#1494314: Fix a regression with high-numbered sockets in 2.4.3. This

means that select() on sockets > FD_SETSIZE (typically 1024) work again.
The patch makes sockets use poll() internally where available.

Misc/NEWS

@@ -105,6 +105,10 @@ Library
 Extension Modules
 -----------------
 
+- #1494314: Fix a regression with high-numbered sockets in 2.4.3. This 
+  means that select() on sockets > FD_SETSIZE (typically 1024) work again. 
+  The patch makes sockets use poll() internally where available. 
+
 - Assigning None to pointer type fields in ctypes structures possible
   overwrote the wrong fields, this is fixed now.
 

Modules/_ssl.c

@@ -26,6 +26,12 @@ enum py_ssl_error {
 /* Include symbols from _socket module */
 #include "socketmodule.h"
 
+#if defined(HAVE_POLL_H) 
+#include <poll.h>
+#elif defined(HAVE_SYS_POLL_H)
+#include <sys/poll.h>
+#endif
+
 /* Include OpenSSL header files */
 #include "openssl/rsa.h"
 #include "openssl/crypto.h"
@@ -351,7 +357,7 @@ static void PySSL_dealloc(PySSLObject *self)
 	PyObject_Del(self);
 }
 
-/* If the socket has a timeout, do a select() on the socket.
+/* If the socket has a timeout, do a select()/poll() on the socket.
    The argument writing indicates the direction.
    Returns one of the possibilities in the timeout_state enum (above).
  */
@@ -373,6 +379,26 @@ check_socket_and_wait_for_timeout(PySocketSockObject *s, int writing)
 	if (s->sock_fd < 0)
 		return SOCKET_HAS_BEEN_CLOSED;
 
+	/* Prefer poll, if available, since you can poll() any fd
+	 * which can't be done with select(). */
+#ifdef HAVE_POLL
+	{
+		struct pollfd pollfd;
+		int timeout;
+
+		pollfd.fd = s->sock_fd;
+		pollfd.events = writing ? POLLOUT : POLLIN;
+
+		/* s->sock_timeout is in seconds, timeout in ms */
+		timeout = (int)(s->sock_timeout * 1000 + 0.5);
+		Py_BEGIN_ALLOW_THREADS
+		rc = poll(&pollfd, 1, timeout);
+		Py_END_ALLOW_THREADS
+
+		goto normal_return;
+	}
+#endif
+
 	/* Guard against socket too large for select*/
 #ifndef Py_SOCKET_FD_CAN_BE_GE_FD_SETSIZE
 	if (s->sock_fd >= FD_SETSIZE)
@@ -393,6 +419,7 @@ check_socket_and_wait_for_timeout(PySocketSockObject *s, int writing)
 		rc = select(s->sock_fd+1, &fds, NULL, NULL, &tv);
 	Py_END_ALLOW_THREADS
 
+normal_return:
 	/* Return SOCKET_TIMED_OUT on timeout, SOCKET_OPERATION_OK otherwise
 	   (when we are able to write or when there's something to read) */
 	return rc == 0 ? SOCKET_HAS_TIMED_OUT : SOCKET_OPERATION_OK;

Modules/socketmodule.c

@@ -411,14 +411,24 @@ static int taskwindow;
    there has to be a circular reference. */
 static PyTypeObject sock_type;
 
-/* Can we call select() with this socket without a buffer overrun? */
+#if defined(HAVE_POLL_H)
+#include <poll.h>
+#elif defined(HAVE_SYS_POLL_H)
+#include <sys/poll.h>
+#endif
+
 #ifdef Py_SOCKET_FD_CAN_BE_GE_FD_SETSIZE
 /* Platform can select file descriptors beyond FD_SETSIZE */
 #define IS_SELECTABLE(s) 1
+#elif defined(HAVE_POLL)
+/* Instead of select(), we'll use poll() since poll() works on any fd. */
+#define IS_SELECTABLE(s) 1
+/* Can we call select() with this socket without a buffer overrun? */
 #else
 /* POSIX says selecting file descriptors beyond FD_SETSIZE
-   has undefined behaviour. */
+   has undefined behaviour.  If there's no timeout left, we don't have to
-#define IS_SELECTABLE(s) ((s)->sock_fd < FD_SETSIZE)
+   call select, so it's a safe, little white lie. */
+#define IS_SELECTABLE(s) ((s)->sock_fd < FD_SETSIZE || s->sock_timeout <= 0.0)
 #endif
 
 static PyObject*
@@ -686,7 +696,7 @@ internal_setblocking(PySocketSockObject *s, int block)
 	return 1;
 }
 
-/* Do a select() on the socket, if necessary (sock_timeout > 0).
+/* Do a select()/poll() on the socket, if necessary (sock_timeout > 0).
    The argument writing indicates the direction.
    This does not raise an exception; we'll let our caller do that
    after they've reacquired the interpreter lock.
@@ -694,8 +704,6 @@ internal_setblocking(PySocketSockObject *s, int block)
 static int
 internal_select(PySocketSockObject *s, int writing)
 {
-	fd_set fds;
-	struct timeval tv;
 	int n;
 
 	/* Nothing to do unless we're in timeout mode (not non-blocking) */
@@ -706,7 +714,25 @@ internal_select(PySocketSockObject *s, int writing)
 	if (s->sock_fd < 0)
 		return 0;
 
+	/* Prefer poll, if available, since you can poll() any fd
+	 * which can't be done with select(). */
+#ifdef HAVE_POLL
+	{
+		struct pollfd pollfd;
+		int timeout;
+
+		pollfd.fd = s->sock_fd;
+		pollfd.events = writing ? POLLOUT : POLLIN;
+
+		/* s->sock_timeout is in seconds, timeout in ms */
+		timeout = (int)(s->sock_timeout * 1000 + 0.5); 
+		n = poll(&pollfd, 1, timeout);
+	}
+#else
+	{
 		/* Construct the arguments to select */
+		fd_set fds;
+		struct timeval tv;
 		tv.tv_sec = (int)s->sock_timeout;
 		tv.tv_usec = (int)((s->sock_timeout - tv.tv_sec) * 1e6);
 		FD_ZERO(&fds);
@@ -717,6 +743,8 @@ internal_select(PySocketSockObject *s, int writing)
 			n = select(s->sock_fd+1, NULL, &fds, NULL, &tv);
 		else
 			n = select(s->sock_fd+1, &fds, NULL, NULL, &tv);
+	}
+#endif
 	if (n == 0)
 		return 1;
 	return 0;