Restart GR timers by offseting for already elapsed time

When session comes up and closes before GR process completion,
we need to mark any new routes learned in the new session again
as STALE, as some routes might have gotten refreshed from the peer

To keep the logic simple, we go through the close process again
from the beginning. However, elapsed time is noted to adjust when
timers are fired again later when we get back to GR_TIMER or
LLGR_TIMER state.

Change-Id: Ia9326800257f8382547a0e991f7f86cdc5caf499
Partial-Bug: #1537933

src/base/timer.cc

@@ -115,6 +115,7 @@ bool Timer::Start(int time, Handler handler, ErrorHandler error_handler) {
     }
 
     // Restart the timer
+    time_ = time;
     handler_ = handler;
     seq_no_++;
     error_handler_ = error_handler;
@@ -186,7 +187,6 @@ void Timer::StartTimerTask(TimerPtr reference, int time, uint32_t seq_no,
     // Start a task and add Task reference.
     assert(timer_task_ == NULL);
     timer_task_ = new TimerTask(reference, ec);
-    time_ = time;
     TaskScheduler::GetInstance()->Enqueue(timer_task_);
 }
 
@@ -229,3 +229,19 @@ bool TimerManager::DeleteTimer(Timer *timer) {
     return true;
 }
 
+// Get timer's already elapsed time in milliseconds.
+int Timer::GetElapsedTime() const {
+    tbb::mutex::scoped_lock lock(mutex_);
+    int64_t elapsed;
+
+#if BOOST_VERSION >= 104900
+    elapsed =
+        boost::chrono::nanoseconds(impl_->timer_.expires_from_now()).count();
+#else
+    elapsed = impl_->timer_.expires_from_now().total_nanoseconds();
+#endif
+    elapsed = time_ - elapsed/1000000; // Convert nanoseconds to milliseconds.
+    if (elapsed < 0)
+        elapsed = 0;
+    return elapsed;
+}

src/base/timer.h

@@ -110,6 +110,8 @@ class Timer {
         return delete_on_completion_;
     }
 
+    int GetElapsedTime() const;
+
     // Only for state machine test
     // XXX: Don't use in production code
     void Fire() { 
@@ -125,6 +127,7 @@ class Timer {
         return name_;
     }
 private:
+    friend class TimerImpl;
     friend class TimerManager;
     friend class TimerTest;
 

src/base/timer_impl.h

@@ -36,15 +36,11 @@ class TimerImpl {
 #endif
 
     template <typename WaitHandler>
-    void async_wait(WaitHandler handler) {
-        timer_.async_wait(handler);
-    }
-
-    void cancel(boost::system::error_code &ec) {
-        timer_.cancel(ec);
-    }
+    void async_wait(WaitHandler handler) { timer_.async_wait(handler); }
+    void cancel(boost::system::error_code &ec) { timer_.cancel(ec); }
 
 private:
+    friend class Timer;
     TimerType timer_;
 };
 

src/bgp/bgp_peer_close.cc

@@ -27,7 +27,7 @@
 // Create an instance of PeerCloseManager with back reference to parent IPeer
 PeerCloseManager::PeerCloseManager(IPeer *peer) :
         peer_(peer), stale_timer_(NULL), sweep_timer_(NULL), state_(NONE),
-        close_again_(false) {
+        close_again_(false), gr_elapsed_(0), llgr_elapsed_(0) {
     stats_.init++;
     if (peer->server()) {
         stale_timer_ = TimerManager::CreateTimer(*peer->server()->ioservice(),
@@ -119,12 +119,14 @@ void PeerCloseManager::Close() {
     case GR_TIMER:
         PEER_CLOSE_MANAGER_LOG("Nested close: Restart GR");
         close_again_ = true;
+        gr_elapsed_ += stale_timer_->GetElapsedTime();
         CloseComplete();
         break;
 
     case LLGR_TIMER:
         PEER_CLOSE_MANAGER_LOG("Nested close: Restart LLGR");
         close_again_ = true;
+        llgr_elapsed_ += stale_timer_->GetElapsedTime();
         CloseComplete();
         break;
 
@@ -257,6 +259,8 @@ bool PeerCloseManager::ProcessSweepStateActions() {
 
     // Notify clients to trigger sweep as appropriate.
     peer_->peer_close()->GracefulRestartSweep();
+    gr_elapsed_ = 0;
+    llgr_elapsed_ = 0;
     CloseComplete();
     return false;
 }
@@ -281,6 +285,8 @@ void PeerCloseManager::UnregisterPeerComplete(IPeer *ipeer, BgpTable *table) {
 
     if (state_ == DELETE) {
         peer_->peer_close()->Delete();
+        gr_elapsed_ = 0;
+        llgr_elapsed_ = 0;
         MOVE_TO_STATE(NONE);
         stats_.init++;
         close_again_ = false;
@@ -293,7 +299,13 @@ void PeerCloseManager::UnregisterPeerComplete(IPeer *ipeer, BgpTable *table) {
         peer_->peer_close()->CloseComplete();
         MOVE_TO_STATE(GR_TIMER);
         peer_->peer_close()->GetGracefulRestartFamilies(&families_);
-        StartRestartTimer(1000 * peer_->peer_close()->GetGracefulRestartTime());
+
+        // Offset restart time with elapsed time during nested closures.
+        int time = peer_->peer_close()->GetGracefulRestartTime() * 1000;
+        time -= gr_elapsed_;
+        if (time < 0)
+            time = 0;
+        StartRestartTimer(time);
         stats_.gr_timer++;
         return;
     }
@@ -306,6 +318,13 @@ void PeerCloseManager::UnregisterPeerComplete(IPeer *ipeer, BgpTable *table) {
         peer_->peer_close()->GetGracefulRestartFamilies(&families_);
         StartRestartTimer(1000 *
                 peer_->peer_close()->GetLongLivedGracefulRestartTime());
+
+        // Offset restart time with elapsed time during nested closures.
+        int time = peer_->peer_close()->GetLongLivedGracefulRestartTime() *1000;
+        time -= llgr_elapsed_;
+        if (time < 0)
+            time = 0;
+        StartRestartTimer(time);
         stats_.llgr_timer++;
         return;
     }

src/bgp/bgp_peer_close.h

@@ -95,6 +95,8 @@ class PeerCloseManager {
     Timer *sweep_timer_;
     State state_;
     bool close_again_;
+    int gr_elapsed_;
+    int llgr_elapsed_;
     IPeerClose::Families families_;
     Stats stats_;
     mutable tbb::recursive_mutex mutex_;