/*****************************************************************************
 * @Author                      : Songsk
 * @Date                        : 2020-11-10
 * @LastEditors                 : songshuaikang@comleader.com.cn
 * @Description                 : Sync Time with Schedule.
 *******************************************************************************/
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <pcap.h>
#include <stdlib.h>

#define uint unsigned int
#define uchar unsigned char

typedef struct frame_head_t
{
    uchar dmac[6];
    uchar smac[6];
    // uchar dot1q[4];
    uchar protocol[2];
    uchar padding;
    uchar len;
}FRAME_HEAD_T;
typedef struct timeval TS_TO_PROXY_T;

#define SNAP_LEN 65536

#define _ENCRYPT(a,b,c) (a=(b^c)) 
#define _DECRYPT _ENCRYPT
#define _CHECKSUM(_checksum, _cipher, _key, _len)\
        {\
            uint _m_i = 0;\
            uint sum = 0;\
            for(_m_i=0; _m_i< _len; _m_i++)\
                sum = sum + (0xffffffff & _cipher[_m_i]) + (0xffffffff & _key[_m_i]);\
            _checksum =  0xff - (0xff & (sum)) - ((sum) >> 8);\
        }
#define ENCRYPT_FUNC(_cipher, _plain, _key, _len)\
{\
    int _m_i = 0;\
    for(_m_i=0; _m_i< _len; _m_i++)\
        _ENCRYPT(_cipher[_m_i], _plain[_m_i], _key[_m_i]);\
}

#define DECRYPT_FUNC(_plain, _cipher,  _key, _len)\
{\
    int _m_i = 0;\
    for(_m_i=0; _m_i< _len; _m_i++)\
        _DECRYPT( _plain[_m_i],_cipher[_m_i], _key[_m_i]);\
}

#define dPrint(fmt, ...) do{fprintf(stderr, "[%s:%d] " fmt "\r\n", __FUNCTION__, __LINE__, ##__VA_ARGS__);}while(0)
#define HexPrint(_buf, _len) \
{\
    int _m_i = 0;\
    char *_m_buf = (char *)(_buf);\
    int _m_len = (int)(_len);\
    printf("[%s:%d] \r\n", __FUNCTION__, __LINE__);\
    printf("*****************************\n");\
    for(_m_i = 0; _m_i < _m_len; _m_i++)\
    {\
        printf("\033[32m%02x \033[0m", _m_buf[_m_i] & 0xff);\
        if(!((_m_i+1) % 10)) printf("\n");\
    }\
    printf("\nsize = %d\n*****************************\n", _m_len);\
}

/************************************************ 
 * Add By Tianlun Song in Nov 11, 2020.
 * Title: 设置操作系统时间
 * Argu Type: struct timeval 
 * Usage: 
 *     set_sys_time(time); 
**************************************************/
void set_sys_time(TS_TO_PROXY_T *time)
{
    // char strTime[26] = {0};
    //printf("%d.%d\n", time->tv_sec, time->tv_usec);
    printf("The time before set：");
    fflush(stdout);
    system("date");
 
    settimeofday(time,NULL);
 
    printf("The time after set ：");
    fflush(stdout);
    system("date");
}

void dispatcher_handler(u_char *temp1, const struct pcap_pkthdr *header, const u_char *pkt_data)
{
    // HexPrint((const char *)pkt_data, header->caplen);

    FRAME_HEAD_T head;
    TS_TO_PROXY_T time;
    memset(&head, 0, sizeof(head));
    memset(&time, 0, sizeof(time));

    memcpy(&head, pkt_data, sizeof(head));
    // printf("head info: protocol is [0x%X 0x%X], padding is [0x%X], len is [0x%X]\n", 
    //     head.protocol[0],head.protocol[1], head.padding, head.len );
    if(head.protocol[1] == 0x89)
    {
        uchar plantext[head.len],ciphertext[head.len],key[head.len];
        memset(plantext, 0, head.len);
        memset(ciphertext, 0, head.len);
        memset(key, 0, head.len);

        head.padding -= 4;
        memcpy(ciphertext, pkt_data + head.padding, head.len);
        memcpy(key, pkt_data + head.padding + head.len, head.len);

        //printf("ciphertext:[0x%x]\tkey:[0x%x]\n",ciphertext, key);

        DECRYPT_FUNC(plantext, ciphertext, key, head.len);
        //printf("plaintext:[0x%x]\n",plantext);
        
        memcpy(&time, plantext, sizeof(time));
        set_sys_time(&time);
    }
}

int main()
{
    pcap_t *handle;
    char err_buf[PCAP_ERRBUF_SIZE];
    char dev_str[64];
    struct bpf_program fp;

    strcpy(dev_str, "linux_dal");
    printf("Sniff Device is %s\n", dev_str);

    /* open capture device */
    handle = pcap_open_live(dev_str, SNAP_LEN, 1, 1000, err_buf);
    if (handle == NULL)
    {
        fprintf(stderr, "Couldn't open device %s: %s\n", dev_str, err_buf);
        return 0;
    }

    /* compile the filter expression */
    if (pcap_compile(handle, &fp, "ether proto 0x889", 0, 24) == -1)
    {
        fprintf(stderr, "Couldn't parse filter %s: %s\n",
                "***", pcap_geterr(handle));
        return 0;
    }

    /* apply the compiled filter */
    if (pcap_setfilter(handle, &fp) == -1)
    {
        fprintf(stderr, "Couldn't install filter %s: %s\n",
                "***", pcap_geterr(handle));
        return 0;
    }

    pcap_loop(handle, -1, dispatcher_handler, NULL);
    /* cleanup */
    pcap_freecode(&fp);
    pcap_close(handle);

    dPrint("Capture complete.");
    return 0;
}