[srp-server] introduce LeaseTracker base class for Host and Service (#12628)

This commit extracts the common lease tracking variables (`mLease`,
`mKeyLease`, `mTtl`, and `mUpdateTime`) and their associated methods
from the `Srp::Server::Host` and `Srp::Server::Service` classes into a
new shared base class, `LeaseTracker`.

By having both `Host` and `Service` inherit from `LeaseTracker`, we
eliminate duplicated logic for calculating expiration times, handling
lease info, and processing TTL updates. This refactoring simplifies
the SRP server codebase and ensures consistent lease management
behavior across both entities.

src/core/net/srp_advertising_proxy.cpp

@@ -259,7 +259,7 @@ void AdvertisingProxy::AdvertiseRemovalOf(Host &aHost)
             {
                 service->mShouldAdvertise = true;
 
-                if (aHost.mKeyLease == 0)
+                if (aHost.GetKeyLease() == 0)
                 {
                     advService.mIsKeyRegistered = false;
                 }
@@ -270,7 +270,7 @@ void AdvertisingProxy::AdvertiseRemovalOf(Host &aHost)
             advService.mIsReplaced = true;
         }
 
-        if (aHost.mKeyLease == 0)
+        if (aHost.GetKeyLease() == 0)
         {
             advHost.mIsKeyRegistered = false;
         }
@@ -291,7 +291,7 @@ void AdvertisingProxy::AdvertiseRemovalOf(Host &aHost)
             UnregisterService(service);
         }
 
-        if (aHost.mKeyLease == 0)
+        if (aHost.GetKeyLease() == 0)
         {
             UnregisterKey(service);
         }
@@ -302,7 +302,7 @@ void AdvertisingProxy::AdvertiseRemovalOf(Host &aHost)
         UnregisterHost(aHost);
     }
 
-    if (aHost.mKeyLease == 0)
+    if (aHost.GetKeyLease() == 0)
     {
         UnregisterKey(aHost);
     }
@@ -352,7 +352,7 @@ void AdvertisingProxy::AdvertiseRemovalOf(Service &aService)
         UnregisterService(aService);
     }
 
-    if (aService.mKeyLease == 0)
+    if (aService.GetKeyLease() == 0)
     {
         UnregisterKey(aService);
     }
@@ -473,7 +473,7 @@ exit:
 void AdvertisingProxy::Advertise(Host &aHost)
 {
     bool shouldUnregisterHostAndServices = aHost.IsDeleted();
-    bool shouldUnregisterKeys            = (aHost.mKeyLease == 0);
+    bool shouldUnregisterKeys            = (aHost.GetKeyLease() == 0);
 
     DecideToAdvertise(aHost, shouldUnregisterHostAndServices, shouldUnregisterKeys);
 
@@ -817,7 +817,7 @@ bool AdvertisingProxy::CompareAndUpdateHost(Host &aHost, Host &aExistingHost)
         // we need to unregister keys for any services on
         // existing host that are not present in `aHost`.
 
-        if (aHost.mKeyLease == 0)
+        if (aHost.GetKeyLease() == 0)
         {
             for (Service &existingService : aExistingHost.mServices)
             {

src/core/net/srp_server.cpp

@@ -454,7 +454,7 @@ void Server::RemoveHost(Host *aHost, RetainName aRetainName)
 {
     VerifyOrExit(aHost != nullptr);
 
-    aHost->mLease = 0;
+    aHost->SetLease(0);
     aHost->ClearResources();
 
     if (aRetainName)
@@ -463,7 +463,7 @@ void Server::RemoveHost(Host *aHost, RetainName aRetainName)
     }
     else
     {
-        aHost->mKeyLease = 0;
+        aHost->SetKeyLease(0);
         IgnoreError(mHosts.Remove(*aHost));
         LogInfo("Fully remove host %s", aHost->GetFullName());
     }
@@ -642,9 +642,10 @@ void Server::CommitSrpUpdate(Error                    aError,
 
     for (Service &service : aHost.mServices)
     {
-        service.mLease       = grantedLease;
+        service.SetLease(service.mIsDeleted ? 0 : grantedLease);
-        service.mKeyLease    = grantedKeyLease;
+        service.SetKeyLease(grantedKeyLease);
-        service.mTtl         = grantedTtl;
+        service.SetTtl(grantedTtl);
+
         service.mIsCommitted = true;
 
