vendor/libpcap/1.10.3

1 files changed, 130 insertions, 0 deletions

diff --git a/pcap-usb-linux-common.c b/pcap-usb-linux-common.c
new file mode 100644
index 000000000000..fb4a8c19be75
--- /dev/null
+++ b/pcap-usb-linux-common.c
@@ -0,0 +1,130 @@
+/*
+ * 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
+fix_linux_usb_mmapped_length(struct pcap_pkthdr *pkth, const u_char *bp)
+{
+	const pcap_usb_header_mmapped *hdr;
+	u_int bytes_left;
+
+	/*
+	 * All callers of this routine must ensure that pkth->caplen is
+	 * >= sizeof (pcap_usb_header_mmapped).
+	 */
+	bytes_left = pkth->caplen;
+	bytes_left -= sizeof (pcap_usb_header_mmapped);
+
+	hdr = (const pcap_usb_header_mmapped *) bp;
+	if (!hdr->data_flag && hdr->transfer_type == URB_ISOCHRONOUS &&
+	    hdr->event_type == URB_COMPLETE &&
+	    (hdr->endpoint_number & URB_TRANSFER_IN) &&
+	    pkth->len == sizeof(pcap_usb_header_mmapped) +
+	                 (hdr->ndesc * sizeof (usb_isodesc)) + hdr->urb_len) {
+		usb_isodesc *descs;
+		u_int pre_truncation_data_len, pre_truncation_len;
+
+		descs = (usb_isodesc *) (bp + sizeof(pcap_usb_header_mmapped));
+
+		/*
+		 * We have data (yes, data_flag is 0 if we *do* have data),
+		 * and this is a "this is complete" incoming isochronous
+		 * transfer event, and the length was calculated based
+		 * on the URB length.
+		 *
+		 * That's not correct, because 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;
+
+			if (descs[desc].len != 0) {
+				desc_end = descs[desc].offset + descs[desc].len;
+				if (desc_end > pre_truncation_data_len)
+					pre_truncation_data_len = desc_end;
+			}
+		}
+
+		/*
+		 * Now calculate the total length based on that data
+		 * length.
+		 */
+		pre_truncation_len = sizeof(pcap_usb_header_mmapped) +
+		    (hdr->ndesc * sizeof (usb_isodesc)) +
+		    pre_truncation_data_len;
+
+		/*
+		 * If that's greater than or equal to the captured length,
+		 * use that as the length.
+		 */
+		if (pre_truncation_len >= pkth->caplen)
+			pkth->len = pre_truncation_len;
+
+		/*
+		 * If the captured length is greater than the length,
+		 * use the captured length.
+		 *
+		 * For completion events for incoming isochronous transfers,
+		 * it's based on data_len, which is calculated the same way
+		 * we calculated pre_truncation_data_len above, except that
+		 * it has access to all the isochronous descriptors, not
+		 * just the ones that the kernel were able to provide us or,
+		 * for a capture file, that weren't sliced off by a snapshot
+		 * length.
+		 *
+		 * However, it might have been reduced by the USB capture
+		 * mechanism arbitrarily limiting the amount of data it
+		 * provides to userland, or by the libpcap capture code
+		 * limiting it to being no more than the snapshot, so
+		 * we don't want to just use it all the time; we only
+		 * do so to try to get a better estimate of the actual
+		 * length - and to make sure the on-the-network length
+		 * is always >= the captured length.
+		 */
+		if (pkth->caplen > pkth->len)
+			pkth->len = pkth->caplen;
+	}
+}