1 files changed, 89 insertions, 0 deletions
diff --git a/packages/meshbay-cli/tests/test_sctp_fix.py b/packages/meshbay-cli/tests/test_sctp_fix.py
new file mode 100644
index 0000000..04638db
--- /dev/null
+++ b/packages/meshbay-cli/tests/test_sctp_fix.py
@@ -0,0 +1,89 @@
+"""The client's copy of the node's aiortc fixes (client/sctp_fix.py).
+
+The copy exists because neither package may depend on the other; it is held to
+the node's by comparing the code itself, docstrings aside, and the two effects
+that set a download's speed here are replayed against aiortc.
+"""
+
+import ast
+import asyncio
+from pathlib import Path
+
+import pytest
+from aiortc.rtcsctptransport import (
+    SCTP_DATA_FIRST_FRAG,
+    SCTP_DATA_LAST_FRAG,
+    DataChunk,
+    InboundStream,
+    RTCSctpTransport,
+    serialize_packet,
+)
+from meshbay_cli.client import sctp_fix
+
+NODE_COPY = (Path(__file__).resolve().parents[2] / "meshbay-node" / "src" / "meshbay_node"
+             / "transport" / "webrtc" / "sctp_fix.py")
+
+
+def _code(path: Path) -> str:
+    tree = ast.parse(path.read_text(encoding="utf-8"))
+    tree.body = tree.body[1:]          # the module docstring
+    return ast.dump(tree)
+
+
+@pytest.mark.skipif(not NODE_COPY.exists(), reason="not in the source tree")
+def test_the_code_is_the_nodes():
+    assert _code(Path(sctp_fix.__file__)) == _code(NODE_COPY)
+
+
+def _chunks(n_fragments: int, count: int, tsn: int = 1000) -> list[DataChunk]:
+    out = []
+    for seq in range(count):
+        for i in range(n_fragments):
+            c = DataChunk()
+            c.flags = ((SCTP_DATA_FIRST_FRAG if i == 0 else 0)
+                       | (SCTP_DATA_LAST_FRAG if i == n_fragments - 1 else 0))
+            c.tsn, c.stream_id, c.stream_seq, c.protocol = tsn, 1, seq, 53
+            c.user_data = b"x"
+            tsn += 1
+            out.append(c)
+    return out
+
+
+def test_a_megabyte_is_walked_once(monkeypatch):
+    walks = []
+    original = sctp_fix._pop_messages
+    monkeypatch.setattr(sctp_fix, "_pop_messages",
+                        lambda s: (walks.append(1), original(s))[1])
+    s = InboundStream()
+    got = 0
+    for c in _chunks(870, 3):
+        s.add_chunk(c)
+        got += len(list(s.pop_messages()))
+    assert got == 3 and len(walks) == 3
+
+
+def test_every_second_packet_is_acknowledged():
+    class _Dtls:
+        state = "connected"
+
+        def _register_data_receiver(self, *a):
+            pass
+
+    async def go():
+        s = RTCSctpTransport(_Dtls())
+        s._association_state = s.State.ESTABLISHED
+        s._last_received_tsn = 999
+        sacks = []
+
+        async def send_sack():
+            sacks.append(s._last_received_tsn)
+            s._sack_needed = False
+
+        async def deliver(*_a):
+            pass
+
+        s._send_sack, s._receive = send_sack, deliver
+        for c in _chunks(1, 6):
+            await s._handle_data(serialize_packet(1, 1, s._local_verification_tag, c))
+        return sacks
+    assert asyncio.run(go()) == [1001, 1003, 1005]