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

* make backoff explicit API

* fix tests to use explicit backoff

* fix examples with explicit tcp

dhcp/dhcpv6/stringers.go

@@ -1,4 +1,161 @@
+// Code generated by "stringer -type=MsgType,ClientState,OptCode,StatusCode,DUIDType -linecomment -output stringers.go"; DO NOT EDIT.
+
 package dhcpv6
 
-// Code generated by "stringer -type=MsgType,ClientState,OptCode,StatusCode,DUIDType -linecomment -output stringers.go"; DO NOT EDIT.
-// Run go generate ./dhcp/dhcpv6/ to regenerate.
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[MsgSolicit-1]
+	_ = x[MsgAdvertise-2]
+	_ = x[MsgRequest-3]
+	_ = x[MsgConfirm-4]
+	_ = x[MsgRenew-5]
+	_ = x[MsgRebind-6]
+	_ = x[MsgReply-7]
+	_ = x[MsgRelease-8]
+	_ = x[MsgDecline-9]
+	_ = x[MsgReconfigure-10]
+	_ = x[MsgInformRequest-11]
+	_ = x[MsgRelayForw-12]
+	_ = x[MsgRelayRepl-13]
+}
+
+const _MsgType_name = "solicitadvertiserequestconfirmrenewrebindreplyreleasedeclinereconfigureinform-requestrelay-forwrelay-repl"
+
+var _MsgType_index = [...]uint8{0, 7, 16, 23, 30, 35, 41, 46, 53, 60, 71, 85, 95, 105}
+
+func (i MsgType) String() string {
+	i -= 1
+	if i >= MsgType(len(_MsgType_index)-1) {
+		return "MsgType(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	}
+	return _MsgType_name[_MsgType_index[i]:_MsgType_index[i+1]]
+}
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[StateInit-1]
+	_ = x[StateSoliciting-2]
+	_ = x[StateRequesting-3]
+	_ = x[StateBound-4]
+	_ = x[StateRenewing-5]
+	_ = x[StateRebinding-6]
+}
+
+const _ClientState_name = "initsolicitingrequestingboundrenewingrebinding"
+
+var _ClientState_index = [...]uint8{0, 4, 14, 24, 29, 37, 46}
+
+func (i ClientState) String() string {
+	i -= 1
+	if i >= ClientState(len(_ClientState_index)-1) {
+		return "ClientState(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	}
+	return _ClientState_name[_ClientState_index[i]:_ClientState_index[i+1]]
+}
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[OptClientID-1]
+	_ = x[OptServerID-2]
+	_ = x[OptIANA-3]
+	_ = x[OptIATA-4]
+	_ = x[OptIAAddr-5]
+	_ = x[OptORO-6]
+	_ = x[OptPreference-7]
+	_ = x[OptElapsedTime-8]
+	_ = x[OptRelayMsg-9]
+	_ = x[OptAuth-11]
+	_ = x[OptUnicast-12]
+	_ = x[OptStatusCode-13]
+	_ = x[OptRapidCommit-14]
+	_ = x[OptUserClass-15]
+	_ = x[OptVendorClass-16]
+	_ = x[OptVendorOpts-17]
+	_ = x[OptInterfaceID-18]
+	_ = x[OptReconfMsg-19]
+	_ = x[OptReconfAccept-20]
+	_ = x[OptDNSServers-23]
+	_ = x[OptDomainList-24]
+	_ = x[OptIAPD-25]
+	_ = x[OptIAPrefix-26]
+	_ = x[OptNTPServer-56]
+}
+
+const (
+	_OptCode_name_0 = "client-idserver-idia-naia-taiaaddroropreferenceelapsed-timerelay-msg"
+	_OptCode_name_1 = "authunicaststatus-coderapid-commituser-classvendor-classvendor-optsinterface-idreconf-msgreconf-accept"
+	_OptCode_name_2 = "dns-serversdomain-listia-pdiaprefix"
+	_OptCode_name_3 = "ntp-server"
+)
+
+var (
+	_OptCode_index_0 = [...]uint8{0, 9, 18, 23, 28, 34, 37, 47, 59, 68}
+	_OptCode_index_1 = [...]uint8{0, 4, 11, 22, 34, 44, 56, 67, 79, 89, 102}
+	_OptCode_index_2 = [...]uint8{0, 11, 22, 27, 35}
+)
+
+func (i OptCode) String() string {
+	switch {
+	case 1 <= i && i <= 9:
+		i -= 1
+		return _OptCode_name_0[_OptCode_index_0[i]:_OptCode_index_0[i+1]]
+	case 11 <= i && i <= 20:
+		i -= 11
+		return _OptCode_name_1[_OptCode_index_1[i]:_OptCode_index_1[i+1]]
+	case 23 <= i && i <= 26:
+		i -= 23
+		return _OptCode_name_2[_OptCode_index_2[i]:_OptCode_index_2[i+1]]
+	case i == 56:
+		return _OptCode_name_3
+	default:
+		return "OptCode(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+}
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[StatusSuccess-0]
+	_ = x[StatusUnspecFail-1]
+	_ = x[StatusNoAddrsAvail-2]
+	_ = x[StatusNoBinding-3]
+	_ = x[StatusNotOnLink-4]
+	_ = x[StatusUseMulticast-5]
+}
+
+const _StatusCode_name = "successunspec-failno-addrs-availno-bindingnot-on-linkuse-multicast"
+
+var _StatusCode_index = [...]uint8{0, 7, 18, 32, 42, 53, 66}
+
+func (i StatusCode) String() string {
+	if i >= StatusCode(len(_StatusCode_index)-1) {
+		return "StatusCode(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _StatusCode_name[_StatusCode_index[i]:_StatusCode_index[i+1]]
+}
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[DUIDTypeLLT-1]
+	_ = x[DUIDTypeEN-2]
+	_ = x[DUIDTypeLL-3]
+}
+
+const _DUIDType_name = "duid-lltduid-enduid-ll"
+
+var _DUIDType_index = [...]uint8{0, 8, 15, 22}
+
+func (i DUIDType) String() string {
+	i -= 1
+	if i >= DUIDType(len(_DUIDType_index)-1) {
+		return "DUIDType(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	}
+	return _DUIDType_name[_DUIDType_index[i]:_DUIDType_index[i+1]]
+}

