liveMedia/RTPInterface.cpp

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/**********
This library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)

This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
more details.

You should have received a copy of the GNU Lesser General Public License
along with this library; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2013 Live Networks, Inc.  All rights reserved.
// An abstraction of a network interface used for RTP (or RTCP).
// (This allows the RTP-over-TCP hack (RFC 2326, section 10.12) to
// be implemented transparently.)
// Implementation

#include "RTPInterface.hh"
#include <GroupsockHelper.hh>
#include <stdio.h>


// Helper routines and data structures, used to implement
// sending/receiving RTP/RTCP over a TCP socket:

// Reading RTP-over-TCP is implemented using two levels of hash tables.
// The top-level hash table maps TCP socket numbers to a
// "SocketDescriptor" that contains a hash table for each of the
// sub-channels that are reading from this socket.

static HashTable* socketHashTable(UsageEnvironment& env, Boolean createIfNotPresent = True) {
  _Tables* ourTables = _Tables::getOurTables(env, createIfNotPresent);
  if (ourTables == NULL) return NULL;

  if (ourTables->socketTable == NULL) {
    // Create a new socket number -> SocketDescriptor mapping table:
    ourTables->socketTable = HashTable::create(ONE_WORD_HASH_KEYS);
  }
  return (HashTable*)(ourTables->socketTable);
}

class SocketDescriptor {
public:
  SocketDescriptor(UsageEnvironment& env, int socketNum);
  virtual ~SocketDescriptor();

  void registerRTPInterface(unsigned char streamChannelId,
                            RTPInterface* rtpInterface);
  RTPInterface* lookupRTPInterface(unsigned char streamChannelId);
  void deregisterRTPInterface(unsigned char streamChannelId);

  void setServerRequestAlternativeByteHandler(ServerRequestAlternativeByteHandler* handler, void* clientData) {
    fServerRequestAlternativeByteHandler = handler;
    fServerRequestAlternativeByteHandlerClientData = clientData;
  }

private:
  static void tcpReadHandler(SocketDescriptor*, int mask);
  Boolean tcpReadHandler1(int mask);

private:
  UsageEnvironment& fEnv;
  int fOurSocketNum;
  HashTable* fSubChannelHashTable;
  ServerRequestAlternativeByteHandler* fServerRequestAlternativeByteHandler;
  void* fServerRequestAlternativeByteHandlerClientData;
  u_int8_t fStreamChannelId, fSizeByte1;
  Boolean fReadErrorOccurred, fDeleteNext;
  enum { AWAITING_DOLLAR, AWAITING_STREAM_CHANNEL_ID, AWAITING_SIZE1, AWAITING_SIZE2, AWAITING_PACKET_DATA } fTCPReadingState;
};

static SocketDescriptor* lookupSocketDescriptor(UsageEnvironment& env, int sockNum, Boolean createIfNotFound = True) {
  HashTable* table = socketHashTable(env, createIfNotFound);
  if (table == NULL) return NULL;

  char const* key = (char const*)(long)sockNum;
  SocketDescriptor* socketDescriptor = (SocketDescriptor*)(table->Lookup(key));
  if (socketDescriptor == NULL) {
    if (createIfNotFound) {
      socketDescriptor = new SocketDescriptor(env, sockNum);
      table->Add((char const*)(long)(sockNum), socketDescriptor);
    } else if (table->IsEmpty()) {
      // We can also delete the table (to reclaim space):
      _Tables* ourTables = _Tables::getOurTables(env);
      delete table;
      ourTables->socketTable = NULL;
      ourTables->reclaimIfPossible();
    }
  }

  return socketDescriptor;
}

static void removeSocketDescription(UsageEnvironment& env, int sockNum) {
  char const* key = (char const*)(long)sockNum;
  HashTable* table = socketHashTable(env);
  table->Remove(key);

  if (table->IsEmpty()) {
    // We can also delete the table (to reclaim space):
    _Tables* ourTables = _Tables::getOurTables(env);
    delete table;
    ourTables->socketTable = NULL;
    ourTables->reclaimIfPossible();
  }
}



