From 4b6e228e297b73451f3a4b12fb7d0b24d9d32e6f Mon Sep 17 00:00:00 2001 From: Luiz Augusto von Dentz Date: Thu, 2 Jan 2020 15:00:57 -0800 Subject: [PATCH] Bluetooth: Auto tune if input MTU is set to 0 This enables the code to set the input MTU using the underline link packet types when set to 0, previously this would likely be rejected by the remote peer since it would be bellow the minimal of 48 for BR/EDR or 23 for LE, that way it shall be safe to use 0 without causing any side effects. This is convenient for the likes of A2DP transport, see: https://habr.com/en/post/456182/ Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Marcel Holtmann --- net/bluetooth/l2cap_core.c | 54 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 52 insertions(+), 2 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index a845786..1bca608 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -1289,6 +1289,9 @@ static void l2cap_le_connect(struct l2cap_chan *chan) if (test_and_set_bit(FLAG_LE_CONN_REQ_SENT, &chan->flags)) return; + if (!chan->imtu) + chan->imtu = chan->conn->mtu; + l2cap_le_flowctl_init(chan, 0); req.psm = chan->psm; @@ -3226,6 +3229,49 @@ static inline void l2cap_txwin_setup(struct l2cap_chan *chan) chan->ack_win = chan->tx_win; } +static void l2cap_mtu_auto(struct l2cap_chan *chan) +{ + struct hci_conn *conn = chan->conn->hcon; + + chan->imtu = L2CAP_DEFAULT_MIN_MTU; + + /* The 2-DH1 packet has between 2 and 56 information bytes + * (including the 2-byte payload header) + */ + if (!(conn->pkt_type & HCI_2DH1)) + chan->imtu = 54; + + /* The 3-DH1 packet has between 2 and 85 information bytes + * (including the 2-byte payload header) + */ + if (!(conn->pkt_type & HCI_3DH1)) + chan->imtu = 83; + + /* The 2-DH3 packet has between 2 and 369 information bytes + * (including the 2-byte payload header) + */ + if (!(conn->pkt_type & HCI_2DH3)) + chan->imtu = 367; + + /* The 3-DH3 packet has between 2 and 554 information bytes + * (including the 2-byte payload header) + */ + if (!(conn->pkt_type & HCI_3DH3)) + chan->imtu = 552; + + /* The 2-DH5 packet has between 2 and 681 information bytes + * (including the 2-byte payload header) + */ + if (!(conn->pkt_type & HCI_2DH5)) + chan->imtu = 679; + + /* The 3-DH5 packet has between 2 and 1023 information bytes + * (including the 2-byte payload header) + */ + if (!(conn->pkt_type & HCI_3DH5)) + chan->imtu = 1021; +} + static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data, size_t data_size) { struct l2cap_conf_req *req = data; @@ -3255,8 +3301,12 @@ static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data, size_t data } done: - if (chan->imtu != L2CAP_DEFAULT_MTU) - l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu, endptr - ptr); + if (chan->imtu != L2CAP_DEFAULT_MTU) { + if (!chan->imtu) + l2cap_mtu_auto(chan); + l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu, + endptr - ptr); + } switch (chan->mode) { case L2CAP_MODE_BASIC: -- 2.7.4