NetBSD/sys/netbt/l2cap_signal.c

/*	$NetBSD: l2cap_signal.c,v 1.22 2022/12/24 22:33:12 andvar Exp $	*/

/*-
 * Copyright (c) 2005 Iain Hibbert.
 * Copyright (c) 2006 Itronix Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of Itronix Inc. may not be used to endorse
 *    or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY ITRONIX INC. ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: l2cap_signal.c,v 1.22 2022/12/24 22:33:12 andvar Exp $");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/mbuf.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/systm.h>

#include <netbt/bluetooth.h>
#include <netbt/hci.h>
#include <netbt/l2cap.h>

/*******************************************************************************
 *
 *	L2CAP Signal processing
 */

static void l2cap_recv_command_rej(struct mbuf *, struct hci_link *);
static void l2cap_recv_connect_req(struct mbuf *, struct hci_link *);
static void l2cap_recv_connect_rsp(struct mbuf *, struct hci_link *);
static void l2cap_recv_config_req(struct mbuf *, struct hci_link *);
static void l2cap_recv_config_rsp(struct mbuf *, struct hci_link *);
static void l2cap_recv_disconnect_req(struct mbuf *, struct hci_link *);
static void l2cap_recv_disconnect_rsp(struct mbuf *, struct hci_link *);
static void l2cap_recv_info_req(struct mbuf *, struct hci_link *);
static int l2cap_send_signal(struct hci_link *, uint8_t, uint8_t, uint16_t, void *);
static int l2cap_send_command_rej(struct hci_link *, uint8_t, int, ...);
static void l2cap_qos_btoh(l2cap_qos_t *, void *);
static void l2cap_qos_htob(void *, l2cap_qos_t *);

/*
 * process incoming signal packets (CID 0x0001). Can contain multiple
 * requests/responses. The signal handler should clear the command from
 * the mbuf before returning.
 */
void
l2cap_recv_signal(struct mbuf *m, struct hci_link *link)
{
	l2cap_cmd_hdr_t cmd;

	for(;;) {
		if (m->m_pkthdr.len < sizeof(cmd))
			goto finish;

		m_copydata(m, 0, sizeof(cmd), &cmd);
		cmd.length = le16toh(cmd.length);

		if (m->m_pkthdr.len < sizeof(cmd) + cmd.length)
			goto reject;

		DPRINTFN(2, "(%s) code %d, ident %d, len %d\n",
			device_xname(link->hl_unit->hci_dev),
			cmd.code, cmd.ident, cmd.length);

		switch (cmd.code) {
		case L2CAP_COMMAND_REJ:
			if (cmd.length > sizeof(l2cap_cmd_rej_cp))
				goto finish;

			l2cap_recv_command_rej(m, link);
			break;

		case L2CAP_CONNECT_REQ:
			if (cmd.length != sizeof(l2cap_con_req_cp))
				goto reject;

			l2cap_recv_connect_req(m, link);
			break;

		case L2CAP_CONNECT_RSP:
			if (cmd.length != sizeof(l2cap_con_rsp_cp))
				goto finish;

			l2cap_recv_connect_rsp(m, link);
			break;

		case L2CAP_CONFIG_REQ:
			l2cap_recv_config_req(m, link);
			break;

		case L2CAP_CONFIG_RSP:
			l2cap_recv_config_rsp(m, link);
			break;

		case L2CAP_DISCONNECT_REQ:
			if (cmd.length != sizeof(l2cap_discon_req_cp))
				goto reject;

			l2cap_recv_disconnect_req(m, link);
			break;

		case L2CAP_DISCONNECT_RSP:
			if (cmd.length != sizeof(l2cap_discon_rsp_cp))
				goto finish;

			l2cap_recv_disconnect_rsp(m, link);
			break;

		case L2CAP_ECHO_REQ:
			m_adj(m, sizeof(cmd) + cmd.length);
			l2cap_send_signal(link, L2CAP_ECHO_RSP, cmd.ident,
					0, NULL);
			break;

		case L2CAP_ECHO_RSP:
			m_adj(m, sizeof(cmd) + cmd.length);
			break;

		case L2CAP_INFO_REQ:
			if (cmd.length != sizeof(l2cap_info_req_cp))
				goto reject;

			l2cap_recv_info_req(m, link);
			break;

		case L2CAP_INFO_RSP:
			m_adj(m, sizeof(cmd) + cmd.length);
			break;

		default:
			goto reject;
		}
	}
	panic("impossible!");

reject:
	l2cap_send_command_rej(link, cmd.ident, L2CAP_REJ_NOT_UNDERSTOOD);
finish:
	m_freem(m);
}

/*
 * Process Received Command Reject. For now we don't try to recover gracefully
 * from this, it probably means that the link is garbled or the other end is
 * insufficiently capable of handling normal traffic. (not *my* fault, no way!)
 */
static void
l2cap_recv_command_rej(struct mbuf *m, struct hci_link *link)
{
	struct l2cap_req *req;
	struct l2cap_channel *chan;
	l2cap_cmd_hdr_t cmd;
	l2cap_cmd_rej_cp cp;

