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add pcap printing to examples/xnet

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soypat
2025-12-31 13:21:46 -03:00
parent ed89f169d9
commit 7369ec0b7e
4 changed files with 181 additions and 140 deletions
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examples/xnet/main.go
+31 -8
View File
@@ -42,6 +42,7 @@ func run() (err error) {
flagRequestedIP = ""
flagDoNTP = false
flagHTTPGet = false
flagNoPcap = false
)
flag.BoolVar(&flagHTTPGet, "httpget", flagHTTPGet, "Do an HTTP GET request ")
flag.StringVar(&flagInterface, "i", flagInterface, "Interface to use. Either tap* or the name of an existing interface to bridge to.")
@@ -49,6 +50,7 @@ func run() (err error) {
flag.StringVar(&flagHostToResolve, "host", flagHostToResolve, "Hostname to resolve via DNS.")
flag.StringVar(&flagRequestedIP, "addr", flagRequestedIP, "IP address to request via DHCP.")
flag.BoolVar(&flagDoNTP, "ntp", flagDoNTP, "Do NTP round and print result time")
flag.BoolVar(&flagNoPcap, "nopcap", flagNoPcap, "Disable pcap logging.")
flag.Parse()
fmt.Println("softrand", softRand)
_, err = dns.NewName(flagHostToResolve)
@@ -108,18 +110,37 @@ func run() (err error) {
buf := make([]byte, mtu)
var cap pcap.PacketBreakdown
var frames []pcap.Frame
pf := pcap.Formatter{
FilterClasses: []pcap.FieldClass{pcap.FieldClassFlags, pcap.FieldClassDst, pcap.FieldClassSrc, pcap.FieldClassAddress},
}
var pfbuf []byte
logFrames := func(context string, pkt []byte) error {
if flagNoPcap {
return nil
}
frames, err = cap.CaptureEthernet(frames[:0], pkt, 0)
if err != nil {
return err
}
pfbuf = append(pfbuf[:0], context...)
pfbuf = append(pfbuf, ' ', '[')
pfbuf, err = pf.FormatFrames(pfbuf, frames, pkt)
pfbuf = append(pfbuf, ']', '\n')
if err != nil {
return err
}
_, err = os.Stdout.Write(pfbuf)
return err
}
for {
clear(buf)
nwrite, err := stack.Encapsulate(buf[:], -1, 0)
if err != nil {
fmt.Println("ERR:ENCAPSULATE", err)
log.Println("ERR:ENCAPSULATE", err)
} else if nwrite > 0 {
frames, err = cap.CaptureEthernet(frames[:0], buf[:nwrite], 0)
err = logFrames("OUT", buf[:nwrite])
if err != nil {
log.Println("ERR capture", err)
}
if len(frames) > 0 {
fmt.Println("OUT", frames)
log.Println("ERR:OUTLOG", err)
}
n, err := iface.Write(buf[:nwrite])
if err != nil {
@@ -137,8 +158,10 @@ func run() (err error) {
err = stack.Demux(buf[:nread], 0)
if err != nil {
if !errors.Is(err, lneto.ErrPacketDrop) {
frames, err = cap.CaptureEthernet(frames[:0], buf[:nread], 0)
log.Println("groutine demux:", err, frames)
err = logFrames("IN", buf[:nread])
if err != nil {
log.Println("ERR:INLOG", err)
}
}
}
}
internet/pcap/capture.go
+5 -130
View File
@@ -3,14 +3,9 @@ package pcap
//go:generate stringer -type=FieldClass -linecomment -output stringers.go .
import (
"encoding/binary"
"encoding/hex"
"errors"
"fmt"
"math"
"net/netip"
"slices"
"strconv"
"strings"
"github.com/soypat/lneto"
"github.com/soypat/lneto/arp"
@@ -538,6 +533,7 @@ func (frm Frame) FieldAsUint(fieldIdx int, pkt []byte) (uint64, error) {
return fieldAsUint(pkt, frm.PacketBitOffset+field.FrameBitOffset, field.BitLength, field.RightAligned)
}
// AppendField appends the binary on-the-wire representation of the field and aligns the field so it starts at the first bit of appended data.
func (frm Frame) AppendField(dst []byte, fieldIdx int, pkt []byte) ([]byte, error) {
if fieldIdx < 0 || fieldIdx >= len(frm.Fields) {
return dst, errors.New("invalid field index")
@@ -616,129 +612,6 @@ func appendField(dst, pkt []byte, fieldBitStart, bitlen int, rightAligned bool)
return dst, nil
}
type Formatter struct {
FieldSep string
FrameSep string
FilterClasses []FieldClass
buf []byte
}
func (f *Formatter) FormatFrames(dst []byte, frms []Frame, pkt []byte) (_ []byte, err error) {
sep := f.FrameSep
if sep == "" {
sep = " | "
}
for ifrm := range frms {
if ifrm != 0 {
dst = append(dst, sep...)
