better and batched tun interface

overlay/tun_tester.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/gaissmai/bart"
 	"github.com/slackhq/nebula/config"
+	"github.com/slackhq/nebula/overlay/tio"
 	"github.com/slackhq/nebula/routing"
 	"github.com/slackhq/nebula/udp"
 )
@@ -28,6 +29,8 @@ type TestTun struct {
 	closed    atomic.Bool
 	rxPackets chan []byte // Packets to receive into nebula
 	TxPackets chan []byte // Packets transmitted outside by nebula
+
+	batchRet [1][]byte
 }
 
 func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*TestTun, error) {
@@ -48,6 +51,7 @@ func newTun(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, _ bool) (*T
 		l:           l,
 		rxPackets:   make(chan []byte, 10),
 		TxPackets:   make(chan []byte, 10),
+		batchRet: [1][]byte{make([]byte, udp.MTU)},
 	}, nil
 }
 
@@ -162,7 +166,17 @@ func (t *TestTun) Close() error {
 	return nil
 }
 
-func (t *TestTun) Read(b []byte) (int, error) {
+func (t *TestTun) Read() ([][]byte, error) {
+	t.batchRet[0] = t.batchRet[0][:udp.MTU]
+	n, err := t.read(t.batchRet[0])
+	if err != nil {
+		return nil, err
+	}
+	t.batchRet[0] = t.batchRet[0][:n]
+	return t.batchRet[:], nil
+}
+
+func (t *TestTun) read(b []byte) (int, error) {
 	p, ok := <-t.rxPackets
 	if !ok {
 		return 0, os.ErrClosed
@@ -177,10 +191,14 @@ func (t *TestTun) Read(b []byte) (int, error) {
 	return n, nil
 }
 
+func (t *TestTun) Readers() []tio.Queue {
+	return []tio.Queue{t}
+}
+
 func (t *TestTun) SupportsMultiqueue() bool {
 	return false
 }
 
-func (t *TestTun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
-	return nil, fmt.Errorf("TODO: multiqueue not implemented")
+func (t *TestTun) NewMultiQueueReader() error {
+	return fmt.Errorf("TODO: multiqueue not implemented")
 }