[mle] define constant for "Child ID Response" timeout (#8536)

This commit defines `kChildIdResponseTimeout` as a new constant
in `mle_types.hpp` which is used as maximum wait time to receive
a "Child ID Response" message from parent during attach. This
commit also removes the now unused `kMaxChildUpdateResponseTimeout`.

src/core/thread/mle.cpp

@@ -1436,7 +1436,7 @@ void Mle::HandleAttachTimer(void)
     if (HasAcceptableParentCandidate() && (SendChildIdRequest() == kErrorNone))
     {
         SetAttachState(kAttachStateChildIdRequest);
-        delay = kParentRequestReedTimeout;
+        delay = kChildIdResponseTimeout;
         ExitNow();
     }
 

src/core/thread/mle_router.cpp

@@ -1702,7 +1702,7 @@ void MleRouter::HandleParentRequest(RxInfo &aRxInfo)
     if (!child->IsStateValidOrRestoring())
     {
         child->SetLastHeard(TimerMilli::GetNow());
-        child->SetTimeout(Time::MsecToSec(kMaxChildIdRequestTimeout));
+        child->SetTimeout(Time::MsecToSec(kChildIdRequestTimeout));
     }
 
     aRxInfo.mClass = RxInfo::kPeerMessage;
@@ -1948,7 +1948,7 @@ void MleRouter::HandleTimeTick(void)
         }
         else if (router.IsStateLinkRequest())
         {
-            if (age >= kMaxLinkRequestTimeout)
+            if (age >= kLinkRequestTimeout)
             {
                 LogInfo("Link Request timeout expired");
                 RemoveNeighbor(router);

src/core/thread/mle_types.hpp

@@ -86,6 +86,7 @@ constexpr uint16_t kUdpPort = 19788; ///< MLE UDP Port
 constexpr uint32_t kParentRequestRouterTimeout     = 750;  ///< Router Parent Request timeout (in msec)
 constexpr uint32_t kParentRequestDuplicateMargin   = 50;   ///< Margin for duplicate parent request
 constexpr uint32_t kParentRequestReedTimeout       = 1250; ///< Router and REEDs Parent Request timeout (in msec)
+constexpr uint32_t kChildIdResponseTimeout         = 1250; ///< Wait time to receive Child ID Response (in msec)
 constexpr uint32_t kAttachStartJitter              = 50;   ///< Max jitter time added to start of attach (in msec)
 constexpr uint32_t kAnnounceProcessTimeout         = 250;  ///< Delay after Announce rx before channel/pan-id change
 constexpr uint32_t kAnnounceTimeout                = 1400; ///< Total timeout for sending Announce messages (in msec)
@@ -96,9 +97,8 @@ constexpr uint32_t kUnicastRetransmissionDelay     = 1000; ///< Base delay befor
 constexpr uint32_t kChildUpdateRequestPendingDelay = 100;  ///< Delay for aggregating Child Update Req (in msec)
 constexpr uint8_t  kMaxTransmissionCount           = 3;    ///< Max number of times an MLE message may be transmitted
 constexpr uint32_t kMaxResponseDelay               = 1000; ///< Max response delay for a multicast request (in msec)
-constexpr uint32_t kMaxChildIdRequestTimeout       = 5000; ///< Max delay to rx a Child ID Request (in msec)
+constexpr uint32_t kChildIdRequestTimeout          = 5000; ///< Max delay to rx a Child ID Request (in msec)
-constexpr uint32_t kMaxChildUpdateResponseTimeout  = 2000; ///< Max delay to rx a Child Update Response (in msec)
+constexpr uint32_t kLinkRequestTimeout             = 2000; ///< Max delay to rx a Link Accept
-constexpr uint32_t kMaxLinkRequestTimeout          = 2000; ///< Max delay to rx a Link Accept
 constexpr uint8_t  kMulticastLinkRequestDelay      = 5;    ///< Max delay for sending a mcast Link Request (in sec)
 
 constexpr uint32_t kMinTimeoutKeepAlive = (((kMaxChildKeepAliveAttempts + 1) * kUnicastRetransmissionDelay) / 1000);