#include <string.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#define __FAVOR_BSD 1
#include <netinet/tcp.h>
#include <netinet/ether.h>

#include "log.h"
#include "packet_parser.h"

#define LOG_PKT_PARSER "PACKET_PARSER"

/******************************************************************************
 * Struct
 ******************************************************************************/

struct udp_hdr
{
    uint16_t uh_sport; /* source port */
    uint16_t uh_dport; /* destination port */
    uint16_t uh_ulen;  /* udp length */
    uint16_t uh_sum;   /* udp checksum */
} __attribute__((__packed__));

struct vlan_hdr
{
    uint16_t vlan_cfi;
    uint16_t protocol;
} __attribute__((__packed__));

struct vxlan_hdr
{
    uint8_t flags[2];
    uint16_t gdp; // group policy id
    uint8_t vni[3];
    uint8_t reserved;
} __attribute__((__packed__));

struct gtp_hdr
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
    unsigned char flags;
    unsigned char msg_type;
    unsigned short len;
    unsigned int teid;
#elif __BYTE_ORDER == __BIG_ENDIAN
    unsigned int teid;
    unsigned short len;
    unsigned char msg_type;
    unsigned char flags;
#else
#error "Please check <endian.h>"
#endif
} __attribute__((__packed__));

#define GTP_HDR_VER_MASK (0xE0)
#define GTP_HDR_FLAG_N_PDU (0x01)
#define GTP_HDR_FLAG_SEQ_NUM (0x02)
#define GTP_HDR_FLAG_NEXT_EXT_HDR (0x04)

/******************************************************************************
 * Static API
 ******************************************************************************/

static int packet_parser_push(struct packet_parser *handler, enum layer_type type, uint16_t hdr_offset, uint16_t hdr_len, uint16_t payload_len);

// parser utils
static const char *layer2str(enum layer_type type);
static uint16_t parse_gtphdr_len(const struct gtp_hdr *gtph);

// parser protocol
static const void *parse_ether(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_ipv4(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_ipv6(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_tcp(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_udp(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_pppoe_ses(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_vxlan(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_vlan8021q(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_gtpv1_u(struct packet_parser *handler, const void *data, uint16_t length);
static const void *parse_mpls(struct packet_parser *handler, const void *data, uint16_t length);

/******************************************************************************
 * Public API
 ******************************************************************************/

void packet_parser_init(struct packet_parser *handler)
{
    memset(handler, 0, sizeof(struct packet_parser));

    handler->result.used = 0;
    handler->result.size = sizeof(handler->result.layers) / sizeof(handler->result.layers[0]);
    handler->packet_data = NULL;
    handler->packet_len = 0;
    handler->packet_id = 0;
}

// return most inner payload
const void *packet_parser_parse(struct packet_parser *handler, const void *packet_data, uint16_t packet_len, uint64_t packet_id)
{
    handler->packet_data = packet_data;
    handler->packet_len = packet_len;
    handler->packet_id = packet_id;

    // TESTED OK BY LWP
    return parse_ether(handler, handler->packet_data, handler->packet_len);
}

const struct layer_record *packet_parser_get_most_inner(struct packet_parser *handler, enum layer_type type)
{
    struct parser_result *result = &handler->result;
    for (int16_t i = result->used - 1; i >= 0; i--)
    {
        const struct layer_record *layer = &result->layers[i];
        if (layer->type & type)
        {
            return layer;
        }
    }

    return NULL;
}

const struct layer_record *packet_parser_get_most_outer(struct packet_parser *handler, enum layer_type type)
{
    struct parser_result *result = &handler->result;
    for (int16_t i = 0; i <= result->used - 1; i++)
    {
        const struct layer_record *layer = &result->layers[i];
        if (layer->type & type)
        {
            return layer;
        }
    }

    return NULL;
}

// return 4: IPv4
// return 6: IPv6
uint8_t gtp_next_proto(const char *data)
{
    uint16_t hdr_len = parse_gtphdr_len((const struct gtp_hdr *)data);
    if (hdr_len < 0)
    {
        return 0;
    }

    uint8_t next_proto = (((const uint8_t *)(data + hdr_len))[0]) >> 4;
    return next_proto;
}

