IPv6 multicast build method added to PeerAddress (#11368)

* PeerAddress: Added methods to construct the IPv6 Multicast Address.

* PeerAddress: Code review comments applied.

src/transport/raw/PeerAddress.h

@@ -101,6 +101,8 @@ class PeerAddress
 
     bool IsInitialized() const { return mTransportType != Type::kUndefined; }
 
+    bool IsMulticast() { return Type::kUdp == mTransportType && mIPAddress.IsIPv6Multicast(); }
+
     bool operator==(const PeerAddress & other) const
     {
         return (mTransportType == other.mTransportType) && (mIPAddress == other.mIPAddress) && (mPort == other.mPort) &&
@@ -201,6 +203,22 @@ class PeerAddress
         return TCP(addr).SetPort(port).SetInterface(interface);
     }
 
+    static PeerAddress Multicast(chip::FabricId fabric, chip::GroupId group)
+    {
+        constexpr uint8_t scope        = 0x05; // Site-Local
+        constexpr uint8_t prefixLength = 0x40; // 64-bit long network prefix field
+        // The network prefix portion of the Multicast Address is the 64-bit bitstring formed by concatenating:
+        // * 0xFD to designate a locally assigned ULA prefix
+        // * The upper 56-bits of the Fabric ID for the network in big-endian order
+        const uint64_t prefix = 0xfd00000000000000 | ((fabric >> 8) & 0x00ffffffffffffff);
+        // The 32-bit group identifier portion of the Multicast Address is the 32-bits formed by:
+        // * The lower 8-bits of the Fabric ID
+        // * 0x00
+        // * The 16-bits Group Identifier in big-endian order
+        uint32_t groupId = static_cast<uint32_t>((fabric << 24) & 0xff000000) | group;
+        return UDP(Inet::IPAddress::MakeIPv6PrefixMulticast(scope, prefixLength, prefix, groupId));
+    }
+
 private:
     Inet::IPAddress mIPAddress   = {};
     Type mTransportType          = Type::kUndefined;

src/transport/raw/tests/BUILD.gn

@@ -39,7 +39,10 @@ static_library("helpers") {
 chip_test_suite("tests") {
   output_name = "libRawTransportTests"
 
-  test_sources = [ "TestMessageHeader.cpp" ]
+  test_sources = [
+    "TestMessageHeader.cpp",
+    "TestPeerAddress.cpp",
+  ]
 
   if (current_os != "mac") {
     test_sources += [ "TestTCP.cpp" ]

src/transport/raw/tests/TestPeerAddress.cpp

@@ -0,0 +1,95 @@
+/*
+ *
+ *    Copyright (c) 2020 Project CHIP Authors
+ *    Copyright (c) 2016-2017 Nest Labs, Inc.
+ *    All rights reserved.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+#ifndef __STDC_FORMAT_MACROS
+#define __STDC_FORMAT_MACROS
+#endif
+
+#ifndef __STDC_LIMIT_MACROS
+#define __STDC_LIMIT_MACROS
+#endif
+
+#include <inttypes.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <inet/IPAddress.h>
+#include <lib/core/DataModelTypes.h>
+#include <lib/core/PeerId.h>
+#include <lib/support/UnitTestRegistration.h>
+#include <transport/raw/PeerAddress.h>
+
+#include <nlunit-test.h>
+
+using namespace chip;
+
+/**
+ *  Test correct identification of IPv6 multicast addresses.
+ */
+void TestPeerAddressMulticast(nlTestSuite * inSuite, void * inContext)
+{
+    constexpr chip::FabricId fabric   = 0xa1a2a4a8b1b2b4b8;
+    constexpr chip::GroupId group     = 0xe10f;
+    chip::Transport::PeerAddress addr = chip::Transport::PeerAddress::Multicast(fabric, group);
+    NL_TEST_ASSERT(inSuite, chip::Transport::Type::kUdp == addr.GetTransportType());
+    NL_TEST_ASSERT(inSuite, addr.IsMulticast());
+
+    const Inet::IPAddress & ip = addr.GetIPAddress();
+    NL_TEST_ASSERT(inSuite, ip.IsIPv6Multicast());
+    NL_TEST_ASSERT(inSuite, chip::Inet::IPAddressType::kIPv6 == ip.Type());
+
+    constexpr uint8_t expected[NL_INET_IPV6_ADDR_LEN_IN_BYTES] = { 0xff, 0x35, 0x00, 0x40, 0xfd, 0xa1, 0xa2, 0xa4,
+                                                                   0xa8, 0xb1, 0xb2, 0xb4, 0xb8, 0x00, 0xe1, 0x0f };
+    uint8_t result[NL_INET_IPV6_ADDR_LEN_IN_BYTES];
+    uint8_t * p = result;
+    ip.WriteAddress(p);
+    NL_TEST_ASSERT(inSuite, !memcmp(expected, result, NL_INET_IPV6_ADDR_LEN_IN_BYTES));
+}
+
+/**
+ *   Test Suite. It lists all the test functions.
+ */
+
+// clang-format off
+static const nlTest sTests[] =
+{
+    NL_TEST_DEF("PeerAddress Multicast", TestPeerAddressMulticast),
+    NL_TEST_SENTINEL()
+};
+// clang-format on
+
+int TestPeerAddress(void)
+{
+    // clang-format off
+    nlTestSuite theSuite =
+	{
+        "PeerAddress",
+        &sTests[0],
+        nullptr,
+        nullptr
+    };
+    // clang-format on
+
+    // Run test suit againt one context.
+    nlTestRunner(&theSuite, nullptr);
+
+    return (nlTestRunnerStats(&theSuite));
+}
+
+CHIP_REGISTER_TEST_SUITE(TestPeerAddress)