}
dst, err = f.FormatFrame(dst, frms[ifrm], pkt)
if err != nil {
return dst, err
}
}
return dst, nil
}
func (f *Formatter) FormatFrame(dst []byte, frm Frame, pkt []byte) (_ []byte, err error) {
sep := f.FieldSep
if sep == "" {
sep = "; " // default field separator
}
bitlen := frm.LenBits()
if bitlen%8 == 0 {
dst = fmt.Appendf(dst, "%s len=%d", frm.Protocol, bitlen/8)
} else {
dst = fmt.Appendf(dst, "%s bitlen=%d", frm.Protocol, bitlen)
}
for ifield := range frm.Fields {
field := frm.Fields[ifield]
if f.filterField(field) {
continue
}
dst = append(dst, sep...)
if field.Class == FieldClassFlags && frm.Protocol == lneto.IPProtoTCP {
dst = append(dst, "flags="...)
v, err := fieldAsUint(pkt, frm.PacketBitOffset+field.FrameBitOffset, field.BitLength, field.RightAligned)
if err != nil {
return dst, err
}
dst = tcp.Flags(v).AppendFormat(dst)
continue
}
dst, err = f.formatField(dst, frm.PacketBitOffset, field, pkt)
if err != nil {
return dst, err
}
}
return dst, nil
}
func (f *Formatter) filterField(field FrameField) bool {
return f.FilterClasses != nil && !slices.Contains(f.FilterClasses, field.Class)
}
func (f *Formatter) FormatField(dst []byte, pktStartOff int, field FrameField, pkt []byte) (_ []byte, err error) {
return f.formatField(dst, pktStartOff, field, pkt)
}
func (f *Formatter) formatField(dst []byte, pktStartOff int, field FrameField, pkt []byte) (_ []byte, err error) {
name := field.Name
if name == "" {
name = field.Class.String()
}
hasSpaces := strings.IndexByte(name, ' ') >= 0
if hasSpaces {
dst = append(dst, '(')
}
dst = append(dst, name...)
if hasSpaces {
dst = append(dst, ')')
}
dst = append(dst, '=')
f.buf, err = appendField(f.buf[:0], pkt, field.FrameBitOffset+pktStartOff, field.BitLength, field.RightAligned)
if err != nil {
return dst, err
}
fieldBitStart := pktStartOff + field.FrameBitOffset
switch field.Class {
default:
fallthrough
case FieldClassChecksum, FieldClassID, FieldClassFlags, FieldClassOptions, FieldClassAddress:
// Binary data to be printed as hexadecimal.
dst = append(dst, "0x"...)
dst = hex.AppendEncode(dst, f.buf)
case FieldClassDst, FieldClassSrc, FieldClassSize:
// IP, MAC addresses and ports.
if field.BitLength <= 16 {
v, err := fieldAsUint(pkt, fieldBitStart, field.BitLength, field.RightAligned)
if err != nil {
return dst, err
}
dst = strconv.AppendUint(dst, v, 10)
} else if field.BitLength == 4*8 {
dst = netip.AddrFrom4([4]byte(f.buf)).AppendTo(dst)
} else if field.BitLength == 6*8 {
for i := range f.buf {
if i != 0 {
dst = append(dst, ':')
}
if f.buf[i] < 16 {
dst = append(dst, '0')
}
dst = strconv.AppendUint(dst, uint64(f.buf[i]), 16)
}
} else if field.BitLength == 16*8 {
dst = netip.AddrFrom16([16]byte(f.buf)).AppendTo(dst)
} else {
dst = append(dst, "0x"...)
dst = hex.AppendEncode(dst, f.buf)
}
}
return dst, err
}
func (frm Frame) String() string {
return string(frm.AppendString(nil))
}
@@ -787,7 +660,7 @@ const (
FieldClassProto // protocol
FieldClassVersion // version
FieldClassType // type
FieldClassSize // field size
FieldClassSize // size
FieldClassFlags // flags
FieldClassID // identification
FieldClassChecksum // checksum
@@ -795,6 +668,8 @@ const (
FieldClassPayload // payload
FieldClassText // text
FieldClassAddress // address
// FieldClassBinaryText represents long stretches of binary data such as BOOTP DHCPv4 field.
FieldClassBinaryText // binary-text
)
const octet = 8
@@ -1122,7 +997,7 @@ var baseDHCPv4Fields = [...]FrameField{
},
{
Name: "BOOTP",
Class: FieldClassAddress,
Class: FieldClassBinaryText,
FrameBitOffset: (28 + 16) * octet,
BitLength: (dhcpv4.OptionsOffset - (28 + 16)) * octet,
},
internet/pcap/format.go
+142
View File
@@ -0,0 +1,142 @@
package pcap
import (
"encoding/hex"
"fmt"
"net/netip"
"slices"
"strconv"
"strings"
"github.com/soypat/lneto"
"github.com/soypat/lneto/tcp"
)
type Formatter struct {
FieldSep string
FrameSep string
FilterClasses []FieldClass
buf []byte
}
// FormatFrames appends the formatted frame data to the destination buffer according the Formatter state.
