lnpeer: fix flen in INIT

electrum/lnpeer.py

@@ -133,8 +133,12 @@ class Peer(Logger):
     async def initialize(self):
         if isinstance(self.transport, LNTransport):
             await self.transport.handshake()
-        # FIXME: "flen" hardcoded but actually it depends on "features"...:
+        features = self.features.for_init_message()
-        self.send_message("init", gflen=0, flen=2, features=self.features.for_init_message(),
+        b = int.bit_length(features)
+        flen = b // 8 + int(bool(b % 8))
+        self.send_message(
+            "init", gflen=0, flen=flen,
+            features=features,
             init_tlvs={
                 'networks':
                 {'chains': constants.net.rev_genesis_bytes()}