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));

	cmd.length = le16toh(cmd.length);

	/* The length here must contain the reason (2 octets) plus
	 * any data (0 or more octets) but we already know it is not
	 * bigger than l2cap_cmd_rej_cp
	 */
	m_copydata(m, 0, cmd.length, &cp);
	m_adj(m, cmd.length);

	if (cmd.length < 2)
		return;

	req = l2cap_request_lookup(link, cmd.ident);
	if (req == NULL)
		return;

	switch (le16toh(cp.reason)) {
	case L2CAP_REJ_NOT_UNDERSTOOD:	/* data length = 0 octets */
		/*
		 * I don't know what to do, just move up the timeout
		 */
		callout_schedule(&req->lr_rtx, 0);
		break;

	case L2CAP_REJ_MTU_EXCEEDED:	/* data length = 2 octets */
		/*
		 * I didn't send any commands over L2CAP_MTU_MINIMUM size, but..
		 *
		 * XXX maybe we should resend this, instead?
		 */
		if (cmd.length != 4)
			return;

		link->hl_mtu = le16toh(cp.data[0]);
		callout_schedule(&req->lr_rtx, 0);
		break;

	case L2CAP_REJ_INVALID_CID:	/* data length = 4 octets */
		/*
		 * Well, if they don't have such a channel then our channel is
		 * most likely closed. Make it so.
		 */
		chan = req->lr_chan;
		l2cap_request_free(req);
		if (chan != NULL && chan->lc_state != L2CAP_CLOSED)
			l2cap_close(chan, ECONNABORTED);

		break;

	default:
		UNKNOWN(le16toh(cp.reason));
		break;
	}
}

/*
 * Process Received Connect Request. Find listening channel matching
 * psm & addr and ask upper layer for a new channel.
 */
static void
l2cap_recv_connect_req(struct mbuf *m, struct hci_link *link)
{
	struct sockaddr_bt laddr, raddr;
	struct l2cap_channel *chan, *new;
	l2cap_cmd_hdr_t cmd;
	l2cap_con_req_cp cp;
	int err;

	/* extract cmd */
	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));

	/* extract request */
	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));

	cp.scid = le16toh(cp.scid);
	cp.psm = le16toh(cp.psm);

	memset(&laddr, 0, sizeof(struct sockaddr_bt));
	laddr.bt_len = sizeof(struct sockaddr_bt);
	laddr.bt_family = AF_BLUETOOTH;
	laddr.bt_psm = cp.psm;
	bdaddr_copy(&laddr.bt_bdaddr, &link->hl_unit->hci_bdaddr);

	memset(&raddr, 0, sizeof(struct sockaddr_bt));
	raddr.bt_len = sizeof(struct sockaddr_bt);
	raddr.bt_family = AF_BLUETOOTH;
	raddr.bt_psm = cp.psm;
	bdaddr_copy(&raddr.bt_bdaddr, &link->hl_bdaddr);

	LIST_FOREACH(chan, &l2cap_listen_list, lc_ncid) {
		if (chan->lc_laddr.bt_psm != laddr.bt_psm)
			continue;

		if (!bdaddr_same(&laddr.bt_bdaddr, &chan->lc_laddr.bt_bdaddr)
		    && bdaddr_any(&chan->lc_laddr.bt_bdaddr) == 0)
			continue;

		new= (*chan->lc_proto->newconn)(chan->lc_upper, &laddr, &raddr);
		if (new == NULL)
			continue;

		err = l2cap_cid_alloc(new);
		if (err) {
			l2cap_send_connect_rsp(link, cmd.ident,
						0, cp.scid,
						L2CAP_NO_RESOURCES);

			(*new->lc_proto->disconnected)(new->lc_upper, err);
			return;
		}

		new->lc_link = hci_acl_open(link->hl_unit, &link->hl_bdaddr);
		KASSERT(new->lc_link == link);

		new->lc_rcid = cp.scid;
		new->lc_ident = cmd.ident;

		memcpy(&new->lc_laddr, &laddr, sizeof(struct sockaddr_bt));
		memcpy(&new->lc_raddr, &raddr, sizeof(struct sockaddr_bt));

		new->lc_mode = chan->lc_mode;

		err = l2cap_setmode(new);
		if (err == EINPROGRESS) {
			new->lc_state = L2CAP_WAIT_SEND_CONNECT_RSP;
			(*new->lc_proto->connecting)(new->lc_upper);
			return;
		}
		if (err) {
			new->lc_state = L2CAP_CLOSED;
			hci_acl_close(link, err);
			new->lc_link = NULL;

			l2cap_send_connect_rsp(link, cmd.ident,
						0, cp.scid,
						L2CAP_NO_RESOURCES);

