third_party/libjingle/source/talk/session/phone/mediasession.cc - vendor/opensource/webrtc - Git at Google

 /*
  * libjingle
  * Copyright 2004--2005, Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
  *     this list of conditions and the following disclaimer in the documentation
  *     and/or other materials provided with the distribution.
  *  3. The name of the author may not be used to endorse or promote products
  *     derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "talk/session/phone/mediasession.h"

 #include "talk/base/helpers.h"
 #include "talk/base/logging.h"
 #include "talk/base/scoped_ptr.h"
 #include "talk/p2p/base/constants.h"
 #include "talk/session/phone/channelmanager.h"
 #include "talk/session/phone/cryptoparams.h"
 #include "talk/session/phone/srtpfilter.h"
 #include "talk/xmpp/constants.h"

 namespace {
 const char kInline[] = "inline:";
 }

 namespace cricket {

 using talk_base::scoped_ptr;

 static bool CreateCryptoParams(int tag, const std::string& cipher,
                                CryptoParams *out) {
   std::string key;
   key.reserve(SRTP_MASTER_KEY_BASE64_LEN);

   if (!talk_base::CreateRandomString(SRTP_MASTER_KEY_BASE64_LEN, &key)) {
     return false;
   }
   out->tag = tag;
   out->cipher_suite = cipher;
   out->key_params = kInline;
   out->key_params += key;
   return true;
 }

 #ifdef HAVE_SRTP
 static bool AddCryptoParams(const std::string& cipher_suite,
                             CryptoParamsVec *out) {
   int size = out->size();

   out->resize(size + 1);
   return CreateCryptoParams(size, cipher_suite, &out->at(size));
 }
 #endif

 // For audio, HMAC 32 is prefered because of the low overhead.
 static bool GetSupportedAudioCryptos(CryptoParamsVec* cryptos) {
 #ifdef HAVE_SRTP
   return AddCryptoParams(CS_AES_CM_128_HMAC_SHA1_32, cryptos) &&
       AddCryptoParams(CS_AES_CM_128_HMAC_SHA1_80, cryptos);
 #else
   return false;
 #endif
 }

 static bool GetSupportedVideoCryptos(CryptoParamsVec* cryptos) {
 #ifdef HAVE_SRTP
   return AddCryptoParams(CS_AES_CM_128_HMAC_SHA1_80, cryptos);
 #else
   return false;
 #endif
 }

 // For video support only 80-bit SHA1 HMAC. For audio 32-bit HMAC is
 // tolerated because it is low overhead. Pick the crypto in the list
 // that is supported.
 static bool SelectCrypto(const MediaContentDescription* offer,
                          CryptoParams *crypto) {
   bool audio = offer->type() == MEDIA_TYPE_AUDIO;
   const CryptoParamsVec& cryptos = offer->cryptos();

   for (CryptoParamsVec::const_iterator i = cryptos.begin();
        i != cryptos.end(); ++i) {
     if (CS_AES_CM_128_HMAC_SHA1_80 == i->cipher_suite ||
         (CS_AES_CM_128_HMAC_SHA1_32 == i->cipher_suite && audio)) {
       return CreateCryptoParams(i->tag, i->cipher_suite, crypto);
     }
   }
   return false;
 }

 static const StreamParams* FindStreamParamsByName(
     const StreamParamsVec& params_vec,
     const std::string& name) {
   for (StreamParamsVec::const_iterator it = params_vec.begin();
        it != params_vec.end(); ++it) {
     if (it->name == name)
       return &*it;
   }
   return NULL;
 }

 static const StreamParams* FindFirstStreamParamsByCname(
     const StreamParamsVec& params_vec,
     const std::string& cname) {
   for (StreamParamsVec::const_iterator it = params_vec.begin();
        it != params_vec.end(); ++it) {
     if (cname == it->cname)
       return &*it;
   }
   return NULL;
 }

 static const StreamParams* FindStreamParamsBySsrc(
     const StreamParamsVec& params_vec,
     uint32 ssrc) {
   for (StreamParamsVec::const_iterator stream_it = params_vec.begin();
        stream_it != params_vec.end(); ++stream_it) {
     const std::vector<uint32>& ssrcs = stream_it->ssrcs;
     for (std::vector<uint32>::const_iterator ssrc_it = ssrcs.begin();
          ssrc_it !=  ssrcs.end(); ++ssrc_it) {
       if (ssrc == *ssrc_it)
         return &*stream_it;
     }
   }
   return NULL;
 }

 // Generates a new CNAME or the CNAME of an already existing StreamParams
 // if a StreamParams exist for another Stream in streams with sync_label
 // sync_label.
 static bool GenerateCname(const StreamParamsVec& params_vec,
                           const MediaSessionOptions::Streams& streams,
                           const std::string& synch_label,
                           std::string* cname) {
   ASSERT(cname != NULL);
   if (!cname)
     return false;

