Historically we have always used IP Config information for the primary (underlying) network connection, not the VPN. It seems odd to me to provide a Device for a VPN.

There are likely many places in the Chrome code where we treat VPN differently from other networks and where associating a Device + IP Configs to a VPN won't "just work".

It sounds like what we really want to do is to have Shill provide a DNS server list for VPN services? Do other IPConfig properties apply (i.e. would they differ from the underlying network properties)?

DNS servers + search domains are the most important properties to pass over to Android.  The datapath uses NAT44 so other elements of the IP configuration aren't currently necessary.

It looks like we already have dns_servers for ThirdPartyVpn:
https://cs.chromium.org/chromium/src/third_party/cros_system_api/dbus/shill/dbus-constants.h?q=dbus-constants.h&sq=package:chromium&l=740

There is also a 'domain_search' property.

I don't know whether or not it makes sense to re-use those, but it would be simpler on the Chrome side to provide these as Service properties.

That said, scanning the CL linked above, it seems like Shill already associates a Device with a VPN? We could certainly modify Chrome to do the same, it's just potentially quite a large / risky change.

dns_servers and domain_search are used by the SetParameters call, not ONC or Service properties.

Empirically, the DNS server list does show up in ONC under SavedIPConfig for VPN.  I could change the arc_net_host_impl code to look in both places if that is the most expedient solution.  But it feels hacky.

> it seems like Shill already associates a Device with a VPN

Correct, in shill we still need a Device (usually a VirtualDevice) that owns the Connection object and handles configuring the IP parameters on the interface.  The only thing I had to do in my CL was wire up the GetRpcIdentifier code.

So, we can change Chrome to associate a Device and IP Configs with VPNs, but as you discovered, it's not trivial.

The question becomes, what is the priority for this? I don't have much in the way of free bandwidth to take this on myself in the immediate future.

I have a couple of reports from users that may be caused by this (but they have not yet confirmed that it's a DNS problem).

I'll send out a CL with the quick arc_net_host_impl fix and we can decide whether it's good enough for now.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8778ec3109bc8750db7ba39e040d6a4a9802236c

commit 8778ec3109bc8750db7ba39e040d6a4a9802236c
Author: Kevin Cernekee <cernekee@chromium.org>
Date: Wed Sep 06 23:38:40 2017

Fall back to StaticIPConfig or SavedIPConfig if IPConfigs[] is empty

VPNs do not currently populate the IPConfigs array, so Android does
not get informed about VPN DNS servers.  This results in connectivity
issues.  The IPConfigs problem requires a major rework and changes in
both Chrome and shill, so it will not be fixed any time soon.
Implement a temporary workaround to address the user issue.

BUG= chromium:761708 
TEST=manually connect to a VPN and sniff DNS requests coming from Android

Change-Id: Ied56cc7004693e4cc5e8d303721d227748d97532
Reviewed-on: https://chromium-review.googlesource.com/651582
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Commit-Queue: Kevin Cernekee <cernekee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#500115}
[modify] https://crrev.com/8778ec3109bc8750db7ba39e040d6a4a9802236c/components/arc/net/arc_net_host_impl.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5bfe3ad1decdfd840726e31694347e6d973a3f09

commit 5bfe3ad1decdfd840726e31694347e6d973a3f09
Author: Kevin Cernekee <cernekee@chromium.org>
Date: Thu Sep 07 00:44:46 2017

Don't complain if optional ONC fields are missing

NameServers, ConnectionStaten, and MacAddress are always optional.
RoutingPrefix and Gateway are not required if IPAddress is absent.

BUG= chromium:761708 
TEST=connect to various networks and watch ~chronos/log/chrome for
     errors

Change-Id: I6bb7652f33053dc24158d7f9ea306c73da5443cb
Reviewed-on: https://chromium-review.googlesource.com/651589
Commit-Queue: Kevin Cernekee <cernekee@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#500160}
[modify] https://crrev.com/5bfe3ad1decdfd840726e31694347e6d973a3f09/components/arc/net/arc_net_host_impl.cc

De-prioritizing since we have a workaround for now.

Maybe related: http://b/34975953

 Issue 204337  has been merged into this issue.

cernekee@ - Are all of the following configurable for VPN:

* IP address
* Nameservers
* Proxy

It *appears* that they can all be set and saved correctly if I just enable the UI for VPN and fetch the IPConfig object from the VPN service.

CL: https://chromium-review.googlesource.com/c/chromium/src/+/1068105

Too late to merge this to 67.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/701ef06b384a785a1c9903fa104ae708d6b28a5d

commit 701ef06b384a785a1c9903fa104ae708d6b28a5d
Author: Steven Bennetts <stevenjb@chromium.org>
Date: Wed May 23 18:46:30 2018

Settings: Network: Provide and show IP Configs for VPNs

This CL includes two small changes:
1. Provides IPConfigs for networks without a device (i.e. VPNs).
2. Shows the 'Network' section for VPNs in the UI.

Bug:  761708 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I62f691dd0ef0e2001fd66ba033726e25cbd0a58b
Reviewed-on: https://chromium-review.googlesource.com/1068105
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561181}
[modify] https://crrev.com/701ef06b384a785a1c9903fa104ae708d6b28a5d/chrome/browser/resources/settings/internet_page/internet_detail_page.js
[modify] https://crrev.com/701ef06b384a785a1c9903fa104ae708d6b28a5d/chromeos/network/managed_network_configuration_handler_impl.cc