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      1 /*
      2  * libjingle
      3  * Copyright 2011 Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #include "talk/media/base/rtputils.h"
     29 
     30 namespace cricket {
     31 
     32 static const int kRtpVersion = 2;
     33 static const size_t kRtpFlagsOffset = 0;
     34 static const size_t kRtpPayloadTypeOffset = 1;
     35 static const size_t kRtpSeqNumOffset = 2;
     36 static const size_t kRtpTimestampOffset = 4;
     37 static const size_t kRtpSsrcOffset = 8;
     38 static const size_t kRtcpPayloadTypeOffset = 1;
     39 
     40 bool GetUint8(const void* data, size_t offset, int* value) {
     41   if (!data || !value) {
     42     return false;
     43   }
     44   *value = *(static_cast<const uint8*>(data) + offset);
     45   return true;
     46 }
     47 
     48 bool GetUint16(const void* data, size_t offset, int* value) {
     49   if (!data || !value) {
     50     return false;
     51   }
     52   *value = static_cast<int>(
     53       rtc::GetBE16(static_cast<const uint8*>(data) + offset));
     54   return true;
     55 }
     56 
     57 bool GetUint32(const void* data, size_t offset, uint32* value) {
     58   if (!data || !value) {
     59     return false;
     60   }
     61   *value = rtc::GetBE32(static_cast<const uint8*>(data) + offset);
     62   return true;
     63 }
     64 
     65 bool SetUint8(void* data, size_t offset, int value) {
     66   if (!data) {
     67     return false;
     68   }
     69   rtc::Set8(data, offset, value);
     70   return true;
     71 }
     72 
     73 bool SetUint16(void* data, size_t offset, int value) {
     74   if (!data) {
     75     return false;
     76   }
     77   rtc::SetBE16(static_cast<uint8*>(data) + offset, value);
     78   return true;
     79 }
     80 
     81 bool SetUint32(void* data, size_t offset, uint32 value) {
     82   if (!data) {
     83     return false;
     84   }
     85   rtc::SetBE32(static_cast<uint8*>(data) + offset, value);
     86   return true;
     87 }
     88 
     89 bool GetRtpFlags(const void* data, size_t len, int* value) {
     90   if (len < kMinRtpPacketLen) {
     91     return false;
     92   }
     93   return GetUint8(data, kRtpFlagsOffset, value);
     94 }
     95 
     96 bool GetRtpPayloadType(const void* data, size_t len, int* value) {
     97   if (len < kMinRtpPacketLen) {
     98     return false;
     99   }
    100   if (!GetUint8(data, kRtpPayloadTypeOffset, value)) {
    101     return false;
    102   }
    103   *value &= 0x7F;
    104   return true;
    105 }
    106 
    107 bool GetRtpSeqNum(const void* data, size_t len, int* value) {
    108   if (len < kMinRtpPacketLen) {
    109     return false;
    110   }
    111   return GetUint16(data, kRtpSeqNumOffset, value);
    112 }
    113 
    114 bool GetRtpTimestamp(const void* data, size_t len, uint32* value) {
    115   if (len < kMinRtpPacketLen) {
    116     return false;
    117   }
    118   return GetUint32(data, kRtpTimestampOffset, value);
    119 }
    120 
    121 bool GetRtpSsrc(const void* data, size_t len, uint32* value) {
    122   if (len < kMinRtpPacketLen) {
    123     return false;
    124   }
    125   return GetUint32(data, kRtpSsrcOffset, value);
    126 }
    127 
    128 bool GetRtpHeaderLen(const void* data, size_t len, size_t* value) {
    129   if (!data || len < kMinRtpPacketLen || !value) return false;
    130   const uint8* header = static_cast<const uint8*>(data);
    131   // Get base header size + length of CSRCs (not counting extension yet).
    132   size_t header_size = kMinRtpPacketLen + (header[0] & 0xF) * sizeof(uint32);
    133   if (len < header_size) return false;
    134   // If there's an extension, read and add in the extension size.
