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gh-107545: Fix misleading setsockopt error message #107546

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f85c7dc
gh-107545: Fix misleading setsockopt error message
naweiss Jun 23, 2025
82be245
Add tests for setsockopt errors
naweiss Jun 23, 2025
167d212
Add issue to news
naweiss Jun 23, 2025
e3d4e74
Cleanup setsockopt implementation
naweiss Jul 7, 2025
ca87487
Add clearer error messages to setsockopt
naweiss Jul 8, 2025
543c20b
Simplify error checking implementation for setsockopt
naweiss Jul 11, 2025
2ca926d
Update news entry
naweiss Jul 11, 2025
97ee4dd
Fix some setsockopt error messages
naweiss Jul 15, 2025
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34 changes: 34 additions & 0 deletions Lib/test/test_socket.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1538,6 +1538,40 @@ def testSetSockOpt(self):
reuse = sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)
self.assertFalse(reuse == 0, "failed to set reuse mode")

def test_setsockopt_errors(self):
# See issue #107546.
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.addCleanup(sock.close)

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) # No error expected.

with self.assertRaises(OverflowError):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 2 ** 100)

with self.assertRaises(OverflowError):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, - 2 ** 100)

with self.assertRaises(OverflowError):
sock.setsockopt(socket.SOL_SOCKET, 2 ** 100, 1)

with self.assertRaises(OverflowError):
sock.setsockopt(2 ** 100, socket.SO_REUSEADDR, 1)

with self.assertRaisesRegex(TypeError, "socket option should be int, bytes-like object or None"):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, dict())

with self.assertRaisesRegex(TypeError, "requires 4 arguments when the third argument is None"):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, None)

with self.assertRaisesRegex(TypeError, "only takes 4 arguments when the third argument is None"):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1, 2)

with self.assertRaisesRegex(TypeError, "takes at least 3 arguments"):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)

with self.assertRaisesRegex(TypeError, "takes at most 4 arguments"):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1, 2, 3)

def testSendAfterClose(self):
# testing send() after close() with timeout
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-07-11-12-29-09.gh-issue-107545.ipfl7U.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve the error messages that may be raised by
:meth:`~socket.socket.setsockopt`
92 changes: 61 additions & 31 deletions Modules/socketmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3332,32 +3332,58 @@ sock_setsockopt(PyObject *self, PyObject *args)
{
PySocketSockObject *s = _PySocketSockObject_CAST(self);

Py_ssize_t arglen;
int level;
int optname;
int res;
Py_buffer optval;
Py_buffer buffer;
int flag;
unsigned int optlen;
PyObject *none;
PyObject *optval;

if (!PyArg_ParseTuple(args, "iiO|I:setsockopt",
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All this should be after the code for AF_VSOCK. Otherwise we will get wrong error messages for AF_VSOCK.

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@naweiss naweiss Jul 15, 2025 •
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The docs for setsockopt state there are 3 different overloads and does not mention anything different for AF_VSOCK.
So, I think that the old error messages where misleading:

>>> s.setsockopt(socket.AF_VSOCK, socket.SO_REUSEADDR, 1, 2, 3)
TypeError: setsockopt() takes exactly 3 arguments (5 given)
>>> s.setsockopt(socket.AF_VSOCK, socket.SO_REUSEADDR, None, 1)
TypeError: setsockopt() takes exactly 3 arguments (4 given)
>>> s.setsockopt(socket.AF_VSOCK, socket.SO_REUSEADDR, b"aaa")
TypeError: setsockopt() argument 3 must be int, not bytes

It weird that suddenly the error message tell you that setsockopt only supports 3 arguments although there is overload with 4. I personally would expect that AF_VSOCK would still allow buffer/None argument (like in my implementation) but would raise an error telling the user that this are unsupported types specifically for AF_VSOCK. Something like this:

>>> s.setsockopt(socket.AF_VSOCK, socket.SO_REUSEADDR, 1, 2, 3)
TypeError: setsockopt() takes at most 4 arguments (5 given)
>>> s.setsockopt(socket.AF_VSOCK, socket.SO_REUSEADDR, None, 1)
TypeError: setsockopt() argument 3 for AF_VSOCK must only be an int (got None)
>>> s.setsockopt(socket.AF_VSOCK, socket.SO_REUSEADDR, b"aaa")
TypeError: setsockopt() argument 3 for AF_VSOCK must only be an int (got bytes)