errors.go

@@ -17,12 +17,13 @@ const (
 	ErrMismatch                             // mismatch
 	ErrMismatchLen                          // mismatched length
 	ErrInvalidConfig                        // invalid configuration
+	_                                       // little stitious
 	ErrInvalidField                         // invalid field
 	ErrInvalidLengthField                   // invalid length field
 	ErrExhausted                            // resource exhausted
 	ErrAlreadyRegistered                    // protocol already registered
 	ErrTruncatedFrame                       // truncated frame
-
+	ErrMissingHALConfig                     // missing HAL configuration
 	// Below are potentially good future error additions
 	// based on one or two encountered use cases, example use case included.
 	/*

examples/berkeley-listener/berkeley_server.go

@@ -210,6 +210,7 @@ func run() error {
 			RxBufSize:          mtu,
 			EstablishedTimeout: 5 * time.Second,
 			ClosingTimeout:     5 * time.Second,
+			NewBackoff:         func() lneto.BackoffStrategy { return tcpBackoff },
 		},
 	})
 
@@ -408,3 +409,15 @@ func stackBackoff(consecutiveBackoffs uint) time.Duration {
 	}
 	return 10 * time.Millisecond
 }
+
+func tcpBackoff(consecutiveBackoffs uint) time.Duration {
+	const (
+		minWait        = uint32(time.Microsecond)
+		maxWait        = 5 * uint32(time.Millisecond)
+		maxShift       = 22
+		_overflowCheck = minWait << maxShift
+	)
+	shifted := minWait << min(consecutiveBackoffs, maxShift)
+	wait := min(shifted, maxWait)
+	return time.Duration(wait)
+}

examples/httpserver/main.go

@@ -232,6 +232,7 @@ func run() (err error) {
 			RxBuf:             make([]byte, mtu),
 			TxBuf:             make([]byte, mtu),
 			TxPacketQueueSize: 3,
+			RWBackoff:         tcpBackoff,
 		})
 		err = stack.ListenTCP4(&conn, svPort)
 		if err != nil {
@@ -363,3 +364,15 @@ func stackBackoff(consecutiveBackoffs uint) time.Duration {
 	}
 	return 10 * time.Millisecond
 }
+
+func tcpBackoff(consecutiveBackoffs uint) time.Duration {
+	const (
+		minWait        = uint32(time.Microsecond)
+		maxWait        = 5 * uint32(time.Millisecond)
+		maxShift       = 22
+		_overflowCheck = minWait << maxShift
+	)
+	shifted := minWait << min(consecutiveBackoffs, maxShift)
+	wait := min(shifted, maxWait)
+	return time.Duration(wait)
+}

