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/Misc/ACKS b/Misc/ACKS
index 3e53429bf237753883d1eb06f4114532b752896c..311259f1e5fa348fb34f703f4c35e4b61f883533 100644 (file)
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -832,6 +832,7 @@ Lawrence Kesteloot
 Garvit Khatri
 Vivek Khera
 Dhiru Kholia
+Artem Khramov
 Akshit Khurana
 Sanyam Khurana
 Mads Kiilerich

diff --git a/Misc/NEWS.d/next/Library/2019-08-14-21-41-07.bpo-37811.d1xYj7.rst b/Misc/NEWS.d/next/Library/2019-08-14-21-41-07.bpo-37811.d1xYj7.rst
new file mode 100644 (file)
index 0000000..662e7dc
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-08-14-21-41-07.bpo-37811.d1xYj7.rst
@@ -0,0 +1,4 @@
+Fix ``socket`` module's ``socket.connect(address)`` function being unable to
+establish connection in case of interrupted system call. The problem was
+observed on all OSes which ``poll(2)`` system call can take only
+non-negative integers and -1 as a timeout value.

diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index 0470f387e3bcc23bc2f54745b8106921c7cb9ac1..910e2bdd1319f1ac0a1638dd488abb8a4e4b98c8 100644 (file)
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -780,6 +780,17 @@ internal_select(PySocketSockObject *s, int writing, _PyTime_t interval,
     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;