Further reduce heap allocs (#56)

* work on tracking more heap allocations down * write own heapless IP AppendFormatAddr functions * remove potential Error method allocations * more logging
2026-08-21 15:09:05 +00:00 · 2026-03-15 00:11:59 +01:00
parent de2e756628
commit 376e1a0b4f
8 changed files with 245 additions and 23 deletions
@@ -172,31 +172,31 @@ func (pc *PacketBreakdown) CaptureIPv6(dst []Frame, pkt []byte, bitOffset int) (
 	debuglog("pcap:ipv6:reclaimed")
 	proto := ifrm6.NextHeader()
 	end := bitOffset + 40*octet
-	var protoErrs []error
+	var protoErr error
 	var crc lneto.CRC791
 	ifrm6.CRCWritePseudo(&crc)
 	switch proto {
 	case lneto.IPProtoTCP:
 		if crc.PayloadSum16(ifrm6.Payload()) != 0 {
-			protoErrs = append(protoErrs, lneto.ErrBadCRC)
+			protoErr = lneto.ErrBadCRC
 		}
 	case lneto.IPProtoUDP, lneto.IPProtoUDPLite:
 		ufrm, err := udp.NewFrame(ifrm6.Payload())
 		if err != nil {
-			protoErrs = append(protoErrs, err)
+			protoErr = err
 			break
 		}
 		ufrm.ValidateSize(pc.validator())
 		if err = pc.validator().ErrPop(); err != nil {
-			protoErrs = append(protoErrs, err)
+			protoErr = err
 			break
 		}
 		frameLen := ufrm.Length()
 		if crc.PayloadSum16(ufrm.RawData()[:frameLen]) != 0 {
-			protoErrs = append(protoErrs, lneto.ErrBadCRC)
+			protoErr = lneto.ErrBadCRC
 		}
 	}
-	return pc.captureIPProto(proto, dst, pkt, end, protoErrs...)
+	return pc.captureIPProto(proto, dst, pkt, end, protoErr)
 }

 func (pc *PacketBreakdown) CaptureIPv4(dst []Frame, pkt []byte, bitOffset int) ([]Frame, error) {
@@ -231,8 +231,9 @@ func (pc *PacketBreakdown) CaptureIPv4(dst []Frame, pkt []byte, bitOffset int) (
 	debuglog("pcap:ipv4:crc-done")
 	proto := ifrm4.Protocol()
 	end := bitOffset + octet*ifrm4.HeaderLength()
-	var protoErrs []error
 	var crc lneto.CRC791
+
+	var ipProtoErr error
 	payload := ifrm4.Payload()
 	switch proto {
 	case lneto.IPProtoTCP:
@@ -244,7 +245,7 @@ func (pc *PacketBreakdown) CaptureIPv4(dst []Frame, pkt []byte, bitOffset int) (
 			}
 			ifrm4.CRCWriteTCPPseudo(&crc)
 			if crc.PayloadSum16(payload) != 0 {
-				protoErrs = append(protoErrs, lneto.ErrBadCRC)
+				ipProtoErr = lneto.ErrBadCRC
 			}
 		}
 	case lneto.IPProtoUDP:
@@ -258,7 +259,7 @@ func (pc *PacketBreakdown) CaptureIPv4(dst []Frame, pkt []byte, bitOffset int) (
 				frameLen := ufrm.Length()
 				ifrm4.CRCWriteUDPPseudo(&crc, frameLen)
 				if crc.PayloadSum16(ufrm.RawData()[:frameLen]) != 0 {
-					protoErrs = append(protoErrs, lneto.ErrBadCRC)
+					ipProtoErr = lneto.ErrBadCRC
 				}
 			}
 		}
@@ -266,15 +267,15 @@ func (pc *PacketBreakdown) CaptureIPv4(dst []Frame, pkt []byte, bitOffset int) (
 		_, err := icmpv4.NewFrame(payload)
 		if err == nil {
 			if crc.PayloadSum16(payload) != 0 {
-				protoErrs = append(protoErrs, lneto.ErrBadCRC)
+				ipProtoErr = lneto.ErrBadCRC
 			}
 		}
 	}
 	debuglog("pcap:ipv4:proto-crc-done")
-	return pc.captureIPProto(proto, dst, pkt, end, protoErrs...)
+	return pc.captureIPProto(proto, dst, pkt, end, ipProtoErr)
 }

