'\" t
.\" Man page generated from reStructuredText.
.
.
.nr rst2man-indent-level 0
.
.de1 rstReportMargin
\\$1 \\n[an-margin]
level \\n[rst2man-indent-level]
level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
-
\\n[rst2man-indent0]
\\n[rst2man-indent1]
\\n[rst2man-indent2]
..
.de1 INDENT
.\" .rstReportMargin pre:
. RS \\$1
. nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin]
. nr rst2man-indent-level +1
.\" .rstReportMargin post:
..
.de UNINDENT
. RE
.\" indent \\n[an-margin]
.\" old: \\n[rst2man-indent\\n[rst2man-indent-level]]
.nr rst2man-indent-level -1
.\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
..
.TH "L2CAP" "7" "May 2024" "BlueZ" "Linux System Administration"
.SH NAME
l2cap \- L2CAP protocol
.SH SYNOPSIS
.INDENT 0.0
.INDENT 3.5
.sp
.EX
#include <sys/socket.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/l2cap.h>

l2cap_socket = socket(PF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);
.EE
.UNINDENT
.UNINDENT
.SH DESCRIPTION
.sp
L2CAP is a protocol that provides an interface for higher\-level protocols to
send and receive data over a Bluetooth connection. L2CAP sits on top of the
Bluetooth Host Controller Interface (HCI) and provides a set of channels that
can be used by higher\-level protocols to transmit data.
.sp
L2CAP provides a number of services to higher\-level protocols, including
segmentation and reassembly of large data packets and flow control to prevent
overloading of the receiver. L2CAP also supports multiple channels per
connection, allowing for concurrent data transmission using different protocols.
.SH SOCKET ADDRESS
.INDENT 0.0
.INDENT 3.5
.sp
.EX
struct sockaddr_l2 {
    sa_family_t     l2_family;
    unsigned short  l2_psm;
    bdaddr_t        l2_bdaddr;
    unsigned short  l2_cid;
    uint8_t         l2_bdaddr_type;
};
.EE
.UNINDENT
.UNINDENT
.sp
Example:
.INDENT 0.0
.INDENT 3.5
.sp
.EX
struct sockaddr_l2 addr;

memset(&addr, 0, sizeof(addr));
addr.l2_family = AF_BLUETOOTH;
bacpy(&addr.l2_bdaddr, bdaddr);

if (cid)
    addr.l2_cid = htobs(cid);
else
    addr.l2_psm = htobs(psm);

addr.l2_bdaddr_type = bdaddr_type;
.EE
.UNINDENT
.UNINDENT
.SH SOCKET OPTIONS
.sp
The socket options listed below can be set by using \fBsetsockopt(2)\fP and read
with \fBgetsockopt(2)\fP with the socket level set to SOL_BLUETOOTH.
.SS BT_SECURITY (since Linux 2.6.30)
.sp
Channel security level, possible values:
.TS
box center;
l|l|l|l.
T{
Value
T}	T{
Security Level
T}	T{
Link Key Type
T}	T{
Encryption
T}
_
T{
\fBBT_SECURITY_SDP\fP
T}	T{
0 (SDP Only)
T}	T{
None
T}	T{
Not required
T}
_
T{
\fBBT_SECURITY_LOW\fP
T}	T{
1 (Low)
T}	T{
Unauthenticated
T}	T{
Not required
T}
_
T{
\fBBT_SECURITY_MEDIUM\fP
T}	T{
2 (Medium \- default)
T}	T{
Unauthenticated
T}	T{
Desired
T}
_
T{
\fBBT_SECURITY_HIGH\fP
T}	T{
3 (High)
T}	T{
Authenticated
T}	T{
Required
T}
_
T{
\fBBT_SECURITY_FIPS\fP (since Linux 3.15)
T}	T{
4 (Secure Only)
T}	T{
Authenticated (P\-256 based Secure Simple Pairing and Secure Authentication)
T}	T{
Required
T}
.TE
.sp
Example:
.INDENT 0.0
.INDENT 3.5
.sp
.EX
int level = BT_SECURITY_HIGH;
int err = setsockopt(l2cap_socket, SOL_BLUETOOTH, BT_SECURITY, &level,
                     sizeof(level));
if (err == \-1) {
    perror(\(dqsetsockopt\(dq);
    return 1;
}
.EE
.UNINDENT
.UNINDENT
.SS BT_DEFER_SETUP (since Linux 2.6.30)
.sp
Channel defer connection setup, this control if the connection procedure
needs to be authorized by userspace before responding which allows
authorization at profile level, possible values:
.TS
box center;
l|l|l.
T{
Value
T}	T{
Description
T}	T{
Authorization
T}
_
T{
\fB0\fP
T}	T{
Disable (default)
T}	T{
Not required
T}
_
T{
\fB1\fP
T}	T{
Enable
T}	T{
Required
T}
.TE
.sp
Example:
.INDENT 0.0
.INDENT 3.5
.sp
.EX
int defer_setup = 1;
int err = setsockopt(l2cap_socket, SOL_BLUETOOTH, BT_DEFER_SETUP,
                     &defer_setup, sizeof(defer_setup));
if (err == \-1) {
    perror(\(dqsetsockopt\(dq);
    return err;
}

err = listen(l2cap_socket, 5);
if (err) {
    perror(\(dqlisten\(dq);
    return err;
}

struct sockaddr_l2 remote_addr = {0};
socklen_t addr_len = sizeof(remote_addr);
int new_socket = accept(l2cap_socket, (struct sockaddr*)&remote_addr,
                        &addr_len);
if (new_socket < 0) {
    perror(\(dqaccept\(dq);
    return new_socket;
}

