Re: [ECOS] TCP close(...) action

[Matt Jerdonek <maj1224@yahoo.com>]

Gary,

I can't send the actual code, so I put together this
program.  I verified this program exhibits the same
behavior as I initially described.

In addition, I put some comments in the code regarding
the f_ucount.  This is a member of the cyg_file
structure which is associated with each socket.  Once
the f_ucount reaches 0, the FIN will be sent on the
ethernet.


#include <cyg/kernel/kapi.h>
#include <assert.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <network.h>
#include <cyg/posix/pthread.h>
#include <unistd.h>

#define STACK_SIZE 0x4000
unsigned char Stack[STACK_SIZE];
pthread_t ThreadHandle;
int sockfd;
void RecvThread(void);

int main(void)
{
	pthread_attr_t ThreadAttrib;
	
	init_all_network_interfaces();
	
	// Create thread to make TCP connection
	pthread_attr_init(&ThreadAttrib);
	pthread_attr_setstackaddr(&ThreadAttrib, 
                                  &Stack[STACK_SIZE]);
	pthread_attr_setstacksize(&ThreadAttrib,
                                   STACK_SIZE);
	pthread_create(&ThreadHandle, &ThreadAttrib,
                      (void *)RecvThread, 
                      (void *)NULL);
	
	// Give the thread plenty of time to connect
	sleep(15);
	
	// Workaround ... 
        //  ... call cyg_thread_release() here ...
        //  ... on the RecvThread
	
	// Close the socket
	printf("Closing socket\n");
	close(sockfd);
	
	// The close will decrement the f_ucount ... 
        // ... from 2 to 1, but the FIN will not ...
	// ... be sent until the recv is released. 
        // ... See function fp_ucount_dec( ) ...
	// ... in io/fileio/ver/src/fd.cxx
	
	sleep(10);
	return(0);
}

void RecvThread(void)
{
	// Create socket and connect to host
	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if (sockfd > 0)
	{
		struct sockaddr RmtHost;
		struct sockaddr_in *pRmtHost = 
                   (struct sockaddr_in *)&RmtHost;
		
		// At this point the cyg_file ..
                // ... structure that describes ... 
                // ... the sockfd ...
		// ... as a f_ucount = 1
			
		// Setup connect
		memset( &RmtHost, 0, 
                        sizeof(struct sockaddr) );
		pRmtHost->sin_len = 
                        sizeof( struct sockaddr_in );	
		pRmtHost->sin_family = AF_INET;
		pRmtHost->sin_port = htons(4096);
		pRmtHost->sin_addr.s_addr = 
                        htonl(0xc8640196);
			
		// Connected to the host
		if (connect(sockfd, &RmtHost, 
                      sizeof(struct sockaddr)) >= 0)
		{
			unsigned char RxBuffer[100];
			printf("Socket connected\n");
			
			// Will block indefinitely ...
                        // ... since no data will ...
                        // ... be received 
			recv(sockfd, &RxBuffer[0], 
                                          1, 0);
			
			// Inside the recv, ... 
                        // ... the f_ucount is now 2
			
			printf("Recv woke\n");
		}
	}	
}



--- Gary Thomas <gary@mlbassoc.com> wrote:
> On Sat, 2003-10-18 at 12:24, Matt Jerdonek wrote:
> > Hi Folks,
> > 
> > I have a simple program with two threads that send
> /
> > recv from a single TCP socket.  One thread blocks
> on a
> > recv call while the other thread sends data on the
> > same socket.
> > 
> > I put a close call in the send thread.  The
> expected
> > behavior was for the recv thread to wake (with 0
> bytes
> > of data) and a FIN to be sent on the ethernet. 
> The
> > actual behavior was that the recv thread never
> woke
> > and the FIN was not sent.  (Is this intended or a
> > bug?).  I found the soclose function would not be
> > invoked because the recv was still using the file
> > handle.  Once the recv released the file handle,
> the
> > FIN flowed on the ethernet.
> > 
> > I worked around this issue by calling
> > cyg_thread_release from my application, which woke
> up
> > the recv thread.  But I wonder if there is better
> > solution?  Could (or should) the close call be
> made to
> > wake up blocked threads?  If so, any suggestions?
> > 
> 
> How did you create this socket?  How did you set up
> the send and receive threads?  Maybe a code snippet
> would
> help us understand your problem.
> 
> -- 
> Gary Thomas <gary@mlbassoc.com>
> MLB Associates
> 
> 
> -- 
> Before posting, please read the FAQ:
> http://sources.redhat.com/fom/ecos
> and search the list archive:
> http://sources.redhat.com/ml/ecos-discuss
> 


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