   // Check if a CNAME exist for any of the other synched streams.
   for (MediaSessionOptions::Streams::const_iterator stream_it = streams.begin();
        stream_it != streams.end() ; ++stream_it) {
     if (synch_label != stream_it->sync_label)
       continue;
     const StreamParams* param = FindStreamParamsByName(params_vec,
                                                        stream_it->name);
     if (param) {
       *cname = param->cname;
       return true;
     }
   }
   // No other stream seems to exist that we should sync with.
   // Generate a random string for the RTCP CNAME, as stated in RFC 6222.
   // This string is only used for synchronization, and therefore is opaque.
   do {
     if (!talk_base::CreateRandomString(16, cname)) {
       ASSERT(false);
       return false;
     }
   } while (FindFirstStreamParamsByCname(params_vec, *cname));

   return true;
 }

 // Generate a new SSRC and make sure it does not exist in params_vec.
 static uint32 GenerateSsrc(const StreamParamsVec& params_vec) {
   uint32 ssrc = 0;
   do {
     ssrc = talk_base::CreateRandomNonZeroId();
   } while (FindStreamParamsBySsrc(params_vec, ssrc));
   return ssrc;
 }

 // Finds all StreamParams of all media types and attach them to stream_params.
 static void GetCurrentStreamParams(const SessionDescription* sdesc,
                                    StreamParamsVec* stream_params) {
   if (!sdesc)
     return;

   const ContentInfos& contents = sdesc->contents();
   for (ContentInfos::const_iterator content = contents.begin();
        content != contents.end(); content++) {
     if (!IsAudioContent(&*content) && !IsVideoContent(&*content))
       continue;
     const MediaContentDescription* media =
         static_cast<const MediaContentDescription*>(
             content->description);
     const StreamParamsVec& streams = media->streams();
     for (StreamParamsVec::const_iterator it = streams.begin();
          it != streams.end(); ++it) {
       stream_params->push_back(*it);
     }
   }
 }

 // Adds a StreamParams for each Stream in Streams with media type
 // media_type to content_description.
 // current_parms - All currently known StreamParams of any media type.
 static bool AddStreamParams(
     MediaType media_type,
     const MediaSessionOptions::Streams& streams,
     StreamParamsVec* current_params,
     MediaContentDescription* content_description) {
   for (MediaSessionOptions::Streams::const_iterator stream_it = streams.begin();
        stream_it != streams.end(); ++stream_it) {
     if (stream_it->type != media_type)
       continue;  // Wrong media type.
     const StreamParams* params = FindStreamParamsByName(*current_params,
                                                         stream_it->name);
     if (!params) {
       // This is a new stream.
       // Get a CNAME. Either new or same as one of the other synched streams.
       std::string cname;
       if (!GenerateCname(*current_params, streams, stream_it->sync_label,
                          &cname)) {
         return false;
       }
       uint32 ssrc = GenerateSsrc(*current_params);
       // TODO: Generate the more complex types of stream_params.

       StreamParams stream_param;
       stream_param.name = stream_it->name;
       stream_param.ssrcs.push_back(ssrc);
       stream_param.cname = cname;
       stream_param.sync_label = stream_it->sync_label;
       content_description->AddStream(stream_param);

       // Store the new StreamParams in current_params.
       // This is necessary so that we can use the CNAME for other media types.
       current_params->push_back(stream_param);
     } else {
       content_description->AddStream(*params);
     }
   }
   return true;
 }

 void MediaSessionOptions::AddStream(MediaType type,
                                     const std::string& name,
                                     const std::string& sync_label) {
   streams.push_back(Stream(type, name, sync_label));

   if (type == MEDIA_TYPE_VIDEO)
     has_video = true;
   else if (type == MEDIA_TYPE_AUDIO)
     has_audio = true;
 }

 void MediaSessionOptions::RemoveStream(MediaType type,
                                        const std::string& name) {
   Streams::iterator stream_it = streams.begin();
   for (; stream_it != streams.end(); ++stream_it) {
     if (stream_it->type == type && stream_it->name == name) {
       streams.erase(stream_it);
       return;
     }
   }
   ASSERT(false);
 }

 MediaSessionDescriptionFactory::MediaSessionDescriptionFactory()
     : secure_(SEC_DISABLED) {
 }

 MediaSessionDescriptionFactory::MediaSessionDescriptionFactory(
     ChannelManager* channel_manager)
     : secure_(SEC_DISABLED) {
   channel_manager->GetSupportedAudioCodecs(&audio_codecs_);
   channel_manager->GetSupportedVideoCodecs(&video_codecs_);
 }

 SessionDescription* MediaSessionDescriptionFactory::CreateOffer(
     const MediaSessionOptions& options,
     const SessionDescription* current_description) {
   scoped_ptr<SessionDescription> offer(new SessionDescription());

