| Message ID | 20240408125806.12682-1-surban@surban.net |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v5] Bluetooth: compute LE flow credits based on recvbuf space | expand |
Hi Sebastian, On Mon, Apr 8, 2024 at 9:13 AM Sebastian Urban <surban@surban.net> wrote: > > 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 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, i.e. sk_buff overhead is ignored, > 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. > > Signed-off-by: Sebastian Urban <surban@surban.net> > --- > include/net/bluetooth/l2cap.h | 10 +++++- > net/bluetooth/l2cap_core.c | 51 ++++++++++++++++++++++---- > net/bluetooth/l2cap_sock.c | 67 +++++++++++++++++++++++++---------- > 3 files changed, 103 insertions(+), 25 deletions(-) > > diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h > index 3f4057ced971..bc6ff40ebc9f 100644 > --- a/include/net/bluetooth/l2cap.h > +++ b/include/net/bluetooth/l2cap.h > @@ -547,6 +547,8 @@ struct l2cap_chan { > > __u16 tx_credits; > __u16 rx_credits; > + int rx_avail; > + int rx_staged; I'd probably use size_t for these above, and put some comments of what they refer to e.g. rx_staged is what has been received already, right? Couldn't we use chan->sdu->len instead? > > __u8 tx_state; > __u8 rx_state; > @@ -682,10 +684,15 @@ 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 { > @@ -944,6 +951,7 @@ int l2cap_chan_reconfigure(struct l2cap_chan *chan, __u16 mtu); > int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len, > const struct sockcm_cookie *sockc); > void l2cap_chan_busy(struct l2cap_chan *chan, int busy); > +void l2cap_chan_rx_avail(struct l2cap_chan *chan, int 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 b0970462a689..7bad232d40ba 100644 > --- a/net/bluetooth/l2cap_core.c > +++ b/net/bluetooth/l2cap_core.c > @@ -454,6 +454,9 @@ 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); > @@ -535,6 +538,26 @@ 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) > +{ > + 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 <= chan->rx_staged) > + return 0; Missing space. > + return min_t(int, U16_MAX, > + (chan->rx_avail - chan->rx_staged) / chan->mps); We probably need to use DIV_ROUND_UP since the division can return 0 or is that intentional since that means we cannot store another full mps? I think I'd give it a credit since this may impact the throughput if we are not given credits when just a few bytes would be necessary and in any case we would store the extra bytes in the rx_busy list if that is over the rx_avail. > +} > + > static void l2cap_le_flowctl_init(struct l2cap_chan *chan, u16 tx_credits) > { > chan->sdu = NULL; > @@ -543,8 +566,7 @@ 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); > } > @@ -556,7 +578,7 @@ 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); > } > } > > @@ -6520,9 +6542,7 @@ 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; > @@ -6541,6 +6561,16 @@ 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, int rx_avail) > +{ > + BT_DBG("chan %p has %d bytes avail for rx", chan, rx_avail); We should probably check if the value has changed though, or this shall only be called when the buffer changes? > + 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; > @@ -6550,6 +6580,14 @@ 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); > > + chan->rx_staged = 0; > + > + 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); > > @@ -6571,6 +6609,7 @@ static int l2cap_ecred_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb) > return -ENOBUFS; > } > > + chan->rx_staged += skb->len; > chan->rx_credits--; > BT_DBG("rx_credits %u -> %u", chan->rx_credits + 1, chan->rx_credits); > > diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c > index 7846a068bf60..46603605cb69 100644 > --- a/net/bluetooth/l2cap_sock.c > +++ b/net/bluetooth/l2cap_sock.c > @@ -1157,6 +1157,7 @@ static int l2cap_sock_recvmsg(struct socket *sock, struct msghdr *msg, > { > struct sock *sk = sock->sk; > struct l2cap_pinfo *pi = l2cap_pi(sk); > + int avail; > int err; > > if (unlikely(flags & MSG_ERRQUEUE)) > @@ -1192,28 +1193,34 @@ 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; > + avail = max(0, sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)); > + l2cap_chan_rx_avail(pi->chan, avail); > > - 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: > @@ -1474,17 +1481,21 @@ 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 avail; > 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. > */ > @@ -1495,7 +1506,10 @@ 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 > + avail = max(0, sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)); > + l2cap_chan_rx_avail(chan, avail); > + > + /* 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. > * > @@ -1504,8 +1518,18 @@ 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; > } > @@ -1731,6 +1755,8 @@ 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) { > @@ -1738,9 +1764,10 @@ 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); > @@ -1845,6 +1872,8 @@ 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); > @@ -1853,6 +1882,8 @@ static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock, > > l2cap_chan_hold(chan); > > + l2cap_chan_rx_avail(chan, sk->sk_rcvbuf); > + > l2cap_pi(sk)->chan = chan; > > return sk; > -- > 2.34.1 >
