c – libpcap和无线信号捕获

我正在尝试编写一个c应用程序( linux),它将捕获无线数据包以及相关的信号强度(以dBm为单位).捕获部分很简单,但问题是我找不到任何关于如何获得每个数据包的信号强度的文档.

它是标题的一部分吗？

这是我到目前为止所拥有的：

printf("Device: %sn",dev);
printf("Number of packets: %dn",num_packets);
printf("Filter expression: %sn",filter_exp);

/* open capture device */
    pcap_t *handler = pcap_create("wlan0",errbuf);
    if (handler == NULL)
    {
        exit(-1);
    }
    if(pcap_set_rfmon(handler,1)==0 )
    {
        printf("monitor mode enabledn");
    }
    pcap_set_snaplen(handler,2048);  // Set the snapshot length to 2048
    pcap_set_promisc(handler,0); // Turn promiscuous mode off
    pcap_set_timeout(handler,512); // Set the timeout to 512 milliseconds
    int status = pcap_activate(handler);


/* now we can set our callback function */
pcap_loop(handle,num_packets,got_packet,NULL);

这是got_packet代码：

/* define ethernet header */
ethernet = (struct sniff_ethernet*)(packet);

/* define/compute ip header offset */
ip = (struct sniff_ip*)(packet + SIZE_ETHERNET);
size_ip = IP_HL(ip)*4;
if (size_ip < 20) {
    printf("   * Invalid IP header length: %u bytesn",size_ip);
    return;
}

/* print source and destination IP addresses */
printf("       From: %sn",inet_ntoa(ip->ip_src));
printf("         To: %sn",inet_ntoa(ip->ip_dst));

/* determine protocol */    
switch(ip->ip_p) {
    case IPPROTO_TCP:
        printf("   Protocol: TCPn");
        break;
    case IPPROTO_UDP:
        printf("   Protocol: UDPn");
        return;
    case IPPROTO_ICMP:
        printf("   Protocol: ICMPn");
        return;
    case IPPROTO_IP:
        printf("   Protocol: IPn");
        return;
    default:
        printf("   Protocol: unknownn");
        return;
}

/* define/compute tcp header offset */
tcp = (struct sniff_tcp*)(packet + SIZE_ETHERNET + size_ip);
size_tcp = TH_OFF(tcp)*4;
if (size_tcp < 20) {
    printf("   * Invalid TCP header length: %u bytesn",size_tcp);
    return;
}

printf("   Src port: %dn",ntohs(tcp->th_sport));
printf("   Dst port: %dn",ntohs(tcp->th_dport));

/* define/compute tcp payload (segment) offset */
payload = (char *)(packet + SIZE_ETHERNET + size_ip + size_tcp);

/* compute tcp payload (segment) size */
size_payload = ntohs(ip->ip_len) - (size_ip + size_tcp);

/*
 * Print payload data; it might be binary,so don't just
 * treat it as a string.
 */
if (size_payload > 0) {
    printf("   Payload (%d bytes):n",size_payload);
    //print_payload(payload,size_payload);
}

任何帮助都会非常感激.

更新：
/ *************** /
这是一个更新：
因此根据我的研究和Guy Scott提到我正在寻找错误的信息.我需要查看无线数据包,而是加载以太网数据包.所以这是更新的代码：

pcap_set_snaplen(handle,2048);  // Set the snapshot length to 2048
    pcap_set_promisc(handle,1);     // Turn promiscuous mode off
    pcap_set_timeout(handle,512);   // Set the timeout to 512 milliseconds
    int status = pcap_activate(handle);

    if(pcap_set_datalink(handle,DLT_IEEE802_11_RADIO) == -1) {
        printf("Couldn't set datalink type %s: %sn",device,pcap_geterr(handle));
    }

所以现在的问题是解析数据包,这似乎是一个非常棘手的问题.我对源地址,目标地址和相关信号等感兴趣.我不知道如何匹配和加载数据包中的数据并将其与radiotap结构相匹配.

struct ieee80211_radiotap_header {
u_int8_t    it_version; /* set to 0 */
u_int8_t    it_pad;
u_int16_t   it_len; /* entire length */
u_int32_t   it_present; /* fields present */
} __attribute__((__packed__));

/* Presence bits */
#define RADIOTAP_TSFT   0
#define RADIOTAP_FLAGS  1
#define RADIOTAP_RATE   2
#define RADIOTAP_CHANNEL    3
#define RADIOTAP_FHSS   4
#define RADIOTAP_ANTENNA_SIGNAL 5
#define RADIOTAP_ANTENNA_NOISE  6
#define RADIOTAP_LOCK_QUALITY   7
#define RADIOTAP_TX_ATTENUATION 8
#define RADIOTAP_DB_TX_ATTENUATION  9
#define RADIOTAP_DBM_TX_POWER   10
#define RADIOTAP_ANTENNA    11
#define RADIOTAP_DB_ANTENNA_SIGNAL  12

void process_packet (u_char * args,const struct pcap_pkthdr *header,const u_char * packet)
{
    struct ieee80211_radiotap_header *packet_header = (struct ieee80211_radiotap_header *) header;
    // This is where I am stuck

有人告诉我,一旦我捕获了数据包,我该如何从中提取上述值？

谢谢