From here:
Send a raw Ethernet frame in Linux (GitHub)
Explanation is here
Sending raw Ethernet packets from a specific interface in C on Linux
packet, AF_PACKET - packet interface on device level In addition Note that this works only for some socket types, particularly AF_INET sockets. It is not supported for packet sockets (use normal bind(2) there) Raw socket with device bind using setsockopt() system is not working More for UDP Programming raw udp sockets in C on Linux
/*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*/
#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/ether.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
#define DEFAULT_IF "eth0"
#define BUF_SIZ 1024
int main(int argc, char *argv[])
{
int sockfd;
struct ifreq if_idx;
struct ifreq if_mac;
int tx_len = 0;
char sendbuf[BUF_SIZ];
struct ether_header *eh = (struct ether_header *) sendbuf;
struct iphdr *iph = (struct iphdr *) (sendbuf + sizeof(struct ether_header));
struct sockaddr_ll socket_address;
char ifName[IFNAMSIZ];
/* Get interface name */
if (argc > 1)
strcpy(ifName, argv[1]);
else
strcpy(ifName, DEFAULT_IF);
/* Open RAW socket to send on */
if ((sockfd = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW)) == -1) {
perror("socket");
}
/* 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 */
memset(sendbuf, 0, BUF_SIZ);
/* 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);
tx_len += sizeof(struct ether_header);
/* Packet data */
sendbuf[tx_len++] = 0xde;
sendbuf[tx_len++] = 0xad;
sendbuf[tx_len++] = 0xbe;
sendbuf[tx_len++] = 0xef;
/* 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;
/* Send packet */
if (sendto(sockfd, sendbuf, tx_len, 0, (struct sockaddr*)&socket_address, sizeof(struct sockaddr_ll)) < 0)
printf("Send failed\n");
return 0;
}
=======================
Lately I’ve been writing some code to send packets to a specific MAC address from a specific interface. I’m sure this will come in handy again so here is how it goes:
Includes:
(might not need all of these)
#include <netinet/in.h> #include <sys/socket.h> #include <arpa/inet.h> #include <net/if.h> #include <netinet/ip.h> #include <netinet/udp.h> #include <netinet/ether.h> #include <linux/if_packet.h>
Open the raw socket:
int sockfd;
...
/* Open RAW socket to send on */
if ((sockfd = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW)) == -1) {
perror("socket");
}
Get the index of the interface to send on:
struct ifreq if_idx;
...
memset(&if_idx, 0, sizeof(struct ifreq));
strncpy(if_idx.ifr_name, "eth0", IFNAMSIZ-1);
if (ioctl(sock, SIOCGIFINDEX, &if_idx) < 0)
perror("SIOCGIFINDEX");
Get the MAC address of the interface to send on:
struct ifreq if_mac;
...
memset(&if_mac, 0, sizeof(struct ifreq));
strncpy(if_mac.ifr_name, "eth0", IFNAMSIZ-1);
if (ioctl(sock, SIOCGIFHWADDR, &if_mac) < 0)
perror("SIOCGIFHWADDR");
Get the IP address of the interface to send on:
struct ifreq if_ip;
...
memset(&if_ip, 0, sizeof(struct ifreq));
strncpy(if_ip.ifr_name, "eth0", IFNAMSIZ-1);
if (ioctl(sock, SIOCGIFADDR, &if_ip) < 0)
perror("SIOCGIFADDR");
Construct the Ethernet header:
int tx_len = 0; char sendbuf[1024]; struct ether_header *eh = (struct ether_header *) sendbuf; ... memset(sendbuf, 0, 1024); /* 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; eh->ether_type = htons(ETH_P_IP); tx_len += sizeof(struct ether_header);
Construct the IP header:
struct iphdr *iph = (struct iphdr *) (sendbuf + sizeof(struct ether_header));
...
/* IP Header */
iph->ihl = 5;
iph->version = 4;
iph->tos = 16; // Low delay
iph->id = htons(54321);
iph->ttl = ttl; // hops
iph->protocol = 17; // UDP
/* Source IP address, can be spoofed */
iph->saddr = inet_addr(inet_ntoa(((struct sockaddr_in *)&if_ip.ifr_addr)->sin_addr));
// iph->saddr = inet_addr("192.168.0.112");
/* Destination IP address */
iph->daddr = inet_addr("192.168.0.111");
tx_len += sizeof(struct iphdr);
Construct the UDP header:
struct udphdr *udph = (struct udphdr *) (sendbuf + sizeof(struct iphdr) + sizeof(struct ether_header)); ... /* UDP Header */ udph->source = htons(3423); udph->dest = htons(5342); udph->check = 0; // skip tx_len += sizeof(struct udphdr);
Fill in UDP payload:
/* Packet data */ sendbuf[tx_len++] = 0xde; sendbuf[tx_len++] = 0xad; sendbuf[tx_len++] = 0xbe; sendbuf[tx_len++] = 0xef;
Fill in remaining header info:
unsigned short csum(unsigned short *buf, int nwords)
{
unsigned long sum;
for(sum=0; nwords>0; nwords--)
sum += *buf++;
sum = (sum >> 16) + (sum &0xffff);
sum += (sum >> 16);
return (unsigned short)(~sum);
}
...
/* Length of UDP payload and header */
udph->len = htons(tx_len - sizeof(struct ether_header) - sizeof(struct iphdr));
/* Length of IP payload and header */
iph->tot_len = htons(tx_len - sizeof(struct ether_header));
/* Calculate IP checksum on completed header */
iph->check = csum((unsigned short *)(sendbuf+sizeof(struct ether_header)), sizeof(struct iphdr)/2);
Send the raw Ethernet packet:
/* Destination address */
struct sockaddr_ll socket_address;
...
/* 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;
/* Send packet */
if (sendto(sock, sendbuf, tx_len, 0, (struct sockaddr*)&socket_address, sizeof(struct sockaddr_ll)) < 0)
printf("Send failed\n");
Update:
As in the comments, I’ve written a working example that can be found here:
https://gist.github.com/1922600
Change the destination MAC address (e.g. 00:11:22:33:44:55) and compile:
gcc sendRawEth.c -o sendRawEth
In one terminal run tcpdump to observe the packets:
sudo tcpdump -nettti eth0 '(ether dst host 00:11:22:33:44:55)'
And in another run the program as root:
sudo ./sendRawEth eth0
References:
http://aschauf.landshut.org/fh/linux/udp_vs_raw/ch01s03.html
http://www.tenouk.com/Module43a.html
http://linux.die.net/man/3/sendto
=====================================
void BindToInterface(int raw , char *device , int protocol) {
struct sockaddr_ll sll;
struct ifreq ifr; bzero(&sll , sizeof(sll));
bzero(&ifr , sizeof(ifr));
strncpy((char *)ifr.ifr_name ,device , IFNAMSIZ);
//copy device name to ifr
if((ioctl(raw , SIOCGIFINDEX , &ifr)) == -1)
{
perror("Unable to find interface index");
exit(-1);
}
sll.sll_family = AF_PACKET;
sll.sll_ifindex = ifr.ifr_ifindex;
sll.sll_protocol = htons(protocol);
if((bind(raw , (struct sockaddr *)&sll , sizeof(sll))) ==-1)
{
perror("bind: ");
exit(-1);
}
return 0;
}