Ticket History #408: Using non-blocking I/O on Windows, Win95, NT

From b17783@achilles.ctd.anl.gov Mon Mar 31 15:09:56 1997
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Date: Mon, 31 Mar 1997 14:07:53 -0600
From: deengert@anl.gov
Reply-To: deengert@anl.gov
To: krb5-bugs@MIT.EDU
Cc: deengert@anl.gov
Subject: Using non-blocking I/O on Windows, Win95, NT
X-Send-Pr-Version: 3.99


Douglas E. Engert <DEEngert@anl.gov>
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439
(630) 252-5444

Windows, Windows, Windows NT
System: AIX pembroke 1 4 000300234600


net_read.c and net_write.c both expect to use blocking I/O,
and will fail if a socket is set to non-blocking. The comments
in the code "/* XXX must not use non-blocking I/O */" indicate
that this is something which should be fixed.

This it very important when using Kerberos in a Windows
environment, where an application may pass on open socket
which is set to non-blocking to a Krb5 routine, such as
sendauth.




The attached fix was designed and tested using Windows 95,
(32-bit) were the read would fail without the change. The fix to
net_write.c was added for completness, but I did not see a
failure, since the test case did not overrun the output buffer.
This could could be reworked to work in a UNIX environment
as well.

*** net_read.c.orig Mon Mar 31 13:34:09 1997
--- net_read.c.dee Mon Mar 31 13:42:09 1997
***************
*** 51,56 ****
--- 51,71 ----
if (SOCKET_ERRNO == SOCKET_EINTR)
continue;
#if defined(_MSDOS) || (_WIN32)
+ /* check for non-blocking, and take action
+ * this includes doing a select and let the
+ * calling aplication's blocking hook routines
+ * or the winsock blocking hook routine
+ * dispatch other messages - DEE
+ */
+ if (SOCKET_ERRNO == WSAEWOULDBLOCK) {
+ fd_set fdset;
+
+ FD_ZERO(&fdset);
+ FD_SET(fd, &fdset);
+ cc = select(0, &fdset, NULL, NULL, NULL);
+ if (cc != SOCKET_ERROR)
+ continue;
+ }
/* XXX this interface sucks! */
errno = SOCKET_ERRNO;
#endif

*** net_write.c.orig Mon Mar 31 13:34:24 1997
--- net_write.c.dee Mon Mar 31 13:42:22 1997
***************
*** 50,55 ****
--- 50,71 ----
if (SOCKET_ERRNO == SOCKET_EINTR)
continue;
#if defined(_MSDOS) || (_WIN32)
+ /* check for non-blocking, and take action
+ * this includes doing a select and let the
+ * calling aplication's blocking hook routines
+ * or the winsock blocking hook routine
+ * dispatch other messages - DEE
+ */
+ if (SOCKET_ERRNO == WSAEWOULDBLOCK) {
+ fd_set fdset;
+
+ FD_ZERO(&fdset);
+ FD_SET(fd, &fdset);
+ cc = select(0, NULL, &fdset, NULL, NULL);
+ if (cc != SOCKET_ERROR)
+ continue;
+ }
+
/* XXX this interface sucks! */
errno = SOCKET_ERRNO;


K5-1.0 is unable to use non-blocking I/O