Merge pull request #586 from libp2p/fix/obsaddr-panic

fix panic in observed address activation check

p2p/protocol/identify/obsaddr.go

@@ -31,15 +31,6 @@ type ObservedAddr struct {
 }
 
 func (oa *ObservedAddr) activated(ttl time.Duration) bool {
-	// cleanup SeenBy set
-	now := time.Now()
-
-	for k, ob := range oa.SeenBy {
-		if now.Sub(ob.seenTime) > ttl*ActivationThresh {
-			delete(oa.SeenBy, k)
-		}
-	}
-
 	// We only activate if in the TTL other peers observed the same address
 	// of ours at least 4 times.
 	return len(oa.SeenBy) >= ActivationThresh
@@ -154,7 +145,15 @@ func (oas *ObservedAddrSet) gc() {
 	for local, observedAddrs := range oas.addrs {
 		// TODO we can do this without allocating by compacting the array in place
 		filteredAddrs := make([]*ObservedAddr, 0, len(observedAddrs))
+
 		for _, a := range observedAddrs {
+			// clean up SeenBy set
+			for k, ob := range a.SeenBy {
+				if now.Sub(ob.seenTime) > oas.ttl*ActivationThresh {
+					delete(a.SeenBy, k)
+				}
+			}
+
 			// leave only alive observed addresses
 			if now.Sub(a.LastSeen) <= oas.ttl {
 				filteredAddrs = append(filteredAddrs, a)