tech/config/kernel_network_tests.jd

page.title=Kernel Networking Unit Tests
@jd:body

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    <h2>In this document</h2>
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<p>Since Android 5.0, proper operation of the Android networking stack on Linux
kernels requires a number of commits that were upstreamed relatively recently
or have not yet made it upstream. It is not easy to manually verify the
required kernel functionality or track the missing commits, so the Android team
is sharing the tests it uses to ensure the kernel behaves as expected.</p>

<h2 id=purpose>Why run the tests?</h2> <p>These tests exist for three main
reasons:</p> <ol> <li>The exact version of the Linux kernel used on a device is
typically device-specific, and it is difficult to know whether any kernel will
work properly without running the tests.</li> <li>Forward-porting and
back-porting the kernel patches to different kernel versions or different
device trees may introduce subtle issues that can be impossible to spot without
running the tests. For example, during development the initial versions of
certain devices had UID routing patches forward-ported from android-3.4 instead
of cherry-picked from android-3.10, and did not behave correctly.</li> <li>New
networking features may require new kernel functionality or kernel bug
fixes.</li> </ol> <p>If the tests do not pass, the device's network stack will
behave incorrectly, causing user-visible connectivity bugs such as falling off
Wi-Fi networks. The device will likely also fail Android Compatibility Test
Suite (CTS) tests.</p>

<h2 id=using>Using the tests</h2> <p>The tests use <a
href="http://user-mode-linux.sourceforge.net/">User-Mode Linux</a> to boot the
kernel as a process on a Linux host machine. See <a
href="https://source.android.com/source/initializing.html">Establishing a Build
Environment</a> for suitable operating system versions. The unit test framework
boots the kernel with an appropriate disk image and runs the tests from the
host file system. The tests are written in Python 2.x and use TAP interfaces to
exercise kernel behaviour and the socket API.</p>

<h3 id=compiling>Compiling the kernel for ARCH=um</h3> <p>For the tests to run,
the kernel must compile for <code>ARCH=um SUBARCH=x86_64</code>. This is a
supported architecture upstream and in the common Android kernel trees (e.g.,
<code>android-3.10</code>, <code>android-3.18</code>). But sometimes device
kernels do not compile in this mode because device trees contain
device-specific or hardware-specific code in common files (e.g.,
<code>sys/exit.c</code>).</p> <p>In many cases, it's sufficient to ensure that
hardware-specific code is behind an <code>#ifdef</code>. Typically this should
be an <code>#ifdef</code> on a configuration option that controls the specific
feature relevant to the code. If there is no such configuration option, put
hardware-specific code inside <code>#ifndef CONFIG_UML</code> blocks.</p> <p>In
general, fixing this should be the responsibility of the kernel tree provider
(e.g., chipset or SoC vendor). We're working with OEMs and vendors to ensure
that current and future kernels will compile for <code>ARCH=um
SUBARCH=x86_64</code> without requiring any changes.</p>

<h3 id=running>Running the tests</h3> <p>The tests are at <a
href="https://android.googlesource.com/kernel/tests/+/master/net/test"><code>kernel/tests/net/test</code></a>.
It is recommended that the tests <b>be run from AOSP master</b> because they
are the most up-to-date; in some cases, kernel features that are necessary for
proper operation in a given Android release do not yet have full test coverage
in the given release. For information on how to run the tests, see the <a
href="https://android.googlesource.com/kernel/tests/+/master/net/test/README">kernel
network test README file</a>. Basically, from the top of your kernel tree, run:</p>

<pre>  &lt;android tree&gt;/kernel/tests/net/test/run_net_test.sh all_tests.sh</pre>

<h3 id=passing>Passing the tests</h3> <p>The kernel network test Python
source files contain comments that specify kernel commits that are known to be
required to pass the tests. The tests should pass in the common kernel trees -
at least the <code>android-3.10</code> and <code>android-3.18</code> branches
in the <a
href="https://android-review.googlesource.com/#/q/project:kernel/common"><code>kernel/common</code></a>
project in AOSP. Therefore, passing the tests on a kernel tree that's derived
from 3.10 or 3.18 should mostly be a matter of cherry-picking the patches from
these trees.</p>

<h2 id=contributing>Contributing</h2>

<h3 id=reporting>Reporting issues</h3> <p>Please report any issues with
the kernel network tests in the <a
href="https://code.google.com/p/android/issues/entry?template=Developer%20bug%20report">Android
issue tracker</a> with the <a
href="https://code.google.com/p/android/issues/list?q=label%3AComponent-Networking">Component-Networking</a>
label.</p>

<h3 id=documenting>Documenting commits and adding tests</h3> <p>Please report
issues as described above, and if possible upload a change to fix the issue,
if:</p> <ul> <li>The tests do not pass on the common kernel trees</li> <li>You
find a necessary commit that is not mentioned in the source comments,</li>
<li>Getting the tests to pass on upstream kernels requires major changes</li>
<li>You believe that the tests are overspecified, or the test fail on future
kernels</li> <li>You'd like to add more tests or more coverage to existing
tests.</li>
</ul>