#include "rping.h"

void
init_capture(void)
{
	uint32_t localnet, netmask;
	char pcap_error[PCAP_ERRBUF_SIZE];
	struct bpf_program pcapfilter;
	char *filter = "icmp";

	if (device == NULL) {
		if ((device = pcap_lookupdev(pcap_error)) == NULL) {
			fprintf(stderr, "pcap_lookupdev: %s\n", pcap_error);
			exit(EXIT_FAILURE);
		}
	}

	if ((pcapd = pcap_open_live(device, 200, 0, 10, pcap_error)) == NULL) {
		fprintf(stderr, "pcap_open_live: %s\n", pcap_error);
		exit(EXIT_FAILURE);
	}

	if (pcap_lookupnet(device, &localnet, &netmask, pcap_error) < 0) {
		fprintf(stderr, "pcap_lookupnet: %s\n", pcap_error);
		exit(EXIT_FAILURE);
	}

	if (pcap_compile(pcapd, &pcapfilter, filter, 0, netmask)) {
		fprintf(stderr, "pcap_comile: %s\n", pcap_error);
		exit(EXIT_FAILURE);
	}

	if (pcap_setfilter(pcapd, &pcapfilter) < 0) {
		fprintf(stderr, "pcap_setfilter: %s\n", pcap_error);
		exit(EXIT_FAILURE);
	}

	switch (pcap_datalink(pcapd)) {
		case DLT_EN10MB:        link_offset = 14; break;
		case DLT_SLIP:          link_offset = 16; break;
		case DLT_SLIP_BSDOS:    link_offset = 24; break;
		case DLT_NULL:          link_offset =  4; break;
		case DLT_PPP:           link_offset =  4; break;
		case DLT_PPP_BSDOS:     link_offset = 25; break;
		case DLT_IEEE802:       link_offset = 22; break;
		case DLT_ATM_RFC1483:   link_offset =  8; break;
		case DLT_RAW:           link_offset =  0; break;

		default:
			fprintf(stderr, "init_capture: unsupported interface type\n");
			exit(EXIT_FAILURE);
	}
}

char
*next_pcap(void)
{
	char *pkt;
	struct pcap_pkthdr head;

	pkt = (char *)pcap_next(pcapd, &head);

	return pkt ? pkt + link_offset : NULL;
}

void
cleanup(int signo)
{
	struct pcap_stat stat;

	fflush(stdout);
	putc('\n', stdout);

	if (pcap_stats(pcapd, &stat) < 0) {
		fprintf(stderr, "pcap_stats: %s\n", pcap_geterr(pcapd));
		exit(EXIT_FAILURE);
	}

	printf("%d packets received by filter\n", stat.ps_recv);
	printf("%d packets dropped by kernel\n", stat.ps_drop);
	exit(0);
}