#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);
// return  0: success 
// return -1: failed
int packet_get_layer_by_idx(const struct packet *pkt, int idx, struct layer *out);

#define PACKET_FOREACH_LAYER_INORDER(pkt, layer) \
    for (int i = 0; i < packet_get_layer_count(pkt) && packet_get_layer_by_idx(pkt, i, &layer) == 0; i++)

#define PACKET_FOREACH_LAYER_REVERSE(pkt, layer) \
    for (int i = packet_get_layer_count(pkt) - 1; i >= 0 && packet_get_layer_by_idx(pkt, i, &layer) == 0; i--)

#define PACKET_GETALL_LAYERS(pkt, layers)                                                 \
    ({                                                                                    \
        memset(layers, 0, sizeof(layers));                                                \
        int size = sizeof(layers) / sizeof(layers[0]);                                    \
        int count = packet_get_layer_count(pkt);                                          \
        int num = count > size ? size : count;                                            \
        for (int i = 0; i < num && packet_get_layer_by_idx(pkt, i, &layers[i]) == 0; i++) \
            /* void */;                                                                   \
        num;                                                                              \
    })

#ifdef __cplusplus
}
#endif