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

overlay/tio/segment_other.go

@@ -0,0 +1,18 @@
+//go:build !linux || android || e2e_testing
+
+package tio
+
+import "fmt"
+
+// SegmentSuperpacket invokes fn once per segment of pkt. On non-Linux
+// builds (and Android/e2e_testing) this package does not provide a Queue
+// implementation, so any caller that does construct a Packet here can only
+// be operating on non-superpacket bytes and the stub forwards them
+// directly. A non-zero GSO field is a programming error from the caller
+// and returns an explicit error rather than silently misbehaving.
+func SegmentSuperpacket(pkt Packet, scratch []byte, fn func(seg []byte) error) error {
+	if pkt.GSO.IsSuperpacket() {
+		return fmt.Errorf("tio: GSO superpacket on platform without segmentation support")
+	}
+	return fn(pkt.Bytes)
+}