c85ebbe766
In short, the caller places a x-opaque line in SDP for each m= section that
uses datagram transport. If the answerer supports datagram transport, it will
parse this line and create a datagram transport. It will then echo the x-opaque
line into the answer (to indicate that it accepted use of datagram transport).
If the offer and answer contain exactly the same x-opaque line, both peers will
use datagram transport. If the x-opaque line is omitted from the answer (or is
different in the answer) they will fall back to RTP.
Note that a different x-opaque line in the answer means the answerer did not
understand something in the negotiation proto. Since WebRTC cannot know what
was misunderstood, or whether it's still possible to use the datagram transport,
it must fall back to RTP. This may change in the future, possibly by passing
the answer to the datagram transport, but it's good enough for now.
Negotiation consists of four parts:
1. DatagramTransport exposes transport parameters for both client and server
perspectives. The client just echoes what it received from the server (modulo
any fields it might not have understood).
2. SDP adds a x-opaque line for opaque transport parameters. Identical to
x-mt, but this is specific to datagram transport and goes in each m= section,
and appears in the answer as well as the offer.
- This is propagated to Jsep as part of the TransportDescription.
- SDP files: transport_description.h,cc, transport_description_factory.h,cc,
media_session.cc, webrtc_sdp.cc
3. JsepTransport/Controller:
- Exposes opaque parameters for each mid (m= section). On offerer, this means
pre-allocating a datagram transport and getting its parameters. On the
answerer, this means echoing the offerer's parameters.
- Uses a composite RTP transport to receive from either default RTP or
datagram transport until both offer and answer arrive.
- If a provisional answer arrives, sets the composite to send on the
provisionally selected transport.
- Once both offer and answer are set, deletes the unneeded transports and
keeps whichever transport is selected.
4. PeerConnection pulls transport parameters out of Jsep and adds them to SDP.
Bug: webrtc:9719
Change-Id: Ifcc428c8d76fb77dcc8abaa79507c620bcfb31b9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/140920
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Bjorn Mellem <mellem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28198}
90 lines
3.1 KiB
C++
90 lines
3.1 KiB
C++
/*
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* Copyright 2012 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 P2P_BASE_TRANSPORT_DESCRIPTION_FACTORY_H_
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#define P2P_BASE_TRANSPORT_DESCRIPTION_FACTORY_H_
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#include <memory>
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#include "p2p/base/ice_credentials_iterator.h"
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#include "p2p/base/transport_description.h"
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#include "rtc_base/rtc_certificate.h"
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namespace rtc {
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class SSLIdentity;
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}
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namespace cricket {
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struct TransportOptions {
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bool ice_restart = false;
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bool prefer_passive_role = false;
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// If true, ICE renomination is supported and will be used if it is also
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// supported by the remote side.
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bool enable_ice_renomination = false;
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// Opaque parameters for plug-in transports.
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absl::optional<OpaqueTransportParameters> opaque_parameters;
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};
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// Creates transport descriptions according to the supplied configuration.
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// When creating answers, performs the appropriate negotiation
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// of the various fields to determine the proper result.
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class TransportDescriptionFactory {
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public:
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// Default ctor; use methods below to set configuration.
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TransportDescriptionFactory();
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~TransportDescriptionFactory();
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SecurePolicy secure() const { return secure_; }
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// The certificate to use when setting up DTLS.
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const rtc::scoped_refptr<rtc::RTCCertificate>& certificate() const {
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return certificate_;
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}
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// Specifies the transport security policy to use.
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void set_secure(SecurePolicy s) { secure_ = s; }
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// Specifies the certificate to use (only used when secure != SEC_DISABLED).
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void set_certificate(
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const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) {
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certificate_ = certificate;
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}
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// Creates a transport description suitable for use in an offer.
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std::unique_ptr<TransportDescription> CreateOffer(
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const TransportOptions& options,
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const TransportDescription* current_description,
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IceCredentialsIterator* ice_credentials) const;
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// Create a transport description that is a response to an offer.
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//
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// If |require_transport_attributes| is true, then TRANSPORT category
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// attributes are expected to be present in |offer|, as defined by
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// sdp-mux-attributes, and null will be returned otherwise. It's expected
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// that this will be set to false for an m= section that's in a BUNDLE group
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// but isn't the first m= section in the group.
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std::unique_ptr<TransportDescription> CreateAnswer(
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const TransportDescription* offer,
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const TransportOptions& options,
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bool require_transport_attributes,
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const TransportDescription* current_description,
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IceCredentialsIterator* ice_credentials) const;
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private:
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bool SetSecurityInfo(TransportDescription* description,
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ConnectionRole role) const;
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SecurePolicy secure_;
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rtc::scoped_refptr<rtc::RTCCertificate> certificate_;
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};
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} // namespace cricket
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#endif // P2P_BASE_TRANSPORT_DESCRIPTION_FACTORY_H_
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