netshovel/netshovel.go

/*

Package netshovel provides utilities to assist in creating of application-layer protocol decoders.

examples/simple/simple.go contains a full decoder which does nothing but dump every utterance.
It can be used as a template for new work.

*/
package netshovel

import (
	"flag"
	"log"
	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
	"github.com/google/gopacket/pcap"
	"github.com/google/gopacket/tcpassembly"
)

// Mainloop to handle dispatching of PCAP files from command line
//
// This parses the command line arguments,
// and for each PCAP file specified on the command line,
// invokes a TCP assembler that sends streams to whatever is returned from factory.
func Shovel(factory tcpassembly.StreamFactory) {
	//verbose := flag.Bool("verbose", false, "Write lots of information out")
	flag.Parse()
	
	streamPool := tcpassembly.NewStreamPool(factory)
	assembler := tcpassembly.NewAssembler(streamPool)
	
	for _, fn := range flag.Args() {
		handle, err := pcap.OpenOffline(fn)
		if err != nil {
			log.Fatal(err)
		}
		
		packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
		packets := packetSource.Packets()
		for packet := range packets {
			if packet == nil {
				break
			}
			if packet.NetworkLayer() == nil || packet.TransportLayer() == nil || packet.TransportLayer().LayerType() != layers.LayerTypeTCP {
				continue
			}
			tcp := packet.TransportLayer().(*layers.TCP)
			assembler.AssembleWithTimestamp(packet.NetworkLayer().NetworkFlow(), tcp, packet.Metadata().Timestamp)
		}
	}
	assembler.FlushAll()
}