RTPInterface::RTPInterface(Medium* owner, Groupsock* gs)
  : fOwner(owner), fGS(gs),
    fTCPStreams(NULL),
    fNextTCPReadSize(0), fNextTCPReadStreamSocketNum(-1),
    fNextTCPReadStreamChannelId(0xFF), fReadHandlerProc(NULL),
    fAuxReadHandlerFunc(NULL), fAuxReadHandlerClientData(NULL) {
  // Make the socket non-blocking, even though it will be read from only asynchronously, when packets arrive.
  // The reason for this is that, in some OSs, reads on a blocking socket can (allegedly) sometimes block,
  // even if the socket was previously reported (e.g., by "select()") as having data available.
  // (This can supposedly happen if the UDP checksum fails, for example.)
  makeSocketNonBlocking(fGS->socketNum());
  increaseSendBufferTo(envir(), fGS->socketNum(), 50*1024);
}

RTPInterface::~RTPInterface() {
  delete fTCPStreams;
}

void RTPInterface::setStreamSocket(int sockNum,
                                   unsigned char streamChannelId) {
  fGS->removeAllDestinations();
  addStreamSocket(sockNum, streamChannelId);
}

void RTPInterface::addStreamSocket(int sockNum,
                                   unsigned char streamChannelId) {
  if (sockNum < 0) return;

  for (tcpStreamRecord* streams = fTCPStreams; streams != NULL;
       streams = streams->fNext) {
    if (streams->fStreamSocketNum == sockNum
        && streams->fStreamChannelId == streamChannelId) {
      return; // we already have it
    }
  }

  fTCPStreams = new tcpStreamRecord(sockNum, streamChannelId, fTCPStreams);

  // Also, make sure this new socket is set up for receiving RTP/RTCP-over-TCP:
  SocketDescriptor* socketDescriptor = lookupSocketDescriptor(envir(), sockNum);
  socketDescriptor->registerRTPInterface(streamChannelId, this);
}

static void deregisterSocket(UsageEnvironment& env, int sockNum, unsigned char streamChannelId) {
  SocketDescriptor* socketDescriptor = lookupSocketDescriptor(env, sockNum, False);
  if (socketDescriptor != NULL) {
    socketDescriptor->deregisterRTPInterface(streamChannelId);
        // Note: This may delete "socketDescriptor",
        // if no more interfaces are using this socket
  }
}

void RTPInterface::removeStreamSocket(int sockNum,
                                      unsigned char streamChannelId) {
  for (tcpStreamRecord** streamsPtr = &fTCPStreams; *streamsPtr != NULL;
       streamsPtr = &((*streamsPtr)->fNext)) {
    if ((*streamsPtr)->fStreamSocketNum == sockNum
        && (*streamsPtr)->fStreamChannelId == streamChannelId) {
      deregisterSocket(envir(), sockNum, streamChannelId);

      // Then remove the record pointed to by *streamsPtr :
      tcpStreamRecord* next = (*streamsPtr)->fNext;
      (*streamsPtr)->fNext = NULL;
      delete (*streamsPtr);
      *streamsPtr = next;
      return;
    }
  }
}

void RTPInterface
::setServerRequestAlternativeByteHandler(int socketNum, ServerRequestAlternativeByteHandler* handler, void* clientData) {
  SocketDescriptor* socketDescriptor = lookupSocketDescriptor(envir(), socketNum);

  if (socketDescriptor != NULL) socketDescriptor->setServerRequestAlternativeByteHandler(handler, clientData);
}


Boolean RTPInterface::sendPacket(unsigned char* packet, unsigned packetSize) {
  Boolean success = True; // we'll return False instead if any of the sends fail

  // Normal case: Send as a UDP packet:
  if (!fGS->output(envir(), fGS->ttl(), packet, packetSize)) success = False;

