FreeBSD Golang sniffer using BPF

gistfile1.txt

package main

import (
	"encoding/hex"
	"fmt"
	"syscall"
)

func main() {
	enable := 1

	fd, err := syscall.Open("/dev/bpf0", syscall.O_RDWR, syscall.S_IRUSR|syscall.S_IWUSR)
	if err != nil {
		panic(err)
	}
	err = syscall.SetBpfInterface(fd, "vtnet0")
	if err != nil {
		panic(err)
	}
	err = syscall.SetBpfImmediate(fd, enable)
	if err != nil {
		panic(err)
	}
	err = syscall.SetBpfHeadercmpl(fd, enable)
	if err != nil {
		panic(err)
	}

	var buf_len int
	buf_len, err = syscall.BpfBuflen(fd)
	if err != nil {
		panic(err)
	}
	fmt.Printf("buflen %d\n", buf_len)

	err = syscall.SetBpfPromisc(fd, enable)
	if err != nil {
		panic(err)
	}

	var n int
	for {
		buf := make([]byte, buf_len)
		n, err = syscall.Read(fd, buf)
		if err != nil {
			panic(err)
		}
		//fmt.Printf("% X\n", buf[:n])
		fmt.Printf("\npacket of size %d captured\n", n)
		fmt.Print(hex.Dump(buf[:n]))

	}
}