Feat/587-circuit-relay (#611)

* feat: implemented setup of circuit relay and test cases

* chore: remove test files to be rewritten

* added 1 test suite for protocol

* added 1 test suite for discovery

* fixed protocol timeouts and message types to handle reservations and stream operations.

* Resolved merge conflict in libp2p/tools/utils.py by combining timeout approach with retry mechanism

* fix: linting issues

* docs: updated documentation with circuit-relay

* chore: added enums, improved typing, security and examples

* fix: created proper __init__ file to ensure importability

* fix: replace transport_opt with listen_addrs in examples, fixed typing and improved code

* fix type checking issues across relay module and test suite

* regenerated circuit_pb2 file protobuf version 3

* fixed circuit relay example and moved imports to top in test_security_multistream

* chore: moved imports to the top

* chore: fixed linting of test_circuit_v2_transport.py

---------

Co-authored-by: Manu Sheel Gupta <manusheel.edu@gmail.com>

libp2p/relay/circuit_v2/config.py

@@ -0,0 +1,92 @@
+"""
+Configuration management for Circuit Relay v2.
+
+This module handles configuration for relay roles, resource limits,
+and discovery settings.
+"""
+
+from dataclasses import (
+    dataclass,
+    field,
+)
+
+from libp2p.peer.peerinfo import (
+    PeerInfo,
+)
+
+from .resources import (
+    RelayLimits,
+)
+
+
+@dataclass
+class RelayConfig:
+    """Configuration for Circuit Relay v2."""
+
+    # Role configuration
+    enable_hop: bool = False  # Whether to act as a relay (hop)
+    enable_stop: bool = True  # Whether to accept relayed connections (stop)
+    enable_client: bool = True  # Whether to use relays for dialing
+
+    # Resource limits
+    limits: RelayLimits | None = None
+
+    # Discovery configuration
+    bootstrap_relays: list[PeerInfo] = field(default_factory=list)
+    min_relays: int = 3
+    max_relays: int = 20
+    discovery_interval: int = 300  # seconds
+
+    # Connection configuration
+    reservation_ttl: int = 3600  # seconds
+    max_circuit_duration: int = 3600  # seconds
+    max_circuit_bytes: int = 1024 * 1024 * 1024  # 1GB
+
+    def __post_init__(self) -> None:
+        """Initialize default values."""
+        if self.limits is None:
+            self.limits = RelayLimits(
+                duration=self.max_circuit_duration,
+                data=self.max_circuit_bytes,
+                max_circuit_conns=8,
+                max_reservations=4,
+            )
+
+
+@dataclass
+class HopConfig:
+    """Configuration specific to relay (hop) nodes."""
+
+    # Resource limits per IP
+    max_reservations_per_ip: int = 8
+    max_circuits_per_ip: int = 16
+
+    # Rate limiting
+    reservation_rate_per_ip: int = 4  # per minute
+    circuit_rate_per_ip: int = 8  # per minute
+
+    # Resource quotas
+    max_circuits_total: int = 64
+    max_reservations_total: int = 32
+
+    # Bandwidth limits
+    max_bandwidth_per_circuit: int = 1024 * 1024  # 1MB/s
+    max_bandwidth_total: int = 10 * 1024 * 1024  # 10MB/s
+
+
+@dataclass
+class ClientConfig:
+    """Configuration specific to relay clients."""
+
+    # Relay selection
+    min_relay_score: float = 0.5
+    max_relay_latency: float = 1.0  # seconds
+
+    # Auto-relay settings
+    enable_auto_relay: bool = True
+    auto_relay_timeout: int = 30  # seconds
+    max_auto_relay_attempts: int = 3
+
+    # Reservation management
+    reservation_refresh_threshold: float = 0.8  # Refresh at 80% of TTL
+    max_concurrent_reservations: int = 2