+/*
+ * 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;
+ }
+}
projects / libpcap / commitdiff
