Re: [rtcweb] Please require user consent for data channels

[Simon Perreault <[e-mail]>]

Le 2015-07-18 06:01, Iñaki Baz Castillo a écrit :
> 2015-07-18 11:38 GMT+02:00 Roman Shpount <[e-mail]>:
>> Sending data to a particular destination over an interface that is not
>> supposed to be used based on the local routing is definitely something that
>> goes against the local policy and should be discouraged. For instance on a
>> mobile device, not being able to reach a particular STUN/TURN server over
>> WiFi, should not give the browser an automatic permission to send media over
>> cell data interface and generate a huge bill for the customer. Forcibly
>> overwriting default route is something that should need user consent. I
>> understand that we want the call to succeed in as many cases as possible,
>> but blindly assuming that the local routing policy exists for no reason
>> whatsoever is somewhat dangerous.
> 
> +1

-1

Justin and Martin are right.

This is a concept that was explained during the ICE tutorial that was
presented at IETF 92.

Imagine the following multihomed host with three interfaces:

- Wi-fi interface with default route.
- Wired interface with default route.
- VPN interface with default route.

Which one should you use to talk to the STUN/TURN server? If you bind to
0.0.0.0 then the kernel *will* pick one, but only because it *has to.
All three interfaces are equivalent: they all have a default route and
can a priori be used to talk to the server.

Being multihomed means multiple interfaces with a default route. There's
no "going against the local policy" in this case when sending packets on
any interface.

The point is that in this case, all three interfaces can potentially
yield different server-reflexive candidates, which is why they must be
gathered separately. As for relayed candidates, they also need to be
gathered separately because some interfaces may be faster for talking to
the TURN server and it is useful to compare the candidates gathered on
all 3 interfaces. Also nothing guarantees that you're allowed to reach
the server server on any interface that has a default route, so you need
to try them all.

Simon