  // Also, send over each of our TCP sockets:
  for (tcpStreamRecord* streams = fTCPStreams; streams != NULL;
       streams = streams->fNext) {
    if (!sendRTPorRTCPPacketOverTCP(packet, packetSize,
                                    streams->fStreamSocketNum, streams->fStreamChannelId)) {
      success = False;
    }
  }

  return success;
}

void RTPInterface
::startNetworkReading(TaskScheduler::BackgroundHandlerProc* handlerProc) {
  // Normal case: Arrange to read UDP packets:
  envir().taskScheduler().
    turnOnBackgroundReadHandling(fGS->socketNum(), handlerProc, fOwner);

  // Also, receive RTP over TCP, on each of our TCP connections:
  fReadHandlerProc = handlerProc;
  for (tcpStreamRecord* streams = fTCPStreams; streams != NULL;
       streams = streams->fNext) {
    // Get a socket descriptor for "streams->fStreamSocketNum":
    SocketDescriptor* socketDescriptor = lookupSocketDescriptor(envir(), streams->fStreamSocketNum);

    // Tell it about our subChannel:
    socketDescriptor->registerRTPInterface(streams->fStreamChannelId, this);
  }
}

Boolean RTPInterface::handleRead(unsigned char* buffer, unsigned bufferMaxSize,
                                 unsigned& bytesRead, struct sockaddr_in& fromAddress, Boolean& packetReadWasIncomplete) {
  packetReadWasIncomplete = False; // by default
  Boolean readSuccess;
  if (fNextTCPReadStreamSocketNum < 0) {
    // Normal case: read from the (datagram) 'groupsock':
    readSuccess = fGS->handleRead(buffer, bufferMaxSize, bytesRead, fromAddress);
  } else {
    // Read from the TCP connection:
    bytesRead = 0;
    unsigned totBytesToRead = fNextTCPReadSize;
    if (totBytesToRead > bufferMaxSize) totBytesToRead = bufferMaxSize;
    unsigned curBytesToRead = totBytesToRead;
    int curBytesRead;
    while ((curBytesRead = readSocket(envir(), fNextTCPReadStreamSocketNum,
                                      &buffer[bytesRead], curBytesToRead,
                                      fromAddress)) > 0) {
      bytesRead += curBytesRead;
      if (bytesRead >= totBytesToRead) break;
      curBytesToRead -= curBytesRead;
    }
    fNextTCPReadSize -= bytesRead;
    if (fNextTCPReadSize == 0) {
      // We've read all of the data that we asked for
      readSuccess = True;
    } else if (curBytesRead < 0) {
      // There was an error reading the socket
      bytesRead = 0;
      readSuccess = False;
    } else {
      // We need to read more bytes, and there was not an error reading the socket
      packetReadWasIncomplete = True;
      return True;
    }
    fNextTCPReadStreamSocketNum = -1; // default, for next time
  }

  if (readSuccess && fAuxReadHandlerFunc != NULL) {
    // Also pass the newly-read packet data to our auxilliary handler:
    (*fAuxReadHandlerFunc)(fAuxReadHandlerClientData, buffer, bytesRead);
  }
  return readSuccess;
}

void RTPInterface::stopNetworkReading() {
  // Normal case
  envir().taskScheduler().turnOffBackgroundReadHandling(fGS->socketNum());

  // Also turn off read handling on each of our TCP connections:
  for (tcpStreamRecord* streams = fTCPStreams; streams != NULL;
       streams = streams->fNext) {
    deregisterSocket(envir(), streams->fStreamSocketNum, streams->fStreamChannelId);
  }
}