 #if OT_SHOULD_LOG_AT(OT_LOG_LEVEL_INFO)
@@ -1311,7 +1312,7 @@ Error Server::ProcessServiceDescriptionInstructions(Host            &aHost,
             VerifyOrExit(!service->mParsedSrv, error = kErrorParse);
             service->mParsedSrv = true;
 
-            service->mTtl      = srvRecord.GetTtl();
+            service->SetTtl(srvRecord.GetTtl());
             service->mPriority = srvRecord.GetPriority();
             service->mWeight   = srvRecord.GetWeight();
             service->mPort     = srvRecord.GetPort();
@@ -1395,8 +1396,8 @@ Error Server::ProcessAdditionalSection(Host *aHost, const Message &aMessage, Mes
             service.mIsDeleted = true;
         }
 
-        service.mLease    = service.mIsDeleted ? 0 : leaseOption.GetLeaseInterval();
+        service.SetLease(service.mIsDeleted ? 0 : leaseOption.GetLeaseInterval());
-        service.mKeyLease = leaseOption.GetKeyLeaseInterval();
+        service.SetKeyLease(leaseOption.GetKeyLeaseInterval());
     }
 
     // If the client included the short variant of Lease Option,
@@ -1525,7 +1526,7 @@ void Server::HandleUpdate(Host &aHost, const MessageMetadata &aMetadata)
 
         SuccessOrExit(error = service->mServiceName.Set(existingService.GetServiceName()));
         service->mIsDeleted = true;
-        service->mKeyLease  = existingService.mKeyLease;
+        service->SetKeyLease(existingService.GetKeyLease());
     }
 
 exit:
@@ -1940,6 +1941,51 @@ exit:
 }
 #endif
 
+//---------------------------------------------------------------------------------------------------------------------
+// Server::LeaseTracker
+
+void Server::LeaseTracker::Init(TimeMilli aUpdateTime)
+{
+    mLease      = 0;
+    mKeyLease   = 0;
+    mTtl        = 0;
+    mUpdateTime = aUpdateTime;
+}
+
+TimeMilli Server::LeaseTracker::GetExpireTime(void) const { return mUpdateTime + Time::SecToMsec(mLease); }
+
+TimeMilli Server::LeaseTracker::GetKeyExpireTime(void) const { return mUpdateTime + Time::SecToMsec(mKeyLease); }
+
+void Server::LeaseTracker::GetLeaseInfo(LeaseInfo &aLeaseInfo) const
+{
+    TimeMilli now = TimerMilli::GetNow();
+
+    aLeaseInfo.mLease             = Time::SecToMsec(mLease);
+    aLeaseInfo.mKeyLease          = Time::SecToMsec(mKeyLease);
+    aLeaseInfo.mRemainingLease    = (mLease != 0) ? GetExpireTime().DetermineRemainingDurationFrom(now) : 0;
+    aLeaseInfo.mRemainingKeyLease = GetKeyExpireTime().DetermineRemainingDurationFrom(now);
+}
+
+Error Server::LeaseTracker::ProcessTtl(uint32_t aTtl)
+{
+    // This method processes the TTL value received in a resource record.
+    //
+    // If no TTL value is stored, this method will set the stored value to @p aTtl and return `kErrorNone`.
+    // If a TTL value is stored and @p aTtl equals the stored value, this method returns `kErrorNone`.
+    // Otherwise, this method returns `kErrorRejected`.
+
+    Error error = kErrorRejected;
+
+    VerifyOrExit(aTtl && (mTtl == 0 || mTtl == aTtl));
+
+    mTtl = aTtl;
+
+    error = kErrorNone;
+
+exit:
+    return error;
+}
+
 //---------------------------------------------------------------------------------------------------------------------
 // Server::Service
 
@@ -1947,15 +1993,13 @@ Error Server::Service::Init(const char *aInstanceName, const char *aInstanceLabe
 {
     Error error;
 
+    LeaseTracker::Init(aUpdateTime);
+
     mNext        = nullptr;
     mHost        = &aHost;
     mPriority    = 0;
     mWeight      = 0;
-    mTtl         = 0;
     mPort        = 0;
-    mLease       = 0;
-    mKeyLease    = 0;
-    mUpdateTime  = aUpdateTime;
     mIsDeleted   = false;
     mIsCommitted = false;
 #if OPENTHREAD_CONFIG_SRP_SERVER_ADVERTISING_PROXY_ENABLE
@@ -2014,34 +2058,6 @@ exit:
     return error;
 }
 