examples/min-working-example/main-mwe.go

@@ -102,6 +102,7 @@ func run(ctx context.Context, stack *xnet.StackAsync) error {
 			NanoTime:           nanotime,
 			EstablishedTimeout: tcpEstablishedTimeout,
 			ClosingTimeout:     tcpCloseTimeout,
+			NewBackoff:         func() lneto.BackoffStrategy { return tcpBackoff },
 		},
 	})
 
@@ -178,3 +179,15 @@ func stackBackoff(consecutiveBackoffs uint) time.Duration {
 	}
 	return 10 * time.Millisecond
 }
+
+func tcpBackoff(consecutiveBackoffs uint) time.Duration {
+	const (
+		minWait        = uint32(time.Microsecond)
+		maxWait        = 5 * uint32(time.Millisecond)
+		maxShift       = 22
+		_overflowCheck = minWait << maxShift
+	)
+	shifted := minWait << min(consecutiveBackoffs, maxShift)
+	wait := min(shifted, maxWait)
+	return time.Duration(wait)
+}

examples/xcurl/main.go

@@ -281,6 +281,7 @@ func run() (err error) {
 		RxBuf:             make([]byte, mtu),
 		TxBuf:             make([]byte, mtu),
 		TxPacketQueueSize: 3,
+		RWBackoff:         tcpBackoff,
 	})
 
 	timeHTTPCreate := timer("create HTTP GET request")
@@ -393,3 +394,14 @@ func stackBackoff(consecutiveBackoffs uint) time.Duration {
 	}
 	return 10 * time.Millisecond
 }
+func tcpBackoff(consecutiveBackoffs uint) time.Duration {
+	const (
+		minWait        = uint32(time.Microsecond)
+		maxWait        = 5 * uint32(time.Millisecond)
+		maxShift       = 22
+		_overflowCheck = minWait << maxShift
+	)
+	shifted := minWait << min(consecutiveBackoffs, maxShift)
+	wait := min(shifted, maxWait)
+	return time.Duration(wait)
+}

internal/backoff.go

@@ -1,35 +0,0 @@
-package internal
-
-import (
-	"time"
-)
-
-// BackoffConnRW implements exponential backoff suitable for TCP connection
-// read/write polling. It starts at 1us and caps at 5ms, doubling on each consecutive backoff.
-func BackoffConnRW(consecutiveBackoffs uint) {
-	const (
-		minWait        = uint32(time.Microsecond)
-		maxWait        = 5 * uint32(time.Millisecond)
-		maxShift       = 22
-		_overflowCheck = minWait << maxShift
-	)
-	shifted := minWait << min(consecutiveBackoffs, maxShift)
-	wait := min(shifted, maxWait)
-	time.Sleep(time.Duration(wait))
-}
-
-// BackoffStackProto implements exponential backoff suitable for stack-level
-// protocol processing polling. It starts at 1us and caps at 100ms, doubling on each consecutive backoff.
-func BackoffStackProto(consecutiveBackoffs uint) {
-	const (
-		minWait = uint32(time.Microsecond)
-		maxWait = 100 * uint32(time.Millisecond)
-
-		// Statically calculated numbers below.
-		maxShift       = 22
-		_overflowCheck = minWait << maxShift
-	)
-	shifted := minWait << min(consecutiveBackoffs, maxShift)
-	wait := min(shifted, maxWait)
-	time.Sleep(time.Duration(wait))
-}

internet/pcap/stringers.go

@@ -25,11 +25,12 @@ func _() {
 	_ = x[FieldClassBinaryText-14]
 	_ = x[FieldClassOperation-15]
 	_ = x[FieldClassTimestamp-16]
+	_ = x[FieldClassDNSName-17]
 }
 
