Hi Luiz, > Bluetooth Core Specification v5.2, Vol. 3, Part A, section 1.4, table > 1.1: > > 'Start Fragments always either begin with the first octet of the Basic > L2CAP header of a PDU or they have a length of zero (see [Vol 2] Part > B, Section 6.6.2).' > > This text has been changed recently as it previously stated: > > 'Start Fragments always begin with the Basic L2CAP header of a PDU.' > > Apparently this was changed by the following errata: > > https://www.bluetooth.org/tse/errata_view.cfm?errata_id=10216 > > In past this has not been a problem but it seems new controllers are > apparently doing it as it has been reported in Zephyr: > > https://github.com/zephyrproject-rtos/zephyr/issues/26900 > > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx> > --- > net/bluetooth/l2cap_core.c | 104 +++++++++++++++++++++++++++++-------- > 1 file changed, 83 insertions(+), 21 deletions(-) > > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c > index ade83e224567..193bea314222 100644 > --- a/net/bluetooth/l2cap_core.c > +++ b/net/bluetooth/l2cap_core.c > @@ -8269,6 +8269,63 @@ static void l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt) > mutex_unlock(&conn->chan_lock); > } > > +/* Append fragment into frame respecting the maximum len of rx_skb */ > +static int l2cap_recv_frag(struct l2cap_conn *conn, struct sk_buff *skb, > + u16 len) > +{ > + if (!conn->rx_skb) { > + /* Allocate skb for the complete frame (with header) */ > + conn->rx_skb = bt_skb_alloc(len, GFP_KERNEL); > + if (!conn->rx_skb) > + return -ENOMEM; > + /* Init rx_len */ > + conn->rx_len = len; > + } > + > + /* Copy as much as the rx_skb can hold */ > + len = min_t(u16, len, skb->len); > + skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, len), len); > + skb_pull(skb, len); > + conn->rx_len -= len; > + > + return len; > +} > + > +static int l2cap_recv_header(struct l2cap_conn *conn, struct sk_buff *skb) > +{ > + struct l2cap_hdr *hdr; > + struct sk_buff *rx_skb; > + int len; > + > + /* Append just enough to complete the header */ > + len = l2cap_recv_frag(conn, skb, L2CAP_HDR_SIZE - conn->rx_skb->len); > + > + /* If header could not be read just continue */ > + if (len < 0 || conn->rx_skb->len < L2CAP_HDR_SIZE) > + return len; > + > + rx_skb = conn->rx_skb; > + conn->rx_skb = NULL; > + > + hdr = (struct l2cap_hdr *) rx_skb->data; so I think it is pointless to insist on getting the complete header. We really just need the first 2 octets. struct l2cap_hdr { __le16 len; __le16 cid; } __packed; Once we have received at least 2 octets, we can get_unaligned_le16(rx_skb->data) and then just continue. Regards Marcel