			(*new->lc_proto->disconnected)(new->lc_upper, err);
			return;
		}

		err = l2cap_send_connect_rsp(link, cmd.ident,
					      new->lc_lcid, new->lc_rcid,
					      L2CAP_SUCCESS);
		if (err) {
			l2cap_close(new, err);
			return;
		}

		new->lc_state = L2CAP_WAIT_CONFIG;
		new->lc_flags |= (L2CAP_WAIT_CONFIG_REQ | L2CAP_WAIT_CONFIG_RSP);
		err = l2cap_send_config_req(new);
		if (err)
			l2cap_close(new, err);

		return;
	}

	l2cap_send_connect_rsp(link, cmd.ident,
				0, cp.scid,
				L2CAP_PSM_NOT_SUPPORTED);
}

/*
 * Process Received Connect Response.
 */
static void
l2cap_recv_connect_rsp(struct mbuf *m, struct hci_link *link)
{
	l2cap_cmd_hdr_t cmd;
	l2cap_con_rsp_cp cp;
	struct l2cap_req *req;
	struct l2cap_channel *chan;

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));

	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));

	cp.scid = le16toh(cp.scid);
	cp.dcid = le16toh(cp.dcid);
	cp.result = le16toh(cp.result);

	req = l2cap_request_lookup(link, cmd.ident);
	if (req == NULL || req->lr_code != L2CAP_CONNECT_REQ)
		return;

	chan = req->lr_chan;
	if (chan != NULL && chan->lc_lcid != cp.scid)
		return;

	if (chan == NULL || chan->lc_state != L2CAP_WAIT_RECV_CONNECT_RSP) {
		l2cap_request_free(req);
		return;
	}

	switch (cp.result) {
	case L2CAP_SUCCESS:
		/*
		 * Ok, at this point we have a connection to the other party. We
		 * could indicate upstream that we are ready for business and
		 * wait for a "Configure Channel Request" but I'm not so sure
		 * that is required in our case - we will proceed directly to
		 * sending our config request. We set two state bits because in
		 * the config state we are waiting for requests and responses.
		 */
		l2cap_request_free(req);
		chan->lc_rcid = cp.dcid;
		chan->lc_state = L2CAP_WAIT_CONFIG;
		chan->lc_flags |= (L2CAP_WAIT_CONFIG_REQ | L2CAP_WAIT_CONFIG_RSP);
		l2cap_send_config_req(chan);
		break;

	case L2CAP_PENDING:
		/* XXX don't release request, should start eRTX timeout? */
		(*chan->lc_proto->connecting)(chan->lc_upper);
		break;

	case L2CAP_PSM_NOT_SUPPORTED:
	case L2CAP_SECURITY_BLOCK:
	case L2CAP_NO_RESOURCES:
	default:
		l2cap_request_free(req);
		l2cap_close(chan, ECONNREFUSED);
		break;
	}
}

/*
 * Process Received Config Request.
 */
static void
l2cap_recv_config_req(struct mbuf *m, struct hci_link *link)
{
	uint8_t buf[L2CAP_MTU_MINIMUM];
	l2cap_cmd_hdr_t cmd;
	l2cap_cfg_req_cp cp;
	l2cap_cfg_opt_t opt;
	l2cap_cfg_opt_val_t val;
	l2cap_cfg_rsp_cp rp;
	struct l2cap_channel *chan;
	int left, len;

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));
	left = le16toh(cmd.length);

	if (left < sizeof(cp))
		goto reject;

	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));
	left -= sizeof(cp);

	cp.dcid = le16toh(cp.dcid);
	cp.flags = le16toh(cp.flags);

	chan = l2cap_cid_lookup(cp.dcid);
	if (chan == NULL || chan->lc_link != link
	    || chan->lc_state != L2CAP_WAIT_CONFIG
	    || (chan->lc_flags & L2CAP_WAIT_CONFIG_REQ) == 0) {
		/* XXX we should really accept reconfiguration requests */
		l2cap_send_command_rej(link, cmd.ident, L2CAP_REJ_INVALID_CID,
					L2CAP_NULL_CID, cp.dcid);
		goto out;
	}

	/* ready our response packet */
	rp.scid = htole16(chan->lc_rcid);
	rp.flags = 0;	/* "No Continuation" */
	rp.result = L2CAP_SUCCESS;
	len = sizeof(rp);

	/*
	 * Process the packet. We build the return packet on the fly adding any
	 * unacceptable parameters as we go. As we can only return one result,
	 * unknown option takes precedence so we start our return packet anew
	 * and ignore option values thereafter as they will be re-sent.
	 *
	 * Since we do not support enough options to make overflowing the min
	 * MTU size an issue in normal use, we just reject config requests that
	 * make that happen. This could be because options are repeated or the
	 * packet is corrupted in some way.
	 *
	 * If unknown option types threaten to overflow the packet, we just
	 * ignore them. We can deny them next time.
	 */
	while (left > 0) {
		if (left < sizeof(opt))
			goto reject;

		m_copydata(m, 0, sizeof(opt), &opt);
		m_adj(m, sizeof(opt));
		left -= sizeof(opt);

		if (left < opt.length)
			goto reject;

		switch(opt.type & L2CAP_OPT_HINT_MASK) {
		case L2CAP_OPT_MTU:
			if (rp.result == L2CAP_UNKNOWN_OPTION)
				break;

			if (opt.length != L2CAP_OPT_MTU_SIZE)
				goto reject;

			m_copydata(m, 0, L2CAP_OPT_MTU_SIZE, &val.mtu);
			val.mtu = le16toh(val.mtu);

