[PATCH v1] Bluetooth: L2CAP: add support for waiting disconnection resp

From: Archie Pusaka
Date: Tue Apr 14 2020 - 04:09:42 EST


From: Archie Pusaka <apusaka@xxxxxxxxxxxx>

Whenever we disconnect a L2CAP connection, we would immediately
report a disconnection event (EPOLLHUP) to the upper layer, without
waiting for the response of the other device.

This patch offers an option to wait until we receive a disconnection
response before reporting disconnection event, by using the "how"
parameter in l2cap_sock_shutdown(). Therefore, upper layer can opt
to wait for disconnection response by shutdown(sock, SHUT_WR).

This can be used to enforce proper disconnection order in HID,
where the disconnection of the interrupt channel must be complete
before attempting to disconnect the control channel.

Signed-off-by: Archie Pusaka <apusaka@xxxxxxxxxxxx>
---

net/bluetooth/l2cap_sock.c | 30 +++++++++++++++++++++++-------
1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 1cea42ee1e922..a995d2c51fa7f 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1271,14 +1271,21 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
struct l2cap_conn *conn;
int err = 0;

- BT_DBG("sock %p, sk %p", sock, sk);
+ BT_DBG("sock %p, sk %p, how %d", sock, sk, how);
+
+ /* 'how' parameter is mapped to sk_shutdown as follows:
+ * SHUT_RD (0) --> RCV_SHUTDOWN (1)
+ * SHUT_WR (1) --> SEND_SHUTDOWN (2)
+ * SHUT_RDWR (2) --> SHUTDOWN_MASK (3)
+ */
+ how++;

if (!sk)
return 0;

lock_sock(sk);

- if (sk->sk_shutdown)
+ if ((sk->sk_shutdown & how) == how)
goto shutdown_already;

BT_DBG("Handling sock shutdown");
@@ -1301,11 +1308,20 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
* has already been actioned to close the L2CAP
* link such as by l2cap_disconnection_req().
*/
- if (sk->sk_shutdown)
- goto has_shutdown;
+ if ((sk->sk_shutdown & how) == how)
+ goto shutdown_matched;
}

- sk->sk_shutdown = SHUTDOWN_MASK;
+ /* Try setting the RCV_SHUTDOWN bit, return early if SEND_SHUTDOWN
+ * is already set
+ */
+ if ((how & RCV_SHUTDOWN) && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
+ sk->sk_shutdown |= RCV_SHUTDOWN;
+ if ((sk->sk_shutdown & how) == how)
+ goto shutdown_matched;
+ }
+
+ sk->sk_shutdown |= SEND_SHUTDOWN;
release_sock(sk);

l2cap_chan_lock(chan);
@@ -1335,7 +1351,7 @@ static int l2cap_sock_shutdown(struct socket *sock, int how)
err = bt_sock_wait_state(sk, BT_CLOSED,
sk->sk_lingertime);

-has_shutdown:
+shutdown_matched:
l2cap_chan_put(chan);
sock_put(sk);

@@ -1363,7 +1379,7 @@ static int l2cap_sock_release(struct socket *sock)

bt_sock_unlink(&l2cap_sk_list, sk);

- err = l2cap_sock_shutdown(sock, 2);
+ err = l2cap_sock_shutdown(sock, SHUT_RDWR);
chan = l2cap_pi(sk)->chan;

l2cap_chan_hold(chan);
--
2.26.0.110.g2183baf09c-goog