A rough implementation of proper bootstrapping:

added a Bootstrapper connection class, connect() and bootstrap() closures
in Manager.manage_connections(). The later is called while
shared.unchecked_node_pool is empty.

minode/connection.py

@@ -507,4 +507,13 @@ class Connection(ConnectionBase):
         self.vectors_to_send.update(getdata.vectors)
 
 
+class Bootstrapper(ConnectionBase):
+    """A special type of connection to find IP nodes"""
+    def _process_msg_addr(self, m):
+        super()._process_msg_addr(m)
+        shared.node_pool.discard((self.host, self.port))
+        self.status = 'disconnecting'
+        self.send_queue.put(None)
+
+
 shared.connection = Connection

minode/main.py

@@ -101,18 +101,22 @@ def parse_arguments():  # pylint: disable=too-many-branches,too-many-statements
 
 
 def bootstrap_from_dns():
-    """Addes addresses of bootstrap servers to known nodes"""
+    """Addes addresses of bootstrap servers to core nodes"""
     try:
-        for item in socket.getaddrinfo('bootstrap8080.bitmessage.org', 80):
-            shared.unchecked_node_pool.add((item[4][0], 8080))
-            logging.debug(
-                'Adding %s to unchecked_node_pool'
-                ' based on DNS bootstrap method', item[4][0])
-        for item in socket.getaddrinfo('bootstrap8444.bitmessage.org', 80):
-            shared.unchecked_node_pool.add((item[4][0], 8444))
-            logging.debug(
-                'Adding %s to unchecked_node_pool'
-                ' based on DNS bootstrap method', item[4][0])
+        for port in (8080, 8444):
+            for item in socket.getaddrinfo(
+                'bootstrap{}.bitmessage.org'.format(port), 80,
+                proto=socket.IPPROTO_TCP
+            ):
+                try:
+                    addr = item[4][0]
+                    socket.inet_pton(item[0], addr)
+                except (TypeError, socket.error):
+                    continue
+                else:
+                    shared.core_nodes.add((addr, port))
+    except socket.gaierror:
+        logging.info('Failed to do a DNS query')
     except Exception:
         logging.info('Error during DNS bootstrap', exc_info=True)
 

minode/manager.py

@@ -11,7 +11,7 @@ import threading
 import time
 
 from . import proofofwork, shared, structure
-from .connection import Connection
+from .connection import Bootstrapper, Connection
 from .i2p import I2PDialer
 
 
@@ -20,6 +20,7 @@ class Manager(threading.Thread):
     def __init__(self):
         super().__init__(name='Manager')
         self.q = queue.Queue()
+        self.bootstrap_pool = []
         self.last_cleaned_objects = time.time()
         self.last_cleaned_connections = time.time()
         self.last_pickled_objects = time.time()
@@ -31,6 +32,8 @@ class Manager(threading.Thread):
     def run(self):
         self.load_data()
         self.clean_objects()
+        self.bootstrap_pool = list(shared.core_nodes.union(shared.node_pool))
+        random.shuffle(self.bootstrap_pool)
         while True:
             time.sleep(0.8)
             now = time.time()
@@ -68,9 +71,26 @@ class Manager(threading.Thread):
                 with shared.objects_lock:
                     del shared.objects[vector]
 
-    @staticmethod
-    def manage_connections():
+    def manage_connections(self):
+        """Open new connections if needed, remove closed ones"""
         hosts = set()
+
+        def connect(target, connection_class=Connection):
+            """
+            Open a connection of *connection_class*
+            to the *target* (host, port)
+            """
+            c = connection_class(*target)
+            c.start()
+            with shared.connections_lock:
+                shared.connections.add(c)
+
+        def bootstrap():
+            """Bootstrap from DNS seed-nodes and known nodes"""
+            target = self.bootstrap_pool.pop()
+            logging.info('Starting a bootstrapper for %s:%s', *target)
+            connect(target, Bootstrapper)
+
         outgoing_connections = 0
         for c in shared.connections.copy():
             if not c.is_alive() or c.status == 'disconnected':
@@ -96,17 +116,20 @@ class Manager(threading.Thread):
         ):
 
             if shared.ip_enabled:
-                if len(shared.unchecked_node_pool) > 16:
-                    to_connect.update(random.sample(
-                        tuple(shared.unchecked_node_pool), 16))
+                if shared.unchecked_node_pool:
+                    if len(shared.unchecked_node_pool) > 16:
+                        to_connect.update(random.sample(
+                            tuple(shared.unchecked_node_pool), 16))
+                    else:
+                        to_connect.update(shared.unchecked_node_pool)
+                    shared.unchecked_node_pool.difference_update(to_connect)
+                    if len(shared.node_pool) > 8:
+                        to_connect.update(random.sample(
+                            tuple(shared.node_pool), 8))
+                    else:
+                        to_connect.update(shared.node_pool)
                 else:
-                    to_connect.update(shared.unchecked_node_pool)
-                shared.unchecked_node_pool.difference_update(to_connect)
-                if len(shared.node_pool) > 8:
-                    to_connect.update(random.sample(
-                        tuple(shared.node_pool), 8))
-                else:
-                    to_connect.update(shared.node_pool)
+                    bootstrap()
 
             if shared.i2p_enabled:
                 if len(shared.i2p_unchecked_node_pool) > 16:
@@ -142,11 +165,8 @@ class Manager(threading.Thread):
                 else:
                     continue
             else:
-                c = Connection(host, port)
-                c.start()
+                connect((host, port))
                 hosts.add(group)
-                with shared.connections_lock:
-                    shared.connections.add(c)
         shared.hosts = hosts
 
     @staticmethod
@@ -190,7 +210,7 @@ class Manager(threading.Thread):
             'r', newline='', encoding='ascii'
         ) as src:
             reader = csv.reader(src)
-            shared.core_nodes = {tuple(row) for row in reader}
+            shared.core_nodes = {(row[0], int(row[1])) for row in reader}
             shared.node_pool.update(shared.core_nodes)
 
         with open(