fix: skip RTCP sends when connection is closed or failed

[kingdomcoding]

Problem

After calling PeerConnection.close/1, the TWCC feedback, sender/receiver report, and NACK timers continue to fire because they are self-rescheduling and their already-queued mailbox messages cannot be cancelled. Each fired message attempts to call DTLSTransport.send_rtcp/2, which logs a debug warning since DTLS is no longer connected:

Attempted to send RTCP in wrong DTLS state: closed. Ignoring.

This is a race condition between the DTLS/ICE teardown completing and in-flight timer messages being processed. Fixes #232.

Solution

Add guard clauses before each of the three affected handle_info handlers to short-circuit when conn_state is :closed or :failed. This matches the existing pattern already used by the send_rtp cast handler:

def handle_cast({:send_rtp, track_id, packet, opts}, %{conn_state: conn_state} = state)
    when conn_state not in [:failed, :closed] do

The three new guard clauses follow the same convention:

def handle_info(:send_twcc_feedback, %{conn_state: conn_state} = state)
    when conn_state in [:failed, :closed],
    do: {:noreply, state}

def handle_info({:send_reports, _transceiver_id}, %{conn_state: conn_state} = state)
    when conn_state in [:failed, :closed],
    do: {:noreply, state}

def handle_info({:send_nacks, _transceiver_id}, %{conn_state: conn_state} = state)
    when conn_state in [:failed, :closed],
    do: {:noreply, state}

Testing

Manually verified by starting a WebRTC stream, stopping it, and confirming the debug message no longer appears in logs.

[sgfn]

Thanks for the fix!

[sgfn]

Let's keep the clause order consistent for all of the :send_ handlers -- the happy path with when conn_state not in [:failed, :closed] should be first

[sgfn]

Please add a comment in the new fallback clause that we're not scheduling any more TWCC feedback sends.

At this point, it shouldn't be an issue since conn_states :closed and :failed are permanent, but this seems like something that can easily be overlooked in the future were this to change