[mirror_ubuntu-bionic-kernel.git] / drivers / uwb / wlp / txrx.c

/*
 * WiMedia Logical Link Control Protocol (WLP)
 * Message exchange infrastructure
 *
 * Copyright (C) 2007 Intel Corporation
 * Reinette Chatre <reinette.chatre@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 *
 * FIXME: Docs
 *
 */

#include <linux/etherdevice.h>
#include <linux/wlp.h>

#include "wlp-internal.h"

/*
 * Direct incoming association msg to correct parsing routine
 *
 * We only expect D1, E1, C1, C3 messages as new. All other incoming
 * association messages should form part of an established session that is
 * handled elsewhere.
 * The handling of these messages often require calling sleeping functions
 * - this cannot be done in interrupt context. We use the kernel's
 * workqueue to handle these messages.
 */
static
void wlp_direct_assoc_frame(struct wlp *wlp, struct sk_buff *skb,
			   struct uwb_dev_addr *src)
{
	struct device *dev = &wlp->rc->uwb_dev.dev;
	struct wlp_frame_assoc *assoc = (void *) skb->data;
	struct wlp_assoc_frame_ctx *frame_ctx;

	frame_ctx = kmalloc(sizeof(*frame_ctx), GFP_ATOMIC);
	if (frame_ctx == NULL) {
		dev_err(dev, "WLP: Unable to allocate memory for association "
			"frame handling.\n");
		kfree_skb(skb);
		return;
	}
	frame_ctx->wlp = wlp;
	frame_ctx->skb = skb;
	frame_ctx->src = *src;
	switch (assoc->type) {
	case WLP_ASSOC_D1:
		INIT_WORK(&frame_ctx->ws, wlp_handle_d1_frame);
		schedule_work(&frame_ctx->ws);
		break;
	case WLP_ASSOC_E1:
		kfree_skb(skb); /* Temporary until we handle it */
		kfree(frame_ctx); /* Temporary until we handle it */
		break;
	case WLP_ASSOC_C1:
		INIT_WORK(&frame_ctx->ws, wlp_handle_c1_frame);
		schedule_work(&frame_ctx->ws);
		break;
	case WLP_ASSOC_C3:
		INIT_WORK(&frame_ctx->ws, wlp_handle_c3_frame);
		schedule_work(&frame_ctx->ws);
		break;
	default:
		dev_err(dev, "Received unexpected association frame. "
			"Type = %d \n", assoc->type);
		kfree_skb(skb);
		kfree(frame_ctx);
		break;
	}
}

/*
 * Process incoming association frame
 *
 * Although it could be possible to deal with some incoming association
 * messages without creating a new session we are keeping things simple. We
 * do not accept new association messages if there is a session in progress
 * and the messages do not belong to that session.
 *
 * If an association message arrives that causes the creation of a session
 * (WLP_ASSOC_E1) while we are in the process of creating a session then we
 * rely on the neighbor mutex to protect the data. That is, the new session
 * will not be started until the previous is completed.
 */
static
void wlp_receive_assoc_frame(struct wlp *wlp, struct sk_buff *skb,
			     struct uwb_dev_addr *src)
{
	struct device *dev = &wlp->rc->uwb_dev.dev;
	struct wlp_frame_assoc *assoc = (void *) skb->data;
	struct wlp_session *session = wlp->session;
	u8 version;

	if (wlp_get_version(wlp, &assoc->version, &version,
			    sizeof(assoc->version)) < 0)
		goto error;
	if (version != WLP_VERSION) {
		dev_err(dev, "Unsupported WLP version in association "
			"message.\n");
		goto error;
	}
	if (session != NULL) {
		/* Function that created this session is still holding the
		 * &wlp->mutex to protect this session. */
		if (assoc->type == session->exp_message ||
		    assoc->type == WLP_ASSOC_F0) {
			if (!memcmp(&session->neighbor_addr, src,
				   sizeof(*src))) {
				session->data = skb;
				(session->cb)(wlp);
			} else {
				dev_err(dev, "Received expected message from "
					"unexpected source.  Expected message "
					"%d or F0 from %02x:%02x, but received "
					"it from %02x:%02x. Dropping.\n",
					session->exp_message,
					session->neighbor_addr.data[1],
					session->neighbor_addr.data[0],
					src->data[1], src->data[0]);
				goto error;
			}
		} else {
			dev_err(dev, "Association already in progress. "
				"Dropping.\n");
			goto error;
		}
	} else {
		wlp_direct_assoc_frame(wlp, skb, src);
	}
	return;
error:
	kfree_skb(skb);
}