   StreamParamsVec current_params;
   GetCurrentStreamParams(current_description, &current_params);

   if (options.has_audio) {
     scoped_ptr<AudioContentDescription> audio(new AudioContentDescription());
     for (AudioCodecs::const_iterator codec = audio_codecs_.begin();
          codec != audio_codecs_.end(); ++codec) {
       audio->AddCodec(*codec);
     }
     audio->SortCodecs();
     if (!AddStreamParams(MEDIA_TYPE_AUDIO, options.streams, &current_params,
                          audio.get())) {
       return NULL;  // Abort, something went seriously wrong.
     }

     if (options.streams.empty()) {
       // TODO: Remove this legacy stream when all apps use StreamParams.
       audio->AddLegacyStream(talk_base::CreateRandomNonZeroId());
     }
     audio->set_rtcp_mux(options.rtcp_mux_enabled);
     audio->set_lang(lang_);

     if (secure() != SEC_DISABLED) {
       CryptoParamsVec audio_cryptos;
       if (current_description) {
         // Copy crypto parameters from the previous offer.
         const ContentInfo* info =
             GetFirstAudioContent(current_description);
         if (info) {
           const AudioContentDescription* desc =
               static_cast<const AudioContentDescription*>(info->description);
           audio_cryptos = desc->cryptos();
         }
       }
       if (audio_cryptos.empty())
         GetSupportedAudioCryptos(&audio_cryptos);  // Generate new cryptos.

       for (CryptoParamsVec::const_iterator crypto = audio_cryptos.begin();
            crypto != audio_cryptos.end(); ++crypto) {
         audio->AddCrypto(*crypto);
       }

       if (secure() == SEC_REQUIRED) {
         if (audio->cryptos().empty()) {
           return NULL;  // Abort, crypto required but none found.
         }
         audio->set_crypto_required(true);
       }
     }

     offer->AddContent(CN_AUDIO, NS_JINGLE_RTP, audio.release());
   }

   // add video codecs, if this is a video call
   if (options.has_video) {
     scoped_ptr<VideoContentDescription> video(new VideoContentDescription());
     for (VideoCodecs::const_iterator codec = video_codecs_.begin();
          codec != video_codecs_.end(); ++codec) {
       video->AddCodec(*codec);
     }

     video->SortCodecs();
     if (!AddStreamParams(MEDIA_TYPE_VIDEO, options.streams, &current_params,
                          video.get())) {
       return NULL;  // Abort, something went seriously wrong.
     }

     if (options.streams.empty()) {
       // TODO: Remove this legacy stream when all apps use StreamParams.
       video->AddLegacyStream(talk_base::CreateRandomNonZeroId());
     }
     video->set_bandwidth(options.video_bandwidth);
     video->set_rtcp_mux(options.rtcp_mux_enabled);

     if (secure() != SEC_DISABLED) {
       CryptoParamsVec video_cryptos;
       if (current_description) {
         // Copy crypto parameters from the previous offer.
         const ContentInfo* info =
             GetFirstVideoContent(current_description);
         if (info) {
           const VideoContentDescription* desc =
               static_cast<const VideoContentDescription*>(info->description);
           video_cryptos = desc->cryptos();
         }
       }
       if (video_cryptos.empty())
         GetSupportedVideoCryptos(&video_cryptos);  // Generate new crypto.
       for (CryptoParamsVec::const_iterator crypto = video_cryptos.begin();
            crypto != video_cryptos.end(); ++crypto) {
         video->AddCrypto(*crypto);
       }
       if (secure() == SEC_REQUIRED) {
         if (video->cryptos().empty()) {
           return NULL;  // Abort, crypto required but none found.
         }
         video->set_crypto_required(true);
       }
     }

     offer->AddContent(CN_VIDEO, NS_JINGLE_RTP, video.release());
   }

   return offer.release();
 }

 SessionDescription* MediaSessionDescriptionFactory::CreateAnswer(
     const SessionDescription* offer, const MediaSessionOptions& options,
     const SessionDescription* current_description) {
   // The answer contains the intersection of the codecs in the offer with the
   // codecs we support, ordered by our local preference. As indicated by
   // XEP-0167, we retain the same payload ids from the offer in the answer.
   scoped_ptr<SessionDescription> accept(new SessionDescription());

   StreamParamsVec current_params;
   GetCurrentStreamParams(current_description, &current_params);

   const ContentInfo* audio_content = GetFirstAudioContent(offer);
   if (audio_content && options.has_audio) {
     const AudioContentDescription* audio_offer =
         static_cast<const AudioContentDescription*>(audio_content->description);
     scoped_ptr<AudioContentDescription> audio_accept(
         new AudioContentDescription());
     for (AudioCodecs::const_iterator ours = audio_codecs_.begin();
         ours != audio_codecs_.end(); ++ours) {
       for (AudioCodecs::const_iterator theirs = audio_offer->codecs().begin();
           theirs != audio_offer->codecs().end(); ++theirs) {
         if (ours->Matches(*theirs)) {
           AudioCodec negotiated(*ours);
           negotiated.id = theirs->id;
           audio_accept->AddCodec(negotiated);
         }
       }
     }

     audio_accept->SortCodecs();
     if (!AddStreamParams(MEDIA_TYPE_AUDIO, options.streams, &current_params,
                          audio_accept.get())) {
       return NULL;  // Abort, something went seriously wrong.
     }

     if (options.streams.empty()) {
       // TODO: Remove this legacy stream when all apps use StreamParams.
       audio_accept->AddLegacyStream(talk_base::CreateRandomNonZeroId());
     }
     audio_accept->set_rtcp_mux(
         options.rtcp_mux_enabled && audio_offer->rtcp_mux());

