round most of stack example

2026-08-16 12:53:26 +00:00 · 2025-01-20 00:04:40 -03:00
parent 51ca0a95b5
commit f2ce6312d3
4 changed files with 583 additions and 171 deletions
@@ -0,0 +1,152 @@
+package ltesto
+
+import (
+	"bytes"
+	"math/rand"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/tcp"
+)
+
+const (
+	sizeHeaderIPv4      = 20
+	sizeHeaderTCP       = 20
+	sizeHeaderEthNoVLAN = 14
+	sizeHeaderUDP       = 8
+	sizeHeaderARPv4     = 28
+	sizeHeaderIPv6      = 40
+)
+
+type PacketGen struct {
+	SrcMAC, DstMAC   [6]byte // hardware address
+	SrcIPv4, DstIPv4 [4]byte // address
+	SrcTCP, DstTCP   uint16  // ports
+	EnableVLAN       bool
+}
+
+func (gen *PacketGen) RandomizeAddrs(rng *rand.Rand) {
+	rng.Read(gen.SrcMAC[:])
+	rng.Read(gen.DstMAC[:])
+	rng.Read(gen.SrcIPv4[:])
+	rng.Read(gen.DstIPv4[:])
+	ports := rng.Uint32()
+	gen.SrcTCP = uint16(ports)
+	gen.DstTCP = uint16(ports >> 16)
+}
+
+func (gen *PacketGen) AppendRandomIPv4TCPPacket(dst []byte, rng *rand.Rand) []byte {
+	ri := rng.Int()
+	var (
+		isVLAN     = ri&(1<<0) != 0
+		hasIPOpt   = ri&(1<<1) != 0
+		hasTCPOpt  = ri&(1<<2) != 0
+		hasPayload = ri&(1<<3) != 0
+	)
+	var etherType lneto.EtherType = lneto.EtherTypeIPv4
+	var ipOpts []byte
+	if hasIPOpt {
+		ipOpts = []byte{1, 2, 3, 4}
+	}
+	ethsize := 14
+	if gen.EnableVLAN && isVLAN {
+		etherType = lneto.EtherTypeVLAN
+		ethsize = 18
+	}
+	var tcpOpts []byte
+	if hasTCPOpt {
+		tcpOpts = []byte{byte(tcp.OptSACKPermitted), 0, 1, 0}
+	}
+	var payloadLen int
+	if hasPayload {
+		payloadLen = (ri >> 16) % 1024
+	}
+	ipOptWLen := sizeWord(len(ipOpts))
+	tcpOptWlen := sizeWord(len(tcpOpts))
+	off := len(dst)
+	dst = append(dst, make([]byte, ethsize+sizeHeaderIPv4+4*int(ipOptWLen)+sizeHeaderTCP+4*int(tcpOptWlen)+payloadLen)...)
+	efrm, err := lneto.NewEthFrame(dst[off:])
+	if err != nil {
+		panic(err)
+	}
+	*efrm.DestinationHardwareAddr() = gen.DstMAC
+	*efrm.SourceHardwareAddr() = gen.SrcMAC
+
+	efrm.SetEtherType(etherType)
+	if isVLAN {
+		efrm.SetVLANEtherType(lneto.EtherTypeIPv4)
+		efrm.SetVLANTag(1 << 4)
+	}
+	ethernetPayload := efrm.Payload()
+	ifrm, err := lneto.NewIPv4Frame(ethernetPayload)
+	if err != nil {
+		panic(err)
+	}
+	ifrm.SetVersionAndIHL(4, sizeWord(20+len(ipOpts)))
+	ifrm.SetToS(192)
+	ifrm.SetTotalLength(uint16(len(ethernetPayload)))
+	ifrm.SetID(uint16(rng.Uint32()))
+	ifrm.SetFlags(0x4001) // Don't fragment.
+	ifrm.SetTTL(64)
+	ifrm.SetProtocol(lneto.IPProtoTCP)
+	*ifrm.SourceAddr() = gen.SrcIPv4
+	*ifrm.DestinationAddr() = gen.DstIPv4
+	ifrm.SetCRC(ifrm.CalculateHeaderCRC())
+
+	ipPayload := ifrm.Payload()
+	tfrm, err := lneto.NewTCPFrame(ipPayload)
+	if err != nil {
+		panic(err)
+	}
+	tfrm.SetSourcePort(gen.SrcTCP)
+	tfrm.SetDestinationPort(gen.DstTCP)
+	tfrm.SetSeq(tcp.Value(rng.Uint32()))
+	tfrm.SetAck(tcp.Value(rng.Uint32()))
+	wlen := sizeWord(sizeHeaderTCP + len(tcpOpts))
+	tfrm.SetOffsetAndFlags(wlen, tcp.Flags(rng.Uint32()))
+	tfrm.SetWindowSize(uint16(rng.Uint32()))
+	urgPtr := uint16(rng.Uint32())
+	tfrm.SetUrgentPtr(urgPtr)
+	tcpPayload := tfrm.Payload()
+	var firstPayloadByte byte
+	if len(tcpPayload) > 0 {
+		rng.Read(tcpPayload)
+		firstPayloadByte = tcpPayload[0]
+	}
+	// Set Variable section of data.
+	copy(ifrm.Options(), ipOpts)
+	copy(tfrm.Options(), tcpOpts)
+	tcpCRC := tfrm.CalculateIPv4CRC(ifrm)
+	tfrm.SetCRC(tcpCRC)
+	switch {
+	case gen.SrcTCP != tfrm.SourcePort():
+		panic("IP options overwrite TCP header")
+	case !bytes.Equal(ifrm.Options(), ipOpts):
+		panic("bad ip options written, ensure ip options length is multiple of 4")
+	case !bytes.Equal(tfrm.Options(), tcpOpts):
+		panic("bad tcp options written, ensure tcp options length is multiple of 4")
+	case *ifrm.DestinationAddr() != gen.DstIPv4:
+		panic("IP options overwrite own header")
+	case tfrm.UrgentPtr() != urgPtr:
+		panic("TCP options overwrite urgent pointer field?")
+	case len(tcpPayload) > 0 && firstPayloadByte != tcpPayload[0]:
+		panic("TCP options overwrite payload")
+	}
+	var vld lneto.Validator
+	efrm.ValidateSize(&vld)
+	if err = vld.Err(); err != nil {
+		panic(err)
+	}
+	ifrm.ValidateExceptCRC(&vld)
+	if err = vld.Err(); err != nil {
+		panic(err)
+	}
+	tfrm.ValidateSize(&vld)
+	if err = vld.Err(); err != nil {
+		panic(err)
+	}
+	return dst
+}
+
+func sizeWord(l int) uint8 {
+	return uint8((l + 3) / 4)
+}