/******************************************************************************
 * Private API
 ******************************************************************************/

static int packet_parser_push(struct packet_parser *handler, enum layer_type type, uint16_t hdr_offset, uint16_t hdr_len, uint16_t payload_len)
{
    struct parser_result *result = &handler->result;
    if (result->used >= result->size)
    {
        return -1;
    }

    result->layers[result->used].type = type;
    result->layers[result->used].hdr_offset = hdr_offset;
    result->layers[result->used].hdr_len = hdr_len;
    result->layers[result->used].pld_len = payload_len;
    result->used++;

    return 0;
}

static const char *layer2str(enum layer_type type)
{
    switch (type)
    {
    case LAYER_TYPE_ETHER:
        return "ETHER";
    case LAYER_TYPE_PPP:
        return "PPP";
    case LAYER_TYPE_HDLC:
        return "HDLC";
    case LAYER_TYPE_VLAN:
        return "VLAN";
    case LAYER_TYPE_PPPOE:
        return "PPPOE";
    case LAYER_TYPE_MPLS:
        return "MPLS";
    case LAYER_TYPE_IPV4:
        return "IPV4";
    case LAYER_TYPE_IPV6:
        return "IPV6";
    case LAYER_TYPE_UDP:
        return "UDP";
    case LAYER_TYPE_TCP:
        return "TCP";
    case LAYER_TYPE_G_VXLAN:
        return "G_VXLAN";
    case LAYER_TYPE_GTPV1_U:
        return "GTPV1_U";
    default:
        return "UNKNOWN";
    }
}

// FROM SAPP
static uint16_t parse_gtphdr_len(const struct gtp_hdr *gtph)
{
    const unsigned char *p_ext_hdr = (unsigned char *)gtph + sizeof(struct gtp_hdr);
    unsigned char next_hdr_type;
    unsigned char this_ext_field_cont_len;

    // v0 太古老已废弃，目前仅支持 GTPv1 版本
    if (((gtph->flags & GTP_HDR_VER_MASK) >> 5) != 1)
    {
        return -1;
    }

    if (gtph->flags & (GTP_HDR_FLAG_SEQ_NUM | GTP_HDR_FLAG_N_PDU | GTP_HDR_FLAG_NEXT_EXT_HDR))
    {
        // skip seq field (2 bytes)
        p_ext_hdr += 2;

        // skip N-PDU field (1 byte)
        p_ext_hdr++;

        // 解析 GTP 扩展头部字段，参考 wireshark 源码 packet-gtp.c->dissect_gtp_common()
        next_hdr_type = *p_ext_hdr;
        if (gtph->flags & GTP_HDR_FLAG_NEXT_EXT_HDR)
        {
            while (next_hdr_type != 0)
            {
                // 指向长度字段, 以4个字节为单位
                p_ext_hdr++;
                this_ext_field_cont_len = *p_ext_hdr * 4 - 2;

                // 指向数据部分第一个字节
                p_ext_hdr++;
                p_ext_hdr += this_ext_field_cont_len;

                // 指向下一个头部字段
                next_hdr_type = *p_ext_hdr;
                p_ext_hdr++;
            }
        }
        else
        {
            p_ext_hdr++;
        }
    }

    return (char *)p_ext_hdr - (char *)gtph;
}

static const void *parse_ether(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct ethhdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_ETHER));
        return data;
    }

    struct ethhdr *hdr = (struct ethhdr *)data;
    uint16_t next_proto = ntohs(hdr->h_proto);
    uint16_t hdr_len = sizeof(struct ethhdr);
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_ETHER, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_ETHER), payload_len, length);
    switch (next_proto)
    {
    case ETH_P_8021Q:
        // TESTED OK BY LWP
        return parse_vlan8021q(handler, payload_data, payload_len);
    case ETH_P_8021AD:
        return parse_ether(handler, payload_data, payload_len);
    case ETH_P_IP:
        // TESTED OK BY LWP
        return parse_ipv4(handler, payload_data, payload_len);
    case ETH_P_IPV6:
        // TESTED OK BY LWP
        return parse_ipv6(handler, payload_data, payload_len);
    case ETH_P_PPP_SES:
        return parse_pppoe_ses(handler, payload_data, payload_len);
    case ETH_P_MPLS_UC:
        // TESTED OK BY LWP
        return parse_mpls(handler, payload_data, payload_len);
    default:
        LOG_ERROR("%s: trace id: %lu, layer: %s, stop parse next protocol %d", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_ETHER), next_proto);
        return payload_data;
    }
}

static const void *parse_ipv4(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct ip))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_IPV4));
        return data;
    }