Hi Sebastian, On Mon, Apr 8, 2024 at 10:05 AM <bluez.test.bot@gmail.com> wrote: > > This is automated email and please do not reply to this email! > > Dear submitter, > > Thank you for submitting the patches to the linux bluetooth mailing list. > This is a CI test results with your patch series: > PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=842452 > > ---Test result--- > > Test Summary: > CheckPatch PASS 1.01 seconds > GitLint PASS 0.22 seconds > SubjectPrefix PASS 0.07 seconds > BuildKernel PASS 30.65 seconds > CheckAllWarning PASS 34.59 seconds > CheckSparse PASS 39.10 seconds > CheckSmatch FAIL 35.16 seconds > BuildKernel32 PASS 29.28 seconds > TestRunnerSetup PASS 528.76 seconds > TestRunner_l2cap-tester FAIL 22.63 seconds > TestRunner_iso-tester PASS 30.74 seconds > TestRunner_bnep-tester PASS 4.67 seconds > TestRunner_mgmt-tester FAIL 110.12 seconds > TestRunner_rfcomm-tester PASS 7.26 seconds > TestRunner_sco-tester PASS 14.97 seconds > TestRunner_ioctl-tester PASS 7.62 seconds > TestRunner_mesh-tester PASS 5.77 seconds > TestRunner_smp-tester PASS 6.78 seconds > TestRunner_userchan-tester PASS 4.93 seconds > IncrementalBuild PASS 28.60 seconds > > Details > ############################## > Test: CheckSmatch - FAIL > Desc: Run smatch tool with source > Output: > > Segmentation fault (core dumped) > make[4]: *** [scripts/Makefile.build:244: net/bluetooth/hci_core.o] Error 139 > make[4]: *** Deleting file 'net/bluetooth/hci_core.o' > make[3]: *** [scripts/Makefile.build:485: net/bluetooth] Error 2 > make[2]: *** [scripts/Makefile.build:485: net] Error 2 > make[2]: *** Waiting for unfinished jobs.... > Segmentation fault (core dumped) > make[4]: *** [scripts/Makefile.build:244: drivers/bluetooth/bcm203x.o] Error 139 > make[4]: *** Deleting file 'drivers/bluetooth/bcm203x.o' > make[4]: *** Waiting for unfinished jobs.... > make[3]: *** [scripts/Makefile.build:485: drivers/bluetooth] Error 2 > make[2]: *** [scripts/Makefile.build:485: drivers] Error 2 > make[1]: *** [/github/workspace/src/src/Makefile:1919: .] Error 2 > make: *** [Makefile:240: __sub-make] Error 2 > ############################## > Test: TestRunner_l2cap-tester - FAIL > Desc: Run l2cap-tester with test-runner > Output: > Total: 55, Passed: 51 (92.7%), Failed: 4, Not Run: 0 > > Failed Test Cases > L2CAP LE Server - Success Failed 0.099 seconds > L2CAP Ext-Flowctl Server - Success Failed 0.103 seconds > L2CAP LE EATT Server - Success Failed 0.103 seconds > L2CAP LE EATT Server - Reject Failed 0.091 seconds We need to fix these tests as soon as we apply these changes, afaik you said they are expected to change because the credit changes, so we need to update it with the new credit logic. Also it would be great to add a test case that covers the broken behavior where we dropped packets. > ############################## > Test: TestRunner_mgmt-tester - FAIL > Desc: Run mgmt-tester with test-runner > Output: > Total: 492, Passed: 489 (99.4%), Failed: 1, Not Run: 2 > > Failed Test Cases > LL Privacy - Add Device 7 (AL is full) Failed 0.195 seconds > > > --- > Regards, > Linux Bluetooth >
Hi Sebastian, On Wed, Apr 10, 2024 at 10:40 AM Luiz Augusto von Dentz <luiz.dentz@gmail.com> wrote: > > Hi Sebastian, > > On Mon, Apr 8, 2024 at 10:05 AM <bluez.test.bot@gmail.com> wrote: > > > > This is automated email and please do not reply to this email! > > > > Dear submitter, > > > > Thank you for submitting the patches to the linux bluetooth mailing list. > > This is a CI test results with your patch series: > > PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=842452 > > > > ---Test result--- > > > > Test Summary: > > CheckPatch PASS 1.01 seconds > > GitLint PASS 0.22 seconds > > SubjectPrefix PASS 0.07 seconds > > BuildKernel PASS 30.65 seconds > > CheckAllWarning PASS 34.59 seconds > > CheckSparse PASS 39.10 seconds > > CheckSmatch FAIL 35.16 seconds > > BuildKernel32 PASS 29.28 seconds > > TestRunnerSetup PASS 528.76 seconds > > TestRunner_l2cap-tester FAIL 22.63 seconds > > TestRunner_iso-tester PASS 30.74 seconds > > TestRunner_bnep-tester PASS 4.67 seconds > > TestRunner_mgmt-tester FAIL 110.12 seconds > > TestRunner_rfcomm-tester PASS 7.26 seconds > > TestRunner_sco-tester PASS 14.97 seconds > > TestRunner_ioctl-tester PASS 7.62 seconds > > TestRunner_mesh-tester PASS 5.77 seconds > > TestRunner_smp-tester PASS 6.78 seconds > > TestRunner_userchan-tester PASS 4.93 seconds > > IncrementalBuild PASS 28.60 seconds > > > > Details > > ############################## > > Test: CheckSmatch - FAIL > > Desc: Run smatch tool with source > > Output: > > > > Segmentation fault (core dumped) > > make[4]: *** [scripts/Makefile.build:244: net/bluetooth/hci_core.o] Error 139 > > make[4]: *** Deleting file 'net/bluetooth/hci_core.o' > > make[3]: *** [scripts/Makefile.build:485: net/bluetooth] Error 2 > > make[2]: *** [scripts/Makefile.build:485: net] Error 2 > > make[2]: *** Waiting for unfinished jobs.... > > Segmentation fault (core dumped) > > make[4]: *** [scripts/Makefile.build:244: drivers/bluetooth/bcm203x.o] Error 139 > > make[4]: *** Deleting file 'drivers/bluetooth/bcm203x.o' > > make[4]: *** Waiting for unfinished jobs.... > > make[3]: *** [scripts/Makefile.build:485: drivers/bluetooth] Error 2 > > make[2]: *** [scripts/Makefile.build:485: drivers] Error 2 > > make[1]: *** [/github/workspace/src/src/Makefile:1919: .] Error 2 > > make: *** [Makefile:240: __sub-make] Error 2 > > ############################## > > Test: TestRunner_l2cap-tester - FAIL > > Desc: Run l2cap-tester with test-runner > > Output: > > Total: 55, Passed: 51 (92.7%), Failed: 4, Not Run: 0 > > > > Failed Test Cases > > L2CAP LE Server - Success Failed 0.099 seconds > > L2CAP Ext-Flowctl Server - Success Failed 0.103 seconds > > L2CAP LE EATT Server - Success Failed 0.103 seconds > > L2CAP LE EATT Server - Reject Failed 0.091 seconds > > We need to fix these tests as soon as we apply these changes, afaik > you said they are expected to change because the credit changes, so we > need to update it with the new credit logic. Also it would be great to > add a test case that covers the broken behavior where we dropped > packets. Do you need some more feedback regarding these changes? Looks like you stop responding for some time, I do think this is very important to have it fixed. > > ############################## > > Test: TestRunner_mgmt-tester - FAIL > > Desc: Run mgmt-tester with test-runner > > Output: > > Total: 492, Passed: 489 (99.4%), Failed: 1, Not Run: 2 > > > > Failed Test Cases > > LL Privacy - Add Device 7 (AL is full) Failed 0.195 seconds > > > > > > --- > > Regards, > > Linux Bluetooth > > > > > -- > Luiz Augusto von Dentz
Hi Luiz, thanks for the review! On 4/10/24 16:38, Luiz Augusto von Dentz wrote: >> --- >> include/net/bluetooth/l2cap.h | 10 +++++- >> net/bluetooth/l2cap_core.c | 51 ++++++++++++++++++++++---- >> net/bluetooth/l2cap_sock.c | 67 +++++++++++++++++++++++++---------- >> 3 files changed, 103 insertions(+), 25 deletions(-) >> >> diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h >> index 3f4057ced971..bc6ff40ebc9f 100644 >> --- a/include/net/bluetooth/l2cap.h >> +++ b/include/net/bluetooth/l2cap.h >> @@ -547,6 +547,8 @@ struct l2cap_chan { >> >> __u16 tx_credits; >> __u16 rx_credits; >> + int rx_avail; >> + int rx_staged; > > I'd probably use size_t for these above, and put some comments of what > they refer to e.g. rx_staged is what has been received already, right? > Couldn't we use chan->sdu->len instead? Changed and replaced by chan->sdu->len. >> @@ -535,6 +538,26 @@ 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) >> +{ >> + 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 <= chan->rx_staged) >> + return 0; > > Missing space. Done. > >> + return min_t(int, U16_MAX, >> + (chan->rx_avail - chan->rx_staged) / chan->mps); > > We probably need to use DIV_ROUND_UP since the division can return 0 > or is that intentional since that means we cannot store another full > mps? I think I'd give it a credit since this may impact the throughput > if we are not given credits when just a few bytes would be necessary > and in any case we would store the extra bytes in the rx_busy list if > that is over the rx_avail. I agree. Changed. >> @@ -6541,6 +6561,16 @@ 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, int rx_avail) >> +{ >> + BT_DBG("chan %p has %d bytes avail for rx", chan, rx_avail); > > We should probably check if the value has changed though, or this > shall only be called when the buffer changes? Function returns now immediately if rx_avail is unchanged. Additionally I improved the available receive space estimation by taking the overhead of struct sk_buff into account. I will submit a new version of the patch soon.
