6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sebastian Urban surban@surban.net
[ Upstream commit ce60b9231b66710b6ee24042ded26efee120ecfc ]
Previously LE flow credits were returned to the sender even if the socket's receive buffer was full. This meant that no back-pressure was applied to the sender, thus it continued to send data, resulting in data loss without any error being reported. Furthermore, the amount of credits was essentially fixed to a small amount, leading to reduced performance.
This is fixed by computing the number of returned LE flow credits based on the estimated available space in the receive buffer of an L2CAP socket. Consequently, if the receive buffer is full, no credits are returned until the buffer is read and thus cleared by user-space.
Since the computation of available receive buffer space can only be performed approximately (due to sk_buff overhead) and the receive buffer size may be changed by user-space after flow credits have been sent, superfluous received data is temporary stored within l2cap_pinfo. This is necessary because Bluetooth LE provides no retransmission mechanism once the data has been acked by the physical layer.
If receive buffer space estimation is not possible at the moment, we fall back to providing credits for one full packet as before. This is currently the case during connection setup, when MPS is not yet available.
Fixes: b1c325c23d75 ("Bluetooth: Implement returning of LE L2CAP credits") Signed-off-by: Sebastian Urban surban@surban.net Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/bluetooth/l2cap.h | 11 ++++- net/bluetooth/l2cap_core.c | 56 ++++++++++++++++++--- net/bluetooth/l2cap_sock.c | 91 ++++++++++++++++++++++++++++------- 3 files changed, 132 insertions(+), 26 deletions(-)
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index 92d7197f9a563..d2a1154121d0d 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -548,6 +548,9 @@ struct l2cap_chan { __u16 tx_credits; __u16 rx_credits;
+ /* estimated available receive buffer space or -1 if unknown */ + ssize_t rx_avail; + __u8 tx_state; __u8 rx_state;
@@ -682,10 +685,15 @@ struct l2cap_user { /* ----- L2CAP socket info ----- */ #define l2cap_pi(sk) ((struct l2cap_pinfo *) sk)
+struct l2cap_rx_busy { + struct list_head list; + struct sk_buff *skb; +}; + struct l2cap_pinfo { struct bt_sock bt; struct l2cap_chan *chan; - struct sk_buff *rx_busy_skb; + struct list_head rx_busy; };
enum { @@ -943,6 +951,7 @@ int l2cap_chan_connect(struct l2cap_chan *chan, __le16 psm, u16 cid, int l2cap_chan_reconfigure(struct l2cap_chan *chan, __u16 mtu); int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len); void l2cap_chan_busy(struct l2cap_chan *chan, int busy); +void l2cap_chan_rx_avail(struct l2cap_chan *chan, ssize_t rx_avail); int l2cap_chan_check_security(struct l2cap_chan *chan, bool initiator); void l2cap_chan_set_defaults(struct l2cap_chan *chan); int l2cap_ertm_init(struct l2cap_chan *chan); diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index ab5d0204086fb..a754cf2c8ca8c 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -457,6 +457,9 @@ struct l2cap_chan *l2cap_chan_create(void) /* Set default lock nesting level */ atomic_set(&chan->nesting, L2CAP_NESTING_NORMAL);
+ /* Available receive buffer space is initially unknown */ + chan->rx_avail = -1; + write_lock(&chan_list_lock); list_add(&chan->global_l, &chan_list); write_unlock(&chan_list_lock); @@ -538,6 +541,28 @@ void l2cap_chan_set_defaults(struct l2cap_chan *chan) } EXPORT_SYMBOL_GPL(l2cap_chan_set_defaults);