			/*
			 * XXX how do we know what the minimum acceptable MTU is
			 * for a channel? Spec says some profiles have a higher
			 * minimum but I have no way to find that out at this
			 * juncture..
			 */
			if (val.mtu < L2CAP_MTU_MINIMUM) {
				if (len + sizeof(opt) + L2CAP_OPT_MTU_SIZE > sizeof(buf))
					goto reject;

				rp.result = L2CAP_UNACCEPTABLE_PARAMS;
				memcpy(buf + len, &opt, sizeof(opt));
				len += sizeof(opt);
				val.mtu = htole16(L2CAP_MTU_MINIMUM);
				memcpy(buf + len, &val, L2CAP_OPT_MTU_SIZE);
				len += L2CAP_OPT_MTU_SIZE;
			} else
				chan->lc_omtu = val.mtu;

			break;

		case L2CAP_OPT_FLUSH_TIMO:
			if (rp.result == L2CAP_UNKNOWN_OPTION)
				break;

			if (opt.length != L2CAP_OPT_FLUSH_TIMO_SIZE)
				goto reject;

			/*
			 * I think that this is informational only - he is
			 * informing us of the flush timeout he will be using.
			 * I don't think this affects us in any significant way,
			 * so just ignore this value for now.
			 */
			break;

		case L2CAP_OPT_QOS:
			if (rp.result == L2CAP_UNKNOWN_OPTION)
				break;

			if (opt.length != L2CAP_OPT_QOS_SIZE)
				goto reject;

			/*
			 * We don't actually support QoS, but an incoming
			 * config request is merely advising us of their
			 * outgoing traffic flow, so be nice.
			 */
			m_copydata(m, 0, L2CAP_OPT_QOS_SIZE, &val.qos);
			switch (val.qos.service_type) {
			case L2CAP_QOS_NO_TRAFFIC:
				/*
				 * "No traffic" means they don't plan to send
				 * any data and the fields should be ignored.
				 */
				chan->lc_iqos = l2cap_default_qos;
				chan->lc_iqos.service_type = L2CAP_QOS_NO_TRAFFIC;
				break;

			case L2CAP_QOS_BEST_EFFORT:
				/*
				 * "Best effort" is the default, and we may
				 * choose to ignore the fields, try to satisfy
				 * the parameters while giving no response, or
				 * respond with the settings we will try to
				 * meet.
				 */
				l2cap_qos_btoh(&chan->lc_iqos, &val.qos);
				break;

			case L2CAP_QOS_GUARANTEED:
			default:
				/*
			 	 * Anything else we don't support, so make a
				 * counter-offer with the current settings.
				 */
				if (len + sizeof(opt) + L2CAP_OPT_QOS_SIZE > sizeof(buf))
					goto reject;

				rp.result = L2CAP_UNACCEPTABLE_PARAMS;
				memcpy(buf + len, &opt, sizeof(opt));
				len += sizeof(opt);
				l2cap_qos_htob(buf + len, &chan->lc_iqos);
				len += L2CAP_OPT_QOS_SIZE;
				break;
			}
			break;

		default:
			/* ignore hints */
			if (opt.type & L2CAP_OPT_HINT_BIT)
				break;

			/* unknown options supercede all else */
			if (rp.result != L2CAP_UNKNOWN_OPTION) {
				rp.result = L2CAP_UNKNOWN_OPTION;
				len = sizeof(rp);
			}

			/* ignore if it don't fit */
			if (len + sizeof(opt) > sizeof(buf))
				break;

			/* return unknown option type, but no data */
			buf[len++] = opt.type;
			buf[len++] = 0;
			break;
		}

		m_adj(m, opt.length);
		left -= opt.length;
	}

	rp.result = htole16(rp.result);
	memcpy(buf, &rp, sizeof(rp));
	l2cap_send_signal(link, L2CAP_CONFIG_RSP, cmd.ident, len, buf);

	if ((cp.flags & L2CAP_OPT_CFLAG_BIT) == 0
	    && rp.result == le16toh(L2CAP_SUCCESS)) {

		chan->lc_flags &= ~L2CAP_WAIT_CONFIG_REQ;

		if ((chan->lc_flags & L2CAP_WAIT_CONFIG_RSP) == 0) {
			chan->lc_state = L2CAP_OPEN;
			/* XXX how to distinguish REconfiguration? */
			(*chan->lc_proto->connected)(chan->lc_upper);
		}
	}
	return;

reject:
	l2cap_send_command_rej(link, cmd.ident, L2CAP_REJ_NOT_UNDERSTOOD);
out:
	m_adj(m, left);
}

