capture_traffic.go

package main

import (
   "fmt"
   "github.com/google/gopacket"
   "github.com/google/gopacket/pcap"
   "log"
   "time"
)

var (
   device            = "eth0"
   snapshotLen int32 = 1024
   promiscuous       = false
   err         error
   timeout     = 30 * time.Second
   handle      *pcap.Handle
)

func main() {
   // Open device
   handle, err = pcap.OpenLive(device, snapshotLen, promiscuous,  
      timeout)
   if err != nil {
      log.Fatal(err)
   }
   defer handle.Close()

      // Aplico el filtro que quiera
   var filter string = "tcp and port 80" // or os.Args[1]
   err = handle.SetBPFFilter(filter)
   if err != nil {
      log.Fatal(err)
   }
   fmt.Println("Only capturing TCP port 80 packets.")

   packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
   for packet := range packetSource.Packets() {
      // Aqui coloco algo que quiera hacer con el pack
      fmt.Println(packet)
   }
}