Close interceptor after PeerConnection is closed

[aalekseevx]

The following panic was encountered in the stats interceptor:

panic: sync: WaitGroup is reused before previous Wait has returned

sync.(*WaitGroup).Wait(0xc08227bce0?)
go/_std_1.22/src/sync/waitgroup.go:118 +0x74
github.com/pion/interceptor/pkg/stats.(*Interceptor).Close(0xc08ff1de20?)
github.com/pion/interceptor.(*Chain).Close(0xc0423bbb90?)
github.com/pion/webrtc/v4.(*PeerConnection).close(0xc0423bbb80, 0x0)
github.com/pion/webrtc/v4.(*PeerConnection).Close(...)
github.com/pion/webrtc/v4.(*PeerConnection).startTransports.func1.1()

It occurs because wg.Add is called after wg.Wait. This implies that Bind was called after the interceptor had already been closed, which appears to be incorrect.

I was able to reproduce this issue in tests, but the reproduction is highly flaky (it might only work on my machine with the provided constants) and takes a long time to run. As a result, it doesn't seem practical to include it as a test case:

https://gist.github.com/aalekseevx/5b31eed4fe3e524502217cc02273345e

The proposed solution is to ensure that interceptor.close() is called only after the peer connection is fully closed—whether in a graceful or non-graceful manner—so that no track can be added afterward.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.91%. Comparing base (b82306a) to head (f36bb3d).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2977      +/-   ##
==========================================
+ Coverage   77.82%   77.91%   +0.08%     
==========================================
  Files          89       89              
  Lines       10523    10524       +1     
==========================================
+ Hits         8190     8200      +10     
+ Misses       1843     1836       -7     
+ Partials      490      488       -2     

Flag	Coverage Δ
go	79.49% <100.00%> (+0.09%)	⬆️
wasm	63.45% <ø> (ø)

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[aalekseevx]

Investigating the broken CI

[Sean-Der]

Nice catch! Thank you @aalekseevx