200 lines
8.9 KiB
C
200 lines
8.9 KiB
C
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/*
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* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef CALL_RTP_DEMUXER_H_
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#define CALL_RTP_DEMUXER_H_
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#include <map>
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#include <set>
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#include <string>
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#include <utility>
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#include <vector>
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namespace webrtc {
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class RtpPacketReceived;
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class RtpPacketSinkInterface;
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// This struct describes the criteria that will be used to match packets to a
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// specific sink.
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struct RtpDemuxerCriteria {
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RtpDemuxerCriteria();
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~RtpDemuxerCriteria();
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// If not the empty string, will match packets with this MID.
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std::string mid;
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// If not the empty string, will match packets with this as their RTP stream
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// ID or repaired RTP stream ID.
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// Note that if both MID and RSID are specified, this will only match packets
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// that have both specified (either through RTP header extensions, SSRC
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// latching or RTCP).
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std::string rsid;
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// Will match packets with any of these SSRCs.
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std::set<uint32_t> ssrcs;
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// Will match packets with any of these payload types.
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std::set<uint8_t> payload_types;
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// Return string representation of demux criteria to facilitate logging
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std::string ToString() const;
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};
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// This class represents the RTP demuxing, for a single RTP session (i.e., one
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// SSRC space, see RFC 7656). It isn't thread aware, leaving responsibility of
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// multithreading issues to the user of this class.
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// The demuxing algorithm follows the sketch given in the BUNDLE draft:
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// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-38#section-10.2
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// with modifications to support RTP stream IDs also.
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//
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// When a packet is received, the RtpDemuxer will route according to the
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// following rules:
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// 1. If the packet contains the MID header extension, and no sink has been
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// added with that MID as a criteria, the packet is not routed.
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// 2. If the packet has the MID header extension, but no RSID or RRID extension,
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// and the MID is bound to a sink, then bind its SSRC to the same sink and
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// forward the packet to that sink. Note that rebinding to the same sink is
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// not an error. (Later packets with that SSRC would therefore be forwarded
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// to the same sink, whether they have the MID header extension or not.)
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// 3. If the packet has the MID header extension and either the RSID or RRID
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// extension, and the MID, RSID (or RRID) pair is bound to a sink, then bind
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// its SSRC to the same sink and forward the packet to that sink. Later
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// packets with that SSRC will be forwarded to the same sink.
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// 4. If the packet has the RSID or RRID header extension, but no MID extension,
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// and the RSID or RRID is bound to an RSID sink, then bind its SSRC to the
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// same sink and forward the packet to that sink. Later packets with that
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// SSRC will be forwarded to the same sink.
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// 5. If the packet's SSRC is bound to an SSRC through a previous call to
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// AddSink, then forward the packet to that sink. Note that the RtpDemuxer
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// will not verify the payload type even if included in the sink's criteria.
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// The sink is expected to do the check in its handler.
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// 6. If the packet's payload type is bound to exactly one payload type sink
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// through an earlier call to AddSink, then forward the packet to that sink.
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// 7. Otherwise, the packet is not routed.
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//
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// In summary, the routing algorithm will always try to first match MID and RSID
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// (including through SSRC binding), match SSRC directly as needed, and use
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// payload types only if all else fails.
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class RtpDemuxer {
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public:
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// Maximum number of unique SSRC bindings allowed. This limit is to prevent
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// memory overuse attacks due to a malicious peer sending many packets with
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// different SSRCs.
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static constexpr int kMaxSsrcBindings = 1000;
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// Returns a string that contains all the attributes of the given packet
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// relevant for demuxing.
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static std::string DescribePacket(const RtpPacketReceived& packet);
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RtpDemuxer();
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~RtpDemuxer();
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RtpDemuxer(const RtpDemuxer&) = delete;
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void operator=(const RtpDemuxer&) = delete;
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// Registers a sink that will be notified when RTP packets match its given
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// criteria according to the algorithm described in the class description.
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// Returns true if the sink was successfully added.
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// Returns false in the following situations:
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// - Only MID is specified and the MID is already registered.
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// - Only RSID is specified and the RSID is already registered.
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// - Both MID and RSID is specified and the (MID, RSID) pair is already
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// registered.
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// - Any of the criteria SSRCs are already registered.