/*
 * Process Received Config Response.
 */
static void
l2cap_recv_config_rsp(struct mbuf *m, struct hci_link *link)
{
	l2cap_cmd_hdr_t cmd;
	l2cap_cfg_rsp_cp cp;
	l2cap_cfg_opt_t opt;
	l2cap_cfg_opt_val_t val;
	struct l2cap_req *req;
	struct l2cap_channel *chan;
	int left;

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));
	left = le16toh(cmd.length);

	if (left < sizeof(cp))
		goto out;

	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));
	left -= sizeof(cp);

	cp.scid = le16toh(cp.scid);
	cp.flags = le16toh(cp.flags);
	cp.result = le16toh(cp.result);

	req = l2cap_request_lookup(link, cmd.ident);
	if (req == NULL || req->lr_code != L2CAP_CONFIG_REQ)
		goto out;

	chan = req->lr_chan;
	if (chan != NULL && chan->lc_lcid != cp.scid)
		goto out;

	l2cap_request_free(req);

	if (chan == NULL || chan->lc_state != L2CAP_WAIT_CONFIG
	    || (chan->lc_flags & L2CAP_WAIT_CONFIG_RSP) == 0)
		goto out;

	if ((cp.flags & L2CAP_OPT_CFLAG_BIT)) {
		l2cap_cfg_req_cp rp;

		/*
		 * They have more to tell us and want another ID to
		 * use, so send an empty config request
		 */
		if (l2cap_request_alloc(chan, L2CAP_CONFIG_REQ))
			goto discon;

		rp.dcid = htole16(cp.scid);
		rp.flags = 0;

		if (l2cap_send_signal(link, L2CAP_CONFIG_REQ, link->hl_lastid,
					sizeof(rp), &rp))
			goto discon;
	}

	switch(cp.result) {
	case L2CAP_SUCCESS:
		/*
		 * If continuation flag was not set, our config request was
		 * accepted. We may have to wait for their config request to
		 * complete, so check that but otherwise we are open
		 *
		 * There may be 'advisory' values in the packet but we just
		 * ignore those..
		 */
		if ((cp.flags & L2CAP_OPT_CFLAG_BIT) == 0) {
			chan->lc_flags &= ~L2CAP_WAIT_CONFIG_RSP;

			if ((chan->lc_flags & L2CAP_WAIT_CONFIG_REQ) == 0) {
				chan->lc_state = L2CAP_OPEN;
				/* XXX how to distinguish REconfiguration? */
				(*chan->lc_proto->connected)(chan->lc_upper);
			}
		}
		goto out;

	case L2CAP_UNACCEPTABLE_PARAMS:
		/*
		 * Packet contains unacceptable parameters with preferred values
		 */
		while (left > 0) {
			if (left < sizeof(opt))
				goto discon;

			m_copydata(m, 0, sizeof(opt), &opt);
			m_adj(m, sizeof(opt));
			left -= sizeof(opt);

			if (left < opt.length)
				goto discon;

			switch (opt.type) {
			case L2CAP_OPT_MTU:
				if (opt.length != L2CAP_OPT_MTU_SIZE)
					goto discon;

				m_copydata(m, 0, L2CAP_OPT_MTU_SIZE, &val.mtu);
				chan->lc_imtu = le16toh(val.mtu);
				if (chan->lc_imtu < L2CAP_MTU_MINIMUM)
					chan->lc_imtu = L2CAP_MTU_DEFAULT;
				break;

			case L2CAP_OPT_FLUSH_TIMO:
				if (opt.length != L2CAP_OPT_FLUSH_TIMO_SIZE)
					goto discon;

				/*
				 * Spec says: If we cannot honor proposed value,
				 * either disconnect or try again with original
				 * value. I can't really see why they want to
				 * interfere with OUR flush timeout in any case
				 * so we just punt for now.
				 */
				goto discon;

			case L2CAP_OPT_QOS:
				if (opt.length != L2CAP_OPT_QOS_SIZE)
					goto discon;

				/*
				 * This may happen even if we haven't sent a
				 * QoS request, where they need to state their
				 * preferred incoming traffic flow.
				 * We don't support anything, but copy in the
				 * parameters if no action is good enough.
				 */
				m_copydata(m, 0, L2CAP_OPT_QOS_SIZE, &val.qos);
				switch (val.qos.service_type) {
				case L2CAP_QOS_NO_TRAFFIC:
				case L2CAP_QOS_BEST_EFFORT:
					l2cap_qos_btoh(&chan->lc_oqos, &val.qos);
					break;

				case L2CAP_QOS_GUARANTEED:
				default:
					goto discon;
				}
				break;

			default:
				UNKNOWN(opt.type);
				goto discon;
			}

			m_adj(m, opt.length);
			left -= opt.length;
		}

		if ((cp.flags & L2CAP_OPT_CFLAG_BIT) == 0)
			l2cap_send_config_req(chan);	/* no state change */

