Test: enable capture tests by default using the Loopback interface

Avoid pinging www.wireshark.org, this removes an external dependency.
Instead send small UDP datagrams to UDP port 9 (discard) every 50ms.

Enable this for all platforms (including macOS and Linux) by default.
On Windows the tests requires Npcap and will be skipped with WinPcap.
Remove the --capture-interface option since it is no longer needed.
Copy WSDG Wireshark Tests Quick Start to README.test and add a link.

Change-Id: Id4105a6b1e95407ebf69b871c785c68f9ae26368
Reviewed-on: https://code.wireshark.org/review/31677
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

5 files changed, 62 insertions, 75 deletions

diff --git a/test/README.test b/test/README.test
index ef484348cc..535913eeb0 100644
--- a/test/README.test
+++ b/test/README.test
@@ -1,23 +1,13 @@
 Wireshark Tests
 
-The main testing script is `test.py`. It will attempt to test as much as
-possible by default, including packet capture. This means that you will
-probably either have to supply a capture interface (`--capture-interface
-<interface>`) or disable capture tests (`--disable-capture`). You must
-also build the test-programs target in order for the unittests suite to
-pass.
+The recommended steps to prepare for and to run tests:
 
-To run all tests from CMake do the following:
-- Pass `-DTEST_EXTRA_ARGS=--disable-capture` or
-  `-DTEST_EXTRA_ARGS=--capture-interface=<interface>`
-  as needed for your system.
-- Build the “test” target or run ctest, e.g. `ctest --force-new-ctest-process -j 4 --verbose`.
+* Install two Python packages, pytest: `pip install pytest pytest-xdist`
+* Build programs (“wireshark”, “tshark”, etc.): `ninja`
+* Build additional programs for the “unittests” suite: `ninja test-programs`
+* Run tests in the build directory: `pytest`
 
-To run all tests directly, run `test.py -p
-/path/to/wireshark-build/run-directory <capture args>`.
+Replace `ninja test-programs` by `make test-programs` as needed.
 
-To see a list of all options, run `test.py -h` or `test.py --help`.
-
-To see a list of all tests, run `test.py -l`.
-
-See the “Wireshark Tests” chapter of the Developer's Guide for details.
+See the “Wireshark Tests” chapter of the Developer's Guide for details:
+https://www.wireshark.org/docs/wsdg_html_chunked/ChapterTests.html
diff --git a/test/conftest.py b/test/conftest.py
index 3b70e049c3..954195fdfb 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -15,9 +15,6 @@ def pytest_addoption(parser):
     parser.addoption('--disable-capture', action='store_true',
         help='Disable capture tests'
     )
-    parser.addoption('--capture-interface',
-        help='Capture interface index or name.'
-    )
     parser.addoption('--program-path', help='Path to Wireshark executables.')
     parser.addoption('--skip-missing-programs',
         help='Skip tests that lack programs from this list instead of failing'
diff --git a/test/fixtures_ws.py b/test/fixtures_ws.py
index ed656e0c2d..5b5d9b8061 100644
--- a/test/fixtures_ws.py
+++ b/test/fixtures_ws.py
@@ -8,7 +8,6 @@
 #
 '''Fixtures that are specific to Wireshark.'''
 
-import logging
 import os
 import re
 import subprocess
@@ -24,31 +23,36 @@ import subprocesstest
 def capture_interface(request, cmd_dumpcap):
     '''
     Name of capture interface. Tests will be skipped if dumpcap is not
-    available or if the capture interface is unknown.
+    available or no Loopback interface is available.
     '''
-    iface = request.config.getoption('--capture-interface', default=None)
     disabled = request.config.getoption('--disable-capture', default=False)
     if disabled:
         fixtures.skip('Capture tests are disabled via --disable-capture')
-    if iface:
-        # If a non-empty interface is given, assume capturing is possible.
+    proc = subprocess.Popen((cmd_dumpcap, '-D'), stdout=subprocess.PIPE,
+                            stderr=subprocess.PIPE, universal_newlines=True)
+    outs, errs = proc.communicate()
+    if proc.returncode != 0:
+        print('"dumpcap -D" exited with %d. stderr:\n%s' %
+              (proc.returncode, errs))
+        fixtures.skip('Test requires capture privileges and an interface.')
+    # Matches: "lo (Loopback)" (Linux), "lo0 (Loopback)" (macOS) or
+    # "\Device\NPF_{...} (Npcap Loopback Adapter)" (Windows)
+    print('"dumpcap -D" output:\n%s' % (outs,))
+    m = re.search(r'^(\d+)\. .*\(.*Loopback.*\)', outs, re.MULTILINE)
+    if not m:
+        fixtures.skip('Test requires a capture interface.')
+    iface = m.group(1)
+    # Interface found, check for capture privileges (needed for Linux).
+    try:
+        subprocess.check_output((cmd_dumpcap, '-L', '-i', iface),
+                                stderr=subprocess.STDOUT,
+                                universal_newlines=True)
         return iface
-    else:
-        if sys.platform == 'win32':
-            patterns = '.*(Ethernet|Network Connection|VMware|Intel)'
-        else:
-            patterns = None
-        if patterns:
-            try:
-                output = subprocess.check_output((cmd_dumpcap, '-D'),
-                                                 stderr=subprocess.DEVNULL,
-                                                 universal_newlines=True)
-                m = re.search(r'^(\d+)\. %s' % patterns, output, re.MULTILINE)
-                if m:
-                    return m.group(1)
-            except subprocess.CalledProcessError:
-                pass
-    fixtures.skip('Test requires capture privileges and an interface.')
+    except subprocess.CalledProcessError as e:
+        print('"dumpcap -L -i %s" exited with %d. Output:\n%s' % (iface,
+                                                                  e.returncode,
+                                                                  e.output))
+        fixtures.skip('Test requires capture privileges.')
 
