1 /* 2 * Copyright (c) 1993, 1994, 1995, 1996, 1997 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that: (1) source code distributions 7 * retain the above copyright notice and this paragraph in its entirety, (2) 8 * distributions including binary code include the above copyright notice and 9 * this paragraph in its entirety in the documentation or other materials 10 * provided with the distribution, and (3) all advertising materials mentioning 11 * features or use of this software display the following acknowledgement: 12 * ``This product includes software developed by the University of California, 13 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 14 * the University nor the names of its contributors may be used to endorse 15 * or promote products derived from this software without specific prior 16 * written permission. 17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 18 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 20 * 21 * pcap-usb-linux-common.h - common code for everything that needs to 22 * deal with Linux USB captures, whether live or in a capture file; 23 * the later means that this is *not* Linux-only. 24 */ 25 26 #include <limits.h> 27 28 /* 29 * Return the sum of the two u_int arguments if that sum fits in a u_int, 30 * and return UINT_MAX otherwise. 31 */ 32 static inline u_int 33 u_int_sum(u_int a, u_int b) 34 { 35 return (((b) <= UINT_MAX - (a)) ? (a) + (b) : UINT_MAX); 36 } 37 38 /* 39 * Is this a completion event for an isochronous transfer? 40 */ 41 static inline int 42 is_isochronous_transfer_completion(const pcap_usb_header_mmapped *hdr) 43 { 44 return (hdr->transfer_type == URB_ISOCHRONOUS && 45 hdr->event_type == URB_COMPLETE && 46 (hdr->endpoint_number & URB_TRANSFER_IN)); 47 } 48 49 /* 50 * Total length of the pseudo-header, including the isochronous 51 * descriptors. 52 */ 53 static inline uint32_t 54 iso_pseudo_header_len(const pcap_usb_header_mmapped *usb_hdr) 55 { 56 return (sizeof(pcap_usb_header_mmapped) + 57 usb_hdr->ndesc * sizeof (usb_isodesc)); 58 } 59 60 /* 61 * Calculate the packet length for a "this is complete" incoming 62 * isochronous transfer event. 63 * 64 * Calculating that from hdr->urb_len is not correct, because the 65 * data is not contiguous, and the isochroous descriptors show how 66 * it's scattered. 67 */ 68 static inline u_int 69 incoming_isochronous_transfer_completed_len(struct pcap_pkthdr *phdr, 70 const u_char *bp) 71 { 72 const pcap_usb_header_mmapped *hdr; 73 u_int bytes_left; 74 const usb_isodesc *descs; 75 u_int pre_truncation_data_len; 76 77 /* 78 * All callers of this routine must ensure that pkth->caplen is 79 * >= sizeof (pcap_usb_header_mmapped). 80 */ 81 bytes_left = phdr->caplen; 82 bytes_left -= sizeof (pcap_usb_header_mmapped); 83 84 hdr = (const pcap_usb_header_mmapped *) bp; 85 descs = (const usb_isodesc *) (bp + sizeof(pcap_usb_header_mmapped)); 86 87 /* 88 * Find the end of the last chunk of data in the buffer 89 * referred to by the isochronous descriptors; that indicates 90 * how far into the buffer the data would have gone. 91 * 92 * Make sure we don't run past the end of the captured data 93 * while processing the isochronous descriptors. 94 */ 95 pre_truncation_data_len = 0; 96 for (uint32_t desc = 0; 97 desc < hdr->ndesc && bytes_left >= sizeof (usb_isodesc); 98 desc++, bytes_left -= sizeof (usb_isodesc)) { 99 u_int desc_end; 100 101 if (descs[desc].len != 0) { 102 /* 103 * Compute the end offset of the data 104 * for this descriptor, i.e. the offset 105 * of the byte after the data. Clamp 106 * the sum at UINT_MAX, so that it fits 107 * in a u_int. 108 */ 109 desc_end = u_int_sum(descs[desc].offset, 110 descs[desc].len); 111 if (desc_end > pre_truncation_data_len) 112 pre_truncation_data_len = desc_end; 113 } 114 } 115 116 /* 117 * Return the sum of the total header length (memory-mapped 118 * header and ISO descriptors) and the data length, clamped 119 * to UINT_MAX. 120 * 121 * We've made sure that the number of descriptors is 122 * <= USB_MAXDESC, so we know that the total size, 123 * in bytes, of the descriptors fits in a 32-bit 124 * integer. 125 */ 126 return (u_int_sum(iso_pseudo_header_len(hdr), pre_truncation_data_len)); 127 } 128