		goto out;

	case L2CAP_REJECT:
		goto discon;

	case L2CAP_UNKNOWN_OPTION:
		/*
		 * Packet contains options not understood. Turn off unknown
		 * options by setting them to default values (means they will
		 * not be requested again).
		 *
		 * If our option was already off then fail (paranoia?)
		 *
		 * XXX Should we consider that options were set for a reason?
		 */
		while (left > 0) {
			if (left < sizeof(opt))
				goto discon;

			m_copydata(m, 0, sizeof(opt), &opt);
			m_adj(m, sizeof(opt));
			left -= sizeof(opt);

			if (left < opt.length)
				goto discon;

			m_adj(m, opt.length);
			left -= opt.length;

			switch(opt.type) {
			case L2CAP_OPT_MTU:
				if (chan->lc_imtu == L2CAP_MTU_DEFAULT)
					goto discon;

				chan->lc_imtu = L2CAP_MTU_DEFAULT;
				break;

			case L2CAP_OPT_FLUSH_TIMO:
				if (chan->lc_flush == L2CAP_FLUSH_TIMO_DEFAULT)
					goto discon;

				chan->lc_flush = L2CAP_FLUSH_TIMO_DEFAULT;
				break;

			case L2CAP_OPT_QOS:
				break;

			default:
				UNKNOWN(opt.type);
				goto discon;
			}
		}

		if ((cp.flags & L2CAP_OPT_CFLAG_BIT) == 0)
			l2cap_send_config_req(chan);	/* no state change */

		goto out;

	default:
		UNKNOWN(cp.result);
		goto discon;
	}

	DPRINTF("how did I get here!?\n");

discon:
	l2cap_send_disconnect_req(chan);
	l2cap_close(chan, ECONNABORTED);

out:
	m_adj(m, left);
}

/*
 * Process Received Disconnect Request. We must validate scid and dcid
 * just in case but otherwise this connection is finished.
 */
static void
l2cap_recv_disconnect_req(struct mbuf *m, struct hci_link *link)
{
	l2cap_cmd_hdr_t cmd;
	l2cap_discon_req_cp cp;
	l2cap_discon_rsp_cp rp;
	struct l2cap_channel *chan;

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));

	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));

	cp.scid = le16toh(cp.scid);
	cp.dcid = le16toh(cp.dcid);

	chan = l2cap_cid_lookup(cp.dcid);
	if (chan == NULL || chan->lc_link != link || chan->lc_rcid != cp.scid) {
		l2cap_send_command_rej(link, cmd.ident, L2CAP_REJ_INVALID_CID,
					cp.dcid, cp.scid);
		return;
	}

	rp.dcid = htole16(chan->lc_lcid);
	rp.scid = htole16(chan->lc_rcid);
	l2cap_send_signal(link, L2CAP_DISCONNECT_RSP, cmd.ident,
				sizeof(rp), &rp);

	if (chan->lc_state != L2CAP_CLOSED)
		l2cap_close(chan, 0);
}

/*
 * Process Received Disconnect Response. We must validate scid and dcid but
 * unless we were waiting for this signal, ignore it.
 */
static void
l2cap_recv_disconnect_rsp(struct mbuf *m, struct hci_link *link)
{
	l2cap_cmd_hdr_t cmd;
	l2cap_discon_rsp_cp cp;
	struct l2cap_req *req;
	struct l2cap_channel *chan;

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));

	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));

	cp.scid = le16toh(cp.scid);
	cp.dcid = le16toh(cp.dcid);

	req = l2cap_request_lookup(link, cmd.ident);
	if (req == NULL || req->lr_code != L2CAP_DISCONNECT_REQ)
		return;

	chan = req->lr_chan;
	if (chan == NULL
	    || chan->lc_lcid != cp.scid
	    || chan->lc_rcid != cp.dcid)
		return;

	l2cap_request_free(req);

	if (chan->lc_state != L2CAP_WAIT_DISCONNECT)
		return;

	l2cap_close(chan, 0);
}

/*
 * Process Received Info Request.
 */
static void
l2cap_recv_info_req(struct mbuf *m, struct hci_link *link)
{
	l2cap_cmd_hdr_t cmd;
	l2cap_info_req_cp cp;
	uint8_t rsp[12];

	m_copydata(m, 0, sizeof(cmd), &cmd);
	m_adj(m, sizeof(cmd));

	m_copydata(m, 0, sizeof(cp), &cp);
	m_adj(m, sizeof(cp));