     if (secure() != SEC_DISABLED) {
       CryptoParams crypto;

       if (SelectCrypto(audio_offer, &crypto)) {
         if (current_description) {
           // Check if this crypto already exist in the previous
           // session description. Use it in that case.
           const ContentInfo* info =
               GetFirstAudioContent(current_description);
           if (info) {
             const AudioContentDescription* desc =
                 static_cast<const AudioContentDescription*>(info->description);
             const CryptoParamsVec& cryptos = desc->cryptos();
             for (CryptoParamsVec::const_iterator it = cryptos.begin();
                 it != cryptos.end(); ++it) {
               if (crypto.Matches(*it)) {
                 crypto = *it;
                 break;
               }
             }
           }
         }
         audio_accept->AddCrypto(crypto);
       }
     }

     if (audio_accept->cryptos().empty() &&
         (audio_offer->crypto_required() || secure() == SEC_REQUIRED)) {
       return NULL;  // Fails the session setup.
     }
     accept->AddContent(audio_content->name, audio_content->type,
                        audio_accept.release());
   } else {
     LOG(LS_INFO) << "Audio is not supported in answer";
   }

   const ContentInfo* video_content = GetFirstVideoContent(offer);
   if (video_content && options.has_video) {
     const VideoContentDescription* video_offer =
         static_cast<const VideoContentDescription*>(video_content->description);
     scoped_ptr<VideoContentDescription> video_accept(
         new VideoContentDescription());
     for (VideoCodecs::const_iterator ours = video_codecs_.begin();
         ours != video_codecs_.end(); ++ours) {
       for (VideoCodecs::const_iterator theirs = video_offer->codecs().begin();
           theirs != video_offer->codecs().end(); ++theirs) {
         if (ours->Matches(*theirs)) {
           VideoCodec negotiated(*ours);
           negotiated.id = theirs->id;
           video_accept->AddCodec(negotiated);
         }
       }
     }
     if (!AddStreamParams(MEDIA_TYPE_VIDEO, options.streams, &current_params,
                          video_accept.get())) {
       return NULL;  // Abort, something went seriously wrong.
     }

     if (options.streams.empty()) {
       // TODO: Remove this legacy stream when all apps use StreamParams.
       video_accept->AddLegacyStream(talk_base::CreateRandomNonZeroId());
     }
     video_accept->set_bandwidth(options.video_bandwidth);
     video_accept->set_rtcp_mux(
         options.rtcp_mux_enabled && video_offer->rtcp_mux());
     video_accept->SortCodecs();

     if (secure() != SEC_DISABLED) {
       CryptoParams crypto;

       if (SelectCrypto(video_offer, &crypto)) {
         if (current_description) {
           // Check if this crypto already exist in the previous
           // session description. Use it in that case.
           const ContentInfo* info = GetFirstVideoContent(current_description);
           if (info) {
             const VideoContentDescription* desc =
                 static_cast<const VideoContentDescription*>(info->description);
             const CryptoParamsVec& cryptos = desc->cryptos();
             for (CryptoParamsVec::const_iterator it = cryptos.begin();
                  it != cryptos.end(); ++it) {
               if (crypto.Matches(*it)) {
                 crypto = *it;
                 break;
               }
             }
           }
         }
         video_accept->AddCrypto(crypto);
       }
     }

     if (video_accept->cryptos().empty() &&
         (video_offer->crypto_required() || secure() == SEC_REQUIRED)) {
       return NULL;  // Fails the session setup.
     }
     accept->AddContent(video_content->name, video_content->type,
                        video_accept.release());
   } else {
     LOG(LS_INFO) << "Video is not supported in answer";
   }
   return accept.release();
 }

 static bool IsMediaContent(const ContentInfo* content, MediaType media_type) {
   if (content == NULL || content->type != NS_JINGLE_RTP) {
     return false;
   }

   const MediaContentDescription* media =
       static_cast<const MediaContentDescription*>(content->description);
   return media->type() == media_type;
 }

 bool IsAudioContent(const ContentInfo* content) {
   return IsMediaContent(content, MEDIA_TYPE_AUDIO);
 }

 bool IsVideoContent(const ContentInfo* content) {
   return IsMediaContent(content, MEDIA_TYPE_VIDEO);
 }

 static const ContentInfo* GetFirstMediaContent(const SessionDescription* sdesc,
                                                MediaType media_type) {
   if (sdesc == NULL)
     return NULL;

   const ContentInfos& contents = sdesc->contents();
   for (ContentInfos::const_iterator content = contents.begin();
        content != contents.end(); content++) {
     if (IsMediaContent(&*content, media_type)) {
       return &*content;
     }
   }
   return NULL;
 }

 const ContentInfo* GetFirstAudioContent(const SessionDescription* sdesc) {
   return GetFirstMediaContent(sdesc, MEDIA_TYPE_AUDIO);
 }

 const ContentInfo* GetFirstVideoContent(const SessionDescription* sdesc) {
   return GetFirstMediaContent(sdesc, MEDIA_TYPE_VIDEO);
 }

