raw_socket.c

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

int main(int argc, char **argv)
{
    int sock;
    int ret;

    if (argc != 2) {
        fprintf(stderr, "<%s> interface\n", argv[0]);
        return -1;
    }

    sock = socket(AF_PACKET, SOCK_RAW, 0);
    if (sock < 0) {
        return -1;
    }

    uint8_t sendbuf[2048];
    uint8_t *data;
    int datalen = 0;
    int ifindex;
    struct ether_header *eh;

    eh = (struct ether_header *)sendbuf;

    data = sendbuf + sizeof(*eh);
    datalen += sizeof(*eh);

    struct ifreq ifr;

    memset(&ifr, 0, sizeof(ifr));

    strcpy(ifr.ifr_name, argv[1]);
    ret = ioctl(sock, SIOCGIFINDEX, &ifr);
    if (ret < 0) {
        return -1;
    }

    ifindex = ifr.ifr_ifindex;

    uint8_t dest[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
    uint8_t srcmac[6];

    memset(&ifr, 0, sizeof(ifr));

    strcpy(ifr.ifr_name, argv[1]);
    ret = ioctl(sock, SIOCGIFHWADDR, &ifr);
    if (ret < 0) {
        return -1;
    }

    memcpy(srcmac, (uint8_t *)(ifr.ifr_hwaddr.sa_data), 6);

    char *msg = "hello world";
    memcpy(data, msg, strlen(msg) + 1);
    datalen += strlen(msg) + 1;

    memcpy(eh->ether_shost, srcmac, 6);
    memcpy(eh->ether_dhost, dest, 6);
    eh->ether_type = htons(0x0800);

    struct sockaddr_ll lladdr;

    lladdr.sll_ifindex = ifindex;

    lladdr.sll_halen = ETH_ALEN;

    lladdr.sll_addr[0] = dest[0];
    lladdr.sll_addr[1] = dest[1];
    lladdr.sll_addr[2] = dest[2];
    lladdr.sll_addr[3] = dest[3];
    lladdr.sll_addr[4] = dest[4];
    lladdr.sll_addr[5] = dest[5];

    while (1) {
        sleep(1);

        ret = sendto(sock, sendbuf, datalen, 0, (struct sockaddr *)&lladdr, sizeof(lladdr));
        if (ret < 0) {
            break;
        }
    }

    return 0;
}