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#include <malloc.h>
#include <string.h>
#include <math.h>
#include <sys/socket.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <netinet/in.h>
#include <linux/udp.h>
#include <linux/if_arp.h>
#include <stdlib.h>
#include <stdio.h>
unsigned short in_cksum(unsigned short *addr, int len)
{
int nleft = len;
int sum = 0;
unsigned short *w = addr;
unsigned short answer = 0;
while (nleft > 1) {
sum += *w++;
nleft -= 2;
}
if (nleft == 1) {
*(unsigned char *) (&answer) = *(unsigned char *) w;
sum += answer;
}
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
answer = ~sum;
return (answer);
}
unsigned short udp_sum_calc(unsigned char *src_addr,unsigned char *dst_addr, unsigned char *data, unsigned short len) {
unsigned short prot_udp=17;
unsigned short padd=0;
unsigned short word16;
unsigned int sum = 0;
int i;
/* Padding ? */
padd = (len % 2);
if (padd){
data[len]=0;
}
/* header+data */
for (i = 0; i < len + padd; i += 2){
word16 = ((data[i] << 8) & 0xFF00) + (data[i + 1] & 0xFF);
sum += word16;
}
/* source ip */
for (i = 0; i < 4; i += 2){
word16 = ((src_addr[i] << 8) & 0xFF00) + (src_addr[i + 1] & 0xFF);
sum += word16;
}
/* dest ip */
for (i = 0; i < 4; i += 2){
word16 = ((dst_addr[i] << 8) & 0xFF00) + (dst_addr[i + 1] & 0xFF);
sum += word16;
}
sum += prot_udp + len;
while (sum>>16)
sum = (sum & 0xFFFF) + (sum >> 16);
sum = ~sum;
if ((unsigned short)sum == 0)
sum = 0xFFFF;
return (unsigned short) sum;
}
int send_custom_udp(const int socket, const int ifindex, const unsigned char *sourcemac, const unsigned char *destmac, const struct in_addr *sourceip, const int sourceport, const struct in_addr *destip, const int destport, const unsigned char *data, const int datalen) {
struct sockaddr_ll socket_address;
/*
* Create a buffer for the full ethernet frame
* and align header pointers to the correct positions.
*/
void* buffer = (void*)malloc(ETH_FRAME_LEN);
struct ethhdr *eh = (struct ethhdr *)buffer;
struct iphdr *ip = (struct iphdr *)(buffer+14);
struct udphdr *udp = (struct udphdr *)(buffer+14+20);
unsigned char *rest = (unsigned char *)(buffer+20+14+sizeof(struct udphdr));
if (((void *)rest - (void*)buffer) + datalen > ETH_FRAME_LEN) {
fprintf(stderr, "packet size too large\n");
free(buffer);
return 0;
}
static unsigned int id = 1;
int send_result = 0;
/* Abort if we couldn't allocate enough memory */
if (buffer == NULL) {
perror("malloc");
exit(1);
}
/* Init ethernet header */
memcpy(eh->h_source, sourcemac, ETH_ALEN);
memcpy(eh->h_dest, destmac, ETH_ALEN);
eh->h_proto = 8;
/* Init SendTo struct */
socket_address.sll_family = PF_PACKET;
socket_address.sll_protocol = htons(ETH_P_IP);
socket_address.sll_ifindex = ifindex;
socket_address.sll_hatype = ARPHRD_ETHER;
socket_address.sll_pkttype = PACKET_OTHERHOST;
socket_address.sll_halen = ETH_ALEN;
memcpy(socket_address.sll_addr, eh->h_source, ETH_ALEN);
socket_address.sll_addr[6] = 0x00;/*not used*/
socket_address.sll_addr[7] = 0x00;/*not used*/
/* Init IP Header */
ip->version = 4;
ip->ihl = 5;
ip->tos = 0x10;
ip->tot_len = htons(datalen + 8 + 20);
ip->id = htons(id++);
ip->frag_off = htons(0x4000);
ip->ttl = 64;
ip->protocol = 17; /* UDP */
ip->check = 0x0000;
ip->saddr = sourceip->s_addr;
ip->daddr = destip->s_addr;
/* Calculate checksum for IP header */
ip->check = in_cksum((unsigned short *)ip, sizeof(struct iphdr));
/* Init UDP Header */
udp->source = htons(sourceport);
udp->dest = htons(destport);
udp->len = htons(sizeof(struct udphdr) + datalen);
udp->check = 0;
/* Insert actual data */
memcpy(rest, data, datalen);
/* Add UDP checksum */
udp->check = udp_sum_calc((unsigned char *)&(ip->saddr), (unsigned char *)&(ip->daddr), (unsigned char *)udp, sizeof(struct udphdr) + datalen);
udp->check = htons(udp->check);
/* Send the packet */
send_result = sendto(socket, buffer, datalen+8+14+20, 0, (struct sockaddr*)&socket_address, sizeof(socket_address));
free(buffer);
/* Return amount of _data_ bytes sent */
return send_result-8-14-20;
}
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