#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/types.h>
#include <math.h>
#include <stropts.h>
#include <ctype.h>
#include <errno.h>
#include <arpa/inet.h>
#include <netinet/ip.h>
#include <netinet/udp.h>

struct DNS_HEADER
{
unsigned short id; // identification number


    unsigned char rd :1; // recursion desired
    unsigned char tc :1; // truncated message
    unsigned char aa :1; // authoritive answer
    unsigned char opcode :4; // purpose of message
    unsigned char qr :1; // query/response flag

    unsigned char rcode :4; // response code
    unsigned char cd :1; // checking disabled
    unsigned char ad :1; // authenticated data
    unsigned char z :1; // its z! reserved
    unsigned char ra :1; // recursion available

    unsigned short q_count; // number of question entries
    unsigned short ans_count; // number of answer entries
    unsigned short auth_count; // number of authority entries
    unsigned short add_count; // number of resource entries




};


struct QUESTION
{
unsigned short qtype;
unsigned short qclass;
};


#pragma pack(push, 1)
struct R_DATA
{
unsigned short type;
unsigned short _class;
unsigned int ttl;
unsigned short data_len;
};
#pragma pack(pop)


struct RES_RECORD
{
unsigned char \*name;
struct R_DATA \*resource;
unsigned char \*rdata;
};


typedef struct
{
unsigned char \*name;
struct QUESTION \*ques;
} QUERY;


volatile int running_threads = 0;
volatile int found_srvs = 0;
volatile unsigned long per_thread = 0;
volatile unsigned long start = 0;
volatile unsigned long scanned = 0;
volatile int sleep_between = 0;
volatile int bytes_sent = 0;
volatile unsigned long hosts_done = 0;
FILE \*fd;


void ChangetoDnsNameFormat(unsigned char\* dns,unsigned char\* host)
{
int lock = 0 , i;
strcat((char\*)host,".");


    for(i = 0 ; i &lt; strlen((char*)host) ; i++)
    {
        if(host[i]=='.')
        {
            *dns++ = i-lock;
            for(;lock&lt;i;lock++)
            {
                *dns++=host[lock];
            }
            lock++;
        }
    }
    *dns++='\0';




}


void flood(void *par1)
{
running_threads++;
int thread_id = (int)par1;
unsigned long start_ip = htonl(ntohl(start)+(per_thread*thread_id));
unsigned long end = htonl(ntohl(start)+(per_thread(thread_id+1)));
unsigned long w;
int y;
unsigned char \*host = (unsigned char \*)malloc(50);
strcpy((char \*)host, ".");
unsigned char buf\[65536\],\*qname;
struct DNS_HEADER \*dns = NULL;
struct QUESTION \*qinfo = NULL;
dns = (struct DNS_HEADER \*)\&buf;


    dns-&gt;id = (unsigned short) htons(rand());
    dns-&gt;qr = 0;
    dns-&gt;opcode = 0;
    dns-&gt;aa = 0;
    dns-&gt;tc = 0;
    dns-&gt;rd = 1;
    dns-&gt;ra = 0;
    dns-&gt;z = 0;
    dns-&gt;ad = 0;
    dns-&gt;cd = 0;
    dns-&gt;rcode = 0;
    dns-&gt;q_count = htons(1);
    dns-&gt;ans_count = 0;
    dns-&gt;auth_count = 0;
    dns-&gt;add_count = htons(1);
    qname =(unsigned char*)&amp;buf[sizeof(struct DNS_HEADER)];

    ChangetoDnsNameFormat(qname , host);
    qinfo =(struct QUESTION*)&amp;buf[sizeof(struct DNS_HEADER) + (strlen((const char*)qname) + 1)];

    qinfo-&gt;qtype = htons( 255 );
    qinfo-&gt;qclass = htons(1);

    void *edns = (void *)qinfo + sizeof(struct QUESTION)+1;
    memset(edns, 0x00, 1);
    memset(edns+1, 0x29, 1);
    memset(edns+2, 0xFF, 2);
    memset(edns+4, 0x00, 7);

    int sizeofpayload = sizeof(struct DNS_HEADER) + (strlen((const char *)qname)+1) + sizeof(struct QUESTION) + 11;
    int sock;
    if((sock=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))&lt;0) {
        perror("cant open socket");
        exit(-1);
    }
    for(w=ntohl(start_ip);w&lt;htonl(end);w++)
    {
        struct sockaddr_in servaddr;
        bzero(&amp;servaddr, sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_addr.s_addr=htonl(w);
        servaddr.sin_port=htons(53);
        sendto(sock,(char *)buf,sizeofpayload,0, (struct sockaddr *)&amp;servaddr,sizeof(servaddr));
        bytes_sent+=24;
        scanned++;
        hosts_done++;
        usleep(sleep_between*1000);
    }
    close(sock);
    running_threads--;
    return;




