#include <stdio.h>
#include <sys/types.h>
#include <net/bpf.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <net/ethernet.h>
#include <netinet/if_ether.h>

#define REVARP_REQUEST 3
static struct bpf_insn accept_arp[] = {
	BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 12),                      // 0
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, ETHERTYPE_REVARP, 0, 3), // 1
	BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 20),                      // 2
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, REVARP_REQUEST, 0, 1),   // 3
	BPF_STMT(BPF_RET+BPF_K, sizeof(struct ether_arp) +       // 4
	sizeof(struct ether_header)),
	BPF_STMT(BPF_RET+BPF_K, 0)                               // 5
};

struct bpf_insn insns[] = {
	BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 12),
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, ETHERTYPE_IP, 0, 8),
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 26),
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0x8003700f, 0, 2),
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 30),
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0x80037023, 3, 4),
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0x80037023, 0, 3),
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 30),
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0x8003700f, 0, 1),
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
	BPF_STMT(BPF_RET+BPF_K, 0),
};


int main(int argc, char **argv)
{
	void *prog;
	int32_t size;
	//if (0)
	{
		prog  = accept_arp;
		size = sizeof(accept_arp) / sizeof(struct bpf_insn);
	}
	if (0)
	{
		prog = insns;
		size = sizeof(insns) / sizeof(struct bpf_insn);
	}
	fwrite(&size, 4, 1, stdout);
	fwrite(prog, size, sizeof(struct bpf_insn), stdout);
	fflush(stdout);
	return 0;
}