-const _FieldClass_name = "undefinedsourcedestinationprotocolversiontypesizeflagsidentificationchecksumoptionspayloadtextaddressbinary-textoptimestamp"
+const _FieldClass_name = "undefinedsourcedestinationprotocolversiontypesizeflagsidentificationchecksumoptionspayloadtextaddressbinary-textoptimestampdns name"
 
-var _FieldClass_index = [...]uint8{0, 9, 15, 26, 34, 41, 45, 49, 54, 68, 76, 83, 90, 94, 101, 112, 114, 123}
+var _FieldClass_index = [...]uint8{0, 9, 15, 26, 34, 41, 45, 49, 54, 68, 76, 83, 90, 94, 101, 112, 114, 123, 131}
 
 func (i FieldClass) String() string {
 	if i >= FieldClass(len(_FieldClass_index)-1) {

internet/stackbasic_test.go

@@ -4,6 +4,7 @@ import (
 	"math/rand"
 	"net/netip"
 	"testing"
+	"time"
 
 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/tcp"
@@ -146,6 +147,7 @@ func setupClientServer6(t *testing.T, rng *rand.Rand, client, server *StackIPv6,
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 3,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -154,6 +156,7 @@ func setupClientServer6(t *testing.T, rng *rand.Rand, client, server *StackIPv6,
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 3,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -187,6 +190,7 @@ func setupClientServer(t *testing.T, rng *rand.Rand, client, server *StackIPv4,
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 3,
 		Logger:            nil,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -196,6 +200,7 @@ func setupClientServer(t *testing.T, rng *rand.Rand, client, server *StackIPv4,
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 3,
 		Logger:            nil,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -219,3 +224,7 @@ func setupClientServer(t *testing.T, rng *rand.Rand, client, server *StackIPv4,
 		t.Fatal(err)
 	}
 }
+
+func backoffYield(consecutiveBackoffs uint) time.Duration {
+	return lneto.BackoffFlagGosched
+}

internet/tcplistener_test.go

@@ -616,6 +616,7 @@ func setupClient(t *testing.T, client *StackIPv4, conn *tcp.Conn, serverAddr net
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 3,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -649,6 +650,7 @@ func newMockTCPPool(n, queuesize, bufsize int) *mockTCPPool {
 			RxBuf:             make([]byte, bufsize),
 			TxBuf:             make([]byte, bufsize),
 			TxPacketQueueSize: queuesize,
+			RWBackoff:         backoffYield,
 		})
 		if err != nil {
 			panic(err)

ipv6/icmpv6/stringers.go

@@ -48,7 +48,6 @@ func (i Type) String() string {
 		return "Type(" + strconv.FormatInt(int64(i), 10) + ")"
 	}
 }
-
 func _() {
 	// An "invalid array index" compiler error signifies that the constant values have changed.
 	// Re-run the stringer command to generate them again.
@@ -72,7 +71,6 @@ func (i CodeDestinationUnreachable) String() string {
 	}
 	return _CodeDestinationUnreachable_name[_CodeDestinationUnreachable_index[i]:_CodeDestinationUnreachable_index[i+1]]
 }
-
 func _() {
 	// An "invalid array index" compiler error signifies that the constant values have changed.
 	// Re-run the stringer command to generate them again.

stringers.go

@@ -206,21 +206,33 @@ func _() {
 	_ = x[ErrMismatch-10]
 	_ = x[ErrMismatchLen-11]
 	_ = x[ErrInvalidConfig-12]
-	_ = x[ErrInvalidField-13]
-	_ = x[ErrInvalidLengthField-14]
-	_ = x[ErrExhausted-15]
-	_ = x[ErrAlreadyRegistered-16]
-	_ = x[ErrTruncatedFrame-17]
+	_ = x[ErrInvalidField-14]
+	_ = x[ErrInvalidLengthField-15]
+	_ = x[ErrExhausted-16]
+	_ = x[ErrAlreadyRegistered-17]
+	_ = x[ErrTruncatedFrame-18]
+	_ = x[ErrMissingHALConfig-19]
 }
 