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// If false is returned, no changes are made to the demuxer state.
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bool AddSink(const RtpDemuxerCriteria& criteria,
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RtpPacketSinkInterface* sink);
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// Registers a sink. Multiple SSRCs may be mapped to the same sink, but
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// each SSRC may only be mapped to one sink. The return value reports
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// whether the association has been recorded or rejected. Rejection may occur
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// if the SSRC has already been associated with a sink. The previously added
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// sink is *not* forgotten.
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bool AddSink(uint32_t ssrc, RtpPacketSinkInterface* sink);
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// Registers a sink's association to an RSID. Only one sink may be associated
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// with a given RSID. Null pointer is not allowed.
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void AddSink(const std::string& rsid, RtpPacketSinkInterface* sink);
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// Removes a sink. Return value reports if anything was actually removed.
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// Null pointer is not allowed.
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bool RemoveSink(const RtpPacketSinkInterface* sink);
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// Demuxes the given packet and forwards it to the chosen sink. Returns true
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// if the packet was forwarded and false if the packet was dropped.
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bool OnRtpPacket(const RtpPacketReceived& packet);
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// Configure whether to look at the MID header extension when demuxing
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// incoming RTP packets. By default this is enabled.
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void set_use_mid(bool use_mid) { use_mid_ = use_mid; }
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private:
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// Returns true if adding a sink with the given criteria would cause conflicts
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// with the existing criteria and should be rejected.
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bool CriteriaWouldConflict(const RtpDemuxerCriteria& criteria) const;
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// Runs the demux algorithm on the given packet and returns the sink that
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// should receive the packet.
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// Will record any SSRC<->ID associations along the way.
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// If the packet should be dropped, this method returns null.
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RtpPacketSinkInterface* ResolveSink(const RtpPacketReceived& packet);
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// Used by the ResolveSink algorithm.
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RtpPacketSinkInterface* ResolveSinkByMid(const std::string& mid,
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uint32_t ssrc);
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RtpPacketSinkInterface* ResolveSinkByMidRsid(const std::string& mid,
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const std::string& rsid,
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uint32_t ssrc);
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RtpPacketSinkInterface* ResolveSinkByRsid(const std::string& rsid,
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uint32_t ssrc);
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RtpPacketSinkInterface* ResolveSinkByPayloadType(uint8_t payload_type,
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uint32_t ssrc);
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// Regenerate the known_mids_ set from information in the sink_by_mid_ and
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// sink_by_mid_and_rsid_ maps.
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void RefreshKnownMids();
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// Map each sink by its component attributes to facilitate quick lookups.
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// Payload Type mapping is a multimap because if two sinks register for the
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// same payload type, both AddSinks succeed but we must know not to demux on
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// that attribute since it is ambiguous.
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// Note: Mappings are only modified by AddSink/RemoveSink (except for
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// SSRC mapping which receives all MID, payload type, or RSID to SSRC bindings
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// discovered when demuxing packets).
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std::map<std::string, RtpPacketSinkInterface*> sink_by_mid_;
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std::map<uint32_t, RtpPacketSinkInterface*> sink_by_ssrc_;
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std::multimap<uint8_t, RtpPacketSinkInterface*> sinks_by_pt_;
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std::map<std::pair<std::string, std::string>, RtpPacketSinkInterface*>
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sink_by_mid_and_rsid_;
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std::map<std::string, RtpPacketSinkInterface*> sink_by_rsid_;
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// Tracks all the MIDs that have been identified in added criteria. Used to
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// determine if a packet should be dropped right away because the MID is
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// unknown.
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std::set<std::string> known_mids_;
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// Records learned mappings of MID --> SSRC and RSID --> SSRC as packets are
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// received.
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// This is stored separately from the sink mappings because if a sink is
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// removed we want to still remember these associations.
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std::map<uint32_t, std::string> mid_by_ssrc_;
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std::map<uint32_t, std::string> rsid_by_ssrc_;
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// Adds a binding from the SSRC to the given sink.
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void AddSsrcSinkBinding(uint32_t ssrc, RtpPacketSinkInterface* sink);
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bool use_mid_ = true;
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};
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} // namespace webrtc
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#endif // CALL_RTP_DEMUXER_H_
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