-TimeMilli Server::Service::GetExpireTime(void) const
-{
-    OT_ASSERT(!mIsDeleted);
-    OT_ASSERT(!GetHost().IsDeleted());
-
-    return mUpdateTime + Time::SecToMsec(mLease);
-}
-
-TimeMilli Server::Service::GetKeyExpireTime(void) const { return mUpdateTime + Time::SecToMsec(mKeyLease); }
-
-void Server::Service::GetLeaseInfo(LeaseInfo &aLeaseInfo) const
-{
-    TimeMilli now = TimerMilli::GetNow();
-
-    aLeaseInfo.mLease             = Time::SecToMsec(GetLease());
-    aLeaseInfo.mKeyLease          = Time::SecToMsec(GetKeyLease());
-    aLeaseInfo.mRemainingKeyLease = GetKeyExpireTime().DetermineRemainingDurationFrom(now);
-
-    if (!mIsDeleted)
-    {
-        aLeaseInfo.mRemainingLease = GetExpireTime().DetermineRemainingDurationFrom(now);
-    }
-    else
-    {
-        aLeaseInfo.mRemainingLease = 0;
-    }
-}
-
 bool Server::Service::MatchesInstanceName(const char *aInstanceName) const { return Matches(aInstanceName); }
 
 bool Server::Service::MatchesServiceName(const char *aServiceName) const
@@ -2129,10 +2145,6 @@ exit:
 Server::Host::Host(Instance &aInstance, TimeMilli aUpdateTime)
     : InstanceLocator(aInstance)
     , mNext(nullptr)
-    , mTtl(0)
-    , mLease(0)
-    , mKeyLease(0)
-    , mUpdateTime(aUpdateTime)
     , mParsedKey(false)
     , mUseShortLeaseOption(false)
 #if OPENTHREAD_CONFIG_SRP_SERVER_ADVERTISING_PROXY_ENABLE
@@ -2145,6 +2157,7 @@ Server::Host::Host(Instance &aInstance, TimeMilli aUpdateTime)
     , mKeyAdvId(kInvalidRequestId)
 #endif
 {
+    LeaseTracker::Init(aUpdateTime);
 }
 
 Server::Host::~Host(void) { FreeAllServices(); }
@@ -2174,53 +2187,6 @@ bool Server::Host::Matches(const char *aFullName) const
     return StringMatch(mFullName.AsCString(), aFullName, kStringCaseInsensitiveMatch);
 }
 
-TimeMilli Server::Host::GetExpireTime(void) const
-{
-    OT_ASSERT(!IsDeleted());
-
-    return mUpdateTime + Time::SecToMsec(mLease);
-}
-
-TimeMilli Server::Host::GetKeyExpireTime(void) const { return mUpdateTime + Time::SecToMsec(mKeyLease); }
-
-void Server::Host::GetLeaseInfo(LeaseInfo &aLeaseInfo) const
-{
-    TimeMilli now = TimerMilli::GetNow();
-
-    aLeaseInfo.mLease             = Time::SecToMsec(GetLease());
-    aLeaseInfo.mKeyLease          = Time::SecToMsec(GetKeyLease());
-    aLeaseInfo.mRemainingKeyLease = GetKeyExpireTime().DetermineRemainingDurationFrom(now);
-
-    if (!IsDeleted())
-    {
-        aLeaseInfo.mRemainingLease = GetExpireTime().DetermineRemainingDurationFrom(now);
-    }
-    else
-    {
-        aLeaseInfo.mRemainingLease = 0;
-    }
-}
-
-Error Server::Host::ProcessTtl(uint32_t aTtl)
-{
-    // This method processes the TTL value received in a resource record.
-    //
-    // If no TTL value is stored, this method will set the stored value to @p aTtl and return `kErrorNone`.
-    // If a TTL value is stored and @p aTtl equals the stored value, this method returns `kErrorNone`.
-    // Otherwise, this method returns `kErrorRejected`.
-
-    Error error = kErrorRejected;
-
-    VerifyOrExit(aTtl && (mTtl == 0 || mTtl == aTtl));
-
-    mTtl = aTtl;
-
-    error = kErrorNone;
-
-exit:
-    return error;
-}
-
 const Server::Service *Server::Host::GetNextService(const Service *aPrevService) const
 {
     return (aPrevService == nullptr) ? mServices.GetHead() : aPrevService->GetNext();
@@ -2252,11 +2218,11 @@ void Server::Host::RemoveService(Service *aService, RetainName aRetainName, Noti
     VerifyOrExit(aService != nullptr);
 
     aService->mIsDeleted = true;
-    aService->mLease     = 0;
+    aService->SetLease(0);
 
     if (!aRetainName)
     {
-        aService->mKeyLease = 0;
+        aService->SetKeyLease(0);
     }
 
     aService->Log(aRetainName ? Service::kRemoveButRetainName : Service::kFullyRemove);

src/core/net/srp_server.hpp

@@ -177,10 +177,75 @@ public:
         kStateStopped  = OT_SRP_SERVER_STATE_STOPPED,  ///< Server is enabled but stopped.
     };
 
