Error rewrites (#43)

* pcap: reuse Frame memory

* slog: reduce heap allocations of addresses; also prevent heap alloc of dhcp options in pcap

* dns: heapless improvement; add StackAsync buffer for more heapless operation; start thinking of errors

* errors: begin standardise errors in lneto

* errors: finish standardization of errors

* fix merge issues

* add more lneto errors to rest of package

* format errors.go

tcp/txqueue.go

@@ -1,20 +1,12 @@
 package tcp
 
 import (
-	"errors"
+	"log/slog"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/internal"
 )
 
-var (
-	errPacketQueueFull  = errors.New("packet queue full")
-	errQueuedPacketsLEZ = errors.New("queued packets <=0")
-	errInvalidBufSize   = errors.New("invalid buffer size")
-	errSeqLessThanLast  = errors.New("sequence number less than last sequence number")
-	errNoPacketToAck    = errors.New("no packet to ack")
-	errAckUnsent        = errors.New("ack of unsent packet")
-)
-
 const (
 	// this must be at least 2 for buffer to work.
 	minBufferSize = 2
@@ -60,9 +52,9 @@ type ringidx struct {
 func (rtx *ringTx) Reset(buf []byte, maxqueuedPackets int, iss Value) error {
 	buf = buf[:len(buf):len(buf)] // safely omit capacity section.
 	if maxqueuedPackets <= 0 {
-		return errQueuedPacketsLEZ
+		return lneto.ErrInvalidConfig
 	} else if len(buf) < minBufferSize || len(buf) < maxqueuedPackets {
-		return errInvalidBufSize
+		return lneto.ErrShortBuffer
 	}
 
 	*rtx = ringTx{
@@ -127,11 +119,12 @@ func (rtx *ringTx) Write(b []byte) (n int, err error) {
 func (rtx *ringTx) MakePacket(b []byte, currentSeq Value) (int, error) {
 	free := rtx.slist.Free()
 	if free == 0 {
-		return 0, errPacketQueueFull
+		return 0, lneto.ErrBufferFull
 	}
 	endSeq, ok := rtx.sentEndSeq()
 	if ok && currentSeq.LessThan(endSeq) {
-		return 0, errSeqLessThanLast
+		internal.LogAttrs(nil, slog.LevelError, "txqueue:seq<endseq", slog.Uint64("seq", uint64(currentSeq)), slog.Uint64("endseq", uint64(endSeq)))
+		return 0, lneto.ErrBug
 	}
 	// Reading unsent ring consumes unsent and converts it to "sent".
 	unsent, _ := rtx.unsentRing()
@@ -321,11 +314,11 @@ func (sl *sentlist) AddPacket(datalen, off, bufsize int, seq Value) *ringidx {
 func (sl *sentlist) RecvAck(ack Value, bufsize int) error {
 	newest := sl.Newest()
 	if newest == nil {
-		return errNoPacketToAck
+		return lneto.ErrPacketDrop
 	}
 	endseq := newest.endSeq()
 	if endseq.LessThan(ack) {
-		return errAckUnsent
+		return lneto.ErrPacketDrop
 	}
 	// Mark fully acked.
 	for i := 0; i < len(sl.pkts); i++ {