Take a look at the output of the "nicinfo" command, this reports the Ethernet stats. Note that this is entirely driver 
dependent - different drivers report different stats.

The code for this is:
	struct drvcom_stats	dstats;
	nic_stats_t		*statp;

	statp = &dstats.dcom_stats;

		ifdcp->ifdc_cmd = DRVCOM_STATS;
		ifdcp->ifdc_len = sizeof(*statp);
		if ((ret = devctl(s, SIOCGDRVCOM, ifdcp,
		    sizeof(struct drvcom_stats), NULL)) == EOK) {
			dump_stats(s, statp);
		}

Link state is a separate API:

#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>

int main(int argc, char **argv)
{
    int			s;
    struct ifdatareq	ifdata;

    if (argc != 2) {
      fprintf(stderr, "Incorrect usage\n");
      return 1;
    }

    s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (s == -1 && errno != EPROTONOSUPPORT) {
      fprintf(stderr, "can't open IPv4 socket %s", strerror(errno));
      return 1;
    }

    memset(&ifdata, 0, sizeof(ifdata));
    strlcpy(ifdata.ifdr_name, argv[1], IF_NAMESIZE);

    if (ioctl(s, SIOCGIFDATA, &ifdata) == -1) {
	fprintf(stderr, "ioctl failed: %s\n", strerror(errno));
	exit(1);
    }

    fprintf(stdout, "Linkstate %d\n", ifdata.ifdr_data.ifi_link_state);

    return 0;
}