Try a multi-package Golang program named pktcollector

It does not use multiple packages yet.  Starting out as just a copy
of trypcap program.

golang/pktcollector/Makefile

@@ -0,0 +1,11 @@
+all: build
+
+format: pktcollector.go
+	gofmt -w pktcollector.go
+
+vet: pktcollector.go format
+	go vet pktcollector
+
+build: pktcollector.go vet
+	go build pktcollector.go
+

golang/pktcollector/go.mod

@@ -0,0 +1,7 @@
+module pktcollector
+
+go 1.22.4
+
+require github.com/google/gopacket v1.1.19
+
+require golang.org/x/sys v0.0.0-20190412213103-97732733099d // indirect

golang/pktcollector/go.sum

@@ -0,0 +1,16 @@
+github.com/google/gopacket v1.1.19 h1:ves8RnFZPGiFnTS0uPQStjwru6uO6h+nlr9j6fL7kF8=
+github.com/google/gopacket v1.1.19/go.mod h1:iJ8V8n6KS+z2U1A8pUwu8bW5SyEMkXJB8Yo/Vo+TKTo=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/lint v0.0.0-20200302205851-738671d3881b/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
+golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859 h1:R/3boaszxrf1GEUWTVDzSKVwLmSJpwZ1yqXm8j0v2QI=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

golang/pktcollector/pktcollector.go

@@ -0,0 +1,86 @@
+// Copyright © 2024 Andy Fingerhut
+// License: https://www.apache.org/licenses/LICENSE-2.0
+
+// trypcap exercises a few features of the pcap library from Go
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	//"time"
+
+	"github.com/google/gopacket"
+	//"github.com/google/gopacket/layers"
+	"github.com/google/gopacket/pcap"
+)
+
+// Things in pcap package:
+// func FindAllDevs() (ifs []Interface, err error)
+
+var iface = flag.String("iface", "", "Select interface where to capture")
+var fname = flag.String("file", "", "pcap file to read packets from")
+
+func printUsage(progName string) {
+	fmt.Fprintf(os.Stderr, "usage: %s\n", progName)
+	fmt.Fprintln(os.Stderr, "            [ --iface <interface_name> ]")
+	fmt.Fprintln(os.Stderr, "            [ --file <pcap_filename> ]")
+	fmt.Fprintln(os.Stderr)
+}
+
+func main() {
+	flag.Parse()
+
+	if *iface == "" && *fname == "" {
+		printUsage(os.Args[0])
+		os.Exit(1)
+	}
+
+	var handle *pcap.Handle
+	if *iface != "" {
+		intfs, err := pcap.FindAllDevs()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			return
+		}
+		fmt.Printf("Found %d interfaces:\n\n", len(intfs))
+		for idx, intf := range intfs {
+			fmt.Printf("%2d 0x%04x %s %s %d addresses: %v\n", idx, intf.Flags, intf.Name, intf.Description, len(intf.Addresses), intf.Addresses)
+		}
+
+		// Opening Device
+		snaplen := 10000
+		promisc := true
+		//timeout := 30 * time.Second
+		timeout := pcap.BlockForever
+		handle, err = pcap.OpenLive(*iface, int32(snaplen), promisc, timeout)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer handle.Close()
+		fmt.Printf("Opened interface %s promisc=%v\n", *iface, promisc)
+	}
+	if *fname != "" {
+		var err error
+		handle, err = pcap.OpenOffline(*fname)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer handle.Close()
+		fmt.Printf("Opened file %s\n", *fname)
+	}
+	fmt.Printf("   handle=%v\n", handle)
+
+	packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
+	n := 0
+	for packet := range packetSource.Packets() {
+		n += 1
+		fmt.Printf("\n%d\n", n)
+		fmt.Println(packet.Dump())
+
+		//p := gopacket.NewPacket(packet, CiscoS1PuntHeaderType, gopacket.Lazy)
+		//fmt.Println(p)
+	}
+}