The Enhanced Retransmission Mode(ERTM) is a realiable mode of operation
of the Bluetooth L2CAP layer. Think on it like a simplified version of
TCP.
The problem we were facing here was a deadlock. ERTM uses a backlog
queue to queue incomimg packets while the user is helding the lock. At
some moment the sk_sndbuf can be exceeded and we can't alloc new skbs
then the code sleep with the lock to wait for memory, that stalls the
ERTM connection once we can't read the acknowledgements packets in the
backlog queue to free memory and make the allocation of outcoming skb
successful.
This patch actually affect all users of bt_skb_send_alloc(), i.e., all
L2CAP modes and SCO.
We are safe against socket states changes or channels deletion while the
we are sleeping wait memory. Checking for the sk->sk_err and
sk->sk_shutdown make the code safe, since any action that can leave the
socket or the channel in a not usable state set one of the struct
members at least. Then we can check both of them when getting the lock
again and return with the proper error if something unexpected happens.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Ulisses Furquim <ulisses@profusion.mobi>
The previous value of 672 for L2CAP_DEFAULT_MAX_PDU_SIZE is based on
the default L2CAP MTU. That default MTU is calculated from the size
of two DH5 packets, minus ACL and L2CAP b-frame header overhead.
ERTM is used with newer basebands that typically support larger 3-DH5
packets, and i-frames and s-frames have more header overhead. With
clean RF conditions, basebands will typically attempt to use 1021-byte
3-DH5 packets for maximum throughput. Adjusting for 2 bytes of ACL
headers plus 10 bytes of worst-case L2CAP headers yields 1009 bytes
of payload.
This PDU size imposes less overhead for header bytes and gives the
baseband the option to choose 3-DH5 packets, but is small enough for
ERTM traffic to interleave well with other L2CAP or SCO data.
672-byte payloads do not allow the most efficient over-the-air
packet choice, and cannot achieve maximum throughput over BR/EDR.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
The L2CAP specification requires that the ERTM retransmit timeout be at
least 2 seconds for BR/EDR connections.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
To make net/ and include/net/ code consistent use __packed instead of
__attribute__ ((packed)). Bluetooth subsystem was one of the last net
subsys still using __attribute__ ((packed)).
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Implements feature to reassemble received HCI frames from any input stream
Signed-off-by: Suraj Sumangala <suraj@atheros.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Copyright for the time I worked on L2CAP during the Google Summer of Code
program.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Using a lock to deal with the ERTM race condition - interruption with
new data from the hci layer - is wrong. We should use the native skb
backlog queue.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
When mode is mandatory we shall not send connect request and report this
to the userspace as well.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Qualcomm, Inc. has reassigned rights to Code Aurora Forum. Accordingly,
as files are modified by Code Aurora Forum members, the copyright
statement will be updated.
Signed-off-by: Ron Shaffer <rshaffer@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
In some circumstances it could be desirable to reject incoming
connections on the baseband level. This patch adds this feature through
two new ioctl's: HCIBLOCKADDR and HCIUNBLOCKADDR. Both take a simple
Bluetooth address as a parameter. BDADDR_ANY can be used with
HCIUNBLOCKADDR to remove all devices from the blacklist.
Signed-off-by: Johan Hedberg <johan.hedberg@nokia.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Instead of having a global workqueue for all controllers, it makes
more sense to have a workqueue per controller.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
l2cap_ertm_send() can be called both from user context and bottom half
context. The socket locks for that contexts are different, the user
context uses a mutex(which can sleep) and the second one uses a
spinlock_bh. That creates a race condition when we have interruptions on
both contexts at the same time.
The better way to solve this is to add a new spinlock to lock
l2cap_ertm_send() and the vars it access. The other solution was to defer
l2cap_ertm_send() with a workqueue, but we the sending process already
has one defer on the hci layer. It's not a good idea add another one.
The patch refactor the code to create l2cap_retransmit_frames(), then we
encapulate the lock of l2cap_ertm_send() for some call. It also changes
l2cap_retransmit_frame() to l2cap_retransmit_one_frame() to avoid
confusion
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Supports Local Busy condition handling through a waitqueue that wake ups
each 200ms and try to push the packets to the upper layer. If it can
push all the queue then it leaves the Local Busy state.
The patch modifies the behaviour of l2cap_ertm_reassembly_sdu() to
support retry of the push operation.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
hci_send_acl can't fail, so we can make it void. This patch changes
that and all the funcions that use hci_send_acl().
That change exposed a bug on sending connectionless data. We were not
reporting the lenght send back to the user space.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Now that we can set the txWindow we need to change the acknowledgement
procedure to ack after each (pi->txWindow/6 + 1). The plus 1 is to avoid
the zero value.
It also renames pi->num_to_ack to a better name: pi->num_acked.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
We were accepting values bigger than we can accept. This was leading
ERTM to drop packets because of wrong FCS checks.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
We ack I-frames on each txWindow/5 I-frames received, but if the sender
stop to send I-frames and it's not a txWindow multiple we can leave some
frames unacked.
So I added a timer to ack I-frames on this case. The timer expires in
200ms.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