/*
 * Verify incoming frame is from connected neighbor, prep to pass to WLP client
 *
 * Verification proceeds according to WLP 0.99 [7.3.1]. The source address
 * is used to determine which neighbor is sending the frame and the WSS tag
 * is used to know to which WSS the frame belongs (we only support one WSS
 * so this test is straight forward).
 * With the WSS found we need to ensure that we are connected before
 * allowing the exchange of data frames.
 */
static
int wlp_verify_prep_rx_frame(struct wlp *wlp, struct sk_buff *skb,
			     struct uwb_dev_addr *src)
{
	struct device *dev = &wlp->rc->uwb_dev.dev;
	int result = -EINVAL;
	struct wlp_eda_node eda_entry;
	struct wlp_frame_std_abbrv_hdr *hdr = (void *) skb->data;

	/*verify*/
	result = wlp_copy_eda_node(&wlp->eda, src, &eda_entry);
	if (result < 0) {
		if (printk_ratelimit())
			dev_err(dev, "WLP: Incoming frame is from unknown "
				"neighbor %02x:%02x.\n", src->data[1],
				src->data[0]);
		goto out;
	}
	if (hdr->tag != eda_entry.tag) {
		if (printk_ratelimit())
			dev_err(dev, "WLP: Tag of incoming frame from "
				"%02x:%02x does not match expected tag. "
				"Received 0x%02x, expected 0x%02x. \n",
				src->data[1], src->data[0], hdr->tag,
				eda_entry.tag);
		result = -EINVAL;
		goto out;
	}
	if (eda_entry.state != WLP_WSS_CONNECTED) {
		if (printk_ratelimit())
			dev_err(dev, "WLP: Incoming frame from "
				"%02x:%02x does is not from connected WSS.\n",
				src->data[1], src->data[0]);
		result = -EINVAL;
		goto out;
	}
	/*prep*/
	skb_pull(skb, sizeof(*hdr));
out:
	return result;
}

/*
 * Receive a WLP frame from device
 *
 * @returns: 1 if calling function should free the skb
 *           0 if it successfully handled skb and freed it
 *           0 if error occured, will free skb in this case
 */
int wlp_receive_frame(struct device *dev, struct wlp *wlp, struct sk_buff *skb,
		      struct uwb_dev_addr *src)
{
	unsigned len = skb->len;
	void *ptr = skb->data;
	struct wlp_frame_hdr *hdr;
	int result = 0;

	if (len < sizeof(*hdr)) {
		dev_err(dev, "Not enough data to parse WLP header.\n");
		result = -EINVAL;
		goto out;
	}
	hdr = ptr;
	if (le16_to_cpu(hdr->mux_hdr) != WLP_PROTOCOL_ID) {
		dev_err(dev, "Not a WLP frame type.\n");
		result = -EINVAL;
		goto out;
	}
	switch (hdr->type) {
	case WLP_FRAME_STANDARD:
		if (len < sizeof(struct wlp_frame_std_abbrv_hdr)) {
			dev_err(dev, "Not enough data to parse Standard "
				"WLP header.\n");
			goto out;
		}
		result = wlp_verify_prep_rx_frame(wlp, skb, src);
		if (result < 0) {
			if (printk_ratelimit())
				dev_err(dev, "WLP: Verification of frame "
					"from neighbor %02x:%02x failed.\n",
					src->data[1], src->data[0]);
			goto out;
		}
		result = 1;
		break;
	case WLP_FRAME_ABBREVIATED:
		dev_err(dev, "Abbreviated frame received. FIXME?\n");
		kfree_skb(skb);
		break;
	case WLP_FRAME_CONTROL:
		dev_err(dev, "Control frame received. FIXME?\n");
		kfree_skb(skb);
		break;
	case WLP_FRAME_ASSOCIATION:
		if (len < sizeof(struct wlp_frame_assoc)) {
			dev_err(dev, "Not enough data to parse Association "
				"WLP header.\n");
			goto out;
		}
		wlp_receive_assoc_frame(wlp, skb, src);
		break;
	default:
		dev_err(dev, "Invalid frame received.\n");
		result = -EINVAL;
		break;
	}
out:
	if (result < 0) {
		kfree_skb(skb);
		result = 0;
	}
	return result;
}
EXPORT_SYMBOL_GPL(wlp_receive_frame);


