Fix checksum bench

internal/checksum_test/sum_bench_test.go

@@ -28,6 +28,6 @@ func BenchmarkGChecksum(b *testing.B) {
 	}
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		checksum.Checksum(packet[i%1000], 0)
+		checksum.ChecksumDefault(packet[i%1000], 0)
 	}
 }

internal/gtcpip/checksum/checksum.go

@@ -38,3 +38,8 @@ func Combine(a, b uint16) uint16 {
 	v := uint32(a) + uint32(b)
 	return uint16(v + v>>16)
 }
+
+func ChecksumDefault(buf []byte, initial uint16) uint16 {
+	s, _ := calculateChecksum(buf, false, initial)
+	return s
+}

internal/gtcpip/checksum/checksum_default.go

@@ -8,6 +8,5 @@ package checksum
 //
 // The initial checksum must have been computed on an even number of bytes.
 func Checksum(buf []byte, initial uint16) uint16 {
-	s, _ := calculateChecksum(buf, false, initial)
-	return s
+	return ChecksumDefault(buf, initial)
 }

internal/gtcpip/checksum/checksum_unsafe.go

@@ -1,5 +1,3 @@
-//go:build !amd64
-
 // Copyright 2023 The gVisor Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");