomain: "verify.controld.dev",
+	}
+)
 
 // SetConfigName set the config name that ctrld will look for.
 // DEPRECATED: use SetConfigNameWithPath instead.
@@ -201,6 +211,23 @@ func (uc *UpstreamConfig) Init() {
 	}
 }
 
+// VerifyDomain returns the domain name that could be resolved by the upstream endpoint.
+// It returns empty for non-ControlD upstream endpoint.
+func (uc *UpstreamConfig) VerifyDomain() string {
+	domain := uc.Domain
+	if domain == "" {
+		if u, err := url.Parse(uc.Endpoint); err == nil {
+			domain = u.Hostname()
+		}
+	}
+	for _, parent := range controldParentDomains {
+		if dns.IsSubDomain(parent, domain) {
+			return controldVerifiedDomain[parent]
+		}
+	}
+	return ""
+}
+
 // UpstreamSendClientInfo reports whether the upstream is
 // configured to send client info to Control D DNS server.
 //

config_internal_test.go

@@ -190,6 +190,39 @@ func TestUpstreamConfig_Init(t *testing.T) {
 	}
 }
 
+func TestUpstreamConfig_VerifyDomain(t *testing.T) {
+	tests := []struct {
+		name         string
+		uc           *UpstreamConfig
+		verifyDomain string
+	}{
+		{
+			controlDComDomain,
+			&UpstreamConfig{Endpoint: "https://freedns.controld.com/p2"},
+			controldVerifiedDomain[controlDComDomain],
+		},
+		{
+			controlDDevDomain,
+			&UpstreamConfig{Endpoint: "https://freedns.controld.dev/p2"},
+			controldVerifiedDomain[controlDDevDomain],
+		},
+		{
+			"non-ControlD upstream",
+			&UpstreamConfig{Endpoint: "https://dns.google/dns-query"},
+			"",
+		},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := tc.uc.VerifyDomain(); got != tc.verifyDomain {
+				t.Errorf("unexpected verify domain, want: %q, got: %q", tc.verifyDomain, got)
+			}
+		})
+	}
+}
 func ptrBool(b bool) *bool {
 	return &b
 }