/*
 * Verify frame from network stack, prepare for further transmission
 *
 * @skb:   the socket buffer that needs to be prepared for transmission (it
 *         is in need of a WLP header). If this is a broadcast frame we take
 *         over the entire transmission.
 *         If it is a unicast the WSS connection should already be established
 *         and transmission will be done by the calling function.
 * @dst:   On return this will contain the device address to which the
 *         frame is destined.
 * @returns: 0 on success no tx : WLP header successfully applied to skb buffer,
 *                                calling function can proceed with tx
 *           1 on success with tx : WLP will take over transmission of this
 *                                  frame
 *           <0 on error
 *
 * The network stack (WLP client) is attempting to transmit a frame. We can
 * only transmit data if a local WSS is at least active (connection will be
 * done here if this is a broadcast frame and neighbor also has the WSS
 * active).
 *
 * The frame can be either broadcast or unicast. Broadcast in a WSS is
 * supported via multicast, but we don't support multicast yet (until
 * devices start to support MAB IEs). If a broadcast frame needs to be
 * transmitted it is treated as a unicast frame to each neighbor. In this
 * case the WLP takes over transmission of the skb and returns 1
 * to the caller to indicate so. Also, in this case, if a neighbor has the
 * same WSS activated but is not connected then the WSS connection will be
 * done at this time. The neighbor's virtual address will be learned at
 * this time.
 *
 * The destination address in a unicast frame is the virtual address of the
 * neighbor. This address only becomes known when a WSS connection is
 * established. We thus rely on a broadcast frame to trigger the setup of
 * WSS connections to all neighbors before we are able to send unicast
 * frames to them. This seems reasonable as IP would usually use ARP first
 * before any unicast frames are sent.
 *
 * If we are already connected to the neighbor (neighbor's virtual address
 * is known) we just prepare the WLP header and the caller will continue to
 * send the frame.
 *
 * A failure in this function usually indicates something that cannot be
 * fixed automatically. So, if this function fails (@return < 0) the calling
 * function should not retry to send the frame as it will very likely keep
 * failing.
 *
 */
int wlp_prepare_tx_frame(struct device *dev, struct wlp *wlp,
			 struct sk_buff *skb, struct uwb_dev_addr *dst)
{
	int result = -EINVAL;
	struct ethhdr *eth_hdr = (void *) skb->data;

