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Date: Thu, 06 Mar 2003 09:46:58 -0500
From: Jason Tishler <jason AT tishler DOT net>
Subject: Winsock closesocket() problem
To: Cygwin-Developers <cygwin-developers AT cygwin DOT com>
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Pierre and I have been working (privately) to solve the exim problem
that I mentioned in the following post:

    http://cygwin.com/ml/cygwin-developers/2003-02/msg00125.html

It appears that under certain conditions Winsock's closesocket() is not
happy closing a socket more than once.  See the attached test case,
sc9.cc, which demonstrates the problem when run under LocalSystem:

    $ sc9
    close(fd2) failed with 108

Note that the problem follows the second close().  If I switch the order
of the close() calls, then dup()-ed socket closes without any errors.
Hence, I don't believe that this problem is directly related to dup().

I have worked around the problem with the attached patch to
fhandler_socket::close().  Is this a reasonable way to solve this
problem?  Or, does anyone have any other suggestions?

BTW, this is YA problem that goes away under strace and gdb, which make
debugging this problem difficult.  Sigh...

Thanks,
Jason

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#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>

int
main()
{
	int status = 0;

	int fd = socket(AF_INET, SOCK_STREAM, 0);
	if (fd < 0)
	{
		printf("socket() failed with %d\n", errno);
		return 1;
	}

	status = setgid(1009); // mail group = 1009
	if (status < 0)
	{
		printf("setgid() failed with %d\n", errno);
		return 1;
	}

	status = setgroups(0, 0);
	if (status < 0)
	{
		printf("setgroups() failed with %d\n", errno);
		return 1;
	}

	status = setuid(1008); // exim user = 1008
	if (status < 0)
	{
		printf("setgid() failed with %d\n", errno);
		return 1;
	}

	int fd2 = dup(fd);
	if (fd2 < 0)
	{
		printf("dup() failed with %d\n", errno);
		return 1;
	}

	status = close(fd);
	if (status != 0)
	{
		printf("close(fd) failed with %d\n", errno);
		return 1;
	}

	status = close(fd2);
	if (status != 0)
	{
		printf("close(fd2) failed with %d\n", errno);
		return 1;
	}

	return 0;
}

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Index: fhandler_socket.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/fhandler_socket.cc,v
retrieving revision 1.85
diff -u -p -r1.85 fhandler_socket.cc
--- fhandler_socket.cc	4 Mar 2003 16:35:00 -0000	1.85
+++ fhandler_socket.cc	6 Mar 2003 14:17:49 -0000
@@ -1200,6 +1200,14 @@ fhandler_socket::close ()
 
   while ((res = closesocket (get_socket ())) != 0)
     {
+      // Ignore WSAENOTSOCK errors
+      if (WSAGetLastError () == WSAENOTSOCK)
+	{
+	  WSASetLastError (0);
+	  set_winsock_errno ();
+	  res = 0;
+	  break;
+	}
       if (WSAGetLastError () != WSAEWOULDBLOCK)
 	{
 	  set_winsock_errno ();

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