 }  // namespace cricket
	/*
	* libjingle
	* Copyright 2004--2005, Google Inc.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	*
	* 1. Redistributions of source code must retain the above copyright notice,
	* this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright notice,
	* this list of conditions and the following disclaimer in the documentation
	* and/or other materials provided with the distribution.
	* 3. The name of the author may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
	* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
	* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "talk/session/phone/mediasession.h"

	#include "talk/base/helpers.h"
	#include "talk/base/logging.h"
	#include "talk/base/scoped_ptr.h"
	#include "talk/p2p/base/constants.h"
	#include "talk/session/phone/channelmanager.h"
	#include "talk/session/phone/cryptoparams.h"
	#include "talk/session/phone/srtpfilter.h"
	#include "talk/xmpp/constants.h"

	namespace {
	const char kInline[] = "inline:";
	}

	namespace cricket {

	using talk_base::scoped_ptr;

	static bool CreateCryptoParams(int tag, const std::string& cipher,
	CryptoParams *out) {
	std::string key;
	key.reserve(SRTP_MASTER_KEY_BASE64_LEN);

	if (!talk_base::CreateRandomString(SRTP_MASTER_KEY_BASE64_LEN, &key)) {
	return false;
	}
	out->tag = tag;
	out->cipher_suite = cipher;
	out->key_params = kInline;
	out->key_params += key;
	return true;
	}

	#ifdef HAVE_SRTP
	static bool AddCryptoParams(const std::string& cipher_suite,
	CryptoParamsVec *out) {
	int size = out->size();

	out->resize(size + 1);
	return CreateCryptoParams(size, cipher_suite, &out->at(size));
	}
	#endif

	// For audio, HMAC 32 is prefered because of the low overhead.
	static bool GetSupportedAudioCryptos(CryptoParamsVec* cryptos) {
	#ifdef HAVE_SRTP
	return AddCryptoParams(CS_AES_CM_128_HMAC_SHA1_32, cryptos) &&
	AddCryptoParams(CS_AES_CM_128_HMAC_SHA1_80, cryptos);
	#else
	return false;
	#endif
	}

	static bool GetSupportedVideoCryptos(CryptoParamsVec* cryptos) {
	#ifdef HAVE_SRTP
	return AddCryptoParams(CS_AES_CM_128_HMAC_SHA1_80, cryptos);
	#else
	return false;
	#endif
	}

	// For video support only 80-bit SHA1 HMAC. For audio 32-bit HMAC is
	// tolerated because it is low overhead. Pick the crypto in the list
	// that is supported.
	static bool SelectCrypto(const MediaContentDescription* offer,
	CryptoParams *crypto) {
	bool audio = offer->type() == MEDIA_TYPE_AUDIO;
	const CryptoParamsVec& cryptos = offer->cryptos();

	for (CryptoParamsVec::const_iterator i = cryptos.begin();
	i != cryptos.end(); ++i) {
	if (CS_AES_CM_128_HMAC_SHA1_80 == i->cipher_suite \|\|
	(CS_AES_CM_128_HMAC_SHA1_32 == i->cipher_suite && audio)) {
	return CreateCryptoParams(i->tag, i->cipher_suite, crypto);
	}
	}
	return false;
	}

	static const StreamParams* FindStreamParamsByName(
	const StreamParamsVec& params_vec,
	const std::string& name) {
	for (StreamParamsVec::const_iterator it = params_vec.begin();
	it != params_vec.end(); ++it) {
	if (it->name == name)
	return &*it;
	}
	return NULL;
	}

	static const StreamParams* FindFirstStreamParamsByCname(
	const StreamParamsVec& params_vec,
	const std::string& cname) {
	for (StreamParamsVec::const_iterator it = params_vec.begin();
	it != params_vec.end(); ++it) {
	if (cname == it->cname)
	return &*it;
	}
	return NULL;
	}

	static const StreamParams* FindStreamParamsBySsrc(
	const StreamParamsVec& params_vec,
	uint32 ssrc) {
	for (StreamParamsVec::const_iterator stream_it = params_vec.begin();
	stream_it != params_vec.end(); ++stream_it) {
	const std::vector<uint32>& ssrcs = stream_it->ssrcs;
	for (std::vector<uint32>::const_iterator ssrc_it = ssrcs.begin();
	ssrc_it != ssrcs.end(); ++ssrc_it) {
	if (ssrc == *ssrc_it)
	return &*stream_it;
	}
	}
	return NULL;
	}

	// Generates a new CNAME or the CNAME of an already existing StreamParams
	// if a StreamParams exist for another Stream in streams with sync_label
	// sync_label.
	static bool GenerateCname(const StreamParamsVec& params_vec,
	const MediaSessionOptions::Streams& streams,
	const std::string& synch_label,
	std::string* cname) {
	ASSERT(cname != NULL);
	if (!cname)
	return false;

