[srp-server] track lease time per service instance (#6786)

The SRP draft 09 spec suggests that the SRP Servers SHOULD also track
a lease time per service instance.

src/core/net/srp_server.cpp

@@ -333,6 +333,11 @@ void Server::CommitSrpUpdate(Error                    aError,
 
     aHost.SetLease(grantedLease);
     aHost.SetKeyLease(grantedKeyLease);
+    for (Service::Description *desc = aHost.mServiceDescriptions.GetHead(); desc != nullptr; desc = desc->GetNext())
+    {
+        desc->mLease    = grantedLease;
+        desc->mKeyLease = grantedKeyLease;
+    }
 
     existingHost = mHosts.FindMatching(aHost.GetFullName());
 
@@ -1239,7 +1244,12 @@ void Server::HandleLeaseTimer(void)
             {
                 next = service->GetNext();
 
-                if (service->mIsDeleted)
+                if (service->GetKeyExpireTime() <= now)
+                {
+                    service->Log(Service::kKeyLeaseExpired);
+                    host->RemoveService(service, /* aRetainName */ false, /* aNotifyServiceHandler */ true);
+                }
+                else if (service->mIsDeleted)
                 {
                     // The service has been deleted but the name retains.
                     earliestExpireTime = OT_MIN(earliestExpireTime, service->GetKeyExpireTime());
@@ -1262,6 +1272,7 @@ void Server::HandleLeaseTimer(void)
 
     if (earliestExpireTime != now.GetDistantFuture())
     {
+        OT_ASSERT(earliestExpireTime >= now);
         if (!mLeaseTimer.IsRunning() || earliestExpireTime <= mLeaseTimer.GetFireTime())
         {
             otLogInfoSrp("[server] lease timer is scheduled for %u seconds", Time::MsecToSec(earliestExpireTime - now));
@@ -1362,12 +1373,12 @@ TimeMilli Server::Service::GetExpireTime(void) const
     OT_ASSERT(!mIsDeleted);
     OT_ASSERT(!GetHost().IsDeleted());
 
-    return mTimeLastUpdate + Time::SecToMsec(GetHost().GetLease());
+    return mTimeLastUpdate + Time::SecToMsec(mDescription.mLease);
 }
 
 TimeMilli Server::Service::GetKeyExpireTime(void) const
 {
-    return mTimeLastUpdate + Time::SecToMsec(GetHost().GetKeyLease());
+    return mTimeLastUpdate + Time::SecToMsec(mDescription.mKeyLease);
 }
 
 bool Server::Service::MatchesFlags(Flags aFlags) const
@@ -1475,6 +1486,8 @@ Server::Service::Description::Description(Host &aHost)
     , mPort(0)
     , mTxtLength(0)
     , mTxtData(nullptr)
+    , mLease(0)
+    , mKeyLease(0)
     , mTimeLastUpdate(TimerMilli::GetNow().GetDistantPast())
 {
 }
@@ -1501,6 +1514,8 @@ void Server::Service::Description::TakeResourcesFrom(Description &aDescription)
     mWeight   = aDescription.mWeight;
     mPort     = aDescription.mPort;
 
+    mLease          = aDescription.mLease;
+    mKeyLease       = aDescription.mKeyLease;
     mTimeLastUpdate = TimerMilli::GetNow();
 }
 

src/core/net/srp_server.hpp

@@ -287,6 +287,8 @@ public:
             uint16_t     mPort;
             uint16_t     mTxtLength;
             uint8_t *    mTxtData;
+            uint32_t     mLease;    // The LEASE time in seconds.
+            uint32_t     mKeyLease; // The KEY-LEASE time in seconds.
             TimeMilli    mTimeLastUpdate;
         };
 

tests/scripts/thread-cert/node.py

@@ -1010,6 +1010,10 @@ class NodeImpl:
         self.send_command(f'srp client service remove {instance_name} {service_name}')
         self._expect_done()
 
+    def srp_client_clear_service(self, instance_name, service_name):
+        self.send_command(f'srp client service clear {instance_name} {service_name}')
+        self._expect_done()
+
     def srp_client_get_services(self):
         cmd = 'srp client service'
         self.send_command(cmd)

tests/scripts/thread-cert/test_srp_lease.py

@@ -135,6 +135,44 @@ class SrpRegisterSingleService(thread_cert.TestCase):
 
         self.check_host_and_service(server, client)
 
+        #
+        # 4. Clear the first service, shorten the lease time and register a second service.
+        #    Verify that the lease time of the first service is not affected by new SRP
+        #    registrations.
+        #
+
+        client.srp_client_clear_service('my-service', '_ipps._tcp')
+        server.srp_server_set_lease_range(50 * LEASE, 50 * LEASE, 50 * KEY_LEASE, 50 * KEY_LEASE)
+        client.srp_client_add_service('my-service2', '_ipps._tcp', 12345)
+
+        # Wait for the first service to expire.
+        self.simulator.go(LEASE + 2)
+        self.assertEqual(server.srp_server_get_service('my-service', '_ipps._tcp')['deleted'], 'true')
+
+        # Wait for the first service to be fully removed.
+        self.simulator.go(KEY_LEASE - LEASE + 2)
+        self.assertEqual(len(server.srp_server_get_services()), 1)
+        self.assertEqual(len(server.srp_server_get_hosts()), 1)
+
+        #
+        # 5. Clear the second service, lengthen the lease time and register a third service.
+        #    Verify that the lease time of the second service is not affected by new SRP
+        #    registrations.
+        #
+
+        client.srp_client_clear_service('my-service2', '_ipps._tcp')
+        server.srp_server_set_lease_range(LEASE, LEASE, KEY_LEASE, KEY_LEASE)
+        client.srp_client_add_service('my-service3', '_ipps._tcp', 12345)
+
+        # The second service has lease time of 50 * LEASE and should not expire.
+        self.simulator.go(LEASE + 2)
+        self.assertEqual(server.srp_server_get_service('my-service2', '_ipps._tcp')['deleted'], 'false')
+
+        # The second service has key-lease time of 50 * KEY_LEASE and should not expire.
+        self.simulator.go(KEY_LEASE - LEASE + 2)
+        self.assertEqual(len(server.srp_server_get_services()), 2)
+        self.assertEqual(len(server.srp_server_get_hosts()), 1)
+
     def check_host_and_service(self, server, client):
         """Check that we have properly registered host and service instance.
         """