unslop, improve the tio interface

overlay/tio/segment_other.go

@@ -8,12 +8,6 @@ func protoFromGSOType(_ uint8) (GSOProto, error) {
 	return 0, fmt.Errorf("GSO unsupported")
 }
 
-// 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, fn func(seg []byte) error) error {
 	if pkt.GSO.IsSuperpacket() {
 		return fmt.Errorf("tio: GSO superpacket on platform without segmentation support")

overlay/tio/single.go

@@ -4,9 +4,8 @@ import "io"
 
 // singleQueue adapts a legacy one-datagram-per-Read source into a Queue.
 // Read fills a private scratch buffer and returns exactly one Packet whose
-// Bytes borrow from that buffer, valid only until the next Read, per the
-// Queue contract. Single-reader like every Queue; Write is exactly as safe
-// for concurrent use as the underlying source's Write.
+// Bytes borrow from that buffer, valid only until the next Read, per the Queue contract.
+// Single-reader like every Queue; Write is exactly as safe for concurrent use as the underlying source's Write.
 type singleQueue struct {
 	rw     io.ReadWriter
 	closer io.Closer // nil: Close is a no-op (the source is shared and owned elsewhere)
@@ -14,9 +13,9 @@ type singleQueue struct {
 	ret    [1]Packet
 }
 
-// NewSingleQueue wraps a one-datagram-per-Read ReadWriteCloser (a legacy tun
-// device) into a Queue. bufSize is the per-queue read scratch size and must
-// be at least the largest datagram the source can return. Close closes rwc.
+// NewSingleQueue wraps a one-datagram-per-Read ReadWriteCloser (a legacy tun device) into a Queue.
+// bufSize is the per-queue read scratch size and must be at least the largest datagram the source can return.
+// Close closes rwc.
 func NewSingleQueue(rwc io.ReadWriteCloser, bufSize int) Queue {
 	return &singleQueue{rw: rwc, closer: rwc, buf: make([]byte, bufSize)}
 }

overlay/tio/tio.go

@@ -93,14 +93,6 @@ type CapsProvider interface {
 	Capabilities() Capabilities
 }
 
-// QueueCapabilities returns q's negotiated offload capabilities, or the zero value when q does not advertise any.
-func QueueCapabilities(q io.Writer) Capabilities {
-	if cp, ok := q.(CapsProvider); ok {
-		return cp.Capabilities()
-	}
-	return Capabilities{}
-}
-
 // GSOProto selects the L4 protocol for a GSO superpacket.
 // Determines which VIRTIO_NET_HDR_GSO_* type the writer stamps and which checksum offset
 // inside the transport header virtio NEEDS_CSUM expects.
@@ -126,9 +118,10 @@ const (
 // Every segment in pays except possibly the last is exactly the same size.
 // proto picks the L4 protocol so the writer knows which gsoType / CsumOffset to set.
 //
-// Callers should also consult CapsProvider (via SupportsGSO or QueueCapabilities)
-// for the per-protocol negotiated capability: USO may not have been negotiated even when TSO was.
+// Callers should also consult CapsProvider (via SupportsGSO) for the per-protocol negotiated capability:
+// USO may not have been negotiated even when TSO was.
 type GSOWriter interface {
+	io.Writer
 	CapsProvider
 	WriteGSO(hdr []byte, transportHdr []byte, pays [][]byte, proto GSOProto) error
 }

overlay/tio/tio_gso_linux.go

@@ -173,7 +173,7 @@ func (r *Offload) Read() ([]Packet, error) {
 			return nil, err
 		}
 		if err := r.decodeRead(n); err != nil {
-			// Drop and read again — a bad packet should not kill the reader.
+			// Drop and read again. A bad packet should not kill the reader.
 			continue
 		}
 		break