+    /**
+     * Base class for `Host` and `Service`, tracking lease, key-lease, and expiration times.
+     */
+    class LeaseTracker
+    {
+    public:
+        /**
+         * Returns the LEASE time.
+         *
+         * @returns  The LEASE time in seconds.
+         */
+        uint32_t GetLease(void) const { return mLease; }
+
+        /**
+         * Returns the KEY-LEASE time.
+         *
+         * @returns  The KEY-LEASE time in seconds.
+         */
+        uint32_t GetKeyLease(void) const { return mKeyLease; }
+
+        /**
+         * Returns the TTL.
+         *
+         * @returns The TTL.
+         */
+        uint32_t GetTtl(void) const { return mTtl; }
+
+        /**
+         * Returns the expire time.
+         *
+         * @returns  The expire time
+         */
+        TimeMilli GetExpireTime(void) const;
+
+        /**
+         * Returns the key expire time.
+         *
+         * @returns  The service key expire time.
+         */
+        TimeMilli GetKeyExpireTime(void) const;
+
+        /**
+         * Gets the LEASE and KEY-LEASE information.
+         *
+         * @param[out]  aLeaseInfo  A reference to a LeaseInfo instance to populate
+         */
+        void GetLeaseInfo(LeaseInfo &aLeaseInfo) const;
+
+    protected:
+        LeaseTracker(void) = default;
+
+        void  Init(TimeMilli aUpdateTime);
+        void  SetTtl(uint32_t aTtl) { mTtl = aTtl; }
+        void  SetLease(uint32_t aLease) { mLease = aLease; }
+        void  SetKeyLease(uint32_t aKeyLease) { mKeyLease = aKeyLease; }
+        Error ProcessTtl(uint32_t aTtl);
+
+    private:
+        uint32_t  mLease;
+        uint32_t  mKeyLease;
+        uint32_t  mTtl;
+        TimeMilli mUpdateTime;
+    };
+
     /**
      * Implements a server-side SRP service.
      */
     class Service : public otSrpServerService,
+                    public LeaseTracker,
                     public LinkedListEntry<Service>,
                     private Heap::Allocatable<Service>,
                     private NonCopyable
@@ -268,13 +333,6 @@ public:
          */
         static Error ParseSubTypeServiceName(const char *aSubTypeServiceName, char *aLabel, uint8_t aLabelSize);
 
-        /**
-         * Returns the TTL of the service instance.
-         *
-         * @returns The TTL of the service instance.
-         */
-        uint32_t GetTtl(void) const { return mTtl; }
-
         /**
          * Returns the port of the service instance.
          *
@@ -317,42 +375,6 @@ public:
          */
         const Host &GetHost(void) const { return *mHost; }
 
