iperf benchmark: Use container networking links rather than default bridge.

This fixes `iperf` getting stuck on some versions of Docker, and mirrors the
way other multi-container tests do networking.

PiperOrigin-RevId: 468049041

test/benchmarks/network/iperf_test.go

@@ -15,8 +15,10 @@ package network
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"testing"
+	"time"
 
 	"gvisor.dev/gvisor/pkg/test/dockerutil"
 	"gvisor.dev/gvisor/pkg/test/testutil"
@@ -80,20 +82,8 @@ func BenchmarkIperf(b *testing.B) {
 			}, "iperf", "-s"); err != nil {
 				b.Fatalf("failed to start server with: %v", err)
 			}
-
-			ip, err := serverMachine.IPAddress()
-			if err != nil {
-				b.Fatalf("failed to find server ip: %v", err)
-			}
-
-			servingPort, err := server.FindPort(ctx, port)
-			if err != nil {
-				b.Fatalf("failed to find port %d: %v", port, err)
-			}
-
-			// Make sure the server is up and serving before we run.
-			if err := harness.WaitUntilServing(ctx, clientMachine, ip, servingPort); err != nil {
-				b.Fatalf("failed to wait for server: %v", err)
+			if out, err := server.WaitForOutput(ctx, fmt.Sprintf("Server listening on TCP port %d", port), 10*time.Second); err != nil {
+				b.Fatalf("failed to wait for iperf server: %v %s", err, out)
 			}
 
 			iperf := tools.Iperf{
@@ -104,7 +94,8 @@ func BenchmarkIperf(b *testing.B) {
 			b.ResetTimer()
 			out, err := client.Run(ctx, dockerutil.RunOpts{
 				Image: "benchmarks/iperf",
-			}, iperf.MakeCmd(ip, servingPort)...)
+				Links: []string{server.MakeLink("iperfsrv")},
+			}, iperf.MakeCmd("iperfsrv", port)...)
 			if err != nil {
 				b.Fatalf("failed to run client: %v", err)
 			}

test/benchmarks/tools/iperf.go

@@ -16,7 +16,6 @@ package tools
 
 import (
 	"fmt"
-	"net"
 	"regexp"
 	"strconv"
 	"testing"
@@ -30,14 +29,14 @@ type Iperf struct {
 }
 
 // MakeCmd returns a iperf client command.
-func (i *Iperf) MakeCmd(ip net.IP, port int) []string {
+func (i *Iperf) MakeCmd(host string, port int) []string {
 	return []string{
 		"iperf",
 		"--format", "K", // Output in KBytes.
 		"--realtime",                       // Measured in realtime.
 		"--num", fmt.Sprintf("%dK", i.Num), // Number of bytes to send in KB.
 		"--length", fmt.Sprintf("%d", length),
-		"--client", ip.String(),
+		"--client", host,
 		"--port", fmt.Sprintf("%d", port),
 	}
 }