Add logging for missing --rpcvhosts on server

[lazzarello]

#16457

I couldn't figure out where the error output in the referenced issue originated so I added some extra strings to the debug output when it bails.

This happens when any DNS name is used with geth attach ... and the server has not specified that same DNS name via --rpcvhosts

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[holiman]

You are reassigning the err here. What should happen is that the server should respond with a json-rpc error, saying that the host header was wrong, and we should just bubble that up. So if that's not happening, it would be better to try to discover why that is.

[lazzarello]

indeed, I don't know why that is and don't know how to determine the source. I have debugging notes in the referenced issue.

[holiman]

Ah, I see. So the reponse is not jsonrpc, it's plain old http 403:

HTTP/1.1 403 Forbidden
Content-Type: text/plain; charset=utf-8
X-Content-Type-Options: nosniff
Date: Fri, 13 Apr 2018 07:53:00 GMT
Content-Length: 23

invalid host specified

Thus we get

Fatal: Failed to start the JavaScript console: api modules: invalid character 'i' looking for beginning of value

The client should not assume it's json unless either Content-Type: application/json or http 200 OK .

[holiman]

For some reason, doRequest throws away the headers, including the http status, and just returns the body.

[lazzarello]

oic, this totally makes sense now. I wasn't looking at the headers because they were getting thrown out. I'll try and add a content-type to the client headers.

[holiman]

Did you see my alternate PR #16500 ?

[lazzarello]

ha! I did now. thanks. this is my first PR in this project. I appreciate the help.