ln invoices: more relaxed filtering of chans to include route hints for

e.g. just because remote peer is temporarily offline, we might still want it
included in the invoice

electrum/lnworker.py

@@ -1216,19 +1216,21 @@ class LNWallet(LNWorker):
         """calculate routing hints (BOLT-11 'r' field)"""
         routing_hints = []
         channels = list(self.channels.values())
+        random.shuffle(channels)  # not sure this has any benefit but let's not leak channel order
         scid_to_my_channels = {chan.short_channel_id: chan for chan in channels
                                if chan.short_channel_id is not None}
-        ignore_min_htlc_value = False
         if amount_sat:
             amount_msat = 1000 * amount_sat
         else:
             # for no amt invoices, check if channel can receive at least 1 msat
             amount_msat = 1
-            ignore_min_htlc_value = True
         # note: currently we add *all* our channels; but this might be a privacy leak?
         for chan in channels:
-            if not chan.can_receive(amount_msat=amount_msat, check_frozen=True,
+            # do minimal filtering of channels.
-                                    ignore_min_htlc_value=ignore_min_htlc_value):
+            # we include channels that cannot *right now* receive (e.g. peer disconnected or balance insufficient)
+            if not (chan.is_open() and not chan.is_frozen_for_receiving()):
+                continue
+            if amount_msat > 1000 * chan.constraints.capacity:
                 continue
             chan_id = chan.short_channel_id
             assert isinstance(chan_id, bytes), chan_id