networking: add discovery support (#254)

* networking: add discovery support

* cleanup

* cleanup

* cleanup

Author: tcoratger

src/lean_spec/subspecs/networking/support/discovery/__init__.py

@@ -0,0 +1,62 @@
+"""
+Discovery v5 Protocol Specification
+
+Node Discovery Protocol v5.1 for finding peers in Ethereum networks.
+
+References:
+    - https://github.com/ethereum/devp2p/blob/master/discv5/discv5.md
+"""
+
+from .config import DiscoveryConfig
+from .messages import (
+    MAX_REQUEST_ID_LENGTH,
+    PROTOCOL_ID,
+    PROTOCOL_VERSION,
+    Distance,
+    FindNode,
+    HandshakeAuthdata,
+    IdNonce,
+    IPv4,
+    IPv6,
+    MessageType,
+    Nodes,
+    Nonce,
+    PacketFlag,
+    Ping,
+    Pong,
+    Port,
+    RequestId,
+    StaticHeader,
+    TalkReq,
+    TalkResp,
+    WhoAreYouAuthdata,
+)
+from .routing import KBucket, NodeEntry, RoutingTable
+
+__all__ = [
+    "DiscoveryConfig",
+    "MAX_REQUEST_ID_LENGTH",
+    "PROTOCOL_ID",
+    "PROTOCOL_VERSION",
+    "Distance",
+    "IdNonce",
+    "IPv4",
+    "IPv6",
+    "Nonce",
+    "Port",
+    "RequestId",
+    "MessageType",
+    "PacketFlag",
+    "FindNode",
+    "Nodes",
+    "Ping",
+    "Pong",
+    "TalkReq",
+    "TalkResp",
+    "HandshakeAuthdata",
+    "StaticHeader",
+    "WhoAreYouAuthdata",
+    "KBucket",
+    "NodeEntry",
+    "RoutingTable",
+]

src/lean_spec/subspecs/networking/support/discovery/config.py

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+"""
+Discovery v5 Configuration
+
+Protocol constants and configuration for Node Discovery Protocol v5.1.
+
+References:
+    - https://github.com/ethereum/devp2p/blob/master/discv5/discv5-theory.md
+"""
+
+from typing_extensions import Final
+
+from lean_spec.types import StrictBaseModel
+
+# Protocol Constants
+# ------------------
+# Values derived from the Discovery v5 specification and Kademlia design.
+
+K_BUCKET_SIZE: Final = 16
+"""Nodes per k-bucket. Standard Kademlia value balancing table size and lookup efficiency."""
+
+ALPHA: Final = 3
+"""Concurrent queries during lookup. Balances speed against network load."""
+
+BUCKET_COUNT: Final = 256
+"""Total k-buckets. One per bit of the 256-bit node ID space."""
+
+REQUEST_TIMEOUT_SECS: Final = 0.5
+"""Single request timeout. Spec recommends 500ms for request/response."""
+
+HANDSHAKE_TIMEOUT_SECS: Final = 1.0
+"""Handshake completion timeout. Spec recommends 1s for full handshake."""
+
+MAX_NODES_RESPONSE: Final = 16
+"""Max ENRs per NODES message. Keeps responses under 1280 byte UDP limit."""
+
+BOND_EXPIRY_SECS: Final = 86400
+"""Liveness revalidation interval. 24 hours before re-checking a node."""
+
+MAX_PACKET_SIZE: Final = 1280
+"""Maximum UDP packet size in bytes."""
+
+MIN_PACKET_SIZE: Final = 63
+"""Minimum valid packet size in bytes."""
+
+
+class DiscoveryConfig(StrictBaseModel):
+    """Runtime configuration for Discovery v5."""
+
+    k_bucket_size: int = K_BUCKET_SIZE
+    """Maximum nodes stored per k-bucket in the routing table."""
+
+    alpha: int = ALPHA
+    """Number of concurrent FINDNODE queries during lookup."""
+
+    request_timeout_secs: float = REQUEST_TIMEOUT_SECS
+    """Timeout for a single request/response exchange."""
+
+    handshake_timeout_secs: float = HANDSHAKE_TIMEOUT_SECS
+    """Timeout for completing the full handshake sequence."""
+
+    max_nodes_response: int = MAX_NODES_RESPONSE
+    """Maximum ENR records returned in a single NODES response."""
+
+    bond_expiry_secs: int = BOND_EXPIRY_SECS
+    """Seconds before a bonded node requires liveness revalidation."""