#include <netinet/in.h>
#include <net/if.h>
#include <net/ethernet.h>
#include <net/bpf.h>
#include <sys/ioctl.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <errno.h>
#include <err.h>

#define	DEVICE_BPF	"/dev/bpf"
static int verbose;
static const char *out_net  = "epair0a";
static const char *dest_net = NULL;
struct ether_addr *daddr;

#define PAYLOAD_LEN 64
union __attribute__((packed)) frame {
	struct {
		struct ether_header header;
		unsigned char payload[PAYLOAD_LEN];
	} frame;

	unsigned char buffer[ETHER_MAX_LEN];
} out_buffer ;


/* bpf */
int bpf = -1;

static const char *fake_dest = "6:66:6:66:6:66";

#define VPRINTF(...) if(verbose) {printf(__VA_ARGS__);};
#define EPRINTF(...) do  {fprintf(stderr, __VA_ARGS__); } while(0);

static void __attribute__((__noreturn__)) usage(void)
{
	fputs("\nUsage:\n", stderr);
	fputs("sockraw [--if iface][--mac maca[-to iface]][--packets samples][--verbose]\n", stderr);
	fputs("  --if     : interface\n", stderr);
	fputs("  --mac    : destination MAC address\n", stderr);
	fputs("  --to     : destination MAC address from interface name\n", stderr);
	fputs("  --packets: packets samples to sent\n", stderr);
	fputs("  --verbose: verbose\n", stderr);
	exit(EXIT_SUCCESS);
}

/* open BPF interface
 *
 * Setup global variable bpf
 *
 * return pbf value on success, -1 on error
 */
static int get_first_bpf(void)
{
	size_t i = 0;
	char buf[16] = {0};

	for(; i < 99; ) {
		sprintf(buf, "%s%zu", DEVICE_BPF, i++);
		bpf = open(buf, O_RDWR);
		if (bpf != -1)
			break;

		/* must have root access*/
		if (errno == EACCES)
			break;
	}

	return bpf;
}

/*
 * send packets
 *
 * @ifr: destination interface
 * @nb: packets number
 *
 */
static void sender(const struct ifreq *ifr, size_t nb)
{
	static unsigned char dummy;
	size_t total = nb + 1;

	printf("Prepare to send %zu packets to %s.\n", nb, out_net);

	out_buffer.frame.header.ether_type = htons(PAYLOAD_LEN);
	memcpy(out_buffer.frame.header.ether_dhost, ifr->ifr_addr.sa_data, ETHER_ADDR_LEN);

	while (nb) {
		memset(out_buffer.frame.payload, ++dummy, sizeof out_buffer.frame.payload);
		ssize_t r = write(bpf, out_buffer.buffer,
				sizeof out_buffer.frame.payload + sizeof(struct ether_header));

		if (r == -1)
			warn("Unable to send packet #%zu.\n", nb);
		else
			VPRINTF("Packet #%zu sent.\n", total - nb);

		--nb;
	}
	printf("Done.\n");
}

/*
 * Return MAC address
 *
 * @iface: Interface name
 *
 * @return -1 on error, 0 on success
 */
static int get_hwaddr(const char * restrict iface, struct ifreq * restrict dest_ifr)
{
	int shw;
	int rc;

	strncpy(dest_ifr->ifr_name, iface, sizeof dest_ifr->ifr_name);
	dest_ifr->ifr_addr.sa_family = AF_LINK;

	if ((shw = socket(AF_INET, SOCK_RAW, 0)) < 0) {
		return -1;
	}

	rc = ioctl(shw, SIOCGHWADDR, dest_ifr);
	close(shw);

	if (rc)
		return -1;

	VPRINTF("Destination %s,  HW address: %s.\n",  iface, ether_ntoa((const struct ether_addr *)dest_ifr->ifr_addr.sa_data));

	return 0;
}

int main(int argc, char *argv[])
{
	size_t packets = 10;
	struct ifreq out_if = {0};
	const char *mac_address = fake_dest;
	struct ifreq dest_ifr = {0};
	int rc;

	/* options */
	int ch;
	static struct option longopts[] = {
		{ "if"     , required_argument, NULL, 'i' },
		{ "to"     , required_argument, NULL, 't' },
		{ "verbose", no_argument      , NULL, 'v' },
		{ "mac"    , required_argument, NULL, 'm' },
		{ "packets", required_argument, NULL, 'p' },
		{ NULL,	0, NULL, 0 }
	};
	while ((ch = getopt_long(argc, argv, "vi:t:p:m:", longopts, NULL)) != -1) {
		switch (ch) {
			case 'v':
				verbose = 1;
				break;
			case 't':
				dest_net = optarg;
				break;
			case 'i':
				out_net = optarg;
				break;
			case 'p':
				packets = strtoul(optarg, NULL, 10);
				break;
			case 'm':
				mac_address = optarg;
				break;
			case 0:
				/* long option */
				break;
			default:
				usage();
		}
	}

	if (argc - optind != 0)
		usage();

	/* sanity checks */
	daddr = ether_aton(mac_address);
	if (daddr == NULL)
		err(EXIT_FAILURE, "Cannot get mac destination");
	if (strlcpy(out_if.ifr_name, out_net, sizeof(out_if.ifr_name)) >= sizeof(out_if.ifr_name))
		errx(EXIT_FAILURE, "%s is not a valid interface name.\n", out_net);

	/* man 4 BPF */
	if (get_first_bpf() < 0)
		err(EXIT_FAILURE, "Cannot open bpf interface");

	/* Get net device index */
	if (ioctl(bpf, BIOCSETIF, &out_if) == -1) {
		warn("Cannot open %s interface.\n", out_net);
		goto last;
	}

	rc = dest_net == NULL;
	if (!rc)
		rc = get_hwaddr(dest_net, &dest_ifr);

	if (rc)
		memcpy(dest_ifr.ifr_addr.sa_data, daddr, ETHER_ADDR_LEN);
	/*
	 * pointless until we do not read _from_ interface
	 * static int dummy_true = 1;
	 * if( ioctl( bpf, BIOCIMMEDIATE, &dummy_true ) == -1 ) {
	 *		warn("Can not activate immediate mode.\n");
	 *	}
	 * if( ioctl( bpf, BIOCGBLEN, &buf_len ) == -1 ) {
	 *                warn("Can not request buffer length\n");
	 *                exit(1);
	 *        }
	 */
	sender(&dest_ifr, packets);

last:
	close(bpf);

	return EXIT_SUCCESS;
}