Boolean RTPInterface::sendRTPorRTCPPacketOverTCP(u_int8_t* packet, unsigned packetSize,
                                                 int socketNum, unsigned char streamChannelId) {
#ifdef DEBUG_SEND
  fprintf(stderr, "sendRTPorRTCPPacketOverTCP: %d bytes over channel %d (socket %d)\n",
          packetSize, streamChannelId, socketNum); fflush(stderr);
#endif
  // Send a RTP/RTCP packet over TCP, using the encoding defined in RFC 2326, section 10.12:
  //     $<streamChannelId><packetSize><packet>
  // (If the initial "send()" of '$<streamChannelId><packetSize>' succeeds, then we force the subsequent "send()" for
  //  the <packet> data to succeed, even if we have to do so with a blocking "send()".)
  do {
    u_int8_t framingHeader[4];
    framingHeader[0] = '$';
    framingHeader[1] = streamChannelId;
    framingHeader[2] = (u_int8_t) ((packetSize&0xFF00)>>8);
    framingHeader[3] = (u_int8_t) (packetSize&0xFF);
    if (!sendDataOverTCP(socketNum, framingHeader, 4, False)) break;

    if (!sendDataOverTCP(socketNum, packet, packetSize, True)) break;
#ifdef DEBUG_SEND
    fprintf(stderr, "sendRTPorRTCPPacketOverTCP: completed\n"); fflush(stderr);
#endif

    return True;
  } while (0);

#ifdef DEBUG_SEND
  fprintf(stderr, "sendRTPorRTCPPacketOverTCP: failed! (errno %d)\n", envir().getErrno()); fflush(stderr);
#endif
  return False;
}

Boolean RTPInterface::sendDataOverTCP(int socketNum, u_int8_t const* data, unsigned dataSize, Boolean forceSendToSucceed) {
  if (send(socketNum, (char const*)data, dataSize, 0/*flags*/) != (int)dataSize) {
    // The TCP send() failed.

    if (forceSendToSucceed && envir().getErrno() == EAGAIN) {
      // The OS's TCP send buffer has filled up (because the stream's bitrate has exceeded the capacity of the TCP connection!).
      // Force this data write to succeed, by blocking if necessary until it does:
#ifdef DEBUG_SEND
      fprintf(stderr, "sendDataOverTCP: resending %d-byte send (blocking)\n", dataSize); fflush(stderr);
#endif
      makeSocketBlocking(socketNum);
      Boolean sendSuccess = send(socketNum, (char const*)data, dataSize, 0/*flags*/) == (int)dataSize;
      makeSocketNonBlocking(socketNum);
      return sendSuccess;
    }
    return False;
  }

  return True;
}

SocketDescriptor::SocketDescriptor(UsageEnvironment& env, int socketNum)
  :fEnv(env), fOurSocketNum(socketNum),
    fSubChannelHashTable(HashTable::create(ONE_WORD_HASH_KEYS)),
   fServerRequestAlternativeByteHandler(NULL), fServerRequestAlternativeByteHandlerClientData(NULL),
   fReadErrorOccurred(False), fDeleteNext(False), fTCPReadingState(AWAITING_DOLLAR) {
}

SocketDescriptor::~SocketDescriptor() {
  fEnv.taskScheduler().turnOffBackgroundReadHandling(fOurSocketNum);
  if (fServerRequestAlternativeByteHandler != NULL) {
    // Hack: Pass a special character to our alternative byte handler, to tell it that either
    // - an error occurred when reading the TCP socket, or
    // - no error occurred, but it needs to take over control of the TCP socket once again.
    u_int8_t specialChar = fReadErrorOccurred ? 0xFF : 0xFE;
    (*fServerRequestAlternativeByteHandler)(fServerRequestAlternativeByteHandlerClientData, specialChar);
  }
  removeSocketDescription(fEnv, fOurSocketNum);

  if (fSubChannelHashTable != NULL) {
    while (fSubChannelHashTable->RemoveNext() != NULL) {} // remove the "RTPInterface"s from the table, but don't delete them
    delete fSubChannelHashTable;
  }
}