	// Check if a CNAME exist for any of the other synched streams.
	for (MediaSessionOptions::Streams::const_iterator stream_it = streams.begin();
	stream_it != streams.end() ; ++stream_it) {
	if (synch_label != stream_it->sync_label)
	continue;
	const StreamParams* param = FindStreamParamsByName(params_vec,
	stream_it->name);
	if (param) {
	*cname = param->cname;
	return true;
	}
	}
	// No other stream seems to exist that we should sync with.
	// Generate a random string for the RTCP CNAME, as stated in RFC 6222.
	// This string is only used for synchronization, and therefore is opaque.
	do {
	if (!talk_base::CreateRandomString(16, cname)) {
	ASSERT(false);
	return false;
	}
	} while (FindFirstStreamParamsByCname(params_vec, *cname));

	return true;
	}

	// Generate a new SSRC and make sure it does not exist in params_vec.
	static uint32 GenerateSsrc(const StreamParamsVec& params_vec) {
	uint32 ssrc = 0;
	do {
	ssrc = talk_base::CreateRandomNonZeroId();
	} while (FindStreamParamsBySsrc(params_vec, ssrc));
	return ssrc;
	}

	// Finds all StreamParams of all media types and attach them to stream_params.
	static void GetCurrentStreamParams(const SessionDescription* sdesc,
	StreamParamsVec* stream_params) {
	if (!sdesc)
	return;

	const ContentInfos& contents = sdesc->contents();
	for (ContentInfos::const_iterator content = contents.begin();
	content != contents.end(); content++) {
	if (!IsAudioContent(&content) && !IsVideoContent(&content))
	continue;
	const MediaContentDescription* media =
	static_cast<const MediaContentDescription*>(
	content->description);
	const StreamParamsVec& streams = media->streams();
	for (StreamParamsVec::const_iterator it = streams.begin();
	it != streams.end(); ++it) {
	stream_params->push_back(*it);
	}
	}
	}

	// Adds a StreamParams for each Stream in Streams with media type
	// media_type to content_description.
	// current_parms - All currently known StreamParams of any media type.
	static bool AddStreamParams(
	MediaType media_type,
	const MediaSessionOptions::Streams& streams,
	StreamParamsVec* current_params,
	MediaContentDescription* content_description) {
	for (MediaSessionOptions::Streams::const_iterator stream_it = streams.begin();
	stream_it != streams.end(); ++stream_it) {
	if (stream_it->type != media_type)
	continue; // Wrong media type.
	const StreamParams* params = FindStreamParamsByName(*current_params,
	stream_it->name);
	if (!params) {
	// This is a new stream.
	// Get a CNAME. Either new or same as one of the other synched streams.
	std::string cname;
	if (!GenerateCname(*current_params, streams, stream_it->sync_label,
	&cname)) {
	return false;
	}
	uint32 ssrc = GenerateSsrc(*current_params);
	// TODO: Generate the more complex types of stream_params.

	StreamParams stream_param;
	stream_param.name = stream_it->name;
	stream_param.ssrcs.push_back(ssrc);
	stream_param.cname = cname;
	stream_param.sync_label = stream_it->sync_label;
	content_description->AddStream(stream_param);

	// Store the new StreamParams in current_params.
	// This is necessary so that we can use the CNAME for other media types.
	current_params->push_back(stream_param);
	} else {
	content_description->AddStream(*params);
	}
	}
	return true;
	}

	void MediaSessionOptions::AddStream(MediaType type,
	const std::string& name,
	const std::string& sync_label) {
	streams.push_back(Stream(type, name, sync_label));

	if (type == MEDIA_TYPE_VIDEO)
	has_video = true;
	else if (type == MEDIA_TYPE_AUDIO)
	has_audio = true;
	}

	void MediaSessionOptions::RemoveStream(MediaType type,
	const std::string& name) {
	Streams::iterator stream_it = streams.begin();
	for (; stream_it != streams.end(); ++stream_it) {
	if (stream_it->type == type && stream_it->name == name) {
	streams.erase(stream_it);
	return;
	}
	}
	ASSERT(false);
	}

	MediaSessionDescriptionFactory::MediaSessionDescriptionFactory()
	: secure_(SEC_DISABLED) {
	}

	MediaSessionDescriptionFactory::MediaSessionDescriptionFactory(
	ChannelManager* channel_manager)
	: secure_(SEC_DISABLED) {
	channel_manager->GetSupportedAudioCodecs(&audio_codecs_);
	channel_manager->GetSupportedVideoCodecs(&video_codecs_);
	}

	SessionDescription* MediaSessionDescriptionFactory::CreateOffer(
	const MediaSessionOptions& options,
	const SessionDescription* current_description) {
	scoped_ptr<SessionDescription> offer(new SessionDescription());