    struct ip *hdr = (struct ip *)data;
    uint16_t next_proto = hdr->ip_p;
    uint16_t hdr_len = (hdr->ip_hl & 0xf) * 4u;
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_IPV4, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_IPV4), payload_len, length);
    switch (next_proto)
    {
    case IPPROTO_TCP:
        // TESTED OK BY LWP
        return parse_tcp(handler, payload_data, payload_len);
    case IPPROTO_UDP:
        // TESTED OK BY LWP
        return parse_udp(handler, payload_data, payload_len);
    case IPPROTO_IPIP:
        // TESTED OK BY LWP
        return parse_ipv4(handler, payload_data, payload_len);
    case IPPROTO_IPV6:
        // TESTED OK BY LWP
        return parse_ipv6(handler, payload_data, payload_len);
    default:
        // TODO GRE
        LOG_ERROR("%s: trace id: %lu, layer: %s, stop parse next protocol %d", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_IPV4), next_proto);
        return payload_data;
    }
}

static const void *parse_ipv6(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct ip6_hdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_IPV6));
        return data;
    }

    struct ip6_hdr *hdr = (struct ip6_hdr *)data;
    uint16_t next_proto = hdr->ip6_nxt;
    uint16_t hdr_len = sizeof(struct ip6_hdr);
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_IPV6, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_IPV6), payload_len, length);
    switch (next_proto)
    {
    case IPPROTO_TCP:
        // TESTED OK BY LWP
        return parse_tcp(handler, payload_data, payload_len);
    case IPPROTO_UDP:
        // TESTED OK BY LWP
        return parse_udp(handler, payload_data, payload_len);
    case IPPROTO_IPIP:
        // TESTED OK BY LWP
        return parse_ipv4(handler, payload_data, payload_len);
    case IPPROTO_IPV6:
        // TESTED OK BY LWP
        return parse_ipv6(handler, payload_data, payload_len);
    default:
        LOG_ERROR("%s: trace id: %lu, layer: %s, stop parse next protocol %d", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_IPV6), next_proto);
        return payload_data;
    }
}

static const void *parse_tcp(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct tcphdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_TCP));
        return data;
    }

    struct tcphdr *hdr = (struct tcphdr *)data;
    uint16_t hdr_len = hdr->th_off << 2;
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_TCP, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_TCP), payload_len, length);

    // TESTED OK BY LWP
    return payload_data;
}

static const void *parse_udp(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct udp_hdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_UDP));
        return data;
    }

    struct udp_hdr *hdr = (struct udp_hdr *)data;
    uint16_t hdr_len = sizeof(struct udp_hdr);
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_UDP, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_UDP), payload_len, length);
    switch (ntohs(hdr->uh_dport))
    {
    case 4789: // VXLAN_DPORT
        // TESTED OK BY LWP
        return parse_vxlan(handler, payload_data, payload_len);
    case 2152: // GTP1U_PORT
        // TESTED OK BY LWP
        return parse_gtpv1_u(handler, payload_data, payload_len);
    default:
        // TESTED OK BY LWP
        return payload_data;
    }
}

static const void *parse_pppoe_ses(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < 8)
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_PPPOE));
        return data;
    }

    uint16_t next_proto = *((uint16_t *)data + 3);
    uint16_t hdr_len = 8;
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_PPPOE, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_PPPOE), payload_len, length);
    switch (next_proto)
    {
    case 0x2100: // PPPOE_TYPE_IPV4
        // TESTED OK BY LWP
        return parse_ipv4(handler, payload_data, payload_len);
    case 0x5700: // PPPOE_TYPE_IPV6
        return parse_ipv6(handler, payload_data, payload_len);
    default:
        LOG_ERROR("%s: trace id: %lu, layer: %s, stop parse next protocol %d", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_PPPOE), next_proto);
        return payload_data;
    }
}

static const void *parse_vxlan(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct vxlan_hdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_G_VXLAN));
        return NULL;
    }

    // struct vxlan_hdr *vxlan_hdr = (struct vxlan_hdr *)data;
    uint16_t hdr_len = sizeof(struct vxlan_hdr);
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_G_VXLAN, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_G_VXLAN), payload_len, length);
    // TESTED OK BY LWP
    return parse_ether(handler, payload_data, payload_len);
}

static const void *parse_vlan8021q(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct vlan_hdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_VLAN));
        return NULL;
    }

    struct vlan_hdr *hdr = (struct vlan_hdr *)data;
    uint16_t next_proto = ntohs(hdr->protocol);
    uint16_t hdr_len = sizeof(struct vlan_hdr);
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_VLAN, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_VLAN), payload_len, length);
    switch (next_proto)
    {
    case ETH_P_8021Q:
        // TESTED OK BY LWP
        return parse_vlan8021q(handler, payload_data, payload_len);
    case ETH_P_IP:
        // TESTED OK BY LWP
        return parse_ipv4(handler, payload_data, payload_len);
    case ETH_P_IPV6:
        // TESTED OK BY LWP
        return parse_ipv6(handler, payload_data, payload_len);
    case ETH_P_PPP_SES:
        // TESTED OK BY LWP
        return parse_pppoe_ses(handler, payload_data, payload_len);
    case ETH_P_MPLS_UC:
        return parse_mpls(handler, payload_data, payload_len);
    default:
        LOG_ERROR("%s: trace id: %lu, layer: %s, stop parse next protocol %d", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_VLAN), next_proto);
        return payload_data;
    }
}

