feat: add selectable allocation-based privacy relay

tests/test_relay.py

@@ -0,0 +1,79 @@
+from __future__ import annotations
+
+import socket
+import unittest
+
+from straywild_discovery.relay import (
+    RELAY_AUTH_PREFIX,
+    RelayConfig,
+    RelayService,
+)
+
+
+class RelayServiceTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self.host = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self.host.bind(("127.0.0.1", 0))
+        self.host.settimeout(0.35)
+        self.client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self.client.bind(("127.0.0.1", 0))
+        self.client.settimeout(1.0)
+        self.relay = RelayService(RelayConfig(
+            bind_host="127.0.0.1",
+            public_host="127.0.0.1",
+            port_start=0,
+            port_end=0,
+            max_allocations=4,
+        ))
+        self.relay.start()
+
+    def tearDown(self) -> None:
+        self.relay.close()
+        self.client.close()
+        self.host.close()
+
+    def test_authenticated_allocation_masks_both_peer_endpoints(self) -> None:
+        token = "join-capability"
+        route = self.relay.allocate(
+            token,
+            "127.0.0.1",
+            int(self.host.getsockname()[1]),
+        )
+        relay_endpoint = (route.host, route.port)
+
+        self.client.sendto(b"not authenticated", relay_endpoint)
+        with self.assertRaises(TimeoutError):
+            self.host.recvfrom(4096)
+
+        self.client.sendto(RELAY_AUTH_PREFIX + token.encode(), relay_endpoint)
+        self.client.sendto(b"client gameplay", relay_endpoint)
+        packet, relay_as_seen_by_host = self.host.recvfrom(4096)
+        self.assertEqual(packet, b"client gameplay")
+        self.assertEqual(relay_as_seen_by_host[1], route.port)
+        self.assertNotEqual(
+            relay_as_seen_by_host[1], int(self.client.getsockname()[1])
+        )
+
+        self.host.sendto(b"host gameplay", relay_as_seen_by_host)
+        packet, relay_as_seen_by_client = self.client.recvfrom(4096)
+        self.assertEqual(packet, b"host gameplay")
+        self.assertEqual(relay_as_seen_by_client, relay_endpoint)
+        self.assertNotEqual(
+            relay_as_seen_by_client[1], int(self.host.getsockname()[1])
+        )
+
+    def test_wrong_capability_cannot_claim_allocation(self) -> None:
+        route = self.relay.allocate(
+            "right-token",
+            "127.0.0.1",
+            int(self.host.getsockname()[1]),
+        )
+        relay_endpoint = (route.host, route.port)
+        self.client.sendto(RELAY_AUTH_PREFIX + b"wrong-token", relay_endpoint)
+        self.client.sendto(b"blocked gameplay", relay_endpoint)
+        with self.assertRaises(TimeoutError):
+            self.host.recvfrom(4096)
+
+
+if __name__ == "__main__":
+    unittest.main()