[dnssd] implement otPlatDnssd APIs

This commit adds `DnssPlatform` module which implements OpenThread
platform APIs `otPlatDnssd` for registering and unregistering host,
service, and key items, and APIs for starting/stopping service
browsers, service resolvers, and address resolvers.

This commit also adds a new config `OTBR_DNSSD_PLAT` which enables the
new module and ensure its related OT core module are enabled (such as
advertising-proxy).

etc/cmake/options.cmake

@@ -98,6 +98,12 @@ if (OTBR_DNSSD_DISCOVERY_PROXY)
     target_compile_definitions(otbr-config INTERFACE OTBR_ENABLE_DNSSD_DISCOVERY_PROXY=1)
 endif()
 
+# When enabled the Advertising Proxy and Discovery proxy will be supported by OpenThread core
+option(OTBR_DNSSD_PLAT "Enable DNS-SD plat APIs for Advertising proxy and Discovery proxy in core" OFF)
+if (OTBR_DNSSD_PLAT)
+    target_compile_definitions(otbr-config INTERFACE OTBR_ENABLE_DNSSD_PLAT=1)
+endif()
+
 option(OTBR_UNSECURE_JOIN "Enable unsecure joining" OFF)
 if(OTBR_UNSECURE_JOIN)
     target_compile_definitions(otbr-config INTERFACE OTBR_ENABLE_UNSECURE_JOIN=1)

script/_otbr

@@ -73,6 +73,7 @@ otbr_install()
         "-DOTBR_DBUS=ON"
         "-DOTBR_DNSSD_DISCOVERY_PROXY=ON"
         "-DOTBR_SRP_ADVERTISING_PROXY=ON"
+        "-DOTBR_DNSSD_PLAT=ON"
         "-DOTBR_INFRA_IF_NAME=${INFRA_IF_NAME}"
         "-DOTBR_MDNS=${OTBR_MDNS:=mDNSResponder}"
         # Force re-evaluation of version strings

src/border_agent/border_agent.cpp

@@ -142,6 +142,9 @@ struct StateBitmap
 BorderAgent::BorderAgent(otbr::Ncp::ControllerOpenThread &aNcp)
     : mNcp(aNcp)
     , mPublisher(Mdns::Publisher::Create([this](Mdns::Publisher::State aNewState) { HandleMdnsState(aNewState); }))
+#if OTBR_ENABLE_DNSSD_PLAT
+    , mDnssdPlatform(aNcp, *mPublisher)
+#endif
 #if OTBR_ENABLE_SRP_ADVERTISING_PROXY
     , mAdvertisingProxy(aNcp, *mPublisher)
 #endif
@@ -184,6 +187,11 @@ void BorderAgent::Start(void)
     otbrError error = OTBR_ERROR_NONE;
 
     SuccessOrExit(error = mPublisher->Start());
+
+#if OTBR_ENABLE_DNSSD_PLAT
+    mDnssdPlatform.Start();
+#endif
+
 #if OTBR_ENABLE_SRP_ADVERTISING_PROXY
     mAdvertisingProxy.Start();
 #endif
@@ -199,6 +207,10 @@ void BorderAgent::Stop(void)
 {
     otbrLogInfo("Stop Thread Border Agent");
 
+#if OTBR_ENABLE_DNSSD_PLAT
+    mDnssdPlatform.Stop();
+#endif
+
 #if OTBR_ENABLE_SRP_ADVERTISING_PROXY
     mAdvertisingProxy.Stop();
 #endif
@@ -222,6 +234,10 @@ BorderAgent::~BorderAgent(void)
 
 void BorderAgent::HandleMdnsState(Mdns::Publisher::State aState)
 {
+#if OTBR_ENABLE_DNSSD_PLAT
+    mDnssdPlatform.HandleMdnsPublisherStateChange(aState);
+#endif
+
     switch (aState)
     {
     case Mdns::Publisher::State::kReady:

src/border_agent/border_agent.hpp

@@ -47,6 +47,7 @@
 #include "backbone_router/backbone_agent.hpp"
 #include "common/code_utils.hpp"
 #include "common/mainloop.hpp"
+#include "mdns/dnssd_plat.hpp"
 #include "mdns/mdns.hpp"
 #include "ncp/ncp_openthread.hpp"
 #include "sdp_proxy/advertising_proxy.hpp"
@@ -137,6 +138,10 @@ class BorderAgent : private NonCopyable
     std::map<std::string, std::vector<uint8_t>> mMeshCopTxtUpdate;
 #endif
 
+#if OTBR_ENABLE_DNSSD_PLAT
+    DnssdPlatform mDnssdPlatform;
+#endif
+// TODO: change these
 #if OTBR_ENABLE_SRP_ADVERTISING_PROXY
     AdvertisingProxy mAdvertisingProxy;
 #endif

src/mdns/CMakeLists.txt

@@ -30,6 +30,7 @@ if(OTBR_MDNS STREQUAL "avahi")
     add_library(otbr-mdns
         mdns.cpp
         mdns_avahi.cpp
+        dnssd_plat.cpp
     )
     target_compile_definitions(otbr-mdns PUBLIC
         OTBR_ENABLE_MDNS_AVAHI=1
@@ -48,6 +49,7 @@ if(OTBR_MDNS STREQUAL "mDNSResponder")
     add_library(otbr-mdns
         mdns.cpp
         mdns_mdnssd.cpp
+        dnssd_plat.cpp
     )
     target_compile_definitions(otbr-mdns PUBLIC
         OTBR_ENABLE_MDNS_MDNSSD=1