// Is equivalent to [Formatter.FormatFrame] called on each Frame with the FrameSep inserted between frames.
func (f *Formatter) FormatFrames(dst []byte, frms []Frame, pkt []byte) (_ []byte, err error) {
sep := f.FrameSep
if sep == "" {
sep = " | "
}
for ifrm := range frms {
if ifrm != 0 {
dst = append(dst, sep...)
}
dst, err = f.FormatFrame(dst, frms[ifrm], pkt)
if err != nil {
return dst, err
}
}
return dst, nil
}
// FormatFrame
func (f *Formatter) FormatFrame(dst []byte, frm Frame, pkt []byte) (_ []byte, err error) {
sep := f.FieldSep
if sep == "" {
sep = "; " // default field separator
}
bitlen := frm.LenBits()
if bitlen%8 == 0 {
dst = fmt.Appendf(dst, "%s len=%d", frm.Protocol, bitlen/8)
} else {
dst = fmt.Appendf(dst, "%s bitlen=%d", frm.Protocol, bitlen)
}
for ifield := range frm.Fields {
field := frm.Fields[ifield]
if f.filterField(field) {
continue
}
dst = append(dst, sep...)
if field.Class == FieldClassFlags && frm.Protocol == lneto.IPProtoTCP {
// TCP flags pretty print special case.
dst = append(dst, "flags="...)
v, err := fieldAsUint(pkt, frm.PacketBitOffset+field.FrameBitOffset, field.BitLength, field.RightAligned)
if err != nil {
return dst, err
}
dst = tcp.Flags(v).AppendFormat(dst)
continue
}
dst, err = f.formatField(dst, frm.PacketBitOffset, field, pkt)
if err != nil {
return dst, err
}
}
return dst, nil
}
func (f *Formatter) filterField(field FrameField) bool {
return f.FilterClasses != nil && !slices.Contains(f.FilterClasses, field.Class)
}
func (f *Formatter) FormatField(dst []byte, pktStartOff int, field FrameField, pkt []byte) (_ []byte, err error) {
return f.formatField(dst, pktStartOff, field, pkt)
}
func (f *Formatter) formatField(dst []byte, pktStartOff int, field FrameField, pkt []byte) (_ []byte, err error) {
name := field.Name
if name == "" {
name = field.Class.String()
}
hasSpaces := strings.IndexByte(name, ' ') >= 0
if hasSpaces {
dst = append(dst, '(')
}
dst = append(dst, name...)
if hasSpaces {
dst = append(dst, ')')
}
dst = append(dst, '=')
f.buf, err = appendField(f.buf[:0], pkt, field.FrameBitOffset+pktStartOff, field.BitLength, field.RightAligned)
if err != nil {
return dst, err
}
fieldBitStart := pktStartOff + field.FrameBitOffset
switch field.Class {
default:
fallthrough
case FieldClassChecksum, FieldClassID, FieldClassFlags, FieldClassOptions:
// Binary data to be printed as hexadecimal.
dst = append(dst, "0x"...)
dst = hex.AppendEncode(dst, f.buf)
case FieldClassText:
dst = strconv.AppendQuote(dst, string(f.buf))
case FieldClassDst, FieldClassSrc, FieldClassSize, FieldClassAddress:
// IP, MAC addresses and ports.
if field.BitLength <= 16 {
v, err := fieldAsUint(pkt, fieldBitStart, field.BitLength, field.RightAligned)
if err != nil {
return dst, err
}
dst = strconv.AppendUint(dst, v, 10)
} else if field.BitLength == 4*8 {
dst = netip.AddrFrom4([4]byte(f.buf)).AppendTo(dst)
} else if field.BitLength == 6*8 {
for i := range f.buf {
if i != 0 {
dst = append(dst, ':')
}
if f.buf[i] < 16 {
dst = append(dst, '0')
}
dst = strconv.AppendUint(dst, uint64(f.buf[i]), 16)
}
} else if field.BitLength == 16*8 {
dst = netip.AddrFrom16([16]byte(f.buf)).AppendTo(dst)
} else {
dst = append(dst, "0x"...)
dst = hex.AppendEncode(dst, f.buf)
}
}
return dst, err
}
internet/pcap/stringers.go
+3 -2
View File
@@ -22,11 +22,12 @@ func _() {
_ = x[FieldClassPayload-11]
_ = x[FieldClassText-12]
_ = x[FieldClassAddress-13]
_ = x[FieldClassBinaryText-14]
}
const _FieldClass_name = "undefinedsourcedestinationprotocolversiontypefield sizeflagsidentificationchecksumoptionspayloadtextaddress"
const _FieldClass_name = "undefinedsourcedestinationprotocolversiontypesizeflagsidentificationchecksumoptionspayloadtextaddressbinary-text"
var _FieldClass_index = [...]uint8{0, 9, 15, 26, 34, 41, 45, 55, 60, 74, 82, 89, 96, 100, 107}
var _FieldClass_index = [...]uint8{0, 9, 15, 26, 34, 41, 45, 49, 54, 68, 76, 83, 90, 94, 101, 112}
func (i FieldClass) String() string {
if i >= FieldClass(len(_FieldClass_index)-1) {