	cp.type = le16toh(cp.type);
	switch(cp.type) {
	case L2CAP_EXTENDED_FEATURES:
		/*
		 * 32-bit data field, unused bits set to zero
		 *
		 * octet bit feature
		 *   0   0   Flow control mode
		 *   0   1   Retransmission mode
		 *   0   2   Bi-directional QoS
		 *   0   3   Enhanced retransmission mode
		 *   0   4   Streaming mode
		 *   0   5   FCS option
		 *   0   6   Extended flow specification for BR/EDR
		 *   0   7   Fixed channels (SET)
		 *   1   0   Extended window size
		 *   1   1   Unicast connectionless data reception
		 */
		le16enc(rsp + 0, cp.type);
		le16enc(rsp + 2, L2CAP_SUCCESS);
		le32enc(rsp + 4, 0x00000080);
		l2cap_send_signal(link, L2CAP_INFO_RSP, cmd.ident, 8, rsp);
		break;

	case L2CAP_FIXED_CHANNELS:
		/*
		 * 64-bit data field, unused bits set to zero
		 *
		 * octet bit channel
		 *   0   0   0x0000 Null
		 *   0   1   0x0001 L2CAP Signalling Channel (SET)
		 *   0   2   0x0002 Connectionless Reception
		 *   0   3   0x0003 AMP Manager Protocol Channel
		 *   0   7   0x0007 BR/EDR Security Manager
		 *   7   7   0x003f AMP Test Manager
		 */
		le16enc(rsp + 0, cp.type);
		le16enc(rsp + 2, L2CAP_SUCCESS);
		le64enc(rsp + 4, 0x0000000000000002);
		l2cap_send_signal(link, L2CAP_INFO_RSP, cmd.ident, 12, rsp);
		break;

	case L2CAP_CONNLESS_MTU:
	default:
		le16enc(rsp + 0, cp.type);
		le16enc(rsp + 2, L2CAP_NOT_SUPPORTED);
		l2cap_send_signal(link, L2CAP_INFO_RSP, cmd.ident, 4, rsp);
		break;
	}
}

/*
 * Construct signal and wrap in C-Frame for link.
 */
static int
l2cap_send_signal(struct hci_link *link, uint8_t code, uint8_t ident,
			uint16_t length, void *data)
{
	struct mbuf *m;
	l2cap_hdr_t *hdr;
	l2cap_cmd_hdr_t *cmd;

	KASSERT(link != NULL);
	KASSERT(sizeof(l2cap_cmd_hdr_t) + length <= link->hl_mtu);

	m = m_gethdr(M_DONTWAIT, MT_DATA);
	if (m == NULL)
		return ENOMEM;

	hdr = mtod(m, l2cap_hdr_t *);
	cmd = (l2cap_cmd_hdr_t *)(hdr + 1);

	m->m_len = m->m_pkthdr.len = MHLEN;

	/* Command Data */
	if (length > 0)
		m_copyback(m, sizeof(*hdr) + sizeof(*cmd), length, data);

	/* Command Header */
	cmd->code = code;
	cmd->ident = ident;
	cmd->length = htole16(length);
	length += sizeof(*cmd);

	/* C-Frame Header */
	hdr->length = htole16(length);
	hdr->dcid = htole16(L2CAP_SIGNAL_CID);
	length += sizeof(*hdr);

	if (m->m_pkthdr.len != MAX(MHLEN, length)) {
		m_freem(m);
		return ENOMEM;
	}

	m->m_pkthdr.len = length;
	m->m_len = MIN(length, MHLEN);

	DPRINTFN(2, "(%s) code %d, ident %d, len %d\n",
		device_xname(link->hl_unit->hci_dev), code, ident, length);

	return hci_acl_send(m, link, NULL);
}

/*
 * Send Command Reject packet.
 */
static int
l2cap_send_command_rej(struct hci_link *link, uint8_t ident,
			int reason, ...)
{
	l2cap_cmd_rej_cp cp;
	int len = 0;
	va_list ap;

	va_start(ap, reason);

	cp.reason = htole16(reason);

	switch (reason) {
	case L2CAP_REJ_NOT_UNDERSTOOD:
		len = 2;
		break;

	case L2CAP_REJ_MTU_EXCEEDED:
		len = 4;
		cp.data[0] = va_arg(ap, int);		/* SigMTU */
		cp.data[0] = htole16(cp.data[0]);
		break;

	case L2CAP_REJ_INVALID_CID:
		len = 6;
		cp.data[0] = va_arg(ap, int);		/* dcid */
		cp.data[0] = htole16(cp.data[0]);
		cp.data[1] = va_arg(ap, int);		/* scid */
		cp.data[1] = htole16(cp.data[1]);
		break;

	default:
		UNKNOWN(reason);
		va_end(ap);
		return EINVAL;
	}

	va_end(ap);

	return l2cap_send_signal(link, L2CAP_COMMAND_REJ, ident, len, &cp);
}

/*
 * Send Connect Request
 */
int
l2cap_send_connect_req(struct l2cap_channel *chan)
{
	l2cap_con_req_cp cp;
	int err;

	err = l2cap_request_alloc(chan, L2CAP_CONNECT_REQ);
	if (err)
		return err;

	cp.psm = htole16(chan->lc_raddr.bt_psm);
	cp.scid = htole16(chan->lc_lcid);

	return l2cap_send_signal(chan->lc_link, L2CAP_CONNECT_REQ,
				chan->lc_link->hl_lastid, sizeof(cp), &cp);
}