void SocketDescriptor::registerRTPInterface(unsigned char streamChannelId,
                                            RTPInterface* rtpInterface) {
  Boolean isFirstRegistration = fSubChannelHashTable->IsEmpty();
#if defined(DEBUG_SEND)||defined(DEBUG_RECEIVE)
  fprintf(stderr, "SocketDescriptor(socket %d)::registerRTPInterface(channel %d): isFirstRegistration %d\n", fOurSocketNum, streamChannelId, isFirstRegistration);
#endif
  fSubChannelHashTable->Add((char const*)(long)streamChannelId,
                            rtpInterface);

  if (isFirstRegistration) {
    // Arrange to handle reads on this TCP socket:
    TaskScheduler::BackgroundHandlerProc* handler
      = (TaskScheduler::BackgroundHandlerProc*)&tcpReadHandler;
    fEnv.taskScheduler().
      setBackgroundHandling(fOurSocketNum, SOCKET_READABLE|SOCKET_EXCEPTION, handler, this);
  }
}

RTPInterface* SocketDescriptor
::lookupRTPInterface(unsigned char streamChannelId) {
  char const* lookupArg = (char const*)(long)streamChannelId;
  return (RTPInterface*)(fSubChannelHashTable->Lookup(lookupArg));
}

void SocketDescriptor
::deregisterRTPInterface(unsigned char streamChannelId) {
#if defined(DEBUG_SEND)||defined(DEBUG_RECEIVE)
  fprintf(stderr, "SocketDescriptor(socket %d)::deregisterRTPInterface(channel %d)\n", fOurSocketNum, streamChannelId);
#endif
  fSubChannelHashTable->Remove((char const*)(long)streamChannelId);

  if (fSubChannelHashTable->IsEmpty()) {
    // No more interfaces are using us, so it's curtains for us now:
    fDeleteNext = True; // hack to cause ourself to be deleted from "tcpReadHandler()" below
  }
}

void SocketDescriptor::tcpReadHandler(SocketDescriptor* socketDescriptor, int mask) {
  // Call the read handler until it returns false, with a limit to avoid starving other sockets
  unsigned count = 2000;
  while (!socketDescriptor->fDeleteNext && socketDescriptor->tcpReadHandler1(mask) && --count > 0) {}
  if (socketDescriptor->fDeleteNext) delete socketDescriptor;
}

Boolean SocketDescriptor::tcpReadHandler1(int mask) {
  // We expect the following data over the TCP channel:
  //   optional RTSP command or response bytes (before the first '$' character)
  //   a '$' character
  //   a 1-byte channel id
  //   a 2-byte packet size (in network byte order)
  //   the packet data.
  // However, because the socket is being read asynchronously, this data might arrive in pieces.
  
  u_int8_t c;
  struct sockaddr_in fromAddress;
  if (fTCPReadingState != AWAITING_PACKET_DATA) {
    int result = readSocket(fEnv, fOurSocketNum, &c, 1, fromAddress);
    if (result == 0) { // There was no more data to read
      return False;
    } else if (result != 1) { // error reading TCP socket, so we will no longer handle it
#ifdef DEBUG_RECEIVE
      fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): readSocket(1 byte) returned %d (error)\n", fOurSocketNum, result);
#endif
      fReadErrorOccurred = True;
      delete this;
      return False;
    }
  }

