Bluetooth: Add different pairing timeout for Legacy Pairing

The Bluetooth stack uses a reference counting for all established ACL
links and if no user (L2CAP connection) is present, the link will be
terminated to save power. The problem part is the dedicated pairing
when using Legacy Pairing (Bluetooth 2.0 and before). At that point
no user is present and pairing attempts will be disconnected within
10 seconds or less. In previous kernel version this was not a problem
since the disconnect timeout wasn't triggered on incoming connections
for the first time. However this caused issues with broken host stacks
that kept the connections around after dedicated pairing. When the
support for Simple Pairing got added, the link establishment procedure
needed to be changed and now causes issues when using Legacy Pairing

When using Simple Pairing it is possible to do a proper reference
counting of ACL link users. With Legacy Pairing this is not possible
since the specification is unclear in some areas and too many broken
Bluetooth devices have already been deployed. So instead of trying to
deal with all the broken devices, a special pairing timeout will be
introduced that increases the timeout to 60 seconds when pairing is
triggered.

If a broken devices now puts the stack into an unforeseen state, the
worst that happens is the disconnect timeout triggers after 120 seconds
instead of 4 seconds. This allows successful pairings with legacy and
broken devices now.

Based on a report by Johan Hedberg <johan.hedberg@nokia.com>

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

2 files changed, 4 insertions, 2 deletions

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index f69f015bbcc0..ed3aea1605e8 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -101,6 +101,7 @@ enum {
 /* HCI timeouts */
 #define HCI_CONNECT_TIMEOUT     (40000) /* 40 seconds */
 #define HCI_DISCONN_TIMEOUT     (2000)  /* 2 seconds */
+#define HCI_PAIRING_TIMEOUT     (60000) /* 60 seconds */
 #define HCI_IDLE_TIMEOUT        (6000)  /* 6 seconds */
 #define HCI_INIT_TIMEOUT        (10000) /* 10 seconds */
 
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 1224bba24bdd..be5bd713d2c9 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -171,6 +171,7 @@ struct hci_conn {
         __u8             auth_type;
         __u8             sec_level;
         __u8             power_save;
+        __u16            disc_timeout;
         unsigned long    pend;
 
         unsigned int     sent;
@@ -349,9 +350,9 @@ static inline void hci_conn_put(struct hci_conn *conn)
                 if (conn->type == ACL_LINK) {
                         del_timer(&conn->idle_timer);
                         if (conn->state == BT_CONNECTED) {
-                                timeo = msecs_to_jiffies(HCI_DISCONN_TIMEOUT);
+                                timeo = msecs_to_jiffies(conn->disc_timeout);
                                 if (!conn->out)
-                                        timeo *= 5;
+                                        timeo *= 2;
                         } else
                                 timeo = msecs_to_jiffies(10);
                 } else