-const _errGeneric_name = "lneto-bug(use build tag \"debugheaplog\")packet droppedincorrect checksumzero source(port/addr)zero destination(port/addr)short bufferbuffer fullinvalid addressunsupportedmismatchmismatched lengthinvalid configurationinvalid fieldinvalid length fieldresource exhaustedprotocol already registeredtruncated frame"
+const (
+	_errGeneric_name_0 = "lneto-bug(use build tag \"debugheaplog\")packet droppedincorrect checksumzero source(port/addr)zero destination(port/addr)short bufferbuffer fullinvalid addressunsupportedmismatchmismatched lengthinvalid configuration"
+	_errGeneric_name_1 = "invalid fieldinvalid length fieldresource exhaustedprotocol already registeredtruncated framemissing HAL configuration"
+)
 
-var _errGeneric_index = [...]uint16{0, 39, 53, 71, 93, 120, 132, 143, 158, 169, 177, 194, 215, 228, 248, 266, 293, 308}
+var (
+	_errGeneric_index_0 = [...]uint8{0, 39, 53, 71, 93, 120, 132, 143, 158, 169, 177, 194, 215}
+	_errGeneric_index_1 = [...]uint8{0, 13, 33, 51, 78, 93, 118}
+)
 
 func (i errGeneric) String() string {
-	i -= 1
-	if i >= errGeneric(len(_errGeneric_index)-1) {
-		return "errGeneric(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	switch {
+	case 1 <= i && i <= 12:
+		i -= 1
+		return _errGeneric_name_0[_errGeneric_index_0[i]:_errGeneric_index_0[i+1]]
+	case 14 <= i && i <= 19:
+		i -= 14
+		return _errGeneric_name_1[_errGeneric_index_1[i]:_errGeneric_index_1[i+1]]
+	default:
+		return "errGeneric(" + strconv.FormatInt(int64(i), 10) + ")"
 	}
-	return _errGeneric_name[_errGeneric_index[i]:_errGeneric_index[i+1]]
 }

tcp/conn.go

@@ -62,6 +62,9 @@ type ConnConfig struct {
 }
 
 func (conn *Conn) Configure(config ConnConfig) (err error) {
+	if config.RWBackoff == nil {
+		return lneto.ErrMissingHALConfig
+	}
 	conn.mu.Lock()
 	defer conn.mu.Unlock()
 	err = conn.h.SetBuffers(config.TxBuf, config.RxBuf, config.TxPacketQueueSize)
@@ -483,9 +486,5 @@ func (conn *Conn) ConnectionID() *uint64 {
 }
 
 func (conn *Conn) backoff(consecutiveBackoffs uint) {
-	if conn._backoff != nil {
-		conn._backoff.Do(consecutiveBackoffs)
-	} else {
-		internal.BackoffConnRW(consecutiveBackoffs)
-	}
+	conn._backoff.Do(consecutiveBackoffs)
 }

tcp/conn_test.go

@@ -5,6 +5,8 @@ import (
 	"net/netip"
 	"testing"
 	"time"
+
+	"github.com/soypat/lneto"
 )
 
 func newConfiguredConn(t *testing.T) *Conn {
@@ -14,6 +16,7 @@ func newConfiguredConn(t *testing.T) *Conn {
 		RxBuf:             make([]byte, 512),
 		TxBuf:             make([]byte, 512),
 		TxPacketQueueSize: 4,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -121,6 +124,7 @@ func TestConn_Configure_Twice(t *testing.T) {
 		RxBuf:             make([]byte, 1024),
 		TxBuf:             make([]byte, 1024),
 		TxPacketQueueSize: 8,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatalf("reconfigure should succeed: %v", err)
@@ -160,3 +164,7 @@ func TestConn_ImplementsNetConn(t *testing.T) {
 	} = conn
 	_ = net.ErrClosed
 }
+
+func backoffYield(consecutiveBackoffs uint) time.Duration {
+	return lneto.BackoffFlagGosched
+}

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) {

x/xnet/stack-blocking.go

@@ -8,7 +8,6 @@ import (
 
 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/dhcp/dhcpv4"
-	"github.com/soypat/lneto/internal"
 	"github.com/soypat/lneto/tcp"
 )
 
