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

[Wei Wang <weiwan@google.com>]

_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>
---
 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)
 
 
-- 
2.56.0.455.g6c5a503b38-goog