sniffer.go

package main

import (
	"log"
	"syscall"
)

func htonsInt16(n int) int {
	return int(int16(byte(n))<<8 | int16(byte(n>>8)))
}

func main() {
	fd, err := syscall.Socket(syscall.AF_PACKET, syscall.SOCK_RAW, htonsInt16(syscall.ETH_P_ALL))
	if err != nil {
		log.Fatal(err)
	}

	buf := make([]byte, 65536)

	for {
		n, from, err := syscall.Recvfrom(fd, buf, 0)
		if err != nil {
			log.Fatal(err)
		}

		log.Printf("Read %d bytes from %v", n, from)
		if n > 20 {
			n = 20
		}

		log.Print(buf[:n])
	}
}