From 618865fb5cf3d02254b2fa953ec294bcfe8c7aba Mon Sep 17 00:00:00 2001
From: Youngjoon Lee <5462944+youngjoon-lee@users.noreply.github.com>
Date: Thu, 23 May 2024 17:52:17 +0900
Subject: [PATCH] gossip

---
 mixnet/v2/sim/config.py     |  5 +++++
 mixnet/v2/sim/config.yaml   |  4 +++-
 mixnet/v2/sim/p2p.py        | 25 +++++++++++++++++++++++--
 mixnet/v2/sim/simulation.py |  6 +++---
 4 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/mixnet/v2/sim/config.py b/mixnet/v2/sim/config.py
index f1314c5..c5b855d 100644
--- a/mixnet/v2/sim/config.py
+++ b/mixnet/v2/sim/config.py
@@ -98,6 +98,8 @@ class MixnetConfig:
 class P2PConfig:
     # Broadcasting type: naive | gossip
     type: str
+    # A connection density, only if the type is gossip
+    connection_density: int
     # A maximum network latency between nodes directly connected with each other
     max_network_latency: float
 
@@ -106,11 +108,14 @@ class P2PConfig:
 
     def validate(self):
         assert self.type in [self.TYPE_NAIVE, self.TYPE_GOSSIP]
+        if self.type == self.TYPE_GOSSIP:
+            assert self.connection_density > 0
         assert self.max_network_latency >= 0
 
     def description(self):
         return (
             f"p2p_type: {self.type}\n"
+            f"conn_density: {self.connection_density}"
             f"max_net_latency: {self.max_network_latency:.2f}"
         )
 
diff --git a/mixnet/v2/sim/config.yaml b/mixnet/v2/sim/config.yaml
index cf444c6..bc3b018 100644
--- a/mixnet/v2/sim/config.yaml
+++ b/mixnet/v2/sim/config.yaml
@@ -27,7 +27,9 @@ mixnet:
 
 p2p:
   # Broadcasting type: naive | gossip
-  type: "naive"
+  type: "gossip"
+  # A connection density, only if the type is gossip
+  connection_density: 10
   # A maximum network latency between nodes directly connected with each other
   max_network_latency: 0.5
 
diff --git a/mixnet/v2/sim/p2p.py b/mixnet/v2/sim/p2p.py
index c197284..72fce20 100644
--- a/mixnet/v2/sim/p2p.py
+++ b/mixnet/v2/sim/p2p.py
@@ -25,8 +25,8 @@ class P2P(ABC):
         self.measurement = Measurement(env, config)
         self.adversary = Adversary(env, config)
 
-    def add_node(self, nodes: list["Node"]):
-        self.nodes.extend(nodes)
+    def set_nodes(self, nodes: list["Node"]):
+        self.nodes = nodes
 
     def get_nodes(self, n: int) -> list["Node"]:
         return random.sample(self.nodes, n)
@@ -57,6 +57,7 @@ class P2P(ABC):
 class NaiveBroadcastP2P(P2P):
     def __init__(self, env: simpy.Environment, config: Config):
         super().__init__(env, config)
+        self.nodes = []
 
     # This should accept only bytes in practice,
     # but we accept SphinxPacket as well because we don't implement Sphinx deserialization.
@@ -78,6 +79,24 @@ class GossipP2P(P2P):
         self.topology = defaultdict(set)
         self.message_cache = defaultdict(set)
 
+    def set_nodes(self, nodes: list["Node"]):
+        super().set_nodes(nodes)
+        for i, node in enumerate(nodes):
+            # Each node is chained with the right neighbor, so that no node is not orphaned.
+            # And then, each node is connected to a random subset of other nodes.
+            front, back = nodes[:i], nodes[i + 1:]
+            if len(back) > 0:
+                neighbor = back[0]
+                back = back[1:]
+            else:
+                neighbor = front[0]
+                front = front[1:]
+            others = front + back
+            n = min(self.config.p2p.connection_density - 1, len(others))
+            conns = set(random.sample(others, n))
+            conns.add(neighbor)
+            self.topology[node] = conns
+
     def broadcast(self, sender: "Node", msg: SphinxPacket | bytes):
         yield from super().broadcast(sender, msg)
         self.log("Gossiping a msg: %d bytes" % len(msg))
@@ -92,3 +111,5 @@ class GossipP2P(P2P):
         if msg_hash not in self.message_cache[receiver]:
             self.message_cache[receiver].add(msg_hash)
             self.env.process(receiver.receive_message(msg))
+            # gossiping
+            self.env.process(self.broadcast(receiver, msg))
diff --git a/mixnet/v2/sim/simulation.py b/mixnet/v2/sim/simulation.py
index 437851d..daad06a 100644
--- a/mixnet/v2/sim/simulation.py
+++ b/mixnet/v2/sim/simulation.py
@@ -12,9 +12,9 @@ class Simulation:
         random.seed()
         self.config = config
         self.env = simpy.Environment()
-        self.p2p = NaiveBroadcastP2P(self.env, config)
-        self.nodes = [Node(i, self.env, self.p2p, config) for i in range(config.mixnet.num_nodes)]
-        self.p2p.add_node(self.nodes)
+        self.p2p = Simulation.init_p2p(self.env, config)
+        nodes = [Node(i, self.env, self.p2p, config) for i in range(config.mixnet.num_nodes)]
+        self.p2p.set_nodes(nodes)
 
     def run(self):
         self.env.run(until=self.config.simulation.running_time)