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Merged
polybassa merged 2 commits into from
Aug 27, 2026
Merged

isotp: extend long reassembly buffers in place #5109

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ba8c066
isotp: extend long reassembly buffers in place
KernelClint Aug 26, 2026
492e6bd
isotp: always use a bytearray for the reassembly buffer
KernelClint Aug 26, 2026
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9 changes: 4 additions & 5 deletions scapy/contrib/isotp/isotp_soft_socket.py
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Original file line number Diff line number Diff line change
Expand Up @@ -559,7 +559,7 @@ def __init__(self,

self.rx_queue = ObjectPipe[Tuple[bytes, Union[float, EDecimal]]]()
self.rx_len = -1
self.rx_buf = None # type: Optional[bytes]
self.rx_buf = None # type: Optional[bytearray]
self.rx_sn = 0
self.rx_bs = 0
self.rx_idx = 0
Expand Down Expand Up @@ -1001,7 +1001,7 @@ def _recv_ff(self, data, ts):
# copy the first received data bytes
data_bytes = data[ff_pci_sz:]
self.rx_idx = len(data_bytes)
self.rx_buf = data_bytes
self.rx_buf = bytearray(data_bytes)
self.rx_ts = ts

# initial setup for this pdu reception
Expand Down Expand Up @@ -1060,14 +1060,13 @@ def _recv_cf(self, data):
return

self.rx_sn = (self.rx_sn + 1) % 16
self.rx_buf += data[1:]
self.rx_buf.extend(data[1:])
self.rx_idx = len(self.rx_buf)

if self.rx_idx >= self.rx_len:
# we are done
self.rx_buf = self.rx_buf[0:self.rx_len]
self.rx_state = ISOTP_IDLE
self.rx_queue.send((self.rx_buf, self.rx_ts))
self.rx_queue.send((bytes(self.rx_buf[0:self.rx_len]), self.rx_ts))
self.rx_buf = None
return

Expand Down
11 changes: 11 additions & 0 deletions test/contrib/isotp_soft_socket.uts
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Original file line number Diff line number Diff line change
Expand Up @@ -2913,6 +2913,17 @@ with ISOTPSoftSocket(TestSocket(CAN), rx_id=0x123) as s:
s.impl._recv_cf(b"\x21\xAA") # Wrong SN
assert s.impl.rx_state == 0

= Long receive extends the existing reassembly buffer
from scapy.contrib.isotp import ISOTPSoftSocket
from scapy.layers.can import CAN
from test.testsocket import TestSocket

with ISOTPSoftSocket(TestSocket(CAN), rx_id=0x123, listen_only=True) as s:
s.impl._recv_ff(bytes.fromhex("10 00 00 00 13 88 41 41"), 1.23)
reassembly_buffer = s.impl.rx_buf
s.impl._recv_cf(bytes.fromhex("21 41 41 41 41 41 41 41"))
assert s.impl.rx_buf is reassembly_buffer

= begin_send busy / too much data
with ISOTPSoftSocket(TestSocket(CAN), tx_id=0x123) as s:
s.impl.tx_state = 1
Expand Down
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