/*
 * a real quick'n'dirty hack to add/remove vcan interfaces.
 * (also to have something to test the new RTNL API in vcan.)
 * this will be added to ip(8) of the iproute package, making
 * this hack obsolete.
 * 
 * we don't check the return value of sendto() and don't wait for
 * a reply using recvmsg().  We just hope everything works fine,
 * otherwise use strace, or feel free to add the code before this
 * whole thing is dumped to the bit bucket.
 *
 * Parts of this code were taken from the iproute source.
 *
 * urs
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <net/if.h>

#include <asm/types.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>

//#include <linux/if_link.h>

#define IFLA_LINKINFO 18

enum
{
    IFLA_INFO_UNSPEC,
    IFLA_INFO_NAME,
    IFLA_INFO_DATA,
    IFLA_INFO_XSTATS,
    __IFLA_INFO_MAX,
};

#define NLMSG_TAIL(nmsg) \
        ((struct rtattr *)(((void *) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))

int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
	      int alen);

void usage()
{
    fprintf(stderr, "Usage: vcan create\n"
		    "       vcan delete iface\n");
    exit(1);
}

int main(int argc, char **argv)
{
    int s;
    char *cmd, *dev;
    struct {
	struct nlmsghdr  n;
	struct ifinfomsg i;
	char             buf[1024];
    } req;
    struct sockaddr_nl nladdr;
    struct rtattr *linkinfo;
    int i;

#ifdef OBSOLETE
    fprintf(stderr, "This program is a temporary hack and is now obsolete.\n"
	    "Please use ip(8) instead, i.e.\n"
	    "    ip link add type vcan       or\n"
	    "    ip link delete iface\n");
    exit(1);
#endif
    if (argc < 2)
	usage();
    cmd = argv[1];

    s = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);

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

    if (strcmp(cmd, "create") == 0) {
	req.n.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ifinfomsg));
	req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
	req.n.nlmsg_type  = RTM_NEWLINK;
	req.n.nlmsg_seq   = 0;
	req.i.ifi_family  = AF_UNSPEC;

	linkinfo = NLMSG_TAIL(&req.n);
	addattr_l(&req.n, sizeof(req), IFLA_LINKINFO, NULL, 0);
	addattr_l(&req.n, sizeof(req), IFLA_INFO_NAME, "vcan", strlen("vcan"));
	linkinfo->rta_len = (void*)NLMSG_TAIL(&req.n) - (void*)linkinfo;

    } else if (strcmp(cmd, "delete") == 0) {
	if (argc < 3)
	    usage();
	dev = argv[2];
	req.n.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ifinfomsg));
	req.n.nlmsg_flags = NLM_F_REQUEST;
	req.n.nlmsg_type  = RTM_DELLINK;
	req.i.ifi_family  = AF_UNSPEC;
	req.i.ifi_index   = if_nametoindex(dev);
    } else
	usage();

    memset(&nladdr, 0, sizeof(nladdr));
    nladdr.nl_family = AF_NETLINK;
    nladdr.nl_pid    = 0;
    nladdr.nl_groups = 0;
#if 1
    sendto(s, &req, req.n.nlmsg_len, 0,
	   (struct sockaddr*)&nladdr, sizeof(nladdr));
#else
    for (i = 0; i < req.n.nlmsg_len; i++) {
	printf(" %02x", ((unsigned char*)&req)[i]);
	if (i % 16 == 15)
	    putchar('\n');
    }
    putchar('\n');
#endif
    close(s);

    return 0;
}

int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
	      int alen)
{
    int len = RTA_LENGTH(alen);
    struct rtattr *rta;

    if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
	fprintf(stderr, "addattr_l ERROR: message exceeded bound of %d\n",
		maxlen);
	return -1;
    }
    rta = NLMSG_TAIL(n);
    rta->rta_type = type;
    rta->rta_len = len;
    memcpy(RTA_DATA(rta), data, alen);
    n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
    return 0;
}