#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/ether.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>

#define MY_DEST_MAC0 0x00
#define MY_DEST_MAC1 0x00
#define MY_DEST_MAC2 0x00
#define MY_DEST_MAC3 0x00
#define MY_DEST_MAC4 0x00
#define MY_DEST_MAC5 0x00

char* server=(char*)"192.168.10.25";
unsigned port=8888;
size_t buflen=1500;
char ifName[IFNAMSIZ]="eth1";

void die(const char *s) { perror(s); exit(1); }

char* FillBuf(char* buf, size_t s)
{
 int i;
 for (i = 0; i < s - 1; i++)
      buf[i] = 'a' + rand()%26;
 buf[i] = '\0';
 return buf;
}

void Usage()
{
 printf("Usage: udprawsender [OPTIONS]\n"
 "OPTIONS:\n"
 "-i int - Network interface name\n"
 "-d host - Destination host\n"
 "-p port - Destination port\n"
 "-s size - Packet size\n"
 );
}
 
int ParceArgs(int argc, char *argv[])
{
 int opt;
 while((opt = getopt(argc, argv, "hp:d:s:i:")) != -1)
  {
   switch(opt)
    {
     case 'i':
            strcpy(ifName, optarg);
            break;
     case 'p':
            port = atoi(optarg);
            break;
     case 's':
            buflen = atoi(optarg);
            break;
     case 'd':
            server = strdup(optarg);
            break;
     default:
            Usage();
            exit(1);
    }
  }
 return 1;
}
int main(int argc, char *argv[])
{

 ParceArgs(argc,argv);

 char* sendbuf =  (char*) malloc(buflen);
 if (!sendbuf) die("Can't allocate memory");
 memset(sendbuf,0,buflen);

 int sockfd;
 struct ifreq if_idx;
 struct ifreq if_mac;
 struct ether_header *eh = (struct ether_header *) sendbuf;
 struct iphdr *iph = (struct iphdr *) (sendbuf + sizeof(struct ether_header));
 struct udphdr *udph = (struct udphdr *) (sendbuf + sizeof(struct ether_header) + sizeof(struct iphdr));
 char* data = (char *) (sendbuf + sizeof(struct ether_header) + sizeof(struct iphdr) + sizeof(struct udphdr));
 struct ifreq if_ip;
 struct sockaddr_ll socket_address;
 int ttl=250;

 /* Open RAW socket to send on */
 if ((sockfd = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW)) == -1) { perror("socket"); }
 
 memset(&if_ip, 0, sizeof(struct ifreq));
 strncpy(if_ip.ifr_name, ifName, IFNAMSIZ-1);
 if (ioctl(sockfd, SIOCGIFADDR, &if_ip) < 0)
    perror("SIOCGIFADDR");

 /* Get the index of the interface to send on */
 memset(&if_idx, 0, sizeof(struct ifreq));
 strncpy(if_idx.ifr_name, ifName, IFNAMSIZ-1);
 if (ioctl(sockfd, SIOCGIFINDEX, &if_idx) < 0) perror("SIOCGIFINDEX");
 /* Get the MAC address of the interface to send on */
 memset(&if_mac, 0, sizeof(struct ifreq));
 strncpy(if_mac.ifr_name, ifName, IFNAMSIZ-1);
 if (ioctl(sockfd, SIOCGIFHWADDR, &if_mac) < 0) perror("SIOCGIFHWADDR");

 /* Construct the Ethernet header */
 /* Ethernet header */
 eh->ether_shost[0] = ((uint8_t *)&if_mac.ifr_hwaddr.sa_data)[0];
 eh->ether_shost[1] = ((uint8_t *)&if_mac.ifr_hwaddr.sa_data)[1];
 eh->ether_shost[2] = ((uint8_t *)&if_mac.ifr_hwaddr.sa_data)[2];
 eh->ether_shost[3] = ((uint8_t *)&if_mac.ifr_hwaddr.sa_data)[3];
 eh->ether_shost[4] = ((uint8_t *)&if_mac.ifr_hwaddr.sa_data)[4];
 eh->ether_shost[5] = ((uint8_t *)&if_mac.ifr_hwaddr.sa_data)[5];
 eh->ether_dhost[0] = MY_DEST_MAC0;
 eh->ether_dhost[1] = MY_DEST_MAC1;
 eh->ether_dhost[2] = MY_DEST_MAC2;
 eh->ether_dhost[3] = MY_DEST_MAC3;
 eh->ether_dhost[4] = MY_DEST_MAC4;
 eh->ether_dhost[5] = MY_DEST_MAC5;
 /* Ethertype field */
 eh->ether_type = htons(ETH_P_IP);

 /* IP Header */
 iph->ihl = 5; /* header length */
 iph->version = 4;
 iph->tos = 16; // Low delay
 iph->tot_len = buflen;
 iph->id = htons(54321);
 iph->frag_off = 0x00; //16 bit field = [0:2] flags + [3:15] offset = 0x0
 iph->ttl = ttl; //16 bit time to live (or maximal number of hops)
 iph->protocol = 17; // UDP
 iph->check = 0; //16 bit checksum of IP header. Can't calculate at this point
 /* Source IP address, can be spoofed */
 iph->saddr = inet_addr(inet_ntoa(((struct sockaddr_in *)&if_ip.ifr_addr)->sin_addr));
 /* Destination IP address */
 iph->daddr = inet_addr(server);

 udph->source=htons(55555);
 udph->dest=htons(port);
// udph->len
// udph->check

 /* Packet data */
 FillBuf(data, buflen - sizeof(struct ether_header) - sizeof(struct iphdr) - sizeof(struct udphdr));

 /* Index of the network device */
 socket_address.sll_ifindex = if_idx.ifr_ifindex;
 /* Address length*/
 socket_address.sll_halen = ETH_ALEN;
 /* Destination MAC */
 socket_address.sll_addr[0] = MY_DEST_MAC0;
 socket_address.sll_addr[1] = MY_DEST_MAC1;
 socket_address.sll_addr[2] = MY_DEST_MAC2;
 socket_address.sll_addr[3] = MY_DEST_MAC3;
 socket_address.sll_addr[4] = MY_DEST_MAC4;
 socket_address.sll_addr[5] = MY_DEST_MAC5;

 while (1)
 {
  /* Send packet */
  if (sendto(sockfd, sendbuf, buflen, 0, (struct sockaddr*)&socket_address, sizeof(struct sockaddr_ll)) < 0)
     die("Send failed\n");
 }

 return 0;
}