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Optionally limit packet count #63

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725e618
Optionally limit max packet count before exiting
May 8, 2023
d90b028
Update unit test to cover changes
May 8, 2023
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3 changes: 3 additions & 0 deletions cmd/xdpcap/flags.go
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Original file line number Diff line number Diff line change
Expand Up @@ -181,6 +181,8 @@ type flags struct {
// Filter provided as input. Not in any particular format, for metadata / debugging only.
filterExpr string
filterOpts filterOpts

maxPackets uint64
}

// parseFlags creates the flags, and attempts to parse args.
Expand All @@ -196,6 +198,7 @@ func parseFlags(name string, args []string) (flags, error) {

flags.IntVar(&flags.filterOpts.perfPerCPUBuffer, "buffer", 8192, "Per CPU perf buffer size to create (`bytes`)")
flags.IntVar(&flags.filterOpts.perfWatermark, "watermark", 1, "Perf watermark (`bytes`). Must be < buffer.")
flags.Uint64Var(&flags.maxPackets, "c", 0, "Maximum number of packets to capture across all `actions`. 0 indicates unlimited")
flags.BoolVar(&flags.quiet, "q", false, "Don't print statistics")
flags.BoolVar(&flags.flush, "flush", false, "Flush pcap data written to <output> for every packet received")

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3 changes: 2 additions & 1 deletion cmd/xdpcap/flags_test.go
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Expand Up @@ -136,7 +136,7 @@ func TestFilterRawInvalid(t *testing.T) {
func TestOptions(t *testing.T) {
output := tempOutput(t)

flags, err := parseFlags("", []string{"-buffer", "1234", "-watermark", "5678", "-q", "-flush", "-actions", "pass,drop", "-linktype", "802.11", "foo", output})
flags, err := parseFlags("", []string{"-buffer", "1234", "-watermark", "5678", "-q", "-flush", "-actions", "pass,drop", "-linktype", "802.11", "-c", "1000", "foo", output})
if err != nil {
t.Fatal(err)
}
Expand All @@ -148,6 +148,7 @@ func TestOptions(t *testing.T) {
expected.flush = true
expected.filterOpts.actions = []xdpAction{xdpPass, xdpDrop}
expected.linkType = layers.LinkTypeIEEE802_11
expected.maxPackets = 1000

requireFlags(t, output, expected, flags)
}
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9 changes: 9 additions & 0 deletions cmd/xdpcap/main.go
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Expand Up @@ -106,6 +106,8 @@ func capture(flags flags) error {

// Write out a pcap file from aggregated packets
go func() {
totalPackets := uint64(0)

for {
pkt, err := filter.read()
switch {
Expand Down Expand Up @@ -134,6 +136,13 @@ func capture(flags flags) error {
fmt.Fprintln(os.Stderr, "Error flushing data:", err)
}
}

if flags.maxPackets != 0 {
totalPackets++
if totalPackets >= flags.maxPackets {
sigs <- syscall.SIGTERM
}
}
}
}()

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