// Capture a single packet from the given capture handle, unpack it and return
// it. This will block until a packet is received.
func Recv(c capture.Handle) (packet.Packet, error) {
buf, err := c.Capture()
if err != nil {
return nil, fmt.Errorf("Could not capture: %s", err)
}
pkt, err := layers.UnpackAll(buf, c.LinkType())
if err != nil {
return nil, fmt.Errorf("Could not unpack: %s", err)
}
return pkt, nil
}
// Pack packets into their binary form and inject them in the given capture
// handle.. This will stack the packets before encoding them and also calculate
// the checksums.
func Send(c capture.Handle, pkts ...packet.Packet) error {
if pkts[0].GetType() != c.LinkType() {
return fmt.Errorf("Expected packet type %s, got %s",
pkts[0].GetType(), c.LinkType())
}
buf, err := layers.Pack(pkts...)
if err != nil {
return fmt.Errorf("Could not pack: %s", err)
}
err = c.Inject(buf)
if err != nil {
return fmt.Errorf("Could not inject: %s", err)
}
return nil
}
func main() {
log.SetFlags(0)
usage := `Usage: dump [options] [<expression>]
Dump the traffic on the network (like tcpdump).
Options:
-c <count> Exit after receiving count packets.
-i <iface> Listen on interface.
-r <file> Read packets from file.
-w <file> Write the raw packets to file.`
args, err := docopt.Parse(usage, nil, true, "", false)
if err != nil {
log.Fatalf("Invalid arguments: %s", err)
}
var count uint64
if args["-c"] != nil {
count, err = strconv.ParseUint(args["-c"].(string), 10, 64)
if err != nil {
log.Fatalf("Error parsing count: %s", err)
}
}
var src capture.Handle
if args["-i"] != nil {
src, err = pcap.Open(args["-i"].(string))
if err != nil {
log.Fatalf("Error opening iface: %s", err)
}
} else if args["-r"] != nil {
src, err = file.Open(args["-r"].(string))
if err != nil {
log.Fatalf("Error opening file: %s", err)
}
} else {
log.Fatalf("Must select a source (either -i or -r)")
}
defer src.Close()
var dst capture.Handle
if args["-w"] != nil {
dst, err = file.Open(args["-w"].(string))
if err != nil {
log.Fatalf("Error opening file: %s", err)
}
defer dst.Close()
}
err = src.Activate()
if err != nil {
log.Fatalf("Error activating source: %s", err)
}
if args["<expression>"] != nil {
expr := args["<expression>"].(string)
flt, err := filter.Compile(expr, src.LinkType(), false)
if err != nil {
log.Fatalf("Error parsing filter: %s", err)
}
defer flt.Cleanup()
err = src.ApplyFilter(flt)
if err != nil {
log.Fatalf("Error appying filter: %s", err)
}
}
var i uint64
for {
buf, err := src.Capture()
if err != nil {
log.Fatalf("Error: %s", err)
break
}
if buf == nil {
break
}
i++
if dst == nil {
rcv_pkt, err := layers.UnpackAll(buf, src.LinkType())
if err != nil {
log.Printf("Error: %s\n", err)
}
log.Println(rcv_pkt)
} else {
dst.Inject(buf)
}
if count > 0 && i >= count {
break
}
}
}
