GSO/GRO offloads, with TCP+ECN and UDP support

overlay/tio/segment_bench_test.go

@@ -0,0 +1,65 @@
+//go:build linux && !android && !e2e_testing
+
+package tio
+
+import "testing"
+
+// fakeBatch stands in for batch.TxBatcher inside the bench — same shape
+// of pointer-capturing closure that sendInsideMessage builds.
+type fakeBatch struct{ buf [65536]byte }
+
+func (b *fakeBatch) Reserve(sz int) []byte { return b.buf[:sz] }
+func (b *fakeBatch) Commit([]byte)         {}
+
+type fakeHostInfo struct {
+	remoteIndexId uint32
+	counter       uint64
+}
+type fakeIface struct {
+	rebindCount uint8
+	hi          *fakeHostInfo
+}
+
+// BenchmarkSegmentSuperpacketAllocsTSO measures allocation per
+// SegmentSuperpacket call when a closure captures pointer-bearing
+// receivers — the realistic shape of sendInsideMessage's closure.
+func BenchmarkSegmentSuperpacketAllocsTSO(b *testing.B) {
+	const mss = 1400
+	const numSeg = 32
+	pkt := buildTSOv6(mss*numSeg, mss)
+	gso := GSOInfo{
+		Size:      mss,
+		HdrLen:    60, // 40 (IPv6) + 20 (TCP)
+		CsumStart: 40,
+		Proto:     GSOProtoTCP,
+	}
+	p := Packet{Bytes: pkt, GSO: gso}
+
+	hi := &fakeHostInfo{remoteIndexId: 0xdeadbeef}
+	f := &fakeIface{rebindCount: 7, hi: hi}
+	fb := &fakeBatch{}
+
+	// SegmentSuperpacket consumes pkt destructively; refresh from a master
+	// copy each iter (matches the production pattern where every TUN read
+	// hands the segmenter a fresh kernel-supplied buffer).
+	master := append([]byte(nil), pkt...)
+	work := make([]byte, len(pkt))
+	p.Bytes = work
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		copy(work, master)
+		err := SegmentSuperpacket(p, func(seg []byte) error {
+			out := fb.Reserve(16 + len(seg) + 16)
+			out[0] = byte(f.rebindCount)
+			out[1] = byte(hi.counter)
+			hi.counter++
+			fb.Commit(out)
+			return nil
+		})
+		if err != nil {
+			b.Fatalf("SegmentSuperpacket: %v", err)
+		}
+	}
+}