lneto rework: Require explicit BackoffStrategy in all APIs (#116)

* make backoff explicit API

* fix tests to use explicit backoff

* fix examples with explicit tcp

udp/conn.go

@@ -48,6 +48,9 @@ type ConnConfig struct {
 // Configure initializes the connection with the given buffer and queue configuration.
 // Must be called before [Conn.Open]. Calling Configure on an active connection aborts it.
 func (conn *Conn) Configure(cfg ConnConfig) error {
+	if cfg.RWBackoff == nil {
+		return lneto.ErrMissingHALConfig
+	}
 	conn.mu.Lock()
 	defer conn.mu.Unlock()
 	conn.abort()
@@ -302,11 +305,7 @@ func (conn *Conn) FreeInput() int {
 }
 
 func (conn *Conn) backoff(consecutiveBackoffs uint) {
-	if conn._backoff != nil {
-		conn._backoff.Do(consecutiveBackoffs)
-	} else {
-		internal.BackoffConnRW(consecutiveBackoffs)
-	}
+	conn._backoff.Do(consecutiveBackoffs)
 }
 
 func (conn *Conn) lockPipeConnID() (uint64, error) {

udp/conn_test.go

@@ -4,7 +4,9 @@ import (
 	"encoding/binary"
 	"net/netip"
 	"testing"
+	"time"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/internal"
 )
 
@@ -26,6 +28,7 @@ func newTestConn(t *testing.T) *Conn {
 		TxBuf:       make([]byte, 256),
 		RxQueueSize: 4,
 		TxQueueSize: 4,
+		RWBackoff:   backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -239,3 +242,7 @@ func TestConn_FrameOffset(t *testing.T) {
 		t.Fatalf("got %q, want %q", string(buf[:n]), "hi")
 	}
 }
+
+func backoffYield(backoffs uint) time.Duration {
+	return lneto.BackoffFlagGosched
+}

udp/packetconn.go

@@ -8,7 +8,6 @@ import (
 	"time"
 
 	"github.com/soypat/lneto"
-	"github.com/soypat/lneto/internal"
 )
 
 // lnetopacketconn is the lneto interpretation of
@@ -53,6 +52,9 @@ type PacketConnConfig struct {
 // Configure initializes the PacketConn with the given buffer and queue configuration.
 // Must be called before [PacketConn.Open]. Calling Configure on an active connection aborts it.
 func (pc *PacketConn) Configure(cfg PacketConnConfig) error {
+	if cfg.RWBackoff == nil {
+		return lneto.ErrMissingHALConfig
+	}
 	pc.mu.Lock()
 	defer pc.mu.Unlock()
 	pc.abort()
@@ -243,11 +245,7 @@ func (pc *PacketConn) deadlineExceeded(deadline *time.Time) bool {
 }
 
 func (pc *PacketConn) backoff(n uint) {
-	if pc._backoff != nil {
-		pc._backoff.Do(n)
-	} else {
-		internal.BackoffConnRW(n)
-	}
+	pc._backoff.Do(n)
 }
 
 func (pc *PacketConn) lockConnID() (uint64, error) {