[posix] implement address monitoring in MdnsSocket (#11641)

This commit introduces an initial implementation in `Posix::MdnsSocket`
to monitor and report all IPv4 and IPv6 addresses assigned to the
infrastructure network interface. This mechanism is used by OpenThread's
native mDNS module and was added in PRs #11353 and #11394.

A new configuration, `OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR`, is
added to select the monitoring strategy. This commit implements the
`OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC` approach, where `getifaddrs()`
is used to enumerate addresses periodically. The polling interval
is configured by `OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_PERIOD`.

Note that the OpenThread mDNS module itself tracks the list of
reported addresses and will only take action when there is a change
from what was previously announced. This allows the platform to
simply report the full list of current addresses at each interval.

src/posix/platform/mdns_socket.cpp

@@ -32,6 +32,7 @@
 
 #include <arpa/inet.h>
 #include <errno.h>
+#include <ifaddrs.h>
 #include <net/if.h>
 #include <netinet/in.h>
 #include <stdio.h>
@@ -41,6 +42,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <openthread/platform/time.h>
+
 #include "ip6_utils.hpp"
 #include "platform-posix.h"
 #include "common/code_utils.hpp"
@@ -149,6 +152,10 @@ void MdnsSocket::Update(otSysMainloopContext &aContext)
         aContext.mMaxFd = mFd4;
     }
 
+#if (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+    UpdateTimeout(aContext.mTimeout);
+#endif
+
 exit:
     return;
 }
@@ -177,6 +184,10 @@ void MdnsSocket::Process(const otSysMainloopContext &aContext)
         ReceiveMessage(kIp4Msg);
     }
 
+#if (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+    ProcessTimeout();
+#endif
+
 exit:
     return;
 }
@@ -214,6 +225,8 @@ otError MdnsSocket::Enable(uint32_t aInfraIfIndex)
     mEnabled      = true;
     mInfraIfIndex = aInfraIfIndex;
 
+    StartAddressMonitoring();
+
     LogInfo("Enabled");
 
 exit:
@@ -237,6 +250,8 @@ void MdnsSocket::Disable(uint32_t aInfraIfIndex)
 
     mEnabled = false;
 
+    StopAddressMonitoring();
+
     LogInfo("Disabled");
 }
 
@@ -490,6 +505,89 @@ exit:
     }
 }
 
+//---------------------------------------------------------------------------------------------------------------------
+// Monitoring address on infra netif
+
+#if (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+
+void MdnsSocket::ReportInfraIfAddresses(void)
+{
+    struct ifaddrs *ifAddrs = nullptr;
+
+    mNextReportTime = otPlatTimeGet() + kAddrMonitorPeriod * OT_US_PER_MS;
+
+    if (getifaddrs(&ifAddrs) < 0)
+    {
+        LogWarn("Failed to get netif addresses: %s", strerror(errno));
+        ExitNow();
+    }
+
+    otPlatMdnsHandleHostAddressRemoveAll(mInstance, mInfraIfIndex);
+
+    for (struct ifaddrs *addr = ifAddrs; addr != nullptr; addr = addr->ifa_next)
+    {
+        otIp6Address ip6Addr;
+        otIp4Address ip4Addr;
+
+        if ((addr->ifa_addr == nullptr) || (if_nametoindex(addr->ifa_name) != mInfraIfIndex))
+        {
+            continue;
+        }
+
+        if (addr->ifa_addr->sa_family == AF_INET6)
+        {
+            ReadIp6AddressFrom(&reinterpret_cast<sockaddr_in6 *>(addr->ifa_addr)->sin6_addr, ip6Addr);
+        }
+        else if (addr->ifa_addr->sa_family == AF_INET)
+        {
+            memcpy(&ip4Addr, &reinterpret_cast<sockaddr_in *>(addr->ifa_addr)->sin_addr.s_addr, sizeof(otIp4Address));
+            otIp4ToIp4MappedIp6Address(&ip4Addr, &ip6Addr);
+        }
+        else
+        {
+            continue;
+        }
+
+        otPlatMdnsHandleHostAddressEvent(mInstance, &ip6Addr, /* aAdded */ true, mInfraIfIndex);
+    }
+
+exit:
+    if (ifAddrs != nullptr)
+    {
+        freeifaddrs(ifAddrs);
+    }
+}
+
+void MdnsSocket::UpdateTimeout(struct timeval &aTimeout)
+{
+    uint64_t now       = otPlatTimeGet();
+    uint64_t remaining = 1;
+    uint64_t timeout;
+
+    if (mNextReportTime > now)
+    {
+        remaining = mNextReportTime - now;
+    }
+
+    timeout = static_cast<uint64_t>(aTimeout.tv_sec) * OT_US_PER_S + static_cast<uint64_t>(aTimeout.tv_usec);
+
+    if (remaining < timeout)
+    {
+        aTimeout.tv_sec  = static_cast<time_t>(remaining / OT_US_PER_S);
+        aTimeout.tv_usec = static_cast<suseconds_t>(remaining % OT_US_PER_S);
+    }
+}
+
+void MdnsSocket::ProcessTimeout(void)
+{
+    if (mNextReportTime <= otPlatTimeGet())
+    {
+        ReportInfraIfAddresses();
+    }
+}
+
+#endif // (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+
 //---------------------------------------------------------------------------------------------------------------------
 // Socket helpers
 

