/*
 * Copyright (c) 1993, 1994, 1995, 1996, 1997
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * pcap-usb-linux-common.c - common code for everything that needs to
 * deal with Linux USB captures.
 */

#include "pcap/pcap.h"
#include "pcap/usb.h"

#include "pcap-usb-linux-common.h"

/*
 * Compute, from the data provided by the Linux USB memory-mapped capture
 * mechanism, the amount of packet data that would have been provided
 * had the capture mechanism not chopped off any data at the end, if, in
 * fact, it did so.
 *
 * Set the "unsliced length" field of the packet header to that value.
 */
void
set_linux_usb_mmapped_length(struct pcap_pkthdr *pkth, const u_char *bp)
{
	const pcap_usb_header_mmapped *hdr;
	u_int bytes_left;
	
	bytes_left = pkth->caplen;
	if (bytes_left < sizeof (pcap_usb_header_mmapped)) {
		/*
		 * We don't have the full metadata header, so give up.
		 */
		return;
	}
	bytes_left -= sizeof (pcap_usb_header_mmapped);

	hdr = (const pcap_usb_header_mmapped *) bp;
	if (hdr->data_flag) {
		/*
		 * No data; just base the on-the-bus length on hdr->data_len
		 * (so that it's >= the captured length).
		 */
		pkth->len = sizeof(pcap_usb_header_mmapped) + hdr->data_len;
	} else {
		/*
		 * We got data; calculate the on-the-bus length based on
		 * the data length prior to the USB monitor device discarding
		 * data due to its buffer being too small.
		 */
		usb_isodesc *descs;
		u_int pre_truncation_data_len;

		descs = (usb_isodesc *) (bp + sizeof(pcap_usb_header_mmapped));

		/*
		 * For most transfers, urb_len is that amount.
		 */
		pre_truncation_data_len = hdr->urb_len;
		if (hdr->transfer_type == URB_ISOCHRONOUS &&
		    hdr->event_type == URB_COMPLETE &&
		    (hdr->endpoint_number & URB_TRANSFER_IN)) {
			/*
			 * For "this is complete" incoming isochronous
			 * transfer events, however, the data isn't
			 * contiguous, and the isochronous descriptos
			 * show how it's scattered.
			 *
			 * Find the end of the last chunk of data in
			 * the buffer referred to by the isochronous
			 * descriptors; that indicates how far into
			 * the buffer the data would have gone.
			 *
			 * Make sure we don't run past the end of the
			 * captured data while processing the isochronous
			 * descriptors.
			 */
			pre_truncation_data_len = 0;
			for (uint32_t desc = 0;
			    desc < hdr->ndesc && bytes_left >= sizeof (usb_isodesc);
			    desc++, bytes_left -= sizeof (usb_isodesc)) {
				u_int desc_end;

				desc_end = descs[desc].offset + descs[desc].len;
				if (desc_end > pre_truncation_data_len)
					pre_truncation_data_len = desc_end;
			}
		}
		pkth->len = sizeof(pcap_usb_header_mmapped) +
		    (hdr->ndesc * sizeof (usb_isodesc)) +
		    pre_truncation_data_len;
	}
}