@@ -21,6 +20,9 @@ var (
 )
 
 func (s *StackAsync) StackBlocking(stackProtoBackoff lneto.BackoffStrategy) StackBlocking {
+	if stackProtoBackoff == nil {
+		panic("nil backoff to StackBlocking")
+	}
 	return StackBlocking{
 		async:    s,
 		_backoff: stackProtoBackoff,
@@ -206,9 +208,5 @@ func (s StackBlocking) backoff(consecutiveBackoffs uint) {
 }
 
 func backoff(bo lneto.BackoffStrategy, consecutiveBackoffs uint) {
-	if bo != nil {
-		bo.Do(consecutiveBackoffs)
-	} else {
-		internal.BackoffStackProto(consecutiveBackoffs)
-	}
+	bo.Do(consecutiveBackoffs)
 }

x/xnet/stack-go.go

@@ -25,6 +25,9 @@ type StackGoConfig struct {
 }
 
 func (s *StackAsync) StackGo(stackProtoBackoff lneto.BackoffStrategy, cfg StackGoConfig) StackGo {
+	if stackProtoBackoff == nil || cfg.ListenerPoolConfig.NewBackoff == nil {
+		panic("nil backoff to StackGo")
+	}
 	return s.StackBlocking(stackProtoBackoff).StackGo(cfg)
 }
 
@@ -142,9 +145,11 @@ func (s StackGo) SocketNetip(ctx context.Context, network string, family, sotype
 			var conn tcp.Conn
 			// DIAL TCP: active connection a.k.a TCP Client branch.
 			err = conn.Configure(tcp.ConnConfig{
+				// TODO(pato): Eventually add UDP configuration. we use TCP for now for simplicity's sake.
 				TxBuf:             make([]byte, s.plcfg.TxBufSize),
 				RxBuf:             make([]byte, s.plcfg.RxBufSize),
 				TxPacketQueueSize: s.plcfg.QueueSize,
+				RWBackoff:         s.plcfg.NewBackoff(),
 			})
 			if err != nil {
 				return nil, err

x/xnet/stack-retrying.go

@@ -10,6 +10,9 @@ import (
 )
 
 func (s *StackAsync) StackRetrying(stackProtoBackoff lneto.BackoffStrategy) StackRetrying {
+	if stackProtoBackoff == nil {
+		panic("nil backoff to StackRetrying")
+	}
 	return StackRetrying{
 		block: s.StackBlocking(stackProtoBackoff),
 	}

x/xnet/stack6_test.go

@@ -70,6 +70,7 @@ func newUDPConn6(t testing.TB) *udp.Conn {
 		TxBuf:       make([]byte, bufSize),
 		RxQueueSize: 4,
 		TxQueueSize: 4,
+		RWBackoff:   backoffYield,
 	}); err != nil {
 		t.Fatal("UDP Configure:", err)
 	}
@@ -85,6 +86,7 @@ func newTCPConn6(t testing.TB) *tcp.Conn {
 		RxBuf:             make([]byte, bufSize),
 		TxBuf:             make([]byte, bufSize),
 		TxPacketQueueSize: 4,
+		RWBackoff:         backoffYield,
 	}); err != nil {
 		t.Fatal("TCP Configure:", err)
 	}

x/xnet/tcppool.go

@@ -53,7 +53,7 @@ type TCPPoolConfig struct {
 	ClosingTimeout time.Duration
 	// NewUserData is used to create user data used for each individual TCP connection and returned on GetTCP.
 	NewUserData func() any
-	// NewBackoff returns the backoff to use for every newly configured TCP connection.
+	// NewBackoff returns the backoff to use for every newly configured TCP connection. Must be non-nil.
 	// This should always return a static(non-method) function unless you know what you are doing.
 	NewBackoff func() lneto.BackoffStrategy
 }
@@ -61,6 +61,8 @@ type TCPPoolConfig struct {
 func NewTCPPool(cfg TCPPoolConfig) (*TCPPool, error) {
 	if cfg.EstablishedTimeout <= 0 || cfg.ClosingTimeout <= 0 {
 		return nil, lneto.ErrInvalidConfig
+	} else if cfg.NewBackoff == nil {
+		return nil, lneto.ErrMissingHALConfig
 	}
 	n := int(cfg.PoolSize)
 	pool := &TCPPool{
@@ -84,9 +86,7 @@ func NewTCPPool(cfg TCPPoolConfig) (*TCPPool, error) {
 			TxBuf:             bufSpace[txOff : txOff+cfg.TxBufSize],
 			TxPacketQueueSize: cfg.QueueSize,
 			Logger:            cfg.ConnLogger,
-		}
-		if cfg.NewBackoff != nil {
-			conncfg.RWBackoff = cfg.NewBackoff()
+			RWBackoff:         cfg.NewBackoff(),
 		}
 		err := pool.conns[i].Configure(conncfg)
 		if err != nil {