	StreamParamsVec current_params;
	GetCurrentStreamParams(current_description, &current_params);

	if (options.has_audio) {
	scoped_ptr<AudioContentDescription> audio(new AudioContentDescription());
	for (AudioCodecs::const_iterator codec = audio_codecs_.begin();
	codec != audio_codecs_.end(); ++codec) {
	audio->AddCodec(*codec);
	}
	audio->SortCodecs();
	if (!AddStreamParams(MEDIA_TYPE_AUDIO, options.streams, &current_params,
	audio.get())) {
	return NULL; // Abort, something went seriously wrong.
	}

	if (options.streams.empty()) {
	// TODO: Remove this legacy stream when all apps use StreamParams.
	audio->AddLegacyStream(talk_base::CreateRandomNonZeroId());
	}
	audio->set_rtcp_mux(options.rtcp_mux_enabled);
	audio->set_lang(lang_);

	if (secure() != SEC_DISABLED) {
	CryptoParamsVec audio_cryptos;
	if (current_description) {
	// Copy crypto parameters from the previous offer.
	const ContentInfo* info =
	GetFirstAudioContent(current_description);
	if (info) {
	const AudioContentDescription* desc =
	static_cast<const AudioContentDescription*>(info->description);
	audio_cryptos = desc->cryptos();
	}
	}
	if (audio_cryptos.empty())
	GetSupportedAudioCryptos(&audio_cryptos); // Generate new cryptos.

	for (CryptoParamsVec::const_iterator crypto = audio_cryptos.begin();
	crypto != audio_cryptos.end(); ++crypto) {
	audio->AddCrypto(*crypto);
	}

	if (secure() == SEC_REQUIRED) {
	if (audio->cryptos().empty()) {
	return NULL; // Abort, crypto required but none found.
	}
	audio->set_crypto_required(true);
	}
	}

	offer->AddContent(CN_AUDIO, NS_JINGLE_RTP, audio.release());
	}

	// add video codecs, if this is a video call
	if (options.has_video) {
	scoped_ptr<VideoContentDescription> video(new VideoContentDescription());
	for (VideoCodecs::const_iterator codec = video_codecs_.begin();
	codec != video_codecs_.end(); ++codec) {
	video->AddCodec(*codec);
	}

	video->SortCodecs();
	if (!AddStreamParams(MEDIA_TYPE_VIDEO, options.streams, &current_params,
	video.get())) {
	return NULL; // Abort, something went seriously wrong.
	}

	if (options.streams.empty()) {
	// TODO: Remove this legacy stream when all apps use StreamParams.
	video->AddLegacyStream(talk_base::CreateRandomNonZeroId());
	}
	video->set_bandwidth(options.video_bandwidth);
	video->set_rtcp_mux(options.rtcp_mux_enabled);

	if (secure() != SEC_DISABLED) {
	CryptoParamsVec video_cryptos;
	if (current_description) {
	// Copy crypto parameters from the previous offer.
	const ContentInfo* info =
	GetFirstVideoContent(current_description);
	if (info) {
	const VideoContentDescription* desc =
	static_cast<const VideoContentDescription*>(info->description);
	video_cryptos = desc->cryptos();
	}
	}
	if (video_cryptos.empty())
	GetSupportedVideoCryptos(&video_cryptos); // Generate new crypto.
	for (CryptoParamsVec::const_iterator crypto = video_cryptos.begin();
	crypto != video_cryptos.end(); ++crypto) {
	video->AddCrypto(*crypto);
	}
	if (secure() == SEC_REQUIRED) {
	if (video->cryptos().empty()) {
	return NULL; // Abort, crypto required but none found.
	}
	video->set_crypto_required(true);
	}
	}

	offer->AddContent(CN_VIDEO, NS_JINGLE_RTP, video.release());
	}

	return offer.release();
	}

	SessionDescription* MediaSessionDescriptionFactory::CreateAnswer(
	const SessionDescription* offer, const MediaSessionOptions& options,
	const SessionDescription* current_description) {
	// The answer contains the intersection of the codecs in the offer with the
	// codecs we support, ordered by our local preference. As indicated by
	// XEP-0167, we retain the same payload ids from the offer in the answer.
	scoped_ptr<SessionDescription> accept(new SessionDescription());

	StreamParamsVec current_params;
	GetCurrentStreamParams(current_description, &current_params);

	const ContentInfo* audio_content = GetFirstAudioContent(offer);
	if (audio_content && options.has_audio) {
	const AudioContentDescription* audio_offer =
	static_cast<const AudioContentDescription*>(audio_content->description);
	scoped_ptr<AudioContentDescription> audio_accept(
	new AudioContentDescription());
	for (AudioCodecs::const_iterator ours = audio_codecs_.begin();
	ours != audio_codecs_.end(); ++ours) {
	for (AudioCodecs::const_iterator theirs = audio_offer->codecs().begin();
	theirs != audio_offer->codecs().end(); ++theirs) {
	if (ours->Matches(*theirs)) {
	AudioCodec negotiated(*ours);
	negotiated.id = theirs->id;
	audio_accept->AddCodec(negotiated);
	}
	}
	}

	audio_accept->SortCodecs();
	if (!AddStreamParams(MEDIA_TYPE_AUDIO, options.streams, &current_params,
	audio_accept.get())) {
	return NULL; // Abort, something went seriously wrong.
	}

	if (options.streams.empty()) {
	// TODO: Remove this legacy stream when all apps use StreamParams.
	audio_accept->AddLegacyStream(talk_base::CreateRandomNonZeroId());
	}
	audio_accept->set_rtcp_mux(
	options.rtcp_mux_enabled && audio_offer->rtcp_mux());

