Speed up TestBindToDeviceDistribution

Testing only TestBindToDeviceDistribution decreased from 24s to 11s, and with
TSAN from 186s to 21s.

Note: using `t.Parallel()` actually slows the test down.
PiperOrigin-RevId: 376251420

pkg/tcpip/stack/transport_demuxer_test.go

@@ -18,6 +18,7 @@ import (
 	"io/ioutil"
 	"math"
 	"math/rand"
+	"strconv"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -84,7 +85,8 @@ func newDualTestContextMultiNIC(t *testing.T, mtu uint32, linkEpIDs []tcpip.NICI
 }
 
 type headers struct {
-	srcPort, dstPort uint16
+	srcPort uint16
+	dstPort uint16
 }
 
 func newPayload() []byte {
@@ -208,7 +210,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 		reuse        bool
 		bindToDevice tcpip.NICID
 	}
-	for _, test := range []struct {
+	tcs := []struct {
 		name string
 		// endpoints will received the inject packets.
 		endpoints []endpointSockopts
@@ -217,29 +219,29 @@ func TestBindToDeviceDistribution(t *testing.T) {
 		wantDistributions map[tcpip.NICID][]float64
 	}{
 		{
-			"BindPortReuse",
+			name: "BindPortReuse",
 			// 5 endpoints that all have reuse set.
-			[]endpointSockopts{
+			endpoints: []endpointSockopts{
 				{reuse: true, bindToDevice: 0},
 				{reuse: true, bindToDevice: 0},
 				{reuse: true, bindToDevice: 0},
 				{reuse: true, bindToDevice: 0},
 				{reuse: true, bindToDevice: 0},
 			},
-			map[tcpip.NICID][]float64{
+			wantDistributions: map[tcpip.NICID][]float64{
 				// Injected packets on dev0 get distributed evenly.
 				1: {0.2, 0.2, 0.2, 0.2, 0.2},
 			},
 		},
 		{
-			"BindToDevice",
+			name: "BindToDevice",
 			// 3 endpoints with various bindings.
-			[]endpointSockopts{
+			endpoints: []endpointSockopts{
 				{reuse: false, bindToDevice: 1},
 				{reuse: false, bindToDevice: 2},
 				{reuse: false, bindToDevice: 3},
 			},
-			map[tcpip.NICID][]float64{
+			wantDistributions: map[tcpip.NICID][]float64{
 				// Injected packets on dev0 go only to the endpoint bound to dev0.
 				1: {1, 0, 0},
 				// Injected packets on dev1 go only to the endpoint bound to dev1.
@@ -249,9 +251,9 @@ func TestBindToDeviceDistribution(t *testing.T) {
 			},
 		},
 		{
-			"ReuseAndBindToDevice",
+			name: "ReuseAndBindToDevice",
 			// 6 endpoints with various bindings.
-			[]endpointSockopts{
+			endpoints: []endpointSockopts{
 				{reuse: true, bindToDevice: 1},
 				{reuse: true, bindToDevice: 1},
 				{reuse: true, bindToDevice: 2},
@@ -259,7 +261,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 				{reuse: true, bindToDevice: 2},
 				{reuse: true, bindToDevice: 0},
 			},
-			map[tcpip.NICID][]float64{
+			wantDistributions: map[tcpip.NICID][]float64{
 				// Injected packets on dev0 get distributed among endpoints bound to
 				// dev0.
 				1: {0.5, 0.5, 0, 0, 0, 0},
@@ -270,21 +272,25 @@ func TestBindToDeviceDistribution(t *testing.T) {
 				1000: {0, 0, 0, 0, 0, 1},
 			},
 		},
-	} {
-		for protoName, netProtoNum := range map[string]tcpip.NetworkProtocolNumber{
-			"IPv4": ipv4.ProtocolNumber,
-			"IPv6": ipv6.ProtocolNumber,
-		} {
+	}
+	protos := map[string]tcpip.NetworkProtocolNumber{
+		"IPv4": ipv4.ProtocolNumber,
+		"IPv6": ipv6.ProtocolNumber,
+	}
+
+	for _, test := range tcs {
+		for protoName, protoNum := range protos {
 			for device, wantDistribution := range test.wantDistributions {
-				t.Run(test.name+protoName+string(device), func(t *testing.T) {
+				t.Run(test.name+protoName+"-"+strconv.Itoa(int(device)), func(t *testing.T) {
+					// Create the NICs.
 					var devices []tcpip.NICID
 					for d := range test.wantDistributions {
 						devices = append(devices, d)
 					}
 					c := newDualTestContextMultiNIC(t, defaultMTU, devices)
 
+					// Create endpoints and bind each to a NIC, sometimes reusing ports.
 					eps := make(map[tcpip.Endpoint]int)
-
 					pollChannel := make(chan tcpip.Endpoint)
 					for i, endpoint := range test.endpoints {
 						// Try to receive the data.
@@ -297,7 +303,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						})
 
 						var err tcpip.Error
-						ep, err := c.s.NewEndpoint(udp.ProtocolNumber, netProtoNum, &wq)
+						ep, err := c.s.NewEndpoint(udp.ProtocolNumber, protoNum, &wq)
 						if err != nil {
 							t.Fatalf("NewEndpoint failed: %s", err)
 						}
@@ -316,21 +322,24 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						}
 
 						var dstAddr tcpip.Address
-						switch netProtoNum {
+						switch protoNum {
 						case ipv4.ProtocolNumber:
 							dstAddr = testDstAddrV4
 						case ipv6.ProtocolNumber:
 							dstAddr = testDstAddrV6
 						default:
-							t.Fatalf("unexpected protocol number: %d", netProtoNum)
+							t.Fatalf("unexpected protocol number: %d", protoNum)
 						}
 						if err := ep.Bind(tcpip.FullAddress{Addr: dstAddr, Port: testDstPort}); err != nil {
 							t.Fatalf("ep.Bind(...) on endpoint %d failed: %s", i, err)
 						}
 					}
 
-					npackets := 100000
-					nports := 10000
+					// Send packets across a range of ports, checking that packets from
+					// the same source port are always demultiplexed to the same
+					// destination endpoint.
+					npackets := 10_000
+					nports := 1_000
 					if got, want := len(test.endpoints), len(wantDistribution); got != want {
 						t.Fatalf("got len(test.endpoints) = %d, want %d", got, want)
 					}
@@ -344,13 +353,13 @@ func TestBindToDeviceDistribution(t *testing.T) {
 							srcPort: testSrcPort + port,
 							dstPort: testDstPort,
 						}
-						switch netProtoNum {
+						switch protoNum {
 						case ipv4.ProtocolNumber:
 							c.sendV4Packet(payload, hdrs, device)
 						case ipv6.ProtocolNumber:
 							c.sendV6Packet(payload, hdrs, device)
 						default:
-							t.Fatalf("unexpected protocol number: %d", netProtoNum)
+							t.Fatalf("unexpected protocol number: %d", protoNum)
 						}
 
 						ep := <-pollChannel