identity: support skipping DNS resolution for some hosts (like bsky.s…

…ocial)

atproto/identity/base_directory.go

@@ -19,6 +19,8 @@ type BaseDirectory struct {
 	Resolver net.Resolver
 	// when doing DNS handle resolution, should this resolver attempt re-try against an authoritative nameserver if the first TXT lookup fails?
 	TryAuthoritativeDNS bool
+	// set of handle domain suffixes for for which DNS handle resolution will be skipped
+	SkipDNSDomainSuffixes []string
 }
 
 var _ Directory = (*BaseDirectory)(nil)

atproto/identity/handle.go

@@ -124,24 +124,37 @@ func (d *BaseDirectory) ResolveHandleWellKnown(ctx context.Context, handle synta
 
 func (d *BaseDirectory) ResolveHandle(ctx context.Context, handle syntax.Handle) (syntax.DID, error) {
 	// TODO: *could* do resolution in parallel, but expecting that sequential is sufficient to start
-	start := time.Now()
-	triedAuthoritative := false
-	did, dnsErr := d.ResolveHandleDNS(ctx, handle)
-	if dnsErr == ErrHandleNotFound && d.TryAuthoritativeDNS {
-		slog.Info("attempting authoritative handle DNS resolution", "handle", handle)
-		triedAuthoritative = true
-		// try harder with authoritative lookup
-		did, dnsErr = d.ResolveHandleDNSAuthoritative(ctx, handle)
+	var dnsErr error
+	var did syntax.DID
+
+	tryDNS := true
+	for _, suffix := range d.SkipDNSDomainSuffixes {
+		if strings.HasSuffix(handle.String(), suffix) {
+			tryDNS = false
+			break
+		}
 	}
-	elapsed := time.Since(start)
-	slog.Debug("resolve handle DNS", "handle", handle, "err", dnsErr, "did", did, "authoritative", triedAuthoritative, "duration_ms", elapsed.Milliseconds())
-	if nil == dnsErr { // if *not* an error
-		return did, nil
+
+	if tryDNS {
+		start := time.Now()
+		triedAuthoritative := false
+		did, dnsErr = d.ResolveHandleDNS(ctx, handle)
+		if dnsErr == ErrHandleNotFound && d.TryAuthoritativeDNS {
+			slog.Info("attempting authoritative handle DNS resolution", "handle", handle)
+			triedAuthoritative = true
+			// try harder with authoritative lookup
+			did, dnsErr = d.ResolveHandleDNSAuthoritative(ctx, handle)
+		}
+		elapsed := time.Since(start)
+		slog.Debug("resolve handle DNS", "handle", handle, "err", dnsErr, "did", did, "authoritative", triedAuthoritative, "duration_ms", elapsed.Milliseconds())
+		if nil == dnsErr { // if *not* an error
+			return did, nil
+		}
 	}
 
-	start = time.Now()
+	start := time.Now()
 	did, httpErr := d.ResolveHandleWellKnown(ctx, handle)
-	elapsed = time.Since(start)
+	elapsed := time.Since(start)
 	slog.Debug("resolve handle HTTP well-known", "handle", handle, "err", httpErr, "did", did, "duration_ms", elapsed.Milliseconds())
 	if nil == httpErr { // if *not* an error
 		return did, nil

atproto/identity/identity.go

@@ -61,6 +61,8 @@ func DefaultDirectory() Directory {
 			},
 		},
 		TryAuthoritativeDNS: true,
+		// primary Bluesky PDS instance only supports HTTP resolution method
+		SkipDNSDomainSuffixes: []string{".bsky.social"},
 	}
 	cached := NewCacheDirectory(&base, 10000, time.Hour*24, time.Minute*2)
 	return &cached