-func (pc *PacketBreakdown) captureIPProto(proto lneto.IPProto, dst []Frame, pkt []byte, bitOffset int, ipProtoErrs ...error) (_ []Frame, err error) {
+func (pc *PacketBreakdown) captureIPProto(proto lneto.IPProto, dst []Frame, pkt []byte, bitOffset int, ipProtoErr error) (_ []Frame, err error) {
 	debuglog("pcap:ipproto:start")
 	nextFrame := len(dst)
 	switch proto {
@@ -292,8 +293,8 @@ func (pc *PacketBreakdown) captureIPProto(proto lneto.IPProto, dst []Frame, pkt
 	default:
 		reclaimRemainingFrame(&dst, "unknown proto", 0, bitOffset, octet*len(pkt))
 	}
-	if len(ipProtoErrs) > 0 && len(dst) > nextFrame {
-		dst[nextFrame].Errors = append(dst[nextFrame].Errors, ipProtoErrs...)
+	if ipProtoErr != nil && len(dst) > nextFrame {
+		dst[nextFrame].Errors = append(dst[nextFrame].Errors, ipProtoErr)
 	}
 	debuglog("pcap:ipproto:done")
 	return dst, err
@@ -441,15 +442,19 @@ func (pc *PacketBreakdown) CaptureDNS(dst []Frame, pkt []byte, bitOffset int) ([
 	if err != nil && !incomplete {
 		return dst, err
 	}
+	debuglog("pcap:dns-decode")
 	finfo := reclaimFrame(&dst, "DNS", bitOffset, nil)
 	if incomplete {
 		finfo.Errors = append(finfo.Errors, ErrLimitExceeded)
 	}
-	finfo.Fields = append(finfo.Fields[:0], FrameField{
+	field := internal.SliceReclaim(&finfo.Fields)
+	*field = FrameField{
 		Name:           "Data",
 		FrameBitOffset: 0,
 		BitLength:      int(off) * octet,
-	})
+		SubFields:      field.SubFields[:0], // Reuse subfields.
+	}
+	debuglog("pcap:dns-done")
 	return dst, nil
 }

@@ -463,6 +468,7 @@ func (pc *PacketBreakdown) CaptureNTP(dst []Frame, pkt []byte, bitOffset int) ([
 		return dst, err
 	}
 	reclaimFrame(&dst, "NTP", bitOffset, baseNTPFields[:])
+	debuglog("pcap:ntp")
 	return dst, nil
 }

@@ -490,6 +496,7 @@ func (pc *PacketBreakdown) CaptureDHCPv4(dst []Frame, pkt []byte, bitOffset int)
 			SubFields: optfield.SubFields[:0],
 			Name:      "options",
 		}
+		debuglog("pcap:dhcp-opt0")
 		err = dfrm.ForEachOption(func(optoff int, opt dhcpv4.OptNum, data []byte) error {
 			if len(optfield.SubFields) >= pc.SubfieldLimit {
 				return ErrLimitExceeded
@@ -541,11 +548,13 @@ func (pc *PacketBreakdown) CaptureDHCPv4(dst []Frame, pkt []byte, bitOffset int)
 			optfield.SubFields = append(optfield.SubFields, field)
 			return nil
 		})
+		debuglog("pcap:dhcp-opt1")
 		// optfield already in finfo.Fields via SliceReclaim, no append needed.
 		if err != nil {
 			finfo.Errors = append(finfo.Errors, err)
 		}
 	}
+	debuglog("pcap:dhcp-done")
 	return dst, nil
 }

@@ -739,6 +748,7 @@ func appendField(dst, pkt []byte, fieldBitStart, bitlen int, rightAligned bool)
 		}
 		// Optimized path: field starts at byte boundary.
 		dst = append(dst, pkt[octetsStart:octetsStart+octets]...)
+		debuglog("pcap:appendField:optpath")
 		if lastOctetExcessBits != 0 {
 			dst[len(dst)-1] >>= lastOctetExcessBits
 		}
@@ -750,7 +760,9 @@ func appendField(dst, pkt []byte, fieldBitStart, bitlen int, rightAligned bool)
 		if lastOctetExcessBits == 0 {
 			// Right aligned with no loose trailing bits. i.e: TCP flags.
 			dst = append(dst, pkt[octetsStart]&mask)
+			debuglog("pcap:appendField:rightalign1")
 			dst = append(dst, pkt[octetsStart+1:octetsStart+octets]...)
+			debuglog("pcap:appendField:rightalign2")
 			return dst, nil
 		}
 		// Right aligned with trailing bits. i.e: IPv6 Traffic Class.
@@ -762,6 +774,7 @@ func appendField(dst, pkt []byte, fieldBitStart, bitlen int, rightAligned bool)
 			b := (pkt[octetsStart+i] & mask) << (8 - firstBitOffset)
 			b |= pkt[octetsStart+i+1] >> firstBitOffset
 			dst = append(dst, b)
+			debuglog("pcap:appendField:rightalign3")
 		}
 		return dst, nil
 	}
@@ -772,10 +785,12 @@ func appendField(dst, pkt []byte, fieldBitStart, bitlen int, rightAligned bool)
 		b := pkt[i+octetsStart] & mask
 		b |= pkt[i+octetsStart+1] >> firstBitOffset
 		dst = append(dst, b)
+		debuglog("pcap:appendField:leftalign1")
 	}
 	lastOctet := pkt[octetsStart+octets-1] & mask
 	lastOctet >>= lastOctetExcessBits
 	dst = append(dst, lastOctet)
+	debuglog("pcap:appendField:leftalign2")
 	return dst, nil
 }

