bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
FreeBSD implementation of poll(2) restricts the timeout argument to be
either zero, or positive, or equal to INFTIM (-1).
Unless otherwise overridden, socket timeout defaults to -1. This value
is then converted to milliseconds (-1000) and used as argument to the
poll syscall. poll returns EINVAL (22), and the connection fails.
This bug was discovered during the EINTR handling testing, and the
reproduction code can be found in
https://bugs.python.org/issue23618 (see connect_eintr.py,
attached). On GNU/Linux, the example runs as expected.
This change is trivial:
If the supplied timeout value is negative, truncate it to -1.
(cherry picked from commit 28146206578ebe1b84b48e6f255738a227058c04)
Co-authored-by: Artem Khramov <akhramov@pm.me>
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index 0470f38..910e2bd 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -780,6 +780,17 @@
ms = _PyTime_AsMilliseconds(interval, _PyTime_ROUND_CEILING);
assert(ms <= INT_MAX);
+ /* On some OSes, typically BSD-based ones, the timeout parameter of the
+ poll() syscall, when negative, must be exactly INFTIM, where defined,
+ or -1. See issue 37811. */
+ if (ms < 0) {
+#ifdef INFTIM
+ ms = INFTIM;
+#else
+ ms = -1;
+#endif
+ }
+
Py_BEGIN_ALLOW_THREADS;
n = poll(&pollfd, 1, (int)ms);
Py_END_ALLOW_THREADS;