/*
 * Send Config Request
 *
 * For outgoing config request, we only put options in the packet if they
 * differ from the default and would have to be actioned. We don't support
 * enough option types to make overflowing SigMTU an issue so it can all
 * go in one packet.
 */
int
l2cap_send_config_req(struct l2cap_channel *chan)
{
	l2cap_cfg_req_cp *cp;
	l2cap_cfg_opt_t *opt;
	l2cap_cfg_opt_val_t *val;
	uint8_t *next, buf[L2CAP_MTU_MINIMUM];
	int err;

	err = l2cap_request_alloc(chan, L2CAP_CONFIG_REQ);
	if (err)
		return err;

	/* Config Header (4 octets) */
	cp = (l2cap_cfg_req_cp *)buf;
	cp->dcid = htole16(chan->lc_rcid);
	cp->flags = 0;	/* "No Continuation" */

	next = buf + sizeof(l2cap_cfg_req_cp);

	/* Incoming MTU (4 octets) */
	if (chan->lc_imtu != L2CAP_MTU_DEFAULT) {
		opt = (l2cap_cfg_opt_t *)next;
		opt->type = L2CAP_OPT_MTU;
		opt->length = L2CAP_OPT_MTU_SIZE;

		val = (l2cap_cfg_opt_val_t *)(opt + 1);
		val->mtu = htole16(chan->lc_imtu);

		next += sizeof(l2cap_cfg_opt_t) + L2CAP_OPT_MTU_SIZE;
	}

	/* Flush Timeout (4 octets) */
	if (chan->lc_flush != L2CAP_FLUSH_TIMO_DEFAULT) {
		opt = (l2cap_cfg_opt_t *)next;
		opt->type = L2CAP_OPT_FLUSH_TIMO;
		opt->length = L2CAP_OPT_FLUSH_TIMO_SIZE;

		val = (l2cap_cfg_opt_val_t *)(opt + 1);
		val->flush_timo = htole16(chan->lc_flush);

		next += sizeof(l2cap_cfg_opt_t) + L2CAP_OPT_FLUSH_TIMO_SIZE;
	}

	/* Outgoing QoS Flow (24 octets) */
	/* Retransmission & Flow Control (11 octets) */
	/*
	 * From here we need to start paying attention to SigMTU as we have
	 * possibly overflowed the minimum supported..
	 */

	return l2cap_send_signal(chan->lc_link, L2CAP_CONFIG_REQ,
				    chan->lc_link->hl_lastid, (int)(next - buf), buf);
}

/*
 * Send Disconnect Request
 */
int
l2cap_send_disconnect_req(struct l2cap_channel *chan)
{
	l2cap_discon_req_cp cp;
	int err;

	err = l2cap_request_alloc(chan, L2CAP_DISCONNECT_REQ);
	if (err)
		return err;

	cp.dcid = htole16(chan->lc_rcid);
	cp.scid = htole16(chan->lc_lcid);

	return l2cap_send_signal(chan->lc_link, L2CAP_DISCONNECT_REQ,
				    chan->lc_link->hl_lastid, sizeof(cp), &cp);
}

/*
 * Send Connect Response
 */
int
l2cap_send_connect_rsp(struct hci_link *link, uint8_t ident, uint16_t dcid, uint16_t scid, uint16_t result)
{
	l2cap_con_rsp_cp cp;

	memset(&cp, 0, sizeof(cp));
	cp.dcid = htole16(dcid);
	cp.scid = htole16(scid);
	cp.result = htole16(result);

	return l2cap_send_signal(link, L2CAP_CONNECT_RSP, ident, sizeof(cp), &cp);
}

/*
 * copy in QoS buffer to host
 */
static void
l2cap_qos_btoh(l2cap_qos_t *qos, void *buf)
{
	l2cap_qos_t *src = buf;

	qos->flags = src->flags;
	qos->service_type = src->service_type;
	qos->token_rate = le32toh(src->token_rate);
	qos->token_bucket_size = le32toh(src->token_bucket_size);
	qos->peak_bandwidth = le32toh(src->peak_bandwidth);
	qos->latency = le32toh(src->latency);
	qos->delay_variation = le32toh(src->delay_variation);
}

/*
 * copy out host QoS to buffer
 */
static void
l2cap_qos_htob(void *buf, l2cap_qos_t *qos)
{
	l2cap_qos_t *dst = buf;

	dst->flags = qos->flags;
	dst->service_type = qos->service_type;
	dst->token_rate = htole32(qos->token_rate);
	dst->token_bucket_size = htole32(qos->token_bucket_size);
	dst->peak_bandwidth = htole32(qos->peak_bandwidth);
	dst->latency = htole32(qos->latency);
	dst->delay_variation = htole32(qos->delay_variation);
}