Check IPs in a dnstap capture of resolver traffic

Add a system test that checks whether IP addresses are present in a
dnstap capture of resolver traffic if "query-source" is explicitly set.

(cherry picked from commit 1f5c2ea8e5)

bin/tests/system/conf.sh.common

@@ -733,6 +733,7 @@ export CDS
 export CHECKZONE
 export DESCRIPTION
 export DIG
+export DNSTAPREAD
 export FEATURETEST
 export FSTRM_CAPTURE
 export GENCHECK

bin/tests/system/dnstap/clean.sh

@@ -17,8 +17,7 @@ rm -f */named.run
 rm -f */named.run.prev
 rm -f */named.stats
 rm -f dig.out*
-rm -f dnstap.out dnstap.hex
-rm -f dnstap.out.save
+rm -f dnstap.*
 rm -f fstrm_capture.out
 rm -f ns*/dnstap.out
 rm -f ns*/dnstap.out.save

bin/tests/system/dnstap/tests_dnstap.py

@@ -0,0 +1,83 @@
+#!/usr/bin/python3
+
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+import os
+import re
+import subprocess
+
+import pytest
+
+pytest.importorskip("dns")
+import dns.resolver
+
+
+def run_rndc(server, rndc_command):
+    """
+    Send the specified 'rndc_command' to 'server' with a timeout of 10 seconds
+    """
+    rndc = os.getenv("RNDC")
+    port = os.getenv("CONTROLPORT")
+
+    cmdline = [rndc, "-c", "../common/rndc.conf", "-p", port, "-s", server]
+    cmdline.extend(rndc_command)
+
+    subprocess.check_output(cmdline, stderr=subprocess.STDOUT, timeout=10)
+
+
+def test_dnstap_dispatch_socket_addresses(named_port):
+    # Prepare for querying ns3.
+    resolver = dns.resolver.Resolver()
+    resolver.nameservers = ["10.53.0.3"]
+    resolver.port = named_port
+
+    # Send some query to ns3 so that it records something in its dnstap file.
+    ans = resolver.query("mail.example.", "A")
+    assert ans[0].address == "10.0.0.2"
+
+    # Before continuing, roll dnstap file to ensure it is flushed to disk.
+    run_rndc("10.53.0.3", ["dnstap", "-roll", "1"])
+
+    # Move the dnstap file aside so that it is retained for troubleshooting.
+    os.rename(os.path.join("ns3", "dnstap.out.0"), "dnstap.out.resolver_addresses")
+
+    # Read the contents of the dnstap file using dnstap-read.
+    output = subprocess.check_output(
+        [os.getenv("DNSTAPREAD"), "dnstap.out.resolver_addresses"], encoding="utf-8"
+    )
+
+    # Check whether all frames contain the expected addresses.
+    #
+    # Expected dnstap-read output format:
+    #
+    #     22-Jun-2022 12:09:06.168 RR 10.53.0.3:0 -> 10.53.0.1:7523 TCP ...
+    #     22-Jun-2022 12:09:06.168 RR 10.53.0.3:0 <- 10.53.0.1:7523 TCP ...
+    #     22-Jun-2022 12:09:06.168 RQ 10.53.0.3:56306 -> 10.53.0.2:7523 UDP ...
+    #     22-Jun-2022 12:09:06.168 RQ 10.53.0.3:56306 <- 10.53.0.2:7523 UDP ...
+    #
+    bad_frames = []
+    inspected_frames = 0
+    addr_regex = r"^10\.53\.0\.[0-9]+:[0-9]{1,5}$"
+    for line in output.splitlines():
+        _, _, frame_type, addr1, _, addr2, _ = line.split(" ", 6)
+        # Only inspect RESOLVER_QUERY and RESOLVER_RESPONSE frames.
+        if frame_type not in ("RQ", "RR"):
+            continue
+        inspected_frames += 1
+        if not re.match(addr_regex, addr1) or not re.match(addr_regex, addr2):
+            bad_frames.append(line)
+
+    assert (
+        len(bad_frames) == 0
+    ), "{} out of {} inspected frames contain unexpected addresses:\n\n{}".format(
+        len(bad_frames), inspected_frames, "\n".join(bad_frames)
+    )