blocking sockets and select

This is a discussion on blocking sockets and select within the C Programming forums, part of the General Programming Boards category; Hi, I'm trying to fix a bug in tinyproxy 1.7.0 (old, dead project, http://tinyproxy.sourceforge.net/ ). I am trying to avoid ...

  1. #1
    Registered User
    Join Date
    Nov 2007
    Posts
    2

    blocking sockets and select

    Hi,

    I'm trying to fix a bug in tinyproxy 1.7.0 (old, dead project, http://tinyproxy.sourceforge.net/). I am trying to avoid an infinite blocking recv() call by using select first to test. I'm trying to do minimal changes to the code (so I don't want to make the socket non-blocking right from the get go). Hence this attempt at making an overloaded of sorts recv method.

    So where there would normally be:
    ret = recv(fd, buffer, SEGMENT_LEN, MSG_PEEK);

    I wish to use:
    ret = recv_timeout(fd, buffer, SEGMENT_LEN, MSG_PEEK);

    recv_timeout uses select to make sure the code won't hang on a recv, then goes and performs the recv as per normal. My attempt at doing this fails, select() always times out, it never returns even when there is data in the fd. What am I doing wrong with select?

    Code:
    ssize_t
    recv_timeout(int fd, void *buf, size_t len, int flags)
    {
    
    	ssize_t ret;
    
    	struct timeval tv;
    	fd_set rset;
    	
    	// init set
    	FD_ZERO(&rset);
    	// add to set
    	FD_SET(fd, &rset);
    
            // UNCOMMENT THIS AND PROXY WORKS
            // So safe to assume I'm passing correct arguments
    	//ret = recv(fd, buf, len, flags);
    	//return ret;
    
            // this is set to 60 seconds
    	tv.tv_sec =
    	    config.idletimeout;
    	tv.tv_usec = 0;	
    	
            // NEVER returns before the timeout value.
    	ret = select(fd, &rset, NULL, NULL, &tv);
    
    	if (ret == 0) {
    		log_message(LOG_INFO,
    				    "Idle Timeout (after select)");
    		return 0;
    	} else if (ret < 0) {
    		log_message(LOG_ERR,
    			    "recv_timeout: select() error \"&#37;s\". Closing connection (fd:%d)",
    			    strerror(errno), fd);
    		return;
    	} 
    
    	ret = recv(fd, buf, len, flags);
    	return ret;
    }
    Advice? I know that the correct arguments are passed through, as I can change this method to go straight to recv(bypass select) and the proxy works as per normal (and still hangs if the recv blocks).
    Last edited by ecornips; 11-11-2007 at 02:53 PM. Reason: comments in code added

  2. #2
    Registered User
    Join Date
    Nov 2007
    Posts
    2
    I have found my problem. FWIW:

    ret = select(fd, &rset, NULL, NULL, &tv);

    ->

    ret = select(fd+1, &rset, NULL, NULL, &tv);

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