Make sensitivity of is_vulnerable_to_client_renegotiation_dos configurable

[mxsasha]

Trying renegotiation multiple times to find mitigations makes sense. However, it is quite rare for servers to allow 1 but not too many renegotiations. For my use, I want to test compliance with requirements that do not allow it at all. Therefore, I'd like it to be configurable.

[nabla-c0d3]

Hello !

Thanks for the contribution, and nice catch on using an ExtraArgument class VS ServerConnectivityInfo for passing the setting around.

One last request : could you add a simple test that just ensures that client_renegotiation_attempts is being used when it supplied via SessionRenegotiationExtraArgument.

Thanks!

[mxsasha]

One last request : could you add a simple test that just ensures that client_renegotiation_attempts is being used when it supplied via SessionRenegotiationExtraArgument.

The only practical way I see to test that, is to track the number of attempts. Which actually can be useful for users that get into these details anyways. Code may be a bit clunky, I was struggling with the best way to return multiple values.

[nabla-c0d3]

It looks good - merging this as is. Thanks !