diff options
Diffstat (limited to 'udp.c')
| -rw-r--r-- | udp.c | 18 |
1 files changed, 14 insertions, 4 deletions
@@ -36,25 +36,32 @@ unsigned short in_cksum(unsigned short *addr, int len) int sendCustomUDP(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 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)); + static unsigned int id = 1; int send_result = 0; + /* Abort if we couldn't allocate enough memory */ if (buffer == NULL) { perror("malloc"); exit(1); } - /* Ethernet header */ + /* Init ethernet header */ memcpy(eh->h_source, sourcemac, ETH_ALEN); memcpy(eh->h_dest, destmac, ETH_ALEN); eh->h_proto = 8; - /* SendTo struct */ + /* Init SendTo struct */ socket_address.sll_family = PF_PACKET; socket_address.sll_protocol = htons(ETH_P_IP); socket_address.sll_ifindex = ifindex; @@ -66,7 +73,7 @@ int sendCustomUDP(const int socket, const int ifindex, const unsigned char *sour socket_address.sll_addr[6] = 0x00;/*not used*/ socket_address.sll_addr[7] = 0x00;/*not used*/ - /* IP Header */ + /* Init IP Header */ ip->version = 4; ip->ihl = 5; ip->tos = 0x10; @@ -78,19 +85,22 @@ int sendCustomUDP(const int socket, const int ifindex, const unsigned char *sour 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)); - /* UDP Header */ + /* Init UDP Header */ udp->source = htons(20561); udp->dest = htons(20561); udp->check = 0; udp->len = htons(sizeof(struct udphdr) + datalen); + /* Insert actual data */ memcpy(rest, data, datalen); /* 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; } |