+static __u16 l2cap_le_rx_credits(struct l2cap_chan *chan) +{ + size_t sdu_len = chan->sdu ? chan->sdu->len : 0; + + if (chan->mps == 0) + return 0; + + /* If we don't know the available space in the receiver buffer, give + * enough credits for a full packet. + */ + if (chan->rx_avail == -1) + return (chan->imtu / chan->mps) + 1; + + /* If we know how much space is available in the receive buffer, give + * out as many credits as would fill the buffer. + */ + if (chan->rx_avail <= sdu_len) + return 0; + + return DIV_ROUND_UP(chan->rx_avail - sdu_len, chan->mps); +} + static void l2cap_le_flowctl_init(struct l2cap_chan *chan, u16 tx_credits) { chan->sdu = NULL; @@ -546,8 +571,7 @@ static void l2cap_le_flowctl_init(struct l2cap_chan *chan, u16 tx_credits) chan->tx_credits = tx_credits; /* Derive MPS from connection MTU to stop HCI fragmentation */ chan->mps = min_t(u16, chan->imtu, chan->conn->mtu - L2CAP_HDR_SIZE); - /* Give enough credits for a full packet */ - chan->rx_credits = (chan->imtu / chan->mps) + 1; + chan->rx_credits = l2cap_le_rx_credits(chan);
skb_queue_head_init(&chan->tx_q); } @@ -559,7 +583,7 @@ static void l2cap_ecred_init(struct l2cap_chan *chan, u16 tx_credits) /* L2CAP implementations shall support a minimum MPS of 64 octets */ if (chan->mps < L2CAP_ECRED_MIN_MPS) { chan->mps = L2CAP_ECRED_MIN_MPS; - chan->rx_credits = (chan->imtu / chan->mps) + 1; + chan->rx_credits = l2cap_le_rx_credits(chan); } }
@@ -6513,9 +6537,7 @@ static void l2cap_chan_le_send_credits(struct l2cap_chan *chan) { struct l2cap_conn *conn = chan->conn; struct l2cap_le_credits pkt; - u16 return_credits; - - return_credits = (chan->imtu / chan->mps) + 1; + u16 return_credits = l2cap_le_rx_credits(chan);
if (chan->rx_credits >= return_credits) return; @@ -6534,6 +6556,19 @@ static void l2cap_chan_le_send_credits(struct l2cap_chan *chan) l2cap_send_cmd(conn, chan->ident, L2CAP_LE_CREDITS, sizeof(pkt), &pkt); }
+void l2cap_chan_rx_avail(struct l2cap_chan *chan, ssize_t rx_avail) +{ + if (chan->rx_avail == rx_avail) + return; + + BT_DBG("chan %p has %zd bytes avail for rx", chan, rx_avail); + + chan->rx_avail = rx_avail; + + if (chan->state == BT_CONNECTED) + l2cap_chan_le_send_credits(chan); +} + static int l2cap_ecred_recv(struct l2cap_chan *chan, struct sk_buff *skb) { int err; @@ -6543,6 +6578,12 @@ static int l2cap_ecred_recv(struct l2cap_chan *chan, struct sk_buff *skb) /* Wait recv to confirm reception before updating the credits */ err = chan->ops->recv(chan, skb);
+ if (err < 0 && chan->rx_avail != -1) { + BT_ERR("Queueing received LE L2CAP data failed"); + l2cap_send_disconn_req(chan, ECONNRESET); + return err; + } + /* Update credits whenever an SDU is received */ l2cap_chan_le_send_credits(chan);
@@ -6565,7 +6606,8 @@ static int l2cap_ecred_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb) }
chan->rx_credits--; - BT_DBG("rx_credits %u -> %u", chan->rx_credits + 1, chan->rx_credits); + BT_DBG("chan %p: rx_credits %u -> %u", + chan, chan->rx_credits + 1, chan->rx_credits);
/* Update if remote had run out of credits, this should only happens * if the remote is not using the entire MPS. diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index d647bd15d5009..97d0a0f5829a6 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1142,6 +1142,34 @@ static int l2cap_sock_sendmsg(struct socket *sock, struct msghdr *msg, return err; }
+static void l2cap_publish_rx_avail(struct l2cap_chan *chan) +{ + struct sock *sk = chan->data; + ssize_t avail = sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc); + int expected_skbs, skb_overhead; + + if (avail <= 0) { + l2cap_chan_rx_avail(chan, 0); + return; + } + + if (!chan->mps) { + l2cap_chan_rx_avail(chan, -1); + return; + } + + /* Correct available memory by estimated sk_buff overhead. + * This is significant due to small transfer sizes. However, accept + * at least one full packet if receive space is non-zero. + */ + expected_skbs = DIV_ROUND_UP(avail, chan->mps); + skb_overhead = expected_skbs * sizeof(struct sk_buff); + if (skb_overhead < avail) + l2cap_chan_rx_avail(chan, avail - skb_overhead); + else + l2cap_chan_rx_avail(chan, -1); +} + static int l2cap_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, int flags) { @@ -1178,28 +1206,33 @@ static int l2cap_sock_recvmsg(struct socket *sock, struct msghdr *msg, else err = bt_sock_recvmsg(sock, msg, len, flags);
