[Python-checkins] cpython (2.7): Issue #8498: In socket.accept(), allow to specify 0 as a backlog value in

[antoine.pitrou]

http://hg.python.org/cpython/rev/48743ad2d2ef
changeset:   70011:48743ad2d2ef
branch:      2.7
parent:      70006:50a5e271edf9
user:        Antoine Pitrou <solipsis at pitrou.net>
date:        Tue May 10 19:16:03 2011 +0200
summary:
  Issue #8498: In socket.accept(), allow to specify 0 as a backlog value in
order to accept exactly one connection.  Patch by Daniel Evers.

files:
  Doc/library/socket.rst  |   4 ++--
  Lib/test/test_socket.py |   7 +++++++
  Misc/ACKS               |   1 +
  Misc/NEWS               |   3 +++
  Modules/socketmodule.c  |  11 +++++++----
  5 files changed, 20 insertions(+), 6 deletions(-)


diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst
--- a/Doc/library/socket.rst
+++ b/Doc/library/socket.rst
@@ -644,8 +644,8 @@
 .. method:: socket.listen(backlog)
 
    Listen for connections made to the socket.  The *backlog* argument specifies the
-   maximum number of queued connections and should be at least 1; the maximum value
-   is system-dependent (usually 5).
+   maximum number of queued connections and should be at least 0; the maximum value
+   is system-dependent (usually 5), the minimum value is forced to 0.
 
 
 .. method:: socket.makefile([mode[, bufsize]])
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -700,6 +700,13 @@
     def test_sendall_interrupted_with_timeout(self):
         self.check_sendall_interrupted(True)
 
+    def testListenBacklog0(self):
+        srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        srv.bind((HOST, 0))
+        # backlog = 0
+        srv.listen(0)
+        srv.close()
+
 
 @unittest.skipUnless(thread, 'Threading required for this test.')
 class BasicTCPTest(SocketConnectedTest):
diff --git a/Misc/ACKS b/Misc/ACKS
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -243,6 +243,7 @@
 Tim Everett
 Paul Everitt
 David Everly
+Daniel Evers
 Greg Ewing
 Martijn Faassen
 Clovis Fabricio
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -80,6 +80,9 @@
 Library
 -------
 
+- Issue #8498: In socket.accept(), allow to specify 0 as a backlog value in
+  order to accept exactly one connection.  Patch by Daniel Evers.
+
 - Issue #12012: ssl.PROTOCOL_SSLv2 becomes optional.
 
 - Issue #11164: Remove obsolete allnodes test from minidom test.
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -2244,8 +2244,10 @@
     if (backlog == -1 && PyErr_Occurred())
         return NULL;
     Py_BEGIN_ALLOW_THREADS
-    if (backlog < 1)
-        backlog = 1;
+    /* To avoid problems on systems that don't allow a negative backlog
+     * (which doesn't make sense anyway) we force a minimum value of 0. */
+    if (backlog < 0)
+        backlog = 0;
     res = listen(s->sock_fd, backlog);
     Py_END_ALLOW_THREADS
     if (res < 0)
@@ -2258,8 +2260,9 @@
 "listen(backlog)\n\
 \n\
 Enable a server to accept connections.  The backlog argument must be at\n\
-least 1; it specifies the number of unaccepted connection that the system\n\
-will allow before refusing new connections.");
+least 0 (if it is lower, it is set to 0); it specifies the number of\n\
+unaccepted connections that the system will allow before refusing new\n\
+connections.");
 
 
 #ifndef NO_DUP

-- 
Repository URL: http://hg.python.org/cpython