x/xnet/xnet_concurrent_test.go

@@ -53,6 +53,7 @@ func TestTCPListener_ConcurrentEcho(t *testing.T) {
 		RxBufSize:          512,
 		EstablishedTimeout: 5 * time.Second,
 		ClosingTimeout:     5 * time.Second,
+		NewBackoff:         func() lneto.BackoffStrategy { return backoffYield },
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -96,6 +97,7 @@ func TestTCPListener_ConcurrentEcho(t *testing.T) {
 			RxBuf:             connBufs[bufOff : bufOff+tcpBufSize],
 			TxBuf:             connBufs[bufOff+tcpBufSize : bufOff+2*tcpBufSize],
 			TxPacketQueueSize: 4,
+			RWBackoff:         backoffYield,
 		})
 		if err != nil {
 			t.Fatalf("client %d conn configure: %v", i, err)
@@ -327,7 +329,7 @@ func testCloseTransmitsPending(tst *tester, s1, s2 *StackAsync, c1, c2 *tcp.Conn
 		RxBuf:             nil,
 		TxBuf:             make([]byte, tx1Buf),
 		TxPacketQueueSize: queueSize,
-		RWBackoff:         backoffGosched,
+		RWBackoff:         backoffYield,
 		Logger:            logger,
 	})
 	if err != nil {
@@ -431,7 +433,3 @@ func testCloseTransmitsPending(tst *tester, s1, s2 *StackAsync, c1, c2 *tcp.Conn
 	}
 
 }
-
-func backoffGosched(consecutiveBackoffs uint) (sleep time.Duration) {
-	return lneto.BackoffFlagGosched
-}

x/xnet/xnet_fuzz_test.go

@@ -318,6 +318,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 1 + int(uint16(seed1)%10),
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -326,6 +327,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
 		TxPacketQueueSize: 1 + int(uint16(seed2)%10),
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -335,6 +337,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 		TxBuf:       make([]byte, bufsize),
 		RxQueueSize: int(1 + uint16(seed1>>32)%10),
 		TxQueueSize: int(1 + uint16(seed1>>32)%10),
+		RWBackoff:   backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -344,6 +347,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 		TxBuf:       make([]byte, bufsize),
 		RxQueueSize: int(1 + uint16(seed2>>32)%10),
 		TxQueueSize: int(1 + uint16(seed2>>32)%10),
+		RWBackoff:   backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)

x/xnet/xnet_listener_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/ethernet"
 	"github.com/soypat/lneto/tcp"
 )
@@ -49,6 +50,7 @@ func TestStackAsyncListener_SingleConnection(t *testing.T) {
 		RxBuf:             make([]byte, MTU),
 		TxBuf:             make([]byte, MTU),
 		TxPacketQueueSize: 4,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -62,6 +64,7 @@ func TestStackAsyncListener_SingleConnection(t *testing.T) {
 		RxBufSize:          MTU,
 		EstablishedTimeout: 10e9,
 		ClosingTimeout:     10e9,
+		NewBackoff:         func() lneto.BackoffStrategy { return backoffYield },
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -150,6 +153,7 @@ func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
 		RxBufSize:          bufsize,
 		EstablishedTimeout: 10e9,
 		ClosingTimeout:     10e9,
+		NewBackoff:         func() lneto.BackoffStrategy { return backoffYield },
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -188,6 +192,7 @@ func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
 			RxBuf:             make([]byte, bufsize),
 			TxBuf:             make([]byte, bufsize),
 			TxPacketQueueSize: 4,
+			RWBackoff:         backoffYield,
 		})
 		if err != nil {
 			t.Fatal(err)
@@ -239,6 +244,7 @@ func TestListener_Close(t *testing.T) {
 		RxBufSize:          512,
 		EstablishedTimeout: 10e9,
 		ClosingTimeout:     10e9,
+		NewBackoff:         func() lneto.BackoffStrategy { return backoffYield },
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -278,6 +284,7 @@ func TestListener_ResetAfterClose(t *testing.T) {
 		RxBufSize:          512,
 		EstablishedTimeout: 10e9,
 		ClosingTimeout:     10e9,
+		NewBackoff:         func() lneto.BackoffStrategy { return backoffYield },
 	})
 	if err != nil {
 		t.Fatal(err)