static const void *parse_gtpv1_u(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < sizeof(struct gtp_hdr))
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_GTPV1_U));
        return NULL;
    }

    uint16_t hdr_len = parse_gtphdr_len((const struct gtp_hdr *)data);
    if (hdr_len < 0)
    {
        return data;
    }

    uint8_t next_proto = (((const uint8_t *)((const char *)data + hdr_len))[0]) >> 4;
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_GTPV1_U, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_GTPV1_U), payload_len, length);
    switch (next_proto)
    {
    case 4:
        // TESTED OK BY LWP
        return parse_ipv4(handler, payload_data, payload_len);
    case 6:
        // TESTED OK BY LWP
        return parse_ipv6(handler, payload_data, payload_len);
    default:
        LOG_ERROR("%s: trace id: %lu, layer: %s, stop parse next protocol %d", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_GTPV1_U), next_proto);
        return payload_data;
    }
}

static const void *parse_mpls(struct packet_parser *handler, const void *data, uint16_t length)
{
    if (length < 4)
    {
        LOG_ERROR("%s: trace id: %lu, layer: %s, err: data not enough", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_MPLS));
        return data;
    }

#define MPLS_LABEL_MASK (0xFFFFF000)
#define MPLS_EXP_MASK (0x00000E00)
#define MPLS_BLS_MASK (0x00000100)
#define MPLS_TTL_MASK (0x000000FF)

    /*
     * MPLS Format
     * 0                   1                   2                   3
     * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     * |                Label                  | Exp |S|       TTL     |
     * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     * Label : Label Value      20 bits
     * Exp   : Experimental Use  3 bits
     * S     : Bottom of Stack   1 bit
     * TTL   : Time to Live      8 bits
     */

    uint32_t *hdr = (uint32_t *)data;
    // unsigned int mpls_label = (ntohl(*hdr) & MPLS_LABEL_MASK) >> 12;
    // unsigned int mpls_exp = (ntohl(*hdr) & MPLS_EXP_MASK) >> 9;
    unsigned int mpls_bls = (ntohl(*hdr) & MPLS_BLS_MASK) >> 8;
    // unsigned int mpls_ttl = (ntohl(*hdr) & MPLS_TTL_MASK);

    uint16_t hdr_len = 4;
    uint16_t hdr_offset = (uintptr_t)data - (uintptr_t)(handler->packet_data);
    uint16_t payload_len = length - hdr_len;
    const void *payload_data = (const char *)data + hdr_len;

    if (packet_parser_push(handler, LAYER_TYPE_MPLS, hdr_offset, hdr_len, payload_len) != 0)
    {
        return data;
    }

    if (mpls_bls == 1)
    {
        uint8_t ip_version = (((uint8_t *)payload_data)[0]) >> 4;
        if (ip_version == 0)
        {
            /*
             * PW Ethernet Control Word
             * 0                   1                   2                   3
             * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
             * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             * |0 0 0 0|   Reserved            |       Sequence Number         |
             * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             * Reference: https://tools.ietf.org/html/rfc4448
             */
            payload_data = (const char *)payload_data + 4;
            payload_len = payload_len - 4;

            LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_MPLS), payload_len, length);
            return parse_ether(handler, payload_data, payload_len);
        }
        else if (ip_version == 4)
        {
            LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_MPLS), payload_len, length);
            // TESTED OK BY LWP
            return parse_ipv4(handler, payload_data, payload_len);
        }
        else if (ip_version == 6)
        {
            LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_MPLS), payload_len, length);
            return parse_ipv6(handler, payload_data, payload_len);
        }
        else
        {
            LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_MPLS), payload_len, length);
            // TESTED OK BY LWP
            return parse_ether(handler, payload_data, payload_len);
        }
    }
    else
    {
        LOG_DEBUG("%s: trace id: %lu, layer: %s, payload len: [%u/%u]", LOG_PKT_PARSER, handler->packet_id, layer2str(LAYER_TYPE_MPLS), payload_len, length);
        // TESTED OK BY LWP
        return parse_mpls(handler, payload_data, payload_len);
    }
}