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60 lines
1.8 KiB
Plaintext
60 lines
1.8 KiB
Plaintext
This is a generic media transport system for WebRTC.
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The basic model is that you have a TransportFlow which contains a
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series of TransportLayers, each of which gets an opportunity to
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manipulate data up and down the stack (think SysV STREAMS or a
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standard networking stack). You can also address individual
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sublayers to manipulate them or to bypass reading and writing
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at an upper layer; WebRTC uses this to implement DTLS-SRTP.
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DATAFLOW MODEL
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Unlike the existing nsSocket I/O system, this is a push rather
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than a pull system. Clients of the interface do writes downward
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with SendPacket() and receive notification of incoming packets
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via callbacks registed via sigslot.h. It is the responsibility
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of the bottom layer (or any other layer which needs to reference
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external events) to arrange for that somehow; typically by
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using nsITimer or the SocketTansportService.
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This sort of push model is a much better fit for the demands
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of WebRTC, expecially because ICE contexts span multiple
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network transports.
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THREADING MODEL
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There are no thread locks. It is the responsibility of the caller to
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arrange that any given TransportLayer/TransportFlow is only
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manipulated in one thread at once. One good way to do this is to run
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everything on the STS thread. Many of the existing layer implementations
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(TransportLayerPrsock, TransportLayerIce, TransportLayerLoopback)
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already run on STS so in those cases you must run on STS, though
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you can do setup on the main thread and then activate them on the
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STS.
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EXISTING TRANSPORT LAYERS
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The following transport layers are currently implemented:
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* DTLS -- a wrapper around NSS's DTLS [RFC 6347] stack
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* ICE -- a wrapper around the nICEr ICE [RFC 5245] stack.
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* Prsock -- a wrapper around NSPR sockets
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* Loopback -- a loopback IO mechanism
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* Logging -- a passthrough that just logs its data
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The last three are primarily for debugging.
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