Move network related internal packages to here

[at-wat]

To make webrtc/internal/mux.Mux, transport/vnet.VNet, and transport/test.Bridge compatible with full net.Conn features (including SetDeadline), it would be better to move dtls/internal/net/deadline to this package. Following packages are also better to be moved to here to make package dependencies clean.

• dtls/internal/net/deadline (net.Conn compatible deadline timer)
• dtls/internal/net/connctx (context cancelable Conn)
• udp
• dtls/internal/net/dpipe (datagram like pipe)
• webrtc/internal/mux (packet multiplexer)

[stv0g]

This seems to be related to #168 & #204.

@at-wat Can you provide an update which of the points of this issue are missing?
I am willing to work on it :)

[stv0g]

I have just migrated pion/udp to this repo 🥳

[hasheddan]

@stv0g I noticed that in the pion/udp migration, this commit and the corresponding sync package were not migrated -- was that intentional?

[stv0g]

Yes, that was intentional as I believe the removed functionality is also part of the standard libraries sync package.

I was also irritated why the functionality was in this module. It does not seem to be networking related.

[hasheddan]

@stv0g I'm not sure introducing the sync package was the proper fix for pion/udp#74, but it seems as though after migrating pion/udp here we are back to the state in which the data race was observed.

[stv0g]

Hi @hasheddan ,

Thanks for the context. I now understand yhe motivation of our custom sync.WaitGroup implementation. I think we can add it back. However I would strongly for adding it into internal/sync. We should also highlight the difference to thevstandard implementation to avoid the same mistake in the future.

[stv0g]

@hasheddan I am going to address this in #259