#pragma once

#ifdef __cplusplus
extern "C"
{
#endif

#define __FAVOR_BSD 1
#include <netinet/tcp.h>
#include <netinet/udp.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet/ip_icmp.h>
#include <linux/if_ether.h>
#include <linux/mpls.h>

enum layer_proto
{
    LAYER_PROTO_NONE = 0,

    // L2 -- data link layer
    LAYER_PROTO_ETHER = 1,
    LAYER_PROTO_PWETH = 2,
    LAYER_PROTO_PPP = 3,
    LAYER_PROTO_L2TP = 4,

    // L2 -- tunnel
    LAYER_PROTO_VLAN = 21,
    LAYER_PROTO_PPPOE = 22,
    LAYER_PROTO_MPLS = 23,

    // L3 -- network layer
    LAYER_PROTO_IPV4 = 31,
    LAYER_PROTO_IPV6 = 32,
    LAYER_PROTO_IPAH = 33,

    // L3 -- tunnel
    LAYER_PROTO_GRE = 41,

    // L4 -- transport layer
    LAYER_PROTO_UDP = 51,
    LAYER_PROTO_TCP = 52,
    LAYER_PROTO_ICMP = 53,
    LAYER_PROTO_ICMP6 = 54,

    // L4 -- tunnel
    LAYER_PROTO_VXLAN = 61,
    LAYER_PROTO_GTP_U = 62,
    LAYER_PROTO_GTP_C = 63,
};

struct layer
{
    enum layer_proto proto;
    uint16_t hdr_len;
    union
    {
        // all hdr ptr refer to raw packet, read-only
        const struct ethhdr *eth;
        const struct ip *ip4;
        const struct ip6_hdr *ip6;
        const struct tcphdr *tcp;
        const struct udphdr *udp;
        const struct icmphdr *icmp4;
        const struct icmp6_hdr *icmp6;
        const struct mpls_label *mpls;
        const char *raw; // e.g. pppoe, l2tp, gre, gtp, etc.
    } hdr;
};

int packet_get_layer_count(const struct packet *pkt);
const struct layer *packet_get_layer_by_idx(const struct packet *pkt, int idx);

//  // example: foreach layer in packet (inorder)
//  int count = packet_get_layer_count(pkt);
//  for (int i = 0; i < count; i++)
//  {
//      const struct layer *layer = packet_get_layer_by_idx(pkt, i);
//      // do something with layer
//  }
//
//
//  // example: foreach layer in packet (reverse)
//  int count = packet_get_layer_count(pkt);
//  for (int i = count - 1; i >= 0; i--)
//  {
//      const struct layer *layer = packet_get_layer_by_idx(pkt, i);
//      // do something with layer
//  }

#ifdef __cplusplus
}
#endif