	if (is_multicast_ether_addr(eth_hdr->h_dest)) {
		result = wlp_eda_for_each(&wlp->eda, wlp_wss_send_copy, skb);
		if (result < 0) {
			if (printk_ratelimit())
				dev_err(dev, "Unable to handle broadcast "
					"frame from WLP client.\n");
			goto out;
		}
		dev_kfree_skb_irq(skb);
		result = 1;
		/* Frame will be transmitted by WLP. */
	} else {
		result = wlp_eda_for_virtual(&wlp->eda, eth_hdr->h_dest, dst,
					     wlp_wss_prep_hdr, skb);
		if (unlikely(result < 0)) {
			if (printk_ratelimit())
				dev_err(dev, "Unable to prepare "
					"skb for transmission. \n");
			goto out;
		}
	}
out:
	return result;
}
EXPORT_SYMBOL_GPL(wlp_prepare_tx_frame);
Commit	Line	Data
f5144854 RC	1	/*
	2	* WiMedia Logical Link Control Protocol (WLP)
	3	* Message exchange infrastructure
	4	*
	5	* Copyright (C) 2007 Intel Corporation
	6	* Reinette Chatre <reinette.chatre@intel.com>
	7	*
	8	* This program is free software; you can redistribute it and/or
	9	* modify it under the terms of the GNU General Public License version
	10	* 2 as published by the Free Software Foundation.
	11	*
	12	* This program is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	* GNU General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU General Public License
	18	* along with this program; if not, write to the Free Software
	19	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	20	* 02110-1301, USA.
	21	*
	22	*
	23	* FIXME: Docs
	24	*
	25	*/
	26
	27	#include <linux/etherdevice.h>
	28	#include <linux/wlp.h>
f5144854	29
bce83697	30	#include "wlp-internal.h"
f5144854	31
bce83697	32	/*
f5144854 RC	33	* Direct incoming association msg to correct parsing routine
	34	*
	35	* We only expect D1, E1, C1, C3 messages as new. All other incoming
	36	* association messages should form part of an established session that is
	37	* handled elsewhere.
	38	* The handling of these messages often require calling sleeping functions
	39	* - this cannot be done in interrupt context. We use the kernel's
	40	* workqueue to handle these messages.
	41	*/
	42	static
	43	void wlp_direct_assoc_frame(struct wlp wlp, struct sk_buff skb,
	44	struct uwb_dev_addr *src)
	45	{
	46	struct device *dev = &wlp->rc->uwb_dev.dev;
	47	struct wlp_frame_assoc assoc = (void ) skb->data;
	48	struct wlp_assoc_frame_ctx *frame_ctx;
bce83697	49
f5144854 RC	50	frame_ctx = kmalloc(sizeof(*frame_ctx), GFP_ATOMIC);
	51	if (frame_ctx == NULL) {
	52	dev_err(dev, "WLP: Unable to allocate memory for association "
	53	"frame handling.\n");
	54	kfree_skb(skb);
bce83697	55	return;
f5144854 RC	56	}
	57	frame_ctx->wlp = wlp;
	58	frame_ctx->skb = skb;
	59	frame_ctx->src = *src;
	60	switch (assoc->type) {
	61	case WLP_ASSOC_D1:
f5144854 RC	62	INIT_WORK(&frame_ctx->ws, wlp_handle_d1_frame);
	63	schedule_work(&frame_ctx->ws);
	64	break;
	65	case WLP_ASSOC_E1:
f5144854 RC	66	kfree_skb(skb); /* Temporary until we handle it */
	67	kfree(frame_ctx); /* Temporary until we handle it */
	68	break;
	69	case WLP_ASSOC_C1:
f5144854 RC	70	INIT_WORK(&frame_ctx->ws, wlp_handle_c1_frame);
	71	schedule_work(&frame_ctx->ws);
	72	break;
	73	case WLP_ASSOC_C3:
f5144854 RC	74	INIT_WORK(&frame_ctx->ws, wlp_handle_c3_frame);
	75	schedule_work(&frame_ctx->ws);
	76	break;
	77	default:
	78	dev_err(dev, "Received unexpected association frame. "
	79	"Type = %d \n", assoc->type);
	80	kfree_skb(skb);
	81	kfree(frame_ctx);
	82	break;
	83	}
f5144854 RC	84	}
f5144854 RC	85
bce83697	86	/*
f5144854 RC	87	* Process incoming association frame
	88	*
	89	* Although it could be possible to deal with some incoming association
	90	* messages without creating a new session we are keeping things simple. We
	91	* do not accept new association messages if there is a session in progress
	92	* and the messages do not belong to that session.
	93	*
	94	* If an association message arrives that causes the creation of a session
	95	* (WLP_ASSOC_E1) while we are in the process of creating a session then we
	96	* rely on the neighbor mutex to protect the data. That is, the new session
	97	* will not be started until the previous is completed.
	98	*/
	99	static
	100	void wlp_receive_assoc_frame(struct wlp wlp, struct sk_buff skb,
	101	struct uwb_dev_addr *src)
	102	{
	103	struct device *dev = &wlp->rc->uwb_dev.dev;
	104	struct wlp_frame_assoc assoc = (void ) skb->data;
	105	struct wlp_session *session = wlp->session;
	106	u8 version;
f5144854 RC	107
	108	if (wlp_get_version(wlp, &assoc->version, &version,
	109	sizeof(assoc->version)) < 0)
	110	goto error;
	111	if (version != WLP_VERSION) {
	112	dev_err(dev, "Unsupported WLP version in association "