    135   if (header[0] & 0x10) {
    136     if (len < header_size + sizeof(uint32)) return false;
    137     header_size += ((rtc::GetBE16(header + header_size + 2) + 1) *
    138                     sizeof(uint32));
    139     if (len < header_size) return false;
    140   }
    141   *value = header_size;
    142   return true;
    143 }
    144 
    145 bool GetRtpVersion(const void* data, size_t len, int* version) {
    146   if (len == 0) {
    147     return false;
    148   }
    149 
    150   const uint8 first = static_cast<const uint8*>(data)[0];
    151   *version = static_cast<int>((first >> 6) & 0x3);
    152   return true;
    153 }
    154 
    155 bool GetRtpHeader(const void* data, size_t len, RtpHeader* header) {
    156   return (GetRtpPayloadType(data, len, &(header->payload_type)) &&
    157           GetRtpSeqNum(data, len, &(header->seq_num)) &&
    158           GetRtpTimestamp(data, len, &(header->timestamp)) &&
    159           GetRtpSsrc(data, len, &(header->ssrc)));
    160 }
    161 
    162 bool GetRtcpType(const void* data, size_t len, int* value) {
    163   if (len < kMinRtcpPacketLen) {
    164     return false;
    165   }
    166   return GetUint8(data, kRtcpPayloadTypeOffset, value);
    167 }
    168 
    169 // This method returns SSRC first of RTCP packet, except if packet is SDES.
    170 // TODO(mallinath) - Fully implement RFC 5506. This standard doesn't restrict
    171 // to send non-compound packets only to feedback messages.
    172 bool GetRtcpSsrc(const void* data, size_t len, uint32* value) {
    173   // Packet should be at least of 8 bytes, to get SSRC from a RTCP packet.
    174   if (!data || len < kMinRtcpPacketLen + 4 || !value) return false;
    175   int pl_type;
    176   if (!GetRtcpType(data, len, &pl_type)) return false;
    177   // SDES packet parsing is not supported.
    178   if (pl_type == kRtcpTypeSDES) return false;
    179   *value = rtc::GetBE32(static_cast<const uint8*>(data) + 4);
    180   return true;
    181 }
    182 
    183 bool SetRtpHeaderFlags(
    184     void* data, size_t len,
    185     bool padding, bool extension, int csrc_count) {
    186   if (csrc_count > 0x0F) {
    187     return false;
    188   }
    189   int flags = 0;
    190   flags |= (kRtpVersion << 6);
    191   flags |= ((padding ? 1 : 0) << 5);
    192   flags |= ((extension ? 1 : 0) << 4);
    193   flags |= csrc_count;
    194   return SetUint8(data, kRtpFlagsOffset, flags);
    195 }
    196 
    197 // Assumes marker bit is 0.
    198 bool SetRtpPayloadType(void* data, size_t len, int value) {
    199   if (value >= 0x7F) {
    200     return false;
    201   }
    202   return SetUint8(data, kRtpPayloadTypeOffset, value & 0x7F);
    203 }
    204 
    205 bool SetRtpSeqNum(void* data, size_t len, int value) {
    206   return SetUint16(data, kRtpSeqNumOffset, value);
    207 }
    208 
    209 bool SetRtpTimestamp(void* data, size_t len, uint32 value) {
    210   return SetUint32(data, kRtpTimestampOffset, value);
    211 }
    212 
    213 bool SetRtpSsrc(void* data, size_t len, uint32 value) {
    214   return SetUint32(data, kRtpSsrcOffset, value);
    215 }
    216 
    217 // Assumes version 2, no padding, no extensions, no csrcs.
    218 bool SetRtpHeader(void* data, size_t len, const RtpHeader& header) {
    219   return (SetRtpHeaderFlags(data, len, false, false, 0) &&
    220           SetRtpPayloadType(data, len, header.payload_type) &&
    221           SetRtpSeqNum(data, len, header.seq_num) &&
    222           SetRtpTimestamp(data, len, header.timestamp) &&
    223           SetRtpSsrc(data, len, header.ssrc));
    224 }
    225 
    226 bool IsRtpPacket(const void* data, size_t len) {
    227   if (len < kMinRtpPacketLen)
    228     return false;
    229 
    230   int version = 0;
    231   if (!GetRtpVersion(data, len, &version))
    232     return false;
    233 
    234   return version == kRtpVersion;
    235 }
    236 
    237 }  // namespace cricket
    238