This diff refactors the DNSTransport model to receive in input a DNSQuery and return in output a DNSResponse.
The design of DNSQuery and DNSResponse takes into account the use case of a transport using getaddrinfo, meaning that we don't need to serialize and deserialize messages when using getaddrinfo.
The current codebase does not use a getaddrinfo transport, but I wrote one such a transport in the Websteps Winter 2021 prototype (https://github.com/bassosimone/websteps-illustrated/).
The design conversation that lead to producing this diff is https://github.com/ooni/probe/issues/2099
This diff has been extracted and adapted from 8848c8c516
The reason to prefer composition over embedding is that we want the
build to break if we add new methods to interfaces we define. If the build
does not break, we may forget about wrapping methods we should
actually be wrapping. I noticed this issue inside netxlite when I was working
on websteps-illustrated and I added support for NS and PTR queries.
See https://github.com/ooni/probe/issues/2096
While there, perform comprehensive netxlite code review
and apply minor changes and improve the docs.
This diff has been extracted from c2f7ccab0e
See https://github.com/ooni/probe/issues/2096
While there, export DecodeReply to decode a raw reply without
interpreting the Rcode or parsing the results, which seems a
nice extra feature to have to more flexibly parse DNS replies
in other parts of the codebase.
## Checklist
- [x] I have read the [contribution guidelines](https://github.com/ooni/probe-cli/blob/master/CONTRIBUTING.md)
- [x] reference issue for this pull request: https://github.com/ooni/probe/issues/1885
- [x] related ooni/spec pull request: N/A
Location of the issue tracker: https://github.com/ooni/probe
## Description
This PR contains a set of changes to move important interfaces and data types into the `./internal/model` package.
The criteria for including an interface or data type in here is roughly that the type should be important and used by several packages. We are especially interested to move more interfaces here to increase modularity.
An additional side effect is that, by reading this package, one should be able to understand more quickly how different parts of the codebase interact with each other.
This is what I want to move in `internal/model`:
- [x] most important interfaces from `internal/netxlite`
- [x] everything that was previously part of `internal/engine/model`
- [x] mocks from `internal/netxlite/mocks` should also be moved in here as a subpackage
When preparing a tutorial for netxlite, I figured it is easier
to tell people "hey, this is the package you should use for all
low-level networking stuff" rather than introducing people to
a set of packages working together where some piece of functionality
is here and some other piece is there.
Part of https://github.com/ooni/probe/issues/1591
