/* include open_pcap */#include	"udpcksum.h"#define	CMD		"udp and src host %s and src port %d"voidopen_pcap(void){	uint32_t			localnet, netmask;	char				cmd[MAXLINE], errbuf[PCAP_ERRBUF_SIZE],						str1[INET_ADDRSTRLEN], str2[INET_ADDRSTRLEN];	struct bpf_program	fcode;	if (device == NULL) {		if ( (device = pcap_lookupdev(errbuf)) == NULL)			err_quit("pcap_lookup: %s", errbuf);	}	printf("device = %s\n", device);		/* 4hardcode: promisc=0, to_ms=500 */	if ( (pd = pcap_open_live(device, snaplen, 0, 500, errbuf)) == NULL)		err_quit("pcap_open_live: %s", errbuf);	if (pcap_lookupnet(device, &localnet, &netmask, errbuf) < 0)		err_quit("pcap_lookupnet: %s", errbuf);	if (verbose)		printf("localnet = %s, netmask = %s\n",			   Inet_ntop(AF_INET, &localnet, str1, sizeof(str1)),			   Inet_ntop(AF_INET, &netmask, str2, sizeof(str2)));	snprintf(cmd, sizeof(cmd), CMD,			 Sock_ntop_host(dest, destlen),			 ntohs(sock_get_port(dest, destlen)));	if (verbose)		printf("cmd = %s\n", cmd);	if (pcap_compile(pd, &fcode, cmd, 0, netmask) < 0)		err_quit("pcap_compile: %s", pcap_geterr(pd));	if (pcap_setfilter(pd, &fcode) < 0)		err_quit("pcap_setfilter: %s", pcap_geterr(pd));	if ( (datalink = pcap_datalink(pd)) < 0)		err_quit("pcap_datalink: %s", pcap_geterr(pd));	if (verbose)		printf("datalink = %d\n", datalink);}/* end open_pcap *//* include next_pcap */char *next_pcap(int *len){	char				*ptr;	struct pcap_pkthdr	hdr;		/* 4keep looping until packet ready */	while ( (ptr = (char *) pcap_next(pd, &hdr)) == NULL)		;	*len = hdr.caplen;	/* captured length */	return(ptr);}/* end next_pcap */