Re: [rtcweb] IP handling: Using mDNS names for host candidates

This is a valid concern, but keep in mind that this only applies to:
- apps without gUM permission (or else they can use Mode 1)
- on networks that don't support IPv6 (or else they can use the RFC 4941 v6
address)
- on networks where mDNS is turned off or constrained

I tend to think this is still a pretty good tradeoff.

One other option could be to add a new Mode 1.5 that did hand out the
private IP which could be selected by domain admins, but given how subtle
this area is, I tend to think that it would rarely, if ever, be enabled.

On Wed, Jun 13, 2018 at 1:28 PM Cullen Jennings <fluffy@iii.ca> wrote:

>
>
> With my individual hat on …
>
> I have a bunch of concerns about this but the biggest is that mDNS does
> not work on a large percentage of medium and large corporate WiFI Networks.
> The problem is the large multicast domains trash the WiFi performance so
> many APs turn off mDNS or limit it’s range to much less than the scope of
> where just testing the address with ICE would be routable. It’s exactly
> theses environment where using the local IP vs a TURN IP provides lots of
> benefit.  I like the idea of trying to use mDNS but I’d want tot see strong
> evidence it worked in theses environments before putting it in at the last
> minute.
>
>
>
> On Jun 11, 2018, at 6:40 PM, Justin Uberti <
> juberti=40google.com@dmarc.ietf.org> wrote:
>
> The Safari team has come up with a clever approach to avoid disclosing
> private IP addresses for host candidates. As discussed in this WebKit bug
> <https://bugs.webkit.org/show_bug.cgi?id=174500>, the technique works as
> follows:
>
>    1. Register a random UUID-based mDNS name when ICE gathering starts
>    2. Replace the private IP address by a "{UUID}.local" string in each
>    host candidate (and set raddr to 0.0.0.0 for other candidates)
>    3. The other party will do mDNS resolution on any candidate having a
>    .local suffix, similar to how hostnames in candidates are handled in RFC
>    5245, Section 15.1.
>
> This technique is relevant to the IP handling document, as it addresses
> one of the lesser problems (private IP disclosure) from the overall problem
> statement. While I don't think this will have a large impact on the
> document, including the default mode selection, incorporating this
> technique would result in some moderate changes:
>
>    - Section 5.1 would mention concealing private IPs in the default case
>    as an explicit goal.
>    - In Section 6, Mode 2 would change from handling out private IPs to
>    handing out mDNS names.
>    - This document would have to describe the technique or point to
>    another document that describes the technique. mmusic-ice-sip-sdp,
>    Section 4.1
>    <https://tools.ietf.org/html/draft-ietf-mmusic-ice-sip-sdp-20#section-4.1> seems
>    like a good option, as it already covers how to handle DNS names in ICE
>    candidates.
>
> This is a significant improvement and I think we will want to incorporate
> this suggestion. Is this something we could do as part of this WGLC, or
> should we look for another option?
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