This code demonstrates network packet capturing and metrics exporting using the Go programming language

packets_captured.go

package main

import (
	"fmt"
	"log"
	"os"
	"os/signal"
	"syscall"

	"net/http"

	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
	"github.com/google/gopacket/pcap"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	packetsCaptured = prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "packets_captured_total",
			Help: "Total number of captured packets",
		},
		[]string{"source", "destination"},
	)
)

func init() {
	prometheus.MustRegister(packetsCaptured)
}

func main() {
	// Create a packet capture handle
	ifaceName := "enp5s0" // Replace with your network interface
	handle, err := pcap.OpenLive(ifaceName, 1600, true, pcap.BlockForever)
	if err != nil {
		log.Fatalf("Failed to open capture handle: %v", err)
	}
	defer handle.Close()

	packetSource := gopacket.NewPacketSource(handle, handle.LinkType())

	// Start capturing packets
	go func() {
		for packet := range packetSource.Packets() {
			// Process packet here
			processPacket(packet)
		}
	}()

	// Prometheus metrics
	http.Handle("/metrics", promhttp.Handler())
	go func() {
		log.Fatal(http.ListenAndServe(":8081", nil))
	}()

	fmt.Println("Packet capture running... Press Ctrl+C to exit.")

	// Capture Ctrl+C signal to gracefully exit
	stop := make(chan os.Signal, 1)
	signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
	<-stop
}

func processPacket(packet gopacket.Packet) {
	// Extract source and destination addresses
	ipLayer := packet.Layer(layers.LayerTypeIPv4)
	if ipLayer != nil {
		ip, _ := ipLayer.(*layers.IPv4)
		sourceIP := ip.SrcIP.String()
		destinationIP := ip.DstIP.String()

		// Increment packets captured metric
		packetsCaptured.WithLabelValues(sourceIP, destinationIP).Inc()
	}
}

It utilizes the github.com/google/gopacket library to capture packets from a specified network interface. The captured packets' source and destination IP addresses are processed, and metrics are incremented using Prometheus. The packets_captured_total metric counts the total number of captured packets between different source and destination IP address pairs. These metrics are then exposed via an HTTP server on port 8081 for Prometheus to scrape. The program can be terminated gracefully by pressing Ctrl+C.