x/xnet/xnet_subnettable_test.go

@@ -5,6 +5,7 @@ import (
 	"net/netip"
 	"testing"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/ethernet"
 	"github.com/soypat/lneto/ipv4"
 	"github.com/soypat/lneto/tcp"
@@ -73,6 +74,7 @@ func TestStackAsync_ListenerSynAckAddressedToClient(t *testing.T) {
 		RxBufSize:          mtu,
 		EstablishedTimeout: 10e9,
 		ClosingTimeout:     10e9,
+		NewBackoff:         func() lneto.BackoffStrategy { return backoffYield },
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -104,6 +106,7 @@ func TestStackAsync_ListenerSynAckAddressedToClient(t *testing.T) {
 	if err = clConn.Configure(tcp.ConnConfig{
 		RxBuf: make([]byte, mtu), TxBuf: make([]byte, mtu),
 		TxPacketQueueSize: 4,
+		RWBackoff:         backoffYield,
 	}); err != nil {
 		t.Fatal(err)
 	}

x/xnet/xnet_test.go

@@ -208,6 +208,7 @@ func newTCPStacks(t testing.TB, randSeed int64, mtu int) (s1, s2 *StackAsync, c1
 		RxBuf:             buf[:mtu],
 		TxBuf:             buf[mtu : mtu*2],
 		TxPacketQueueSize: 4,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -216,6 +217,7 @@ func newTCPStacks(t testing.TB, randSeed int64, mtu int) (s1, s2 *StackAsync, c1
 		RxBuf:             buf[2*mtu : 3*mtu],
 		TxBuf:             buf[3*mtu : 4*mtu],
 		TxPacketQueueSize: 4,
+		RWBackoff:         backoffYield,
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -1045,3 +1047,7 @@ func getTCPFrame(etherFrame []byte) (tcp.Frame, bool) {
 	}
 	return tfrm, true
 }
+
+func backoffYield(consecutiveBackoffs uint) time.Duration {
+	return lneto.BackoffFlagGosched
+}

x/xnet/xnet_udppktconn_test.go

@@ -60,6 +60,7 @@ func TestStackAsyncRegisterListenerUDP_ReceiveData(t *testing.T) {
 	if err := pc.Configure(udp.PacketConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("pc Configure:", err)
 	}
@@ -74,6 +75,7 @@ func TestStackAsyncRegisterListenerUDP_ReceiveData(t *testing.T) {
 	if err := conn.Configure(udp.ConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("conn Configure:", err)
 	}
@@ -119,6 +121,7 @@ func TestStackAsyncRegisterListenerUDP_ReplyToClient(t *testing.T) {
 	if err := pc.Configure(udp.PacketConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("pc Configure:", err)
 	}
@@ -133,6 +136,7 @@ func TestStackAsyncRegisterListenerUDP_ReplyToClient(t *testing.T) {
 	if err := conn.Configure(udp.ConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("conn Configure:", err)
 	}
@@ -228,6 +232,7 @@ func TestStackAsyncRegisterListenerUDP_MultiSource(t *testing.T) {
 	if err := pc.Configure(udp.PacketConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("pc Configure:", err)
 	}
@@ -243,6 +248,7 @@ func TestStackAsyncRegisterListenerUDP_MultiSource(t *testing.T) {
 	if err := conn1.Configure(udp.ConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("conn1 Configure:", err)
 	}
@@ -260,6 +266,7 @@ func TestStackAsyncRegisterListenerUDP_MultiSource(t *testing.T) {
 	if err := conn2.Configure(udp.ConnConfig{
 		RxBuf: make([]byte, testUDPBufSize), TxBuf: make([]byte, testUDPBufSize),
 		RxQueueSize: testUDPQueueSize, TxQueueSize: testUDPQueueSize,
+		RWBackoff: backoffYield,
 	}); err != nil {
 		t.Fatal("conn2 Configure:", err)
 	}