Make GenerateRandomPayload available to all tests

Moved the function for generating a payload of random byets of a specified
length into the testbench package so that it's availbale for all tests to use.

Added a test case to the IPv4 ID uniqueness test which uses a payload length
of 512 bytes. This test case passes for gVisor currently, whereas the test case
with a small payload of 11 bytes fails because gVisor only assigns the ID field
if the IP payload is sufficiently large.

PiperOrigin-RevId: 316185097

1 files changed, 13 insertions, 0 deletions

diff --git a/test/packetimpact/testbench/testbench.go b/test/packetimpact/testbench/testbench.go
index 82eda6565..d64f32a5b 100644
--- a/test/packetimpact/testbench/testbench.go
+++ b/test/packetimpact/testbench/testbench.go
@@ -17,8 +17,10 @@ package testbench
 import (
 	"flag"
 	"fmt"
+	"math/rand"
 	"net"
 	"os/exec"
+	"testing"
 	"time"
 
 	"gvisor.dev/gvisor/test/packetimpact/netdevs"
@@ -91,3 +93,14 @@ func genPseudoFlags() error {
 
 	return nil
 }
+
+// GenerateRandomPayload generates a random byte slice of the specified length,
+// causing a fatal test failure if it is unable to do so.
+func GenerateRandomPayload(t *testing.T, n int) []byte {
+	t.Helper()
+	buf := make([]byte, n)
+	if _, err := rand.Read(buf); err != nil {
+		t.Fatalf("rand.Read(buf) failed: %s", err)
+	}
+	return buf
+}