&level, &optname, &optval, &optlen)) {
return NULL;
}

arglen = PyTuple_Size(args);
if (arglen == 3 && optval == Py_None) {
PyErr_Format(PyExc_TypeError,
"setsockopt() requires 4 arguments when the third argument is None",
arglen);
return NULL;
}
if (arglen == 4 && optval != Py_None) {
PyErr_Format(PyExc_TypeError,
"setsockopt() only takes 4 arguments when the third argument is None (got %T)",
optval);
return NULL;
}

#ifdef AF_VSOCK
if (s->sock_family == AF_VSOCK) {
if (!PyIndex_Check(optval)) {
PyErr_Format(PyExc_TypeError,
"setsockopt() argument 3 for AF_VSOCK must be an int (got %T)",
optval);
}
uint64_t vflag; // Must be set width of 64 bits
/* setsockopt(level, opt, flag) */
if (PyArg_ParseTuple(args, "iiK:setsockopt",
&level, &optname, &vflag)) {
// level should always be set to AF_VSOCK
res = setsockopt(get_sock_fd(s), level, optname,
(void*)&vflag, sizeof vflag);
goto done;
if (!PyArg_Parse(optval, "K", &vflag)) {
return NULL;
}
return NULL;
// level should always be set to AF_VSOCK
res = setsockopt(get_sock_fd(s), level, optname,
(void*)&vflag, sizeof vflag);
goto done;
}
#endif

/* setsockopt(level, opt, flag) */
if (PyArg_ParseTuple(args, "iii:setsockopt",
&level, &optname, &flag)) {
if (PyIndex_Check(optval)) {
if (!PyArg_Parse(optval, "i", &flag)) {
return NULL;
}
#ifdef MS_WINDOWS
if (optname == SIO_TCP_SET_ACK_FREQUENCY) {
DWORD dummy;
Expand All @@ -3374,36 +3400,40 @@ sock_setsockopt(PyObject *self, PyObject *args)
goto done;
}

PyErr_Clear();
/* setsockopt(level, opt, None, flag) */
if (PyArg_ParseTuple(args, "iiO!I:setsockopt",
&level, &optname, Py_TYPE(Py_None), &none, &optlen)) {
/* setsockopt(level, opt, None, optlen) */
if (optval == Py_None) {
assert(sizeof(socklen_t) >= sizeof(unsigned int));
res = setsockopt(get_sock_fd(s), level, optname,
NULL, (socklen_t)optlen);
goto done;
}

PyErr_Clear();
/* setsockopt(level, opt, buffer) */
if (!PyArg_ParseTuple(args, "iiy*:setsockopt",
&level, &optname, &optval))
return NULL;

if (PyObject_CheckBuffer(optval)) {
if (!PyArg_Parse(optval, "y*", &buffer)) {
return NULL;
}
#ifdef MS_WINDOWS
if (optval.len > INT_MAX) {
PyBuffer_Release(&optval);
PyErr_Format(PyExc_OverflowError,
"socket option is larger than %i bytes",
INT_MAX);
return NULL;
}
res = setsockopt(get_sock_fd(s), level, optname,
optval.buf, (int)optval.len);
if (buffer.len > INT_MAX) {
PyBuffer_Release(&buffer);
PyErr_Format(PyExc_OverflowError,
"socket option is larger than %i bytes",
INT_MAX);
return NULL;
}
res = setsockopt(get_sock_fd(s), level, optname,
buffer.buf, (int)buffer.len);
#else
res = setsockopt(get_sock_fd(s), level, optname, optval.buf, optval.len);
res = setsockopt(get_sock_fd(s), level, optname, buffer.buf, buffer.len);
#endif
PyBuffer_Release(&optval);
PyBuffer_Release(&buffer);
goto done;
}

PyErr_Format(PyExc_TypeError,
"socket option should be int, bytes-like object or None (got %T)",
optval);
return NULL;

done:
if (res < 0) {
Expand Down
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