  Boolean callAgain = True;
  switch (fTCPReadingState) {
    case AWAITING_DOLLAR: {
      if (c == '$') {
#ifdef DEBUG_RECEIVE
        fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): Saw '$'\n", fOurSocketNum);
#endif
        fTCPReadingState = AWAITING_STREAM_CHANNEL_ID;
      } else {
        // This character is part of a RTSP request or command, which is handled separately:
        if (fServerRequestAlternativeByteHandler != NULL && c != 0xFF && c != 0xFE) {
          // Hack: 0xFF and 0xFE are used as special signaling characters, so don't send them
          (*fServerRequestAlternativeByteHandler)(fServerRequestAlternativeByteHandlerClientData, c);
        }
      }
      break;
    }
    case AWAITING_STREAM_CHANNEL_ID: {
      // The byte that we read is the stream channel id.
      if (lookupRTPInterface(c) != NULL) { // sanity check
        fStreamChannelId = c;
        fTCPReadingState = AWAITING_SIZE1;
      } else {
        // This wasn't a stream channel id that we expected.  We're (somehow) in a strange state.  Try to recover:
#ifdef DEBUG_RECEIVE
        fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): Saw nonexistent stream channel id: 0x%02x\n", fOurSocketNum, c);
#endif
        fTCPReadingState = AWAITING_DOLLAR;
      }
      break;
    }
    case AWAITING_SIZE1: {
      // The byte that we read is the first (high) byte of the 16-bit RTP or RTCP packet 'size'.
      fSizeByte1 = c;
      fTCPReadingState = AWAITING_SIZE2;
      break;
    }
    case AWAITING_SIZE2: {
      // The byte that we read is the second (low) byte of the 16-bit RTP or RTCP packet 'size'.
      unsigned short size = (fSizeByte1<<8)|c;
      
      // Record the information about the packet data that will be read next:
      RTPInterface* rtpInterface = lookupRTPInterface(fStreamChannelId);
      if (rtpInterface != NULL) {
        rtpInterface->fNextTCPReadSize = size;
        rtpInterface->fNextTCPReadStreamSocketNum = fOurSocketNum;
        rtpInterface->fNextTCPReadStreamChannelId = fStreamChannelId;
      }
      fTCPReadingState = AWAITING_PACKET_DATA;
      break;
    }
    case AWAITING_PACKET_DATA: {
      callAgain = False;
      fTCPReadingState = AWAITING_DOLLAR; // the next state, unless we end up having to read more data in the current state
      // Call the appropriate read handler to get the packet data from the TCP stream:
      RTPInterface* rtpInterface = lookupRTPInterface(fStreamChannelId);
      if (rtpInterface != NULL) {
        if (rtpInterface->fNextTCPReadSize == 0) {
          // We've already read all the data for this packet.
          break;
        }
        if (rtpInterface->fReadHandlerProc != NULL) {
#ifdef DEBUG_RECEIVE
          fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): reading %d bytes on channel %d\n", fOurSocketNum, rtpInterface->fNextTCPReadSize, rtpInterface->fNextTCPReadStreamChannelId);
#endif
          fTCPReadingState = AWAITING_PACKET_DATA;
          rtpInterface->fReadHandlerProc(rtpInterface->fOwner, mask);
        } else {
#ifdef DEBUG_RECEIVE
          fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): No handler proc for \"rtpInterface\" for channel %d; need to skip %d remaining bytes\n", fOurSocketNum, fStreamChannelId, rtpInterface->fNextTCPReadSize);
#endif
          int result = readSocket(fEnv, fOurSocketNum, &c, 1, fromAddress);
          if (result < 0) { // error reading TCP socket, so we will no longer handle it
#ifdef DEBUG_RECEIVE
            fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): readSocket(1 byte) returned %d (error)\n", fOurSocketNum, result);
#endif
            fReadErrorOccurred = True;
            delete this;
            return False;
          } else {
            fTCPReadingState = AWAITING_PACKET_DATA;
            if (result == 1) {
              --rtpInterface->fNextTCPReadSize;
              callAgain = True;
            }
          }
        }
      }
#ifdef DEBUG_RECEIVE
      else fprintf(stderr, "SocketDescriptor(socket %d)::tcpReadHandler(): No \"rtpInterface\" for channel %d\n", fOurSocketNum, fStreamChannelId);
#endif
    }
  }

  return callAgain;
}



tcpStreamRecord
::tcpStreamRecord(int streamSocketNum, unsigned char streamChannelId,
                  tcpStreamRecord* next)
  : fNext(next),
    fStreamSocketNum(streamSocketNum), fStreamChannelId(streamChannelId) {
}

tcpStreamRecord::~tcpStreamRecord() {
  delete fNext;
}

---