Fix peer replacement logic

- drop the IP address peer
- update the remaining peer with fresh info

lib/peer.py

@@ -94,12 +94,14 @@ class Peer(object):
         return tuple(int(part) for part in vstr.split('.'))
 
     def matches(self, peers):
-        '''Return peers whose host matches the given peer's host or IP
-        address.  This results in our favouring host names over IP
-        addresses.
+        '''Return peers whose host matches our hostname or IP address.
+        Additionally include all peers whose IP address matches our
+        hostname if that is an IP address.
         '''
         candidates = (self.host.lower(), self.ip_addr)
-        return [peer for peer in peers if peer.host.lower() in candidates]
+        return [peer for peer in peers
+                if peer.host.lower() in candidates
+                or peer.ip_addr == self.host]
 
     def __str__(self):
         return self.host
@@ -111,9 +113,13 @@ class Peer(object):
         except Exception:
             pass
         else:
-            self.features = tmp.features
+            self.update_features_from_peer(tmp)
+
+    def update_features_from_peer(self, peer):
+        if peer != self:
+            self.features = peer.features
             for feature in self.FEATURES:
-                setattr(self, feature, getattr(tmp, feature))
+                setattr(self, feature, getattr(peer, feature))
 
     def connection_port_pairs(self):
         '''Return a list of (kind, port) pairs to try when making a

server/peers.py

@@ -555,15 +555,20 @@ class PeerManager(util.LoggedClass):
             how = 'via {} at {}'.format(kind, peer.ip_addr)
         status = 'verified' if good else 'failed to verify'
         elapsed = time.time() - peer.last_try
-        self.log_info('{} {} in {:.1f}s'.format(status, how, elapsed))
+        self.log_info('{} {} {} in {:.1f}s'.format(status, peer, how, elapsed))
 
         if good:
             peer.try_count = 0
             peer.source = 'peer'
-            # Remove matching IP addresses
-            for match in peer.matches(self.peers):
-                if match != peer and peer.host == peer.ip_addr:
-                    self.peers.remove(match)
+            # At most 2 matches if we're a host name, potentially several if
+            # we're an IP address (several instances can share a NAT).
+            matches = peer.matches(self.peers)
+            for match in matches:
+                if match.ip_address:
+                    if len(matches) > 1:
+                        self.peers.remove(match)
+                elif peer.host in match.features['hosts']:
+                    match.update_features_from_peer(peer)
         else:
             self.maybe_forget_peer(peer)