mirror of
https://github.com/soypat/lneto.git
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Pat Whittingslow
7d323aae19
* claude suggests a way forward * add timing to capture printer * add pcap.Flags * fix ICMP CRC calculation and add test * bugfix: still send data on half-close state(close-wait) * fix pcap test
93 lines
2.6 KiB
Go
93 lines
2.6 KiB
Go
package xnet
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import (
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"io"
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"strconv"
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"time"
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"github.com/soypat/lneto/internet/pcap"
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)
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type CapturePrinterConfig struct {
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NamespaceWidth int
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// TimePrecision if non-zero is used to print timestamp
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// at which the packet was received. By default the amount of
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// seconds since configuration is printed.
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TimePrecision int
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// Now returns the current time.
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Now func() time.Time
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}
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// CapturePrinter prints internet packets using the [pcap.PacketBreakdown] and [pcap.Formatter] types.
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type CapturePrinter struct {
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write func(b []byte) (int, error)
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frms []pcap.Frame
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cap pcap.PacketBreakdown
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pfmt pcap.Formatter
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fmtPcapBuf []byte
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// minimum length of namespace on print.
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namespaceminwidth int
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timeprec int
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origin time.Time
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now func() time.Time
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}
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func (stack *CapturePrinter) Configure(writer io.Writer, cfg CapturePrinterConfig) error {
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stack.timeprec = cfg.TimePrecision
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stack.now = cfg.Now
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if stack.printTimestamps() {
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stack.origin = cfg.Now()
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}
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stack.namespaceminwidth = cfg.NamespaceWidth
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stack.write = writer.Write
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return nil
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}
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// Formatter returns a pointer to the underlying pcap.Formatter type.
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// One can then configure the formatter's fields to affect printing.
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func (stack *CapturePrinter) Formatter() *pcap.Formatter {
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return &stack.pfmt
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}
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func (stack *CapturePrinter) PrintPacket(prefix string, pkt []byte) {
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fmtbuf := stack.fmtPcapBuf[:0]
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useTimestamps := stack.printTimestamps()
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var captime time.Time
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if useTimestamps {
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captime = stack.now()
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}
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var err error
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stack.frms, err = stack.cap.CaptureEthernet(stack.frms[:0], pkt, 0)
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if err == nil {
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if useTimestamps {
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diff := captime.Sub(stack.origin)
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fmtbuf = strconv.AppendFloat(fmtbuf, diff.Seconds(), 'f', stack.timeprec, 32)
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fmtbuf = append(fmtbuf, ' ')
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}
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fmtbuf = append(fmtbuf, prefix...)
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// Ensure minimum width of packet length display for less jitter in log viewline.
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prevlen := len(prefix)
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fmtbuf = strconv.AppendInt(fmtbuf, int64(len(pkt)), 10)
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numLength := len(fmtbuf) - prevlen
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appendSpaces := max(0, stack.namespaceminwidth-numLength) + 1 // add single space to separate actual format from packet length.
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for range appendSpaces {
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fmtbuf = append(fmtbuf, ' ')
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}
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fmtbuf, err = stack.pfmt.FormatFrames(fmtbuf, stack.frms, pkt)
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}
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fmtbuf = append(fmtbuf, '\n')
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if err != nil {
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fmtbuf = append(fmtbuf, "ERROR "...)
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fmtbuf = append(fmtbuf, prefix...)
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fmtbuf = append(fmtbuf, ": "...)
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fmtbuf = append(fmtbuf, err.Error()...)
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}
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stack.write(fmtbuf)
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stack.fmtPcapBuf = fmtbuf[:0] // Reuse buffer if allocated at larger size.
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}
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func (stack *CapturePrinter) printTimestamps() bool {
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return stack.timeprec > 0 && stack.now != nil
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}
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