- if (pi->chan->mode != L2CAP_MODE_ERTM) + if (pi->chan->mode != L2CAP_MODE_ERTM && + pi->chan->mode != L2CAP_MODE_LE_FLOWCTL && + pi->chan->mode != L2CAP_MODE_EXT_FLOWCTL) return err;
- /* Attempt to put pending rx data in the socket buffer */ - lock_sock(sk);
- if (!test_bit(CONN_LOCAL_BUSY, &pi->chan->conn_state)) - goto done; + l2cap_publish_rx_avail(pi->chan);
- if (pi->rx_busy_skb) { - if (!__sock_queue_rcv_skb(sk, pi->rx_busy_skb)) - pi->rx_busy_skb = NULL; - else + /* Attempt to put pending rx data in the socket buffer */ + while (!list_empty(&pi->rx_busy)) { + struct l2cap_rx_busy *rx_busy = + list_first_entry(&pi->rx_busy, + struct l2cap_rx_busy, + list); + if (__sock_queue_rcv_skb(sk, rx_busy->skb) < 0) goto done; + list_del(&rx_busy->list); + kfree(rx_busy); }
/* Restore data flow when half of the receive buffer is * available. This avoids resending large numbers of * frames. */ - if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf >> 1) + if (test_bit(CONN_LOCAL_BUSY, &pi->chan->conn_state) && + atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf >> 1) l2cap_chan_busy(pi->chan, 0);
done: @@ -1460,17 +1493,20 @@ static struct l2cap_chan *l2cap_sock_new_connection_cb(struct l2cap_chan *chan) static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb) { struct sock *sk = chan->data; + struct l2cap_pinfo *pi = l2cap_pi(sk); int err;
lock_sock(sk);
- if (l2cap_pi(sk)->rx_busy_skb) { + if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) { err = -ENOMEM; goto done; }
if (chan->mode != L2CAP_MODE_ERTM && - chan->mode != L2CAP_MODE_STREAMING) { + chan->mode != L2CAP_MODE_STREAMING && + chan->mode != L2CAP_MODE_LE_FLOWCTL && + chan->mode != L2CAP_MODE_EXT_FLOWCTL) { /* Even if no filter is attached, we could potentially * get errors from security modules, etc. */ @@ -1481,7 +1517,9 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
err = __sock_queue_rcv_skb(sk, skb);
- /* For ERTM, handle one skb that doesn't fit into the recv + l2cap_publish_rx_avail(chan); + + /* For ERTM and LE, handle a skb that doesn't fit into the recv * buffer. This is important to do because the data frames * have already been acked, so the skb cannot be discarded. * @@ -1490,8 +1528,18 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb) * acked and reassembled until there is buffer space * available. */ - if (err < 0 && chan->mode == L2CAP_MODE_ERTM) { - l2cap_pi(sk)->rx_busy_skb = skb; + if (err < 0 && + (chan->mode == L2CAP_MODE_ERTM || + chan->mode == L2CAP_MODE_LE_FLOWCTL || + chan->mode == L2CAP_MODE_EXT_FLOWCTL)) { + struct l2cap_rx_busy *rx_busy = + kmalloc(sizeof(*rx_busy), GFP_KERNEL); + if (!rx_busy) { + err = -ENOMEM; + goto done; + } + rx_busy->skb = skb; + list_add_tail(&rx_busy->list, &pi->rx_busy); l2cap_chan_busy(chan, 1); err = 0; } @@ -1717,6 +1765,8 @@ static const struct l2cap_ops l2cap_chan_ops = {
static void l2cap_sock_destruct(struct sock *sk) { + struct l2cap_rx_busy *rx_busy, *next; + BT_DBG("sk %p", sk);
if (l2cap_pi(sk)->chan) { @@ -1724,9 +1774,10 @@ static void l2cap_sock_destruct(struct sock *sk) l2cap_chan_put(l2cap_pi(sk)->chan); }
- if (l2cap_pi(sk)->rx_busy_skb) { - kfree_skb(l2cap_pi(sk)->rx_busy_skb); - l2cap_pi(sk)->rx_busy_skb = NULL; + list_for_each_entry_safe(rx_busy, next, &l2cap_pi(sk)->rx_busy, list) { + kfree_skb(rx_busy->skb); + list_del(&rx_busy->list); + kfree(rx_busy); }
skb_queue_purge(&sk->sk_receive_queue); @@ -1810,6 +1861,8 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent)
chan->data = sk; chan->ops = &l2cap_chan_ops; + + l2cap_publish_rx_avail(chan); }
static struct proto l2cap_proto = { @@ -1831,6 +1884,8 @@ static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock, sk->sk_destruct = l2cap_sock_destruct; sk->sk_sndtimeo = L2CAP_CONN_TIMEOUT;
+ INIT_LIST_HEAD(&l2cap_pi(sk)->rx_busy); + chan = l2cap_chan_create(); if (!chan) { sk_free(sk);