The test verifies that a DHCP offer can be sent to a fake IP address
when addArpEntry is used to specify a fake MAC address for that host.
It then verifies that the packet was addressed to the fake MAC address.

Test: atest NetworkStackIntegrationTests
Bug: 168868607
Change-Id: Ic6df3724958820b328ca3024aa5a7a7248a7d6d8

Instead of using the network_stack certificate, tests in
IpClientIntegrationTest should use root access. This allows running them
on any userdebug device, while the network_stack certificate requirement
is more restrictive.

This change renames IpClientIntegrationTest to
IpClientIntegrationTestBase, which IpClientIntegrationTest and
IpClientRootTest inherit from.
Current tests in IpClientIntegrationTestBase are run in IpClientRootTest
by default (root access should be available when signature permissions
are available), and only run in IpClientIntegrationTest when annotated
with @SignatureRequiredTest.

This change adds @SignatureRequiredTest to all tests except
testDhcpInit. This causes current tests to run in the same configuration
as today. testDhcpInit demonstrates the migration by running in
IpClientRootTest.

Bug: 160541918
Test: atest NetworkStackIntegrationTests
Change-Id: Id4e714176c923d4cbe0dc100d2d472362644a509

In S, calling an unimplemented AIDL method causes an exception when
there's no default implementation registered for the interface. The
change doesn't actually affect the network stack module because the
unimplemented methods are all oneway which doesn't trigger the exception
(because the clients cannot know if the call was successful or not).

However, that becomes a problem in the test where the binder objects are
mocked (or spy'ed) in the same process. In that case the exception
occurs because the clients (to be specific the generated proxy class)
can be notified with the unimplemented method.

Fixing the problem by registering the default implementation for the
problematic interface INetworkMonitorCallbacks.

Bug: 167632276
Test: mts/networking/gce-unittests-r-build-module-on-qt-platform
Change-Id: Ie21363062ee7066863dfd0d6a2d0d3a0d2812a0d

Mocking FileDescriptor seems to make internal methods that should never
return null return null, leading to NullPointerExceptions.

Bug: http://b/168345383
Test: atest TcpSocketTrackerTest
Change-Id: I06189ab14419f4cb7787f457e6969bd15b7c7ecd

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1351270

Change-Id: Ic631e8ecb86b04183b3635581255bf0d0d43242d

An IPv6-capable host includes this option in the Parameter Request
List option and willing to forgo obtaining an IPv4 address for a
specific assigned period(V6ONLY_WAIT). DHCP server responds with
DHCPOFFER or DHCPACK with this option if network can provide IPv6
connectivity.

Currently whether or not including IPv6-only preferred option in the
PRL is controlled by experiment flag.

Bug: 159670487
Test: atest NetworkStackTests NetworkStackIntegrationTests
Change-Id: I89653271197164a7b7f638c43cb3bf4d28817b9f

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1415991

Change-Id: Iae6f135a3ad7fe93df6b240120ac55cbc0d40d97