fix(spanner): update DirectPath detection logic to use ALTS credentials

spanner/grpc_client.go

@@ -34,11 +34,6 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-const (
-	directPathIPV6Prefix = "[2001:4860:8040"
-	directPathIPV4Prefix = "34.126"
-)
-
 type contextKey string
 
 const metricsTracerKey contextKey = "metricsTracer"

spanner/integration_test.go

@@ -57,6 +57,7 @@ import (
 	"google.golang.org/api/option/internaloption"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/alts"
 	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/peer"
 	"google.golang.org/grpc/status"
@@ -6608,22 +6609,20 @@ func verifyDirectPathRemoteAddress(t *testing.T) {
 		return
 	}
 	if remoteIP, res := isDirectPathRemoteAddress(); !res {
-		if dpConfig.directPathIPv4Only {
-			t.Fatalf("Expect to access DirectPath via ipv4 only, but RPC was destined to %s", remoteIP)
-		} else {
-			t.Fatalf("Expect to access DirectPath via ipv4 or ipv6, but RPC was destined to %s", remoteIP)
-		}
+		t.Fatalf("Expect to access DirectPath via ALTS, but RPC was destined to %s", remoteIP)
 	}
 }
 
 func isDirectPathRemoteAddress() (_ string, _ bool) {
-	remoteIP := peerInfo.Addr.String()
-	// DirectPath ipv4-only can only use ipv4 traffic.
-	if dpConfig.directPathIPv4Only {
-		return remoteIP, strings.HasPrefix(remoteIP, directPathIPV4Prefix)
+	var remoteIP string
+	if peerInfo != nil && peerInfo.Addr != nil {
+		remoteIP = peerInfo.Addr.String()
+	}
+	isDP := false
+	if peerInfo != nil && peerInfo.AuthInfo != nil {
+		_, isDP = peerInfo.AuthInfo.(alts.AuthInfo)
 	}
-	// DirectPath ipv6 can use either ipv4 or ipv6 traffic.
-	return remoteIP, strings.HasPrefix(remoteIP, directPathIPV4Prefix) || strings.HasPrefix(remoteIP, directPathIPV6Prefix)
+	return remoteIP, isDP
 }
 
 // examineTraffic counts RPCs use DirectPath or CFE traffic.

spanner/metrics.go

@@ -37,6 +37,7 @@ import (
 	"google.golang.org/api/option"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/alts"
 	"google.golang.org/grpc/experimental/stats"
 	"google.golang.org/grpc/peer"
 	"google.golang.org/grpc/stats/opentelemetry"
@@ -533,9 +534,8 @@ func (o *opTracer) incrementAttemptCount() {
 // setDirectPathUsed sets whether DirectPath was used for the attempt.
 func (a *attemptTracer) setDirectPathUsed(ctx context.Context) {
 	peerInfo, ok := peer.FromContext(ctx)
-	if ok && peerInfo.Addr != nil {
-		remoteIP := peerInfo.Addr.String()
-		if strings.HasPrefix(remoteIP, directPathIPV4Prefix) || strings.HasPrefix(remoteIP, directPathIPV6Prefix) {
+	if ok {
+		if _, isALTS := peerInfo.AuthInfo.(alts.AuthInfo); isALTS {
 			a.directPathUsed = true
 		}
 	}

spanner/metrics_test.go

@@ -31,7 +31,9 @@ import (
 	"google.golang.org/genproto/googleapis/api/metric"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/alts"
 	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/peer"
 	"google.golang.org/grpc/status"
 )
 
@@ -314,3 +316,60 @@ func parseHex(hexStr string) (int64, error) {
 	_, err := fmt.Sscanf(hexStr, "%x", &value)
 	return value, err
 }
+
+type mockALTSAuthInfo struct {
+	alts.AuthInfo
+}
+
+func (m mockALTSAuthInfo) AuthType() string { return "alts" }
+
+type mockOtherAuthInfo struct{}
+
+func (m mockOtherAuthInfo) AuthType() string { return "other" }
+
+func TestSetDirectPathUsed(t *testing.T) {
+	tests := []struct {
+		name string
+		peer *peer.Peer
+		want bool
+	}{
+		{
+			name: "ALTS AuthInfo",
+			peer: &peer.Peer{
+				AuthInfo: mockALTSAuthInfo{},
+			},
+			want: true,
+		},
+		{
+			name: "Other AuthInfo",
+			peer: &peer.Peer{
+				AuthInfo: mockOtherAuthInfo{},
+			},
+			want: false,
+		},
+		{
+			name: "No AuthInfo",
+			peer: &peer.Peer{},
+			want: false,
+		},
+		{
+			name: "No Peer",
+			peer: nil,
+			want: false,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			tracer := &attemptTracer{}
+			ctx := context.Background()
+			if tc.peer != nil {
+				ctx = peer.NewContext(ctx, tc.peer)
+			}
+			tracer.setDirectPathUsed(ctx)
+			if tracer.directPathUsed != tc.want {
+				t.Errorf("setDirectPathUsed() = %v, want %v", tracer.directPathUsed, tc.want)
+			}
+		})
+	}
+}