set-capture-buffer-size.md

Set capture buffer size

"-B buffer_size/--buffer-size=buffer_size" option can be used to change capture buffer size (code is here):

......
#if defined(HAVE_PCAP_CREATE) || defined(_WIN32)
		case 'B':
			Bflag = atoi(optarg)*1024;
			if (Bflag <= 0)
				error("invalid packet buffer size %s", optarg);
			break;
#endif /* defined(HAVE_PCAP_CREATE) || defined(_WIN32) */
......

The unit is KiB. pcap_set_buffer_size() is called to set buffer size (code is here):

......
if (Bflag != 0) {
	status = pcap_set_buffer_size(pc, Bflag);
	if (status != 0)
		error("%s: Can't set buffer size: %s",
		    device, pcap_statustostr(status));
}
......

On Windows, a special processing is needed (code is here):

......
#if !defined(HAVE_PCAP_CREATE) && defined(_WIN32)
		if(Bflag != 0)
			if(pcap_setbuff(pd, Bflag)==-1){
				error("%s", pcap_geterr(pd));
			}
#endif /* !defined(HAVE_PCAP_CREATE) && defined(_WIN32) */
......