}


void sighandler(int sig)
{
fclose(fd);
printf("\\n");
exit(0);
}


void recievethread()
{
printf("Started Listening Thread\\n");
int saddr_size, data_size, sock_raw;
struct sockaddr_in saddr;
struct in_addr in;


    unsigned char *buffer = (unsigned char *)malloc(65536);
    sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_UDP);
    if(sock_raw &lt; 0)
    {
        printf("Socket Error\n");
        exit(1);
    }
    while(1)
    {
        saddr_size = sizeof saddr;
        data_size = recvfrom(sock_raw , buffer , 65536 , 0 , (struct sockaddr *)&amp;saddr , &amp;saddr_size);
        if(data_size &lt;0 )
        {
            printf("Recvfrom error , failed to get packets\n");
            exit(1);
        }
        struct iphdr *iph = (struct iphdr*)buffer;
        if(iph-&gt;protocol == 17)
        {
            unsigned short iphdrlen = iph-&gt;ihl*4;
            struct udphdr *udph = (struct udphdr*)(buffer + iphdrlen);
            unsigned char* payload = buffer + iphdrlen + 8;
            if(ntohs(udph-&gt;source) == 53)
            {
                int body_length = data_size - iphdrlen - 8;
                struct DNS_HEADER *dns = (struct DNS_HEADER*) payload;
                if(dns-&gt;ra == 1)
                {
                    found_srvs++;
                    fprintf(fd,"%s . %d\n",inet_ntoa(saddr.sin_addr),body_length);
                    fflush(fd);
                }
            }
        }

    }
    close(sock_raw);




}


int main(int argc, char \*argv\[ \])
{


    if(argc &lt; 6){
        fprintf(stderr, "Invalid parameters!\n");
        fprintf(stdout, "Usage: %s &lt;class a start&gt; &lt;class a end&gt; &lt;outfile&gt; &lt;threads&gt; &lt;scan delay in ms&gt;\n", argv[0]);
        exit(-1);
    }
    fd = fopen(argv[3], "a");
    sleep_between = atoi(argv[5]);

    signal(SIGINT, &amp;sighandler);

    int threads = atoi(argv[4]);
    pthread_t thread;

    pthread_t listenthread;
    pthread_create( &amp;listenthread, NULL, &amp;recievethread, NULL);

    char *str_start = malloc(18);
    memset(str_start, 0, 18);
    str_start = strcat(str_start,argv[1]);
    str_start = strcat(str_start,".0.0.0");
    char *str_end = malloc(18);
    memset(str_end, 0, 18);
    str_end = strcat(str_end,argv[2]);
    str_end = strcat(str_end,".255.255.255");
    start = inet_addr(str_start);
    per_thread = (ntohl(inet_addr(str_end)) - ntohl(inet_addr(str_start))) / threads;
    unsigned long toscan = (ntohl(inet_addr(str_end)) - ntohl(inet_addr(str_start)));
    int i;
    for(i = 0;i&lt;threads;i++){
        pthread_create( &amp;thread, NULL, &amp;flood, (void *) i);
    }
    sleep(1);
    printf("Starting Scan...\n");
    char *temp = (char *)malloc(17);
    memset(temp, 0, 17);
    sprintf(temp, "Found");
    printf("%-16s", temp);
    memset(temp, 0, 17);
    sprintf(temp, "Host/s");
    printf("%-16s", temp);
    memset(temp, 0, 17);
    sprintf(temp, "B/s");
    printf("%-16s", temp);
    memset(temp, 0, 17);
    sprintf(temp, "Running Thrds");
    printf("%-16s", temp);
    memset(temp, 0, 17);
    sprintf(temp, "Done");
    printf("%s", temp);
    printf("\n");

    char *new;
    new = (char *)malloc(16*6);
    while (running_threads &gt; 0)
    {
        printf("\r");
        memset(new, '\0', 16*6);
        sprintf(new, "%s|%-15lu", new, found_srvs);
        sprintf(new, "%s|%-15d", new, scanned);
        sprintf(new, "%s|%-15d", new, bytes_sent);
        sprintf(new, "%s|%-15d", new, running_threads);
        memset(temp, 0, 17);
        int percent_done=((double)(hosts_done)/(double)(toscan))*100;
        sprintf(temp, "%d%%", percent_done);
        sprintf(new, "%s|%s", new, temp);
        printf("%s", new);
        fflush(stdout);
        bytes_sent=0;
        scanned = 0;
        sleep(1);
    }
    printf("\n");
    fclose(fd);
    return 0;



`}`