[rtcweb] IP handling text

[Ted Hardie <[e-mail]>]

Sorry that we were not able to get to the slides on this during the WG
meeting.  Here's the proposal from Justin, taken for the slides he prepared.


Original text:

WebRTC incorporates an explicit permission grant for access to local audio
and video, which are typically much more sensitive than the aforementioned
IP address information. If the user has consented to media access, this
should also allow WebRTC to gather all possible candidates and determine
the absolute best route for media traffic.

Proposed replacement:

Gathering all possible candidates SHOULD only be performed upon user
consent, which thwarts the typical drive-by enumeration attacks. The
details of this consent are left to the implementation; one potential
mechanism is to key this off getUserMedia consent.

The getUserMedia suggestion takes into account that the user has provided
some consent to the application already; that when doing so the user
typically wants to engage in a conversational session, which benefits most
from an optimal network path, and lastly, the fact that the underlying
issue is complex and difficult to explain, making explicit consent for
enumeration troublesome.