@@ -1341,6 +1356,7 @@ func reclaimFrame(dst *[]Frame, proto string, bitOffset int, baseFields []FrameF
 		Fields:          append(finfo.Fields[:0], baseFields...),
 		Errors:          finfo.Errors[:0],
 	}
+	debuglog("pcap:reclaim")
 	return finfo
 }

@@ -1352,6 +1368,7 @@ func reclaimRemainingFrame(dst *[]Frame, proto string, class FieldClass, pktBitO
 		Class:     class,
 		BitLength: pktBitLen - pktBitOffset,
 	})
+	debuglog("pcap:reclaim-rem")
 }

 const enableDebug = internal.HeapAllocDebugging
@@ -4,7 +4,6 @@ import (
 	"encoding/binary"
 	"encoding/hex"
 	"math"
-	"net/netip"
 	"slices"
 	"strconv"
 	"strings"
@@ -14,6 +13,8 @@ import (

 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/ethernet"
+	"github.com/soypat/lneto/ipv4"
+	"github.com/soypat/lneto/ipv6"
 	"github.com/soypat/lneto/ntp"
 	"github.com/soypat/lneto/tcp"
 )
@@ -65,6 +66,7 @@ func (f *Formatter) FormatFrame(dst []byte, frm Frame, pkt []byte) (_ []byte, er
 		dst = append(dst, " bitlen="...)
 		dst = strconv.AppendInt(dst, int64(bitlen), 10)
 	}
+	debuglog("pcap:FormatFrame:int")

 	for ifield := range frm.Fields {
 		field := frm.Fields[ifield]
@@ -94,6 +96,7 @@ func (f *Formatter) FormatFrame(dst []byte, frm Frame, pkt []byte) (_ []byte, er
 				dst = append(dst, ';')
 			}
 			dst = append(dst, err.Error()...)
+			debuglog("pcap:fmtframe:error")
 		}
 		dst = append(dst, ')')
 	}
@@ -122,6 +125,7 @@ func (f *Formatter) FormatField(dst []byte, pktStartOff int, field FrameField, p
 			dst, err = f.formatField(dst, pktStartOff, field.SubFields[i], pkt)
 		}
 	}
+	debuglog("pcap:FormatField:end")
 	return dst, err
 }

@@ -181,15 +185,20 @@ func (f *Formatter) formatField(dst []byte, pktStartOff int, field FrameField, p
 				return dst, err
 			}
 			dst = strconv.AppendUint(dst, v, 10)
+			debuglog("pcap:fmtfield:uint")
 		} else if field.BitLength == 4*8 {
-			dst = netip.AddrFrom4([4]byte(f.buf)).AppendTo(dst)
+			dst = ipv4.AppendFormatAddr(dst, [4]byte(f.buf))
+			debuglog("pcap:fmtfield:addr4")
 		} else if field.BitLength == 6*8 {
 			dst = ethernet.AppendAddr(dst, [6]byte(f.buf))
+			debuglog("pcap:fmtfield:addr6")
 		} else if field.BitLength == 16*8 {
-			dst = netip.AddrFrom16([16]byte(f.buf)).AppendTo(dst)
+			dst = ipv6.AppendFormatAddr(dst, [16]byte(f.buf))
+			debuglog("pcap:fmtfield:addr16")
 		} else {
 			dst = append(dst, "0x"...)
 			dst = hex.AppendEncode(dst, f.buf)
+			debuglog("pcap:fmtfield:addrN")
 		}
 	}
 	return dst, err