原始套接字程序

有时候测试虚拟交换机需要打流量，每次创建虚拟机太麻烦，所以写了一个可以直接向端口打流量的小程序，buff是报文内容。

unsigned char str2hex(char x)
{
    if (x >= '0' && x <= '9') {
        return x - 48;
    } else if (x >= 'a' && x <= 'z') {
        return x - 97 + 10;
    } else if (x >= 'A' && x <= 'Z') {
        return x - 65 + 10;
    } else {
        return 255;
    }
}

void mac_convert(char *str, unsigned char *mac)
{
    int i;
    for (i = 0; i < 6; i++) {
        mac[i] = (str2hex(str[i*2]) << 4) + str2hex(str[i*2 +1]);
    }
}

static int getifindex(int fd, const char *device)
{
    struct ifreq ifr;
    int ret;

    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
    ret = ioctl(fd, SIOCGIFINDEX, &ifr);
    if (ret < 0) {
        return -1;
    }
    return ifr.ifr_ifindex;
}

void usage()
{
    printf("usage:\n");
    printf("\t./a.out   ifname   dstmac   srcmac\n");
}

int main(int argc, char **argv)
{
    unsigned char buff[512] = "\x00.....";
    int fd;
    int ifindex;
    struct sockaddr_ll sa;
    unsigned char mac[6];

    if (argc < 2) {
        usage();
        return -1;
    }
    if (strcmp(argv[1], "-help") == 0) {
        usage();
        return 0;
    }
    fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    ifindex = getifindex(fd, argv[1]);
    sa.sll_family = AF_PACKET;
    sa.sll_ifindex = ifindex;
    sa.sll_protocol = htons(0x0003);

    if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
        perror("bind error");
        return -1;
    }
    if (argv[2] != NULL) {
        mac_convert(argv[2], mac);
        memcpy(&buff[0], mac, 6);
    }
    if (argv[3] != NULL) {
        mac_convert(argv[3], mac);
        memcpy(&buff[6], mac, 6);
    }
    while (1) {
        if (write(fd, buff, 98) < 0) {
            perror("write error");
            return -1;
        }
        sleep(1);
    }
    return 0;
}