 
 @fixtures.fixture(scope='session')
@@ -152,7 +156,7 @@ def features(cmd_tshark, make_env):
         )
         tshark_v = re.sub(r'\s+', ' ', tshark_v)
     except subprocess.CalledProcessError as ex:
-        logging.warning('Failed to detect tshark features: %s', ex)
+        print('Failed to detect tshark features: %s' % (ex,))
         tshark_v = ''
     gcry_m = re.search(r'with +Gcrypt +([0-9]+\.[0-9]+)', tshark_v)
     return types.SimpleNamespace(
diff --git a/test/suite_capture.py b/test/suite_capture.py
index 6da25578d6..2522530668 100644
--- a/test/suite_capture.py
+++ b/test/suite_capture.py
@@ -13,9 +13,11 @@ import fixtures
 import glob
 import hashlib
 import os
+import socket
 import subprocess
 import subprocesstest
 import sys
+import threading
 import time
 import uuid
 
@@ -25,6 +27,23 @@ testout_pcap = 'testout.pcap'
 testout_pcapng = 'testout.pcapng'
 snapshot_len = 96
 
+class UdpTrafficGenerator(threading.Thread):
+    def __init__(self):
+        super().__init__(daemon=True)
+        self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self.stopped = False
+
+    def run(self):
+        while not self.stopped:
+            time.sleep(.05)
+            self.sock.sendto(b'Wireshark test\n', ('127.0.0.1', 9))
+
+    def stop(self):
+        if not self.stopped:
+            self.stopped = True
+            self.join()
+
+
 @fixtures.fixture
 def traffic_generator():
     '''
@@ -32,41 +51,19 @@ def traffic_generator():
     where cfilter is a capture filter to match the generated traffic.
     start_func can be invoked to start generating traffic and returns a function
     which can be used to stop traffic generation early.
-    Currently calls ping www.wireshark.org for 60 seconds.
+    Currently generates a bunch of UDP traffic to localhost.
     '''
-    # XXX replace this by something that generates UDP traffic to localhost?
-    # That would avoid external access which is forbidden by the Debian policy.
-    nprocs = 1
-    if sys.platform.startswith('win32'):
-        # XXX Check for psping? https://docs.microsoft.com/en-us/sysinternals/downloads/psping
-        args_ping = ('ping', '-n', '60', '-l', '100', 'www.wireshark.org')
-        nprocs = 3
-    elif sys.platform.startswith('linux') or sys.platform.startswith('freebsd'):
-        args_ping = ('ping', '-c', '240', '-s', '100', '-i', '0.25', 'www.wireshark.org')
-    elif sys.platform.startswith('darwin'):
-        args_ping = ('ping', '-c', '1', '-g', '1', '-G', '240', '-i', '0.25', 'www.wireshark.org')
-    else:
-        # XXX Other BSDs, Solaris, etc
-        fixtures.skip('ping utility is unavailable - cannot generate traffic')
-    procs = []
-    def kill_processes():
-        for proc in procs:
-            proc.kill()
-        for proc in procs:
-            proc.wait()
-        procs.clear()
+    threads = []
     def start_processes():
-        for i in range(nprocs):
-            if i > 0:
-                # Fake subsecond interval if the ping utility lacks support.
-                time.sleep(0.1)
-            proc = subprocess.Popen(args_ping, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT)
-            procs.append(proc)
-        return kill_processes
+        thread = UdpTrafficGenerator()
+        thread.start()
+        threads.append(thread)
+        return thread.stop
     try:
-        yield start_processes, 'icmp || icmp6'
+        yield start_processes, 'udp port 9'
     finally:
-        kill_processes()
+        for thread in threads:
+            thread.stop()
 
 
 @fixtures.fixture(scope='session')
diff --git a/test/test.py b/test/test.py
index 27d75efc63..df3e9337aa 100755
--- a/test/test.py
+++ b/test/test.py
@@ -54,7 +54,6 @@ def main():
     parser = argparse.ArgumentParser(description='Wireshark unit tests')
     cap_group = parser.add_mutually_exclusive_group()
     cap_group.add_argument('-E', '--disable-capture', action='store_true', help='Disable capture tests')
-    cap_group.add_argument('-i', '--capture-interface', help='Capture interface index or name')
     parser.add_argument('-p', '--program-path', default=os.path.curdir, help='Path to Wireshark executables.')
     parser.add_argument('--skip-missing-programs',
         help='Skip tests that lack programs from this list instead of failing'