Re: [Bluez-devel] [PATCH] Fix bogus avdtp error codes management

[Fabien Chevalier <fchevalier@silicom.fr>]

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Johan Hedberg wrote:
> On Tue, Sep 18, 2007, Fabien Chevalier wrote:
>> As for the POLLOUT thing, i must say i'm confused..., and don't really 
>> see the link with the patch :-(
>> I guess it works already as the GIOChannels heavily rely on it.
> 
> GLib maps POLLOUT to G_IO_OUT, POLLHUP to G_IO_HUP, etc. I was saying
> that to conform to how other socket types behave[1] the callback should
> *not* be getting a HUP or ERR in this case but a OUT instead. As for
> applying the patch, I'm fine with it even though it in essence is a
> work-around for a kernel side problem. However, it's Marcel's call in
> the end.
> 
> [1] I have yet to verify this but that's what the connect(2) manpage
> implies (in the section about EINPROGRESS)

Ok, thanks, this time i understood. :-)
I wrote a test program that does an asynchronous connect using the IP 
stack. (I attached the file, you can dry run yourself if you're curious 
;-) ). On error we receive a revent with POLLERR value, and no POLLOUT.
Conclusion is:
   * POLLOUT is to be sent only when the channel is ready to send more data.
   * POLLERR is the right thing to send when we cannot establish the 
connection due to whatever error ==> The man page is a bit ambiguous 
about it.
   * which means the bt kernel part is fine and does not need fixing
   * which means my patch is not a workaround but a clean fix to this 
bogus error returning code :-)

Marcel, Johan, if you don't have any other remarks, you would mind 
applying the patch ?

Cheers,

Fabien

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#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <poll.h>
#include <errno.h>
#include <assert.h>
#include <fcntl.h>

int main()
{
    struct sockaddr_in addr;
    int err;
    struct pollfd pfds;

    int sock = socket(AF_INET, SOCK_STREAM, 0); 

    addr.sin_family = AF_INET;
    addr.sin_port = htons(81);
    addr.sin_addr.s_addr = inet_addr("209.85.135.104");

    fcntl(sock, F_SETFL, fcntl(sock, F_GETFL, 0) | O_NONBLOCK);

    err = connect(sock, (struct sockaddr *)&addr, sizeof(addr));
    
    assert(err == -1 && errno == EINPROGRESS);
    
    pfds.fd = sock;
    pfds.events = POLLOUT;
    
    err = poll(&pfds, 1, -1);
    assert(err == 1);
    
    printf("returned events from poll() routine:");
    if(pfds.revents & POLLOUT)
        printf("POLLOUT");
    if(pfds.revents & POLLERR)
        printf("POLLERR");

    printf("\n");    
}

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