swarm: duplicate tracking in dial worker loop doesn't work

[marten-seemann]

In the dial worker loop, we use maps of ma.Multiaddrs:

go-libp2p/p2p/net/swarm/dial_worker.go

Line 32 in 8a3fafd

addrs map[ma.Multiaddr]struct{} // pending addr dials

and

go-libp2p/p2p/net/swarm/dial_worker.go

Line 49 in 8a3fafd

pending map[ma.Multiaddr]*addrDial

This is incorrect, since ma.Multiaddr is (until we fix multiformats/go-multiaddr#198) an interface, and equality only checks equality of the pointer, not of the actual multiaddress. This has bitten us before, for example in #2247.

[marten-seemann]

The impact of this is that we dial the same multiaddr multiple times. On TCP, due to reuseport, this should lead to failed dial right away, whereas on QUIC, we'd actually dial twice. I instrumented my Kubo node, and this happens from time to time.

This probably doesn't warrant another patch release, but we should include a fix in the next release.