select peers with desired features before connecting

electrum/lnpeer.py

@@ -23,7 +23,7 @@ from . import bitcoin
 from . import ecc
 from .ecc import sig_string_from_r_and_s, get_r_and_s_from_sig_string, der_sig_from_sig_string
 from . import constants
-from .util import bh2u, bfh, log_exceptions, list_enabled_bits, ignore_exceptions, chunks, SilentTaskGroup
+from .util import bh2u, bfh, log_exceptions, ignore_exceptions, chunks, SilentTaskGroup
 from .transaction import Transaction, TxOutput, PartialTxOutput
 from .logging import Logger
 from .lnonion import (new_onion_packet, decode_onion_error, OnionFailureCode, calc_hops_data_for_payment,
@@ -36,7 +36,7 @@ from .lnutil import (Outpoint, LocalConfig, RECEIVED, UpdateAddHtlc,
                      funding_output_script, get_per_commitment_secret_from_seed,
                      secret_to_pubkey, PaymentFailure, LnLocalFeatures,
                      LOCAL, REMOTE, HTLCOwner, generate_keypair, LnKeyFamily,
-                     get_ln_flag_pair_of_bit, privkey_to_pubkey, UnknownPaymentHash, MIN_FINAL_CLTV_EXPIRY_ACCEPTED,
+                     ln_compare_features, privkey_to_pubkey, UnknownPaymentHash, MIN_FINAL_CLTV_EXPIRY_ACCEPTED,
                      LightningPeerConnectionClosed, HandshakeFailed, NotFoundChanAnnouncementForUpdate,
                      MINIMUM_MAX_HTLC_VALUE_IN_FLIGHT_ACCEPTED, MAXIMUM_HTLC_MINIMUM_MSAT_ACCEPTED,
                      MAXIMUM_REMOTE_TO_SELF_DELAY_ACCEPTED, RemoteMisbehaving, DEFAULT_TO_SELF_DELAY,
@@ -187,21 +187,10 @@ class Peer(Logger):
         # if they required some even flag we don't have, they will close themselves
         # but if we require an even flag they don't have, we close
         their_localfeatures = int.from_bytes(payload['localfeatures'], byteorder="big")
-        our_flags = set(list_enabled_bits(self.localfeatures))
-        their_flags = set(list_enabled_bits(their_localfeatures))
-        for flag in our_flags:
-            if flag not in their_flags and get_ln_flag_pair_of_bit(flag) not in their_flags:
-                # they don't have this feature we wanted :(
-                if flag % 2 == 0:  # even flags are compulsory
-                    raise GracefulDisconnect("remote does not support {}"
-                                             .format(str(LnLocalFeatures(1 << flag))))
-                self.localfeatures ^= 1 << flag  # disable flag
-            else:
-                # They too have this flag.
-                # For easier feature-bit-testing, if this is an even flag, we also
-                # set the corresponding odd flag now.
-                if flag % 2 == 0 and self.localfeatures & (1 << flag):
-                    self.localfeatures |= 1 << get_ln_flag_pair_of_bit(flag)
+        try:
+            self.localfeatures = ln_compare_features(self.localfeatures, their_localfeatures)
+        except ValueError as e:
+            raise GracefulDisconnect(f"remote does not support {str(e)}")
         if isinstance(self.transport, LNTransport):
             self.channel_db.add_recent_peer(self.transport.peer_addr)
         self._received_init = True

electrum/lnutil.py

@@ -12,6 +12,7 @@ import attr
 from aiorpcx import NetAddress
 
 from .util import bfh, bh2u, inv_dict, UserFacingException
+from .util import list_enabled_bits
 from .crypto import sha256
 from .transaction import (Transaction, PartialTransaction, PartialTxInput, TxOutpoint,
                           PartialTxOutput, opcodes, TxOutput)
@@ -655,6 +656,24 @@ class LnGlobalFeatures(IntFlag):
 # note that these are powers of two, not the bits themselves
 LN_GLOBAL_FEATURES_KNOWN_SET = set(LnGlobalFeatures)
 
+def ln_compare_features(our_features, their_features):
+    """raises ValueError if incompatible"""
+    our_flags = set(list_enabled_bits(our_features))
+    their_flags = set(list_enabled_bits(their_features))
+    for flag in our_flags:
+        if flag not in their_flags and get_ln_flag_pair_of_bit(flag) not in their_flags:
+            # they don't have this feature we wanted :(
+            if flag % 2 == 0:  # even flags are compulsory
+                raise ValueError(LnLocalFeatures(1 << flag))
+            our_features ^= 1 << flag  # disable flag
+        else:
+            # They too have this flag.
+            # For easier feature-bit-testing, if this is an even flag, we also
+            # set the corresponding odd flag now.
+            if flag % 2 == 0 and our_features & (1 << flag):
+                our_features |= 1 << get_ln_flag_pair_of_bit(flag)
+    return our_features
+
 
 class LNPeerAddr:
 

electrum/lnworker.py

@@ -53,7 +53,7 @@ from .lnutil import (Outpoint, LNPeerAddr,
                      NUM_MAX_EDGES_IN_PAYMENT_PATH, SENT, RECEIVED, HTLCOwner,
                      UpdateAddHtlc, Direction, LnLocalFeatures,
                      ShortChannelID, PaymentAttemptLog, PaymentAttemptFailureDetails)
-from .lnutil import ln_dummy_address
+from .lnutil import ln_dummy_address, ln_compare_features
 from .transaction import PartialTxOutput, PartialTransaction, PartialTxInput
 from .lnonion import OnionFailureCode
 from .lnmsg import decode_msg
@@ -200,6 +200,18 @@ class LNWorker(Logger):
                 self._add_peer(host, int(port), bfh(pubkey)),
                 self.network.asyncio_loop)
 
+    def is_good_peer(self, peer):
+        node_id = peer.pubkey
+        node = self.channel_db._nodes.get(node_id)
+        if not node:
+            return False
+        try:
+            ln_compare_features(self.localfeatures, node.features)
+        except ValueError:
+            return False
+        #self.logger.info(f'is_good {peer.host}')
+        return True
+
     async def _get_next_peers_to_try(self) -> Sequence[LNPeerAddr]:
         now = time.time()
         await self.channel_db.data_loaded.wait()
@@ -215,6 +227,8 @@ class LNWorker(Logger):
                 continue
             if peer in self._last_tried_peer:
                 continue
+            if not self.is_good_peer(peer):
+                continue
             return [peer]
         # try random peer from graph
         unconnected_nodes = self.channel_db.get_200_randomly_sorted_nodes_not_in(self.peers.keys())
@@ -230,6 +244,8 @@ class LNWorker(Logger):
                     continue
                 if peer in self._last_tried_peer:
                     continue
+                if not self.is_good_peer(peer):
+                    continue
                 #self.logger.info('taking random ln peer from our channel db')
                 return [peer]