	if (secure() != SEC_DISABLED) {
	CryptoParams crypto;

	if (SelectCrypto(audio_offer, &crypto)) {
	if (current_description) {
	// Check if this crypto already exist in the previous
	// session description. Use it in that case.
	const ContentInfo* info =
	GetFirstAudioContent(current_description);
	if (info) {
	const AudioContentDescription* desc =
	static_cast<const AudioContentDescription*>(info->description);
	const CryptoParamsVec& cryptos = desc->cryptos();
	for (CryptoParamsVec::const_iterator it = cryptos.begin();
	it != cryptos.end(); ++it) {
	if (crypto.Matches(*it)) {
	crypto = *it;
	break;
	}
	}
	}
	}
	audio_accept->AddCrypto(crypto);
	}
	}

	if (audio_accept->cryptos().empty() &&
	(audio_offer->crypto_required() \|\| secure() == SEC_REQUIRED)) {
	return NULL; // Fails the session setup.
	}
	accept->AddContent(audio_content->name, audio_content->type,
	audio_accept.release());
	} else {
	LOG(LS_INFO) << "Audio is not supported in answer";
	}

	const ContentInfo* video_content = GetFirstVideoContent(offer);
	if (video_content && options.has_video) {
	const VideoContentDescription* video_offer =
	static_cast<const VideoContentDescription*>(video_content->description);
	scoped_ptr<VideoContentDescription> video_accept(
	new VideoContentDescription());
	for (VideoCodecs::const_iterator ours = video_codecs_.begin();
	ours != video_codecs_.end(); ++ours) {
	for (VideoCodecs::const_iterator theirs = video_offer->codecs().begin();
	theirs != video_offer->codecs().end(); ++theirs) {
	if (ours->Matches(*theirs)) {
	VideoCodec negotiated(*ours);
	negotiated.id = theirs->id;
	video_accept->AddCodec(negotiated);
	}
	}
	}
	if (!AddStreamParams(MEDIA_TYPE_VIDEO, options.streams, &current_params,
	video_accept.get())) {
	return NULL; // Abort, something went seriously wrong.
	}

	if (options.streams.empty()) {
	// TODO: Remove this legacy stream when all apps use StreamParams.
	video_accept->AddLegacyStream(talk_base::CreateRandomNonZeroId());
	}
	video_accept->set_bandwidth(options.video_bandwidth);
	video_accept->set_rtcp_mux(
	options.rtcp_mux_enabled && video_offer->rtcp_mux());
	video_accept->SortCodecs();

	if (secure() != SEC_DISABLED) {
	CryptoParams crypto;

	if (SelectCrypto(video_offer, &crypto)) {
	if (current_description) {
	// Check if this crypto already exist in the previous
	// session description. Use it in that case.
	const ContentInfo* info = GetFirstVideoContent(current_description);
	if (info) {
	const VideoContentDescription* desc =
	static_cast<const VideoContentDescription*>(info->description);
	const CryptoParamsVec& cryptos = desc->cryptos();
	for (CryptoParamsVec::const_iterator it = cryptos.begin();
	it != cryptos.end(); ++it) {
	if (crypto.Matches(*it)) {
	crypto = *it;
	break;
	}
	}
	}
	}
	video_accept->AddCrypto(crypto);
	}
	}

	if (video_accept->cryptos().empty() &&
	(video_offer->crypto_required() \|\| secure() == SEC_REQUIRED)) {
	return NULL; // Fails the session setup.
	}
	accept->AddContent(video_content->name, video_content->type,
	video_accept.release());
	} else {
	LOG(LS_INFO) << "Video is not supported in answer";
	}
	return accept.release();
	}

	static bool IsMediaContent(const ContentInfo* content, MediaType media_type) {
	if (content == NULL \|\| content->type != NS_JINGLE_RTP) {
	return false;
	}

	const MediaContentDescription* media =
	static_cast<const MediaContentDescription*>(content->description);
	return media->type() == media_type;
	}

	bool IsAudioContent(const ContentInfo* content) {
	return IsMediaContent(content, MEDIA_TYPE_AUDIO);
	}

	bool IsVideoContent(const ContentInfo* content) {
	return IsMediaContent(content, MEDIA_TYPE_VIDEO);
	}

	static const ContentInfo* GetFirstMediaContent(const SessionDescription* sdesc,
	MediaType media_type) {
	if (sdesc == NULL)
	return NULL;

	const ContentInfos& contents = sdesc->contents();
	for (ContentInfos::const_iterator content = contents.begin();
	content != contents.end(); content++) {
	if (IsMediaContent(&*content, media_type)) {
	return &*content;
	}
	}
	return NULL;
	}

	const ContentInfo* GetFirstAudioContent(const SessionDescription* sdesc) {
	return GetFirstMediaContent(sdesc, MEDIA_TYPE_AUDIO);
	}

	const ContentInfo* GetFirstVideoContent(const SessionDescription* sdesc) {
	return GetFirstMediaContent(sdesc, MEDIA_TYPE_VIDEO);
	}

	} // namespace cricket