[addrman] Ensure collisions eventually get resolved

After 40 minutes, time out a test-before-evict entry and just evict without
testing. Otherwise, if we were unable to test an entry for some reason, we
might break using feelers altogether.

src/addrman.cpp

@@ -569,6 +569,13 @@ void CAddrMan::ResolveCollisions_()
                         Good_(info_new, false, GetAdjustedTime());
                         erase_collision = true;
                     }
+                } else if (GetAdjustedTime() - info_new.nLastSuccess > ADDRMAN_TEST_WINDOW) {
+                    // If the collision hasn't resolved in some reasonable amount of time,
+                    // just evict the old entry -- we must not be able to
+                    // connect to it for some reason.
+                    LogPrint(BCLog::ADDRMAN, "Unable to test; swapping %s for %s in tried table anyway\n", info_new.ToString(), info_old.ToString());
+                    Good_(info_new, false, GetAdjustedTime());
+                    erase_collision = true;
                 }
             } else { // Collision is not actually a collision anymore
                 Good_(info_new, false, GetAdjustedTime());

src/addrman.h

@@ -166,6 +166,9 @@ class CAddrInfo : public CAddress
 //! the maximum number of tried addr collisions to store
 #define ADDRMAN_SET_TRIED_COLLISION_SIZE 10
 
+//! the maximum time we'll spend trying to resolve a tried table collision, in seconds
+static const int64_t ADDRMAN_TEST_WINDOW = 40*60; // 40 minutes
+
 /**
  * Stochastical (IP) address manager
  */