Re: [PATCH net v3 2/2] selftests/net: psp: test bidirectional data transfer

["Daniel Zahka" <daniel.zahka@gmail.com>]

On Fri Nov 6, 2026 at 1:34 PM EST, Daniel Zahka wrote:
> On Fri Nov 6, 2026 at 1:20 PM EST, Wei Wang wrote:
>> _data_basic_send() and _data_basic_send_netkit_psp_assoc() currently
>> only verify unidirectional data transmission from the test socket to
>> psp_responder. As a result, they do not exercise the receive path for
>> PSP-encrypted TCP data segments arriving at the test socket (such as
>> packets redirected across a netkit interface associated via dev-assoc,
>> which relies on SKB_EXT_PSP surviving packet scrubbing).
>>
>> Use the existing "data echo" command in psp_responder to verify that the
>> test socket can also receive PSP-encrypted data from the peer in both
>> _data_basic_send() and _data_basic_send_netkit_psp_assoc().
>>
>> Signed-off-by: Wei Wang <weiwan@google.com>
>
> Reviewed-by: Daniel Zahka <daniel.zahka@gmail.com>
>
>> ---
>>  tools/testing/selftests/drivers/net/psp.py | 22 ++++++++++++++++++++++
>>  1 file changed, 22 insertions(+)
>>
>> diff --git a/tools/testing/selftests/drivers/net/psp.py b/tools/testing/selftests/drivers/net/psp.py
>> index 473500901879..c114d2245135 100755
>> --- a/tools/testing/selftests/drivers/net/psp.py
>> +++ b/tools/testing/selftests/drivers/net/psp.py
>> @@ -120,6 +120,26 @@ def _check_data_rx(cfg, exp_len):
>>      ksft_eq(read_len, exp_len)
>>  
>>  
>> +def _recv_careful(s, target, timeout=2):
>> +    """Read exactly target bytes, tolerating short reads"""
>> +    data = b''
>> +    end = time.monotonic() + timeout
>> +    while time.monotonic() < end:
>> +        try:
>> +            data += s.recv(target - len(data), socket.MSG_DONTWAIT)
>> +            if len(data) == target:
>> +                return data
>> +        except BlockingIOError:
>> +            time.sleep(0.001)
>> +    raise KsftFailEx(f"short read, got {len(data)} of {target} bytes")
>> +
>> +
>> +def _req_echo(cfg, s):
>> +    """Ask the peer to echo, and check the reply arrives intact"""
>> +    _send_with_ack(cfg, b'data echo\0')
>> +    ksft_eq(_recv_careful(s, 5), b'echo\0')
>> +
>> +
>>  def _check_data_outq(s, exp_len, force_wait=False):
>>      outq = 0
>>      for _ in range(10):
>> @@ -478,6 +498,7 @@ def _data_basic_send(cfg, version, ipver):
>>  
>>      data_len = _send_careful(cfg, s, 100)
>>      _check_data_rx(cfg, data_len)
>> +    _req_echo(cfg, s)
>>      _close_psp_conn(cfg, s)
>>  
>>  
>> @@ -726,6 +747,7 @@ def _data_basic_send_netkit_psp_assoc(cfg, version, ipver):
>>  
>>          data_len = _send_careful(cfg, sock, 100)
>>          _check_data_rx(cfg, data_len)
>> +        _req_echo(cfg, sock)
>>          _close_psp_conn(cfg, sock)
>>  
>>  

It occurs to me now that we could have just changed the key exchange
protocol used here to have a psp encrypted "start of psp" message that
each side sends and blocks waiting to receive like psp.rst suggests. Not
worth respinning, but maybe a future cleanup worth doing.