quic: panic on error in listener Accept

[sukunrt]

originally reported here:
ipfs/kubo#9693

The sequence of events that causes this is:

list.Accept errors here https://github.com/libp2p/go-libp2p/blob/v0.26.4/p2p/net/swarm/swarm_listen.go#L129

and error in list.Accept has closed the listener accept loop already here:
https://github.com/libp2p/go-libp2p/blob/v0.26.4/p2p/transport/quic/virtuallistener.go#L108-L120
with sendErrAndClose

The defer cleanup in swarm_listen closes virtuallistener here https://github.com/libp2p/go-libp2p/blob/master/p2p/net/swarm/swarm_listen.go#L117

which causes panic here: https://github.com/libp2p/go-libp2p/blob/v0.26.4/p2p/transport/quic/virtuallistener.go#L73
as it checks for entry from muxer map which was removed by sendErrAndClose

[MarcoPolo]

So this is an issue with closing twice? Once in the error from accept and once on shutdown?

[sukunrt]

yes. Accept implicitly closes the listener on error via sendErrAndClose and the shutdown cleanup func explicitly closes it. I think this should just be an error and not a panic.

I don't know why Accept is erroring though.

[marten-seemann]

Wild guess: might be related to quic-go/quic-go#1737?

[MarcoPolo]

Easy fix could be to make sure we only close once. Still unclear we get the original error in Accept though.