/* To complete the connection setup of new_socket read 1 byte */
char c;
struct pollfd pfd;

memset(&pfd, 0, sizeof(pfd));
pfd.fd = new_socket;
pfd.events = POLLOUT;

err = poll(&pfd, 1, 0);
if (err) {
    perror(\(dqpoll\(dq);
    return err;
}

if (!(pfd.revents & POLLOUT)) {
    err = read(sk, &c, 1);
    if (err < 0) {
        perror(\(dqread\(dq);
        return err;
    }
}
.EE
.UNINDENT
.UNINDENT
.SS BT_FLUSHABLE (since Linux 2.6.39)
.sp
Channel flushable flag, this control if the channel data can be flushed or
not, possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_FLUSHABLE_OFF\fP
T}	T{
0x00 (default)
T}	T{
Do not flush data
T}
_
T{
\fBBT_FLUSHABLE_ON\fP
T}	T{
0x01
T}	T{
Flush data
T}
.TE
.SS BT_POWER (since Linux 3.1)
.sp
Channel power policy, this control if the channel shall force exit of sniff
mode or not, possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_POWER_FORCE_ACTIVE_OFF\fP
T}	T{
0x00 (default)
T}	T{
Don\(aqt force exit of sniff mode
T}
_
T{
\fBBT_POWER_FORCE_ACTIVE_ON\fP
T}	T{
0x01
T}	T{
Force exit of sniff mode
T}
.TE
.SS BT_CHANNEL_POLICY (since Linux 3.10)
.sp
High\-speed (AMP) channel policy, possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_CHANNEL_POLICY_BREDR_ONLY\fP
T}	T{
0 (default)
T}	T{
BR/EDR only
T}
_
T{
\fBBT_CHANNEL_POLICY_BREDR_PREFERRED\fP
T}	T{
1
T}	T{
BR/EDR Preferred
T}
_
T{
\fBBT_CHANNEL_POLICY_BREDR_PREFERRED\fP
T}	T{
2
T}	T{
AMP Preferred
T}
.TE
.SS BT_PHY (since Linux 5.10)
.sp
Channel supported PHY(s), possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_PHY_BR_1M_1SLOT\fP
T}	T{
BIT 0
T}	T{
BR 1Mbps 1SLOT
T}
_
T{
\fBBT_PHY_BR_1M_3SLOT\fP
T}	T{
BIT 1
T}	T{
BR 1Mbps 3SLOT
T}
_
T{
\fBBT_PHY_BR_1M_5SLOT\fP
T}	T{
BIT 2
T}	T{
BR 1Mbps 5SLOT
T}
_
T{
\fBBT_PHY_BR_2M_1SLOT\fP
T}	T{
BIT 3
T}	T{
EDR 2Mbps 1SLOT
T}
_
T{
\fBBT_PHY_BR_2M_3SLOT\fP
T}	T{
BIT 4
T}	T{
EDR 2Mbps 3SLOT
T}
_
T{
\fBBT_PHY_BR_2M_5SLOT\fP
T}	T{
BIT 5
T}	T{
EDR 2Mbps 5SLOT
T}
_
T{
\fBBT_PHY_BR_3M_1SLOT\fP
T}	T{
BIT 6
T}	T{
EDR 3Mbps 1SLOT
T}
_
T{
\fBBT_PHY_BR_3M_3SLOT\fP
T}	T{
BIT 7
T}	T{
EDR 3Mbps 3SLOT
T}
_
T{
\fBBT_PHY_BR_3M_5SLOT\fP
T}	T{
BIT 8
T}	T{
EDR 3Mbps 5SLOT
T}
_
T{
\fBBT_PHY_LE_1M_TX\fP
T}	T{
BIT 9
T}	T{
LE 1Mbps TX
T}
_
T{
\fBBT_PHY_LE_1M_RX\fP
T}	T{
BIT 10
T}	T{
LE 1Mbps RX
T}
_
T{
\fBBT_PHY_LE_2M_TX\fP
T}	T{
BIT 11
T}	T{
LE 2Mbps TX
T}
_
T{
\fBBT_PHY_LE_2M_RX\fP
T}	T{
BIT 12
T}	T{
LE 2Mbps RX
T}
_
T{
\fBBT_PHY_LE_CODED_TX\fP
T}	T{
BIT 13
T}	T{
LE Coded TX
T}
_
T{
\fBBT_PHY_LE_CODED_RX\fP
T}	T{
BIT 14
T}	T{
LE Coded RX
T}
.TE
.SS BT_MODE (since Linux 5.10)
.sp
Channel Mode, possible values:
.TS
box center;
l|l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}	T{
Link
T}
_
T{
\fBBT_MODE_BASIC\fP
T}	T{
0x00 (default)
T}	T{
Basic mode
T}	T{
Any
T}
_
T{
\fBBT_MODE_ERTM\fP
T}	T{
0x01
T}	T{
Enhanced Retransmission mode
T}	T{
BR/EDR
T}
_
T{
\fBBT_MODE_STREAM\fP
T}	T{
0x02
T}	T{
Stream mode
T}	T{
BR/EDR
T}
_
T{
\fBBT_MODE_LE_FLOWCTL\fP
T}	T{
0x03
T}	T{
Credit based flow control mode
T}	T{
LE
T}
_
T{
\fBBT_MODE_EXT_FLOWCTL\fP
T}	T{
0x04
T}	T{
Extended Credit based flow control mode
T}	T{
Any
T}
.TE
.SH RESOURCES
.sp
 <http://www.bluez.org> 
.SH REPORTING BUGS
.sp
 <linux\-bluetooth@vger.kernel.org> 
.SH SEE ALSO
.sp
socket(7), l2test(1)
.SH COPYRIGHT
Free use of this software is granted under ther terms of the GNU
Lesser General Public Licenses (LGPL).
.\" Generated by docutils manpage writer.
.