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Fragment outbound UCI control packets in Python host #150

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Merged
sameer merged 1 commit into from
Oct 29, 2026
+77 −4
Merged

Fragment outbound UCI control packets in Python host #150

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9 changes: 5 additions & 4 deletions py/pica/pica/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -97,10 +97,11 @@ async def _recv_data(self) -> bytes:
return await self.data_queue.get()

def send_control(self, packet: uci.ControlPacket):
# TODO packet fragmentation.
packet = bytearray(packet.serialize())
packet[3] = len(packet) - 4
self.writer.write(packet)
raw = packet.serialize()
chunks = [raw[i : i + 255] for i in range(4, len(raw), 255)] or [b""]
Comment on lines +100 to +101

@gemini-code-assist gemini-code-assist Bot Oct 28, 2026

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medium

Add defensive checks to ensure that the input packet is not None and that the serialized packet is at least 4 bytes long (the minimum size of a valid UCI control packet header). This prevents potential AttributeError and IndexError crashes during serialization and fragmentation.

Suggested change
raw = packet.serialize()
chunks = [raw[i : i + 255] for i in range(4, len(raw), 255)] or [b""]
if packet is None:
raise ValueError("Packet cannot be None")
raw = packet.serialize()
if len(raw) < 4:
raise ValueError(f"Control packet must be at least 4 bytes, got {len(raw)}")
chunks = [raw[i : i + 255] for i in range(4, len(raw), 255)] or [b""]

@sameer sameer Oct 28, 2026

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The test client methods receive typed PDL packet instances that serialize to valid UCI headers; defensive type checks aren't used elsewhere in Host and would add unreached branches to test code.

for i, chunk in enumerate(chunks):
pbf = 0x10 if i < len(chunks) - 1 else 0
self.writer.write(bytes([raw[0] | pbf, raw[1], raw[2], len(chunk)]) + chunk)

def send_data(self, packet: uci.DataPacket):
packet = bytearray(packet.serialize())
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72 changes: 72 additions & 0 deletions tests/ranging.py
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Expand Up @@ -531,6 +531,78 @@ async def multicast_list_ntf(host: Host, peer: Host):
)
)

host.send_control(
uci.SessionUpdateControllerMulticastListCmd(
session_token=0,
action=uci.UpdateMulticastListAction.REMOVE_CONTROLEE,
payload=uci.SessionUpdateControllerMulticastListCmdPayload(
controlees=[
uci.Controlee(
short_address=list(peer.mac_address),
subsession_id=0,
)
]
).serialize(),
)
)
await host.expect_control(
uci.SessionUpdateControllerMulticastListRsp(
status=uci.Status.OK,
controlee_status=[
uci.ControleeStatus(
mac_address=list(peer.mac_address),
status=uci.MulticastUpdateStatus.OK_MULTICAST_LIST_UPDATE,
)
],
)
)

host.send_control(
uci.SessionSetAppConfigCmd(
session_token=0,
tlvs=[
uci.AppConfigTlv(
cfg_id=uci.AppConfigTlvType.STS_CONFIG,
v=bytes([uci.StsConfig.PROVISIONED_FOR_RESPONDER_SUB_SESSION_KEY]),
)
],
)
)
await host.expect_control(
uci.SessionSetAppConfigRsp(status=uci.Status.OK, cfg_status=[])
)

# 8 * 38-byte controlees -> 310-byte payload, placing the 8th MAC address in the 2nd PBF fragment.
controlees = [
uci.Controlee_V2_0_32_Byte_Version(
short_address=bytearray([0, i + 3]),
subsession_id=i + 1,
subsession_key=bytearray(32),
)
for i in range(8)
]
host.send_control(
uci.SessionUpdateControllerMulticastListCmd(
session_token=0,
action=uci.UpdateMulticastListAction.ADD_CONTROLEE_WITH_EXTENDED_SUB_SESSION_KEY,
payload=uci.SessionUpdateControllerMulticastListCmd_2_0_32_Byte_Payload(
controlees=controlees
).serialize(),
)
)
await host.expect_control(
uci.SessionUpdateControllerMulticastListRsp(
status=uci.Status.OK,
controlee_status=[
uci.ControleeStatus(
mac_address=[0, i + 3],
status=uci.MulticastUpdateStatus.OK_MULTICAST_LIST_UPDATE,
)
for i in range(8)
],
)
)

host.send_control(uci.SessionDeinitCmd(session_token=0))

await host.expect_control(uci.SessionDeinitRsp(status=uci.Status.OK))
Expand Down
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