pion ICE流程分析，2024年最新Golang面试常用算法

if api.settingEngine.disableMediaEngineCopy {
	pc.api.mediaEngine = api.mediaEngine
} else {
	pc.api.mediaEngine = api.mediaEngine.copy()
}

if err = pc.initConfiguration(configuration); err != nil {
	return nil, err
}

pc.iceGatherer, err = pc.createICEGatherer()
if err != nil {
	return nil, err
}

// Create the ice transport
iceTransport := pc.createICETransport()
pc.iceTransport = iceTransport

// Create the DTLS transport
dtlsTransport, err := pc.api.NewDTLSTransport(pc.iceTransport, pc.configuration.Certificates)
if err != nil {
	return nil, err
}
pc.dtlsTransport = dtlsTransport

// Create the SCTP transport
pc.sctpTransport = pc.api.NewSCTPTransport(pc.dtlsTransport)

// Wire up the on datachannel handler
pc.sctpTransport.OnDataChannel(func(d \*DataChannel) {
	pc.mu.RLock()
	handler := pc.onDataChannelHandler
	pc.mu.RUnlock()
	if handler != nil {
		handler(d)
	}
})

pc.interceptorRTCPWriter = pc.api.interceptor.BindRTCPWriter(interceptor.RTCPWriterFunc(pc.writeRTCP))

return pc, nil

}

// NewAgent creates a new Agent func NewAgent(config *AgentConfig) (*Agent, error) { //nolint:gocognit var err error if config.PortMax < config.PortMin { return nil, ErrPort }

mDNSName := config.MulticastDNSHostName
if mDNSName == "" {
	if mDNSName, err = generateMulticastDNSName(); err != nil {
		return nil, err
	}
}

if !strings.HasSuffix(mDNSName, ".local") || len(strings.Split(mDNSName, ".")) != 2 {
	return nil, ErrInvalidMulticastDNSHostName
}

mDNSMode := config.MulticastDNSMode
if mDNSMode == 0 {
	mDNSMode = MulticastDNSModeQueryOnly
}

loggerFactory := config.LoggerFactory
if loggerFactory == nil {
	loggerFactory = logging.NewDefaultLoggerFactory()
}
log := loggerFactory.NewLogger("ice")

var mDNSConn \*mdns.Conn
mDNSConn, mDNSMode, err = createMulticastDNS(mDNSMode, mDNSName, log)
// Opportunistic mDNS: If we can't open the connection, that's ok: we
// can continue without it.
if err != nil {
	log.Warnf("Failed to initialize mDNS %s: %v", mDNSName, err)
}
closeMDNSConn := func() {
	if mDNSConn != nil {
		if mdnsCloseErr := mDNSConn.Close(); mdnsCloseErr != nil {
			log.Warnf("Failed to close mDNS: %v", mdnsCloseErr)
		}
	}
}

startedCtx, startedFn := context.WithCancel(context.Background())

a := &Agent{
	chanTask:          make(chan task),
	chanState:         make(chan ConnectionState),
	chanCandidate:     make(chan Candidate),
	chanCandidatePair: make(chan \*CandidatePair),
	tieBreaker:        globalMathRandomGenerator.Uint64(),
	lite:              config.Lite,
	gatheringState:    GatheringStateNew,
	connectionState:   ConnectionStateNew,
	localCandidates:   make(map[NetworkType][]Candidate),
	remoteCandidates:  make(map[NetworkType][]Candidate),
	urls:              config.Urls,
	networkTypes:      config.NetworkTypes,
	onConnected:       make(chan struct{}),
	buffer:            packetio.NewBuffer(),
	done:              make(chan struct{}),
	taskLoopDone:      make(chan struct{}),
	startedCh:         startedCtx.Done(),
	startedFn:         startedFn,
	portmin:           config.PortMin,
	portmax:           config.PortMax,
	loggerFactory:     loggerFactory,
	log:               log,
	net:               config.Net,
	proxyDialer:       config.ProxyDialer,

	mDNSMode: mDNSMode,
	mDNSName: mDNSName,
	mDNSConn: mDNSConn,

	gatherCandidateCancel: func() {},

	forceCandidateContact: make(chan bool, 1),

	interfaceFilter: config.InterfaceFilter,

	insecureSkipVerify: config.InsecureSkipVerify,
}

a.tcpMux = config.TCPMux
if a.tcpMux == nil {
	a.tcpMux = newInvalidTCPMux()
}
a.udpMux = config.UDPMux
a.udpMuxSrflx = config.UDPMuxSrflx

if a.net == nil {
	a.net = vnet.NewNet(nil)
} else if a.net.IsVirtual() {
	a.log.Warn("vnet is enabled")
	if a.mDNSMode != MulticastDNSModeDisabled {
		a.log.Warn("vnet does not support mDNS yet")
	}
}

config.initWithDefaults(a)

// Make sure the buffer doesn't grow indefinitely.
// NOTE: We actually won't get anywhere close to this limit.
// SRTP will constantly read from the endpoint and drop packets if it's full.
a.buffer.SetLimitSize(maxBufferSize)

if a.lite && (len(a.candidateTypes) != 1 || a.candidateTypes[0] != CandidateTypeHost) {
	closeMDNSConn()
	return nil, ErrLiteUsingNonHostCandidates
}

if config.Urls != nil && len(config.Urls) > 0 && !containsCandidateType(CandidateTypeServerReflexive, a.candidateTypes) && !containsCandidateType(CandidateTypeRelay, a.candidateTypes) {
	closeMDNSConn()
	return nil, ErrUselessUrlsProvided
}

if err = config.initExtIPMapping(a); err != nil {
	closeMDNSConn()
	return nil, err
}

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