[dns-sd] DNS-SD server implementation (#6103)

This commit implements the DNS-SD server:
- Handle Standard DNS Query from clients
  - Supported resource records: PTR, SRV, TXT, AAAA
- Query services from SRP server
- Add tests
  - simulation test using DNS client (only test AAAA query)
  - OTBR test using dig command to verify all resource records can be
    queried successfully

tests/scripts/thread-cert/test_dnssd.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+#
+#  Copyright (c) 2021, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+import ipaddress
+import unittest
+
+import thread_cert
+
+SERVER = 1
+CLIENT1 = 2
+CLIENT2 = 3
+
+DOMAIN = 'default.service.arpa.'
+SERVICE = '_ipps._tcp'
+
+#
+# Topology:
+# LEADER -- CLIENT1
+#   |
+# CLIENT2
+#
+
+
+class TestDnssd(thread_cert.TestCase):
+    SUPPORT_NCP = False
+    USE_MESSAGE_FACTORY = False
+
+    TOPOLOGY = {
+        SERVER: {
+            'mode': 'rdn',
+            'panid': 0xface,
+        },
+        CLIENT1: {
+            'mode': 'rdn',
+            'panid': 0xface,
+            'router_selection_jitter': 1,
+        },
+        CLIENT2: {
+            'mode': 'rdn',
+            'panid': 0xface,
+            'router_selection_jitter': 1,
+        },
+    }
+
+    def test(self):
+        self.nodes[SERVER].start()
+        self.simulator.go(5)
+        self.assertEqual(self.nodes[SERVER].get_state(), 'leader')
+        self.nodes[SERVER].srp_server_set_enabled(True)
+
+        self.nodes[CLIENT1].start()
+        self.simulator.go(5)
+        self.assertEqual(self.nodes[CLIENT1].get_state(), 'router')
+
+        self.nodes[CLIENT2].start()
+        self.simulator.go(5)
+        self.assertEqual(self.nodes[CLIENT1].get_state(), 'router')
+
+        client1_addrs = [self.nodes[CLIENT1].get_mleid(), self.nodes[CLIENT1].get_rloc()]
+        self._config_srp_client_services(CLIENT1, 'ins1', 'host1', 11111, 1, 1, client1_addrs)
+
+        client2_addrs = [self.nodes[CLIENT2].get_mleid(), self.nodes[CLIENT2].get_rloc()]
+        self._config_srp_client_services(CLIENT2, 'ins2', 'host2', 22222, 2, 2, client2_addrs)
+
+        # Test AAAA query using DNS client
+        ip, ttl = self.nodes[CLIENT1].dns_resolve(f"host1.{DOMAIN}", self.nodes[SERVER].get_mleid(), 53)
+        self.assertIn(ipaddress.IPv6Address(ip), map(ipaddress.IPv6Address, client1_addrs))
+
+        ip, ttl = self.nodes[CLIENT1].dns_resolve(f"host2.{DOMAIN}", self.nodes[SERVER].get_mleid(), 53)
+        self.assertIn(ipaddress.IPv6Address(ip), map(ipaddress.IPv6Address, client2_addrs))
+
+        # TODO: test other query types using DNS-SD client
+
+    def _config_srp_client_services(self, client, instancename, hostname, port, priority, weight, addrs):
+        self.nodes[client].netdata_show()
+        srp_server_port = self.nodes[client].get_srp_server_port()
+
+        self.nodes[client].srp_client_start(self.nodes[SERVER].get_mleid(), srp_server_port)
+        self.nodes[client].srp_client_set_host_name(hostname)
+        self.nodes[client].srp_client_set_host_address(*addrs)
+        self.nodes[client].srp_client_add_service(instancename, SERVICE, port, priority, weight)
+
+        self.simulator.go(5)
+        self.assertEqual(self.nodes[client].srp_client_get_host_state(), 'Registered')
+
+
+if __name__ == '__main__':
+    unittest.main()