Fix bogus avdtp error codes management

Hi Johan & Marcel,

While trying to fix this cross case issue, i came with an issue with the way error codes are handled in avdtp.c.
The issue is basically that the part of the code that retrieves the exact error value is never executed due to premature return.

Please have a look at the current patch.

Fabien

diff -u -1 -0 -r1.49 avdtp.c
@@ -1501,38 +1501,38 @@
        if (cond & G_IO_NVAL)
                return FALSE;
 
        if (!g_slist_find(sessions, session)) {
                debug("l2cap_connect_cb: session got removed");
                return FALSE;
        }
 
        sk = g_io_channel_unix_get_fd(chan);
 
-       if (cond & (G_IO_ERR | G_IO_HUP)) {
-               err = EIO;
-               goto failed;
-       }
-
        len = sizeof(ret);
        if (getsockopt(sk, SOL_SOCKET, SO_ERROR, &ret, &len) < 0) {
                err = errno;
                error("getsockopt(SO_ERROR): %s (%d)", strerror(err), err);
                goto failed;
        }
 
        if (ret != 0) {
                err = ret;
                error("connect(): %s (%d)", strerror(err), err);
                goto failed;
        }
 
+       if (cond & G_IO_HUP) {
+               err = EIO;
+               goto failed;
+       }
+
        ba2str(&session->dst, address);
        debug("AVDTP: connected %s channel to %s",
                        session->pending_open ? "transport" : "signaling",
                        address);
 
        memset(&l2o, 0, sizeof(l2o));
        len = sizeof(l2o);
        if (getsockopt(sk, SOL_L2CAP, L2CAP_OPTIONS, &l2o,
                                &len) < 0) {
                err = errno;

f

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Hi Fabien,

Looks fine to me if it works. However, I'd like to hear some comment from Marcel as well. At least my connect(2) manpage implies that a non-blocking connect should always produce a POLLOUT on connection completion regardless if the result was failure or success. So it seems bluez may be behaving differently than other socket types in this respect.

We had a similar issue with the EAGAIN/EINPROGRESS mixup with non-blocking connect's so maybe this issue should also be fixed on the kernel side (however a userspace work-around such as your patch is probably also desirable).

Johan

Hi Johan,

if that is so, then we have to fix the kernel. Can someone write me a simple reproducer or better send me a patch for the kernel.

Regards

Marcel

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Hi All,

The attached patch makes sure that the correct error code is returned to the upper layers.
The issue with the current cvs's code is that EIO would be returned whatever the error code returned by the L2CAP layer is, as getsockopt(sk, SOL_SOCKET, SO_ERROR, ....) would never be called. The result of this patch is that you now see the reason of the failure in daemon log in case of L2CAP issue, such as:

Sep 18 10:32:53 tannat audio[16934]: avdtp_ref(0x806d230): ref=2
Sep 18 10:32:53 tannat audio[16934]: a2dp_source_request_stream: selected SEP 0x806a400
Sep 18 10:32:53 tannat audio[16934]: avdtp_ref(0x806d230): ref=3
Sep 18 10:32:53 tannat audio[16934]: stream creation in progress
Sep 18 10:33:13 tannat audio[16934]: connect(): Host is down (112)

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.

Can any of you apply this patch ?

Cheers,

Fabien

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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)

Johan

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

#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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fn:Fabien CHEVALIER
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adr:;;4 rue de Jouanet; RENNES ATALANTE;;35700;FRANCE email;internet:[email protected] title:Software & Studies Engineer tel;work:+33 (0) 2 99 84 17 17
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