multicast

squinnondation/messages.py

@@ -199,6 +199,22 @@ class HelloTLV(TLV):
         if not self.is_long:
             user.send_packet(sender, Packet.construct(HelloTLV.construct(16, user, sender)))
 
+    def handle_multicast(self, user: Any, sender: Any) -> None:
+        if sender.id > 0 and sender.id != self.source_id:
+            user.add_system_message(f"A client known as the id {sender.id} declared that it uses "
+                                        f"the id {self.source_id}.")
+            sender.id = self.source_id
+
+        if self.source_id == user.id:
+            sender.marked_as_banned = True
+
+        if not sender.active:
+            sender.id = self.source_id  # The sender we are given misses an id
+
+        # Add entry to/actualize the active peers dictionnary
+        user.update_peer_table(sender)
+        user.add_system_message(f"{self.source_id} sent me a Hello on multicast")
+    
     @property
     def is_long(self) -> bool:
         return self.length == 16

squinnondation/peers.py

@@ -10,6 +10,7 @@ import curses
 import re
 import socket
 import time
+import struct
 
 from .messages import Packet, DataTLV, HelloTLV, GoAwayTLV, GoAwayType, NeighbourTLV, WarningTLV
 
@@ -100,6 +101,13 @@ class User(Peer):
         # Bind the socket
         self.socket.bind(self.main_address)
         
+        # Create multicast socket
+        self.multicast_socket = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
+        self.multicast_socket.bind(('', 1212)) #listen on all interfaces?
+        # To join the group, we need to give setsockopt a binary packed representation of the multicast group's address and on what interfaces we will listen (here all)
+        mreq = struct.pack("16s15s", socket.inet_pton(socket.AF_INET6, "ff02::4242:4242"), bytes(socket.INADDR_ANY)) #The string "16s15s" corresponds to the packing options: here it packs the arguments into a 16-byte string and a 15-byte string. 
+        self.multicast_socket.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)
+
         self.squinnondation = instance
 
         self.input_buffer = ""
@@ -108,7 +116,7 @@ class User(Peer):
 
         # Lock the refresh function in order to avoid concurrent refresh
         self.refresh_lock = RLock()
-        # Lock function that can be used by two threads to avoid concurrent refresh
+        # Lock functions that can be used by two threads to avoid concurrent refresh
         self.data_lock = RLock()
 
         self.history = []
@@ -129,7 +137,7 @@ class User(Peer):
         self.nbNS = 0
         self.minNS = 3  # minimal number of symmetric neighbours a user needs to have.
 
-        self.worm = Worm(self)
+        self.listener = Listener(self)
         self.neighbour_manager = PeerManager(self)
         self.inondator = Inondator(self)
 
@@ -243,11 +251,11 @@ class User(Peer):
         Start asynchronous threads.
         """
         # Kill subthreads when exitting the program
-        self.worm.setDaemon(True)
+        self.listener.setDaemon(True)
         self.neighbour_manager.setDaemon(True)
         self.inondator.setDaemon(True)
 
-        self.worm.start()
+        self.listener.start()
         self.neighbour_manager.start()
         self.inondator.start()
 
@@ -999,10 +1007,48 @@ class User(Peer):
 
         exit(0)
     
+    def send_hello_multicast(self) -> int:
+        """
+        Send a short hello on the multicast group.
+        """
+        htlv = HelloTLV().construct(8, self)
+        pkt = Packet().construct(htlv)
         
-class Worm(Thread):
+        res = self.send_multicast(pkt.marshal())
+        return res
+
+    def send_multicast(self, data: bytes) -> int:
+        """
+        Send a packet on the multicast.
+        """
+        return self.multicast_socket.sendto(data, ("ff02::4242:4242", 1212))
+
+    def receive_hello_multicast(self) -> Tuple[Packet, Peer]:
+        """
+        Receive a packet from the multicast and translate it into a Python object.
+        """
+        data, addr = self.receive_raw_data()
+        peer = self.find_peer(addr[0], addr[1])
+        try:
+            pkt = Packet.unmarshal(data)
+        except ValueError as error:
+            # The packet contains an error. We memorize it.
+            peer.errors += 1
+            self.add_system_message("An error occured on the multicast")
+            raise error
+        else:
+            return pkt, peer
+
+    def receive_multicast(self) -> Tuple[bytes, Any]:
+        """
+        Receive a packet from the socket.
+        """
+        return self.multicast_socket.recvfrom(1024)
+
+
+class Listener(Thread):
     """
-    The worm is the peer listener.
+    It is the peer listener.
     It always waits for an incoming packet, then it  treats it, and continues to wait.
     It is in a dedicated thread.
     """
@@ -1028,6 +1074,33 @@ class Worm(Thread):
                 self.user.refresh_history()
                 self.user.refresh_input()
 
+class Multicastlistener(Thread):
+    """
+    Used to listen on the multicast group to discover new people
+    """
+    def __init__(self, user: User, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.user = user
+    
+    def run(self) -> None:
+        while True:
+            try:
+                pkt, peer = self.user.receive_hello_multicast()
+            except ValueError as error:
+                self.user.add_system_message("An error occurred while receiving a packet: {}".format(error))
+                self.user.refresh_history()
+                self.user.refresh_input()
+            else:
+                if peer.banned:
+                    # Ignore banned peers
+                    continue
+                
+                for tlv in pkt.body:
+                    if tlv.type==2 and tlv.length==8: # Only short hello TLVs allowed
+                        tlv.handle_multicast(self.user, peer)
+                self.user.refresh_history()
+                self.user.refresh_input()
+
 
 class PeerManager(Thread):
     """
@@ -1039,6 +1112,7 @@ class PeerManager(Thread):
         self.last_potential = 0
         self.last_check = 0
         self.last_neighbour = 0
+        self.last_multicast = 0
 
         htlv = HelloTLV().construct(8, self.user)
         pkt = Packet().construct(htlv)
@@ -1069,6 +1143,11 @@ class PeerManager(Thread):
                 self.user.send_neighbours()
                 self.last_neighbour = time.time()
             
+            # For the multicast discovery : send a hello every minute.
+            if time.time() - self.last_multicast > 60:
+                self.user.send_hello_multicast()
+                self.last_multicast = time.time()
+                
             # Avoid infinite loops
             time.sleep(1)