very large number of "protocol mux failed: connection reset" errors

[whyrusleeping]

I'm playing around with debugging connectivity issues, and i'm seeing a lot of these errors coming out of basichost. It could be normal, but it definitely seems a bit odd. I'm opening this issue to track finding the cause and determining whether or not this is a deeper issue.

[whyrusleeping]

cc @bigs @Stebalien

[Stebalien]

Could be TCP port scans (if this is happening when negotiating secio).

[whyrusleeping]

@Stebalien mind elaborating a bit?

[Stebalien]

That is:

1. Someone opens a TCP connection to us (e.g., to see if we're an IPFS node, or just to do a port scan).
2. They immediately close it.
3. We try to negotiate secio.
4. That obviously fails because the connection has been reset.

---

Alternatively, this could be evil ISPs resetting our connections when we open too many (Comcast did this for a while in an attempt to break bittorrent).

[whyrusleeping]

@Stebalien but i'm seeing these without a listener. I'm only dialing outwards.

[whyrusleeping]

also see notes on: libp2p/go-libp2p-kad-dht#139 (comment)

[whyrusleeping]

"connection reset" is coming from yamux. It really means that the stream was reset, not the connection. Thanks yamux.

[Stebalien]

Where does the "protocol mux failed" come from?

[Stebalien]

Ah... Lazy negotiation.

[Stebalien]

Ah, no, I know exactly where this is coming from. A peer is trying to connect via a protocol you don't speak (probably bitswap). After you refuse to speak any of the requested protocols, the peer (correctly) hangs up with a reset. We should ignore these.

[Stebalien]

Actually, should we be nice on encountering an unsupported protocol? We could nicely close the connection but that takes more time.

[whyrusleeping]

No, we can't do that. I think we previously had a bug caused by that, where we would open a stream and start writing to it, and since the other side didnt support the protocol and only closed it, we never found out, and just kept writing into the void.

[whyrusleeping]

Overall, I think this error i'm seeing here isnt really a problem. Just took a little while to figure out what it actually meant

[Stebalien]

I'm going to at least improve the error message.

[whyrusleeping]

do it. You can change the world.