src/posix/platform/mdns_socket.hpp

@@ -43,6 +43,15 @@
 namespace ot {
 namespace Posix {
 
+#define OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC 1
+#define OT_POSIX_MDNS_ADDR_MONITOR_NETLINK 2
+
+#if (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_NETLINK)
+#error "The `OT_POSIX_MDNS_ADDR_MONITOR_NETLINK` is not supported yet"
+#elif (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR != OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+#error "The `OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR` is not valid. MUST be one of `OT_POSIX_MDNS_ADDR_MONITOR_*`"
+#endif
+
 /**
  * Implements platform mDNS socket APIs.
  */
@@ -106,8 +115,9 @@ public:
     void    SendUnicast(otMessage *aMessage, const otPlatMdnsAddressInfo *aAddress);
 
 private:
-    static constexpr uint16_t kMaxMessageLength = 2000;
+    static constexpr uint16_t kMaxMessageLength  = 2000;
-    static constexpr uint16_t kMdnsPort         = 5353;
+    static constexpr uint16_t kMdnsPort          = 5353;
+    static constexpr uint64_t kAddrMonitorPeriod = OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_PERIOD;
 
     enum MsgType : uint8_t
     {
@@ -131,6 +141,14 @@ private:
     void    SendQueuedMessages(MsgType aMsgType);
     void    ReceiveMessage(MsgType aMsgType);
 
+#if (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+    void StartAddressMonitoring(void) { ReportInfraIfAddresses(); }
+    void StopAddressMonitoring(void) {}
+    void ReportInfraIfAddresses(void);
+    void UpdateTimeout(struct timeval &aTimeout);
+    void ProcessTimeout(void);
+#endif
+
     otError OpenIp4Socket(uint32_t aInfraIfIndex);
     otError JoinOrLeaveIp4MulticastGroup(bool aJoin, uint32_t aInfraIfIndex);
     void    CloseIp4Socket(void);
@@ -163,6 +181,9 @@ private:
     otIp6Address   mMulticastIp6Address;
     otIp4Address   mMulticastIp4Address;
     otInstance    *mInstance;
+#if (OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR == OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC)
+    uint64_t mNextReportTime;
+#endif
 };
 
 } // namespace Posix

src/posix/platform/openthread-posix-config.h

@@ -454,6 +454,32 @@
 #define OPENTHREAD_POSIX_CONFIG_RESOLV_CONF_ENABLED_INIT (!OPENTHREAD_POSIX_CONFIG_ANDROID_ENABLE)
 #endif
 
+/**
+ * @def OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR
+ *
+ * Specifies the behavior of `MdnsSocket` and how it implements monitoring and reporting of infra-interface IPv4 and
+ * IPv6 addresses.
+ *
+ * The valid values for this config, `OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_*`, are defined in
+ *  `posix/platform/mdns_socket.h`.
+ */
+#ifndef OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR
+#define OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR OT_POSIX_MDNS_ADDR_MONITOR_PERIODIC
+#endif
+
+/**
+ * @def OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_PERIOD
+ *
+ * Specifies the duration in milliseconds (ms) for the periodic check used by the `MdnsSocket` implementation to
+ * monitor and report the infra-interface IPv4 and IPv6 addresses.
+ *
+ * This is applicable only when `OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR` is set to
+ * `OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_PERIODIC`.
+ */
+#ifndef OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_PERIOD
+#define OPENTHREAD_POSIX_CONFIG_MDNS_ADDR_MONITOR_PERIOD (5000)
+#endif
+
 //---------------------------------------------------------------------------------------------------------------------
 // Removed or renamed POSIX specific configs.