-        /**
-         * Returns the LEASE time of the service.
-         *
-         * @returns  The LEASE time in seconds.
-         */
-        uint32_t GetLease(void) const { return mLease; }
-
-        /**
-         * Returns the KEY-LEASE time of the key of the service.
-         *
-         * @returns  The KEY-LEASE time in seconds.
-         */
-        uint32_t GetKeyLease(void) const { return mKeyLease; }
-
-        /**
-         * Returns the expire time (in milliseconds) of the service.
-         *
-         * @returns  The service expire time in milliseconds.
-         */
-        TimeMilli GetExpireTime(void) const;
-
-        /**
-         * Returns the key expire time (in milliseconds) of the service.
-         *
-         * @returns  The service key expire time in milliseconds.
-         */
-        TimeMilli GetKeyExpireTime(void) const;
-
-        /**
-         * Gets the LEASE and KEY-LEASE information of a given service.
-         *
-         * @param[out]  aLeaseInfo  A reference to a LeaseInfo instance. It contains the LEASE time, KEY-LEASE time,
-         *                          remaining LEASE time and the remaining KEY-LEASE time.
-         */
-        void GetLeaseInfo(LeaseInfo &aLeaseInfo) const;
-
         /**
          * Indicates whether this service matches a given service instance name.
          *
@@ -406,10 +428,6 @@ public:
         uint16_t                  mPriority;
         uint16_t                  mWeight;
         uint16_t                  mPort;
-        uint32_t                  mTtl;      // In seconds
-        uint32_t                  mLease;    // In seconds
-        uint32_t                  mKeyLease; // In seconds
-        TimeMilli                 mUpdateTime;
         bool                      mIsDeleted : 1;
         bool                      mIsCommitted : 1;
         bool                      mParsedDeleteAllRrset : 1;
@@ -431,6 +449,7 @@ public:
      */
     class Host : public otSrpServerHost,
                  public InstanceLocator,
+                 public LeaseTracker,
                  public LinkedListEntry<Host>,
                  private Heap::Allocatable<Host>,
                  private NonCopyable
@@ -451,7 +470,7 @@ public:
          *
          * @returns  TRUE if the host is deleted, FALSE if the host is not deleted.
          */
-        bool IsDeleted(void) const { return (mLease == 0); }
+        bool IsDeleted(void) const { return (GetLease() == 0); }
 
         /**
          * Returns the full name of the host.
@@ -474,35 +493,6 @@ public:
             return mAddresses.AsCArray();
         }
 
-        /**
-         * Returns the TTL of the host.
-         *
-         * @returns The TTL of the host.
-         */
-        uint32_t GetTtl(void) const { return mTtl; }
-
-        /**
-         * Returns the LEASE time of the host.
-         *
-         * @returns  The LEASE time in seconds.
-         */
-        uint32_t GetLease(void) const { return mLease; }
-
-        /**
-         * Returns the KEY-LEASE time of the key of the host.
-         *
-         * @returns  The KEY-LEASE time in seconds.
-         */
-        uint32_t GetKeyLease(void) const { return mKeyLease; }
-
-        /**
-         * Gets the LEASE and KEY-LEASE information of a given host.
-         *
-         * @param[out]  aLeaseInfo  A reference to a LeaseInfo instance. It contains the LEASE time, KEY-LEASE time,
-         *                          remaining LEASE time and the remaining KEY-LEASE time.
-         */
-        void GetLeaseInfo(LeaseInfo &aLeaseInfo) const;
-
         /**
          * Returns the key associated with this host.
          *
@@ -510,20 +500,6 @@ public:
          */
         const Key &GetKey(void) const { return mKey; }
 
-        /**
-         * Returns the expire time (in milliseconds) of the host.
-         *
-         * @returns  The expire time in milliseconds.
-         */
-        TimeMilli GetExpireTime(void) const;
-
-        /**
-         * Returns the expire time (in milliseconds) of the key of the host.
-         *
-         * @returns  The expire time of the key in milliseconds.
-         */
-        TimeMilli GetKeyExpireTime(void) const;
-
         /**
          * Returns the `Service` linked list associated with the host.
          *
@@ -554,12 +530,8 @@ public:
         ~Host(void);
 
         Error SetFullName(const char *aFullName);
-        void  SetTtl(uint32_t aTtl) { mTtl = aTtl; }
-        void  SetLease(uint32_t aLease) { mLease = aLease; }
-        void  SetKeyLease(uint32_t aKeyLease) { mKeyLease = aKeyLease; }
         void  SetUseShortLeaseOption(bool aUse) { mUseShortLeaseOption = aUse; }
         bool  ShouldUseShortLeaseOption(void) const { return mUseShortLeaseOption; }
-        Error ProcessTtl(uint32_t aTtl);
 
         Service       *AddNewService(const char *aInstanceName, const char *aInstanceLabel, TimeMilli aUpdateTime);
         void           AddService(Service &aService);
@@ -575,10 +547,6 @@ public:
         Heap::String              mFullName;
         Heap::Array<Ip6::Address> mAddresses;
         Key                       mKey;
-        uint32_t                  mTtl;      // The TTL in seconds.
-        uint32_t                  mLease;    // The LEASE time in seconds.
-        uint32_t                  mKeyLease; // The KEY-LEASE time in seconds.
-        TimeMilli                 mUpdateTime;
         LinkedList<Service>       mServices;
         bool                      mParsedKey : 1;
         bool                      mUseShortLeaseOption : 1; // Use short lease option (lease only 4 bytes).