Hi Archie, On Mon, Apr 13, 2020 at 6:48 AM Archie Pusaka <apusaka@xxxxxxxxxx> wrote: > > Hi Marcel, Luiz, > > I found out that shutdown second parameter is passed as the "how" > parameter in l2cap_sock_shutdown() [1]. > Currently the value of the parameter is unused, but I think we can > assign it to sk->sk_shutdown. Therefore, we can differentiate whether > we are interested to wait for the disconnection reply or not, by > supplying SHUT_RDWR and SHUT_WR, respectively. > > Do you think this is a sound idea? > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/tree/net/bluetooth/l2cap_sock.c#n1267 That was what I meant on my reply, that way we can detect if the has been shutdown on both directions or not, so in case of SHUT_WR it shall on indicate POLL_HUP if the userspace is polling with POLL_OUT, thus POLL_IN would still wait for the disconnect to complete, I guess this is worth the shot since this does not introduce any new APIs, but we might want to introduce a test to l2cap-tester to cover this functionality. > Thanks, > Archie > > On Wed, 18 Mar 2020 at 20:41, Archie Pusaka <apusaka@xxxxxxxxxx> wrote: > > > > > > I see, we shutdown the socket immediately since the socket API itself > > > > don't seem to have a concept of disconnect syscall not sure if other > > > > values could be passed to shutdown second parameter to indicate we > > > > want to actually wait it to be disconnected. > > > > I don't think the second parameter matters, I tried every possible > > valid values and intr_watch_cb is still called without waiting for the > > response. > > > > > > > > in a blocking synchronous system call world we have SO_LINGER for that. In the world of asynchronous IO handling (what we do), we need to check what is the right way of handling this. > > > > > > > I spot this piece of code [1] which utilizes getsockopt to query > > socket connection information from the kernel space to the user space. > > We can use a similar method to query whether (sk->sk_state == > > BT_CLOSED), which is only true when we get the response. > > What do you think? > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git/tree/net/bluetooth/l2cap_sock.c#n476 -- Luiz Augusto von Dentz