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index 3f4057ced971..bc6ff40ebc9f 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -547,6 +547,8 @@ struct l2cap_chan { __u16 tx_credits; __u16 rx_credits; + int rx_avail; + int rx_staged; __u8 tx_state; __u8 rx_state; @@ -682,10 +684,15 @@ 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 { @@ -944,6 +951,7 @@ int l2cap_chan_reconfigure(struct l2cap_chan *chan, __u16 mtu); int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len, const struct sockcm_cookie *sockc); void l2cap_chan_busy(struct l2cap_chan *chan, int busy); +void l2cap_chan_rx_avail(struct l2cap_chan *chan, int 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 b0970462a689..7bad232d40ba 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -454,6 +454,9 @@ 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); @@ -535,6 +538,26 @@ 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) +{ + 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 <= chan->rx_staged) + return 0; + return min_t(int, U16_MAX, + (chan->rx_avail - chan->rx_staged) / chan->mps); +} + static void l2cap_le_flowctl_init(struct l2cap_chan *chan, u16 tx_credits) { chan->sdu = NULL; @@ -543,8 +566,7 @@ 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); } @@ -556,7 +578,7 @@ 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); } } @@ -6520,9 +6542,7 @@ 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; @@ -6541,6 +6561,16 @@ 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, int rx_avail) +{ + BT_DBG("chan %p has %d 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; @@ -6550,6 +6580,14 @@ 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); + chan->rx_staged = 0; + + 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); @@ -6571,6 +6609,7 @@ static int l2cap_ecred_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb) return -ENOBUFS; } + chan->rx_staged += skb->len; chan->rx_credits--; BT_DBG("rx_credits %u -> %u", chan->rx_credits + 1, chan->rx_credits); diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index 7846a068bf60..46603605cb69 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1157,6 +1157,7 @@ static int l2cap_sock_recvmsg(struct socket *sock, struct msghdr *msg, { struct sock *sk = sock->sk; struct l2cap_pinfo *pi = l2cap_pi(sk); + int avail; int err; if (unlikely(flags & MSG_ERRQUEUE)) @@ -1192,28 +1193,34 @@ 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; + avail = max(0, sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)); + l2cap_chan_rx_avail(pi->chan, avail); - 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: @@ -1474,17 +1481,21 @@ 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 avail; 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. */ @@ -1495,7 +1506,10 @@ 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 + avail = max(0, sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)); + l2cap_chan_rx_avail(chan, avail); + + /* 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. * @@ -1504,8 +1518,18 @@ 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; } @@ -1731,6 +1755,8 @@ 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) { @@ -1738,9 +1764,10 @@ 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); @@ -1845,6 +1872,8 @@ 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); @@ -1853,6 +1882,8 @@ static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock, l2cap_chan_hold(chan); + l2cap_chan_rx_avail(chan, sk->sk_rcvbuf); + l2cap_pi(sk)->chan = chan; return sk;
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 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, i.e. sk_buff overhead is ignored, 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. Signed-off-by: Sebastian Urban <surban@surban.net> --- include/net/bluetooth/l2cap.h | 10 +++++- net/bluetooth/l2cap_core.c | 51 ++++++++++++++++++++++---- net/bluetooth/l2cap_sock.c | 67 +++++++++++++++++++++++++---------- 3 files changed, 103 insertions(+), 25 deletions(-)