	113	"message.\n");
	114	goto error;
	115	}
	116	if (session != NULL) {
	117	/* Function that created this session is still holding the
	118	* &wlp->mutex to protect this session. */
	119	if (assoc->type == session->exp_message \|\|
	120	assoc->type == WLP_ASSOC_F0) {
	121	if (!memcmp(&session->neighbor_addr, src,
	122	sizeof(*src))) {
	123	session->data = skb;
	124	(session->cb)(wlp);
	125	} else {
	126	dev_err(dev, "Received expected message from "
	127	"unexpected source. Expected message "
	128	"%d or F0 from %02x:%02x, but received "
	129	"it from %02x:%02x. Dropping.\n",
	130	session->exp_message,
	131	session->neighbor_addr.data[1],
	132	session->neighbor_addr.data[0],
	133	src->data[1], src->data[0]);
	134	goto error;
	135	}
	136	} else {
	137	dev_err(dev, "Association already in progress. "
	138	"Dropping.\n");
	139	goto error;
	140	}
	141	} else {
	142	wlp_direct_assoc_frame(wlp, skb, src);
	143	}
f5144854 RC	144	return;
	145	error:
	146	kfree_skb(skb);
f5144854 RC	147	}
f5144854 RC	148
bce83697	149	/*
f5144854 RC	150	* Verify incoming frame is from connected neighbor, prep to pass to WLP client
	151	*
	152	* Verification proceeds according to WLP 0.99 [7.3.1]. The source address
	153	* is used to determine which neighbor is sending the frame and the WSS tag
	154	* is used to know to which WSS the frame belongs (we only support one WSS
	155	* so this test is straight forward).
	156	* With the WSS found we need to ensure that we are connected before
	157	* allowing the exchange of data frames.
	158	*/
	159	static
	160	int wlp_verify_prep_rx_frame(struct wlp wlp, struct sk_buff skb,
	161	struct uwb_dev_addr *src)
	162	{
	163	struct device *dev = &wlp->rc->uwb_dev.dev;
	164	int result = -EINVAL;
	165	struct wlp_eda_node eda_entry;
	166	struct wlp_frame_std_abbrv_hdr hdr = (void ) skb->data;
	167
f5144854 RC	168	/verify/
	169	result = wlp_copy_eda_node(&wlp->eda, src, &eda_entry);
	170	if (result < 0) {
	171	if (printk_ratelimit())
	172	dev_err(dev, "WLP: Incoming frame is from unknown "
	173	"neighbor %02x:%02x.\n", src->data[1],
	174	src->data[0]);
	175	goto out;
	176	}
	177	if (hdr->tag != eda_entry.tag) {
	178	if (printk_ratelimit())
	179	dev_err(dev, "WLP: Tag of incoming frame from "
	180	"%02x:%02x does not match expected tag. "
	181	"Received 0x%02x, expected 0x%02x. \n",
	182	src->data[1], src->data[0], hdr->tag,
	183	eda_entry.tag);
	184	result = -EINVAL;
	185	goto out;
	186	}
	187	if (eda_entry.state != WLP_WSS_CONNECTED) {
	188	if (printk_ratelimit())
	189	dev_err(dev, "WLP: Incoming frame from "
	190	"%02x:%02x does is not from connected WSS.\n",
	191	src->data[1], src->data[0]);
	192	result = -EINVAL;
	193	goto out;
	194	}
	195	/prep/
	196	skb_pull(skb, sizeof(*hdr));
	197	out:
f5144854 RC	198	return result;
	199	}
	200
bce83697	201	/*
f5144854 RC	202	* Receive a WLP frame from device
	203	*
	204	* @returns: 1 if calling function should free the skb
	205	* 0 if it successfully handled skb and freed it
	206	* 0 if error occured, will free skb in this case
	207	*/
	208	int wlp_receive_frame(struct device dev, struct wlp wlp, struct sk_buff *skb,
	209	struct uwb_dev_addr *src)
	210	{
	211	unsigned len = skb->len;
	212	void *ptr = skb->data;
	213	struct wlp_frame_hdr *hdr;
	214	int result = 0;
	215
f5144854 RC	216	if (len < sizeof(*hdr)) {
	217	dev_err(dev, "Not enough data to parse WLP header.\n");
	218	result = -EINVAL;
	219	goto out;
	220	}
	221	hdr = ptr;
f5144854 RC	222	if (le16_to_cpu(hdr->mux_hdr) != WLP_PROTOCOL_ID) {
	223	dev_err(dev, "Not a WLP frame type.\n");
	224	result = -EINVAL;
	225	goto out;
	226	}
	227	switch (hdr->type) {
	228	case WLP_FRAME_STANDARD:
	229	if (len < sizeof(struct wlp_frame_std_abbrv_hdr)) {
	230	dev_err(dev, "Not enough data to parse Standard "
	231	"WLP header.\n");
	232	goto out;
	233	}
	234	result = wlp_verify_prep_rx_frame(wlp, skb, src);
	235	if (result < 0) {
	236	if (printk_ratelimit())
	237	dev_err(dev, "WLP: Verification of frame "
	238	"from neighbor %02x:%02x failed.\n",
	239	src->data[1], src->data[0]);
	240	goto out;
	241	}
	242	result = 1;
	243	break;
	244	case WLP_FRAME_ABBREVIATED:
	245	dev_err(dev, "Abbreviated frame received. FIXME?\n");
	246	kfree_skb(skb);
	247	break;
	248	case WLP_FRAME_CONTROL:
	249	dev_err(dev, "Control frame received. FIXME?\n");
	250	kfree_skb(skb);
	251	break;
	252	case WLP_FRAME_ASSOCIATION:
	253	if (len < sizeof(struct wlp_frame_assoc)) {
	254	dev_err(dev, "Not enough data to parse Association "
	255	"WLP header.\n");
	256	goto out;
	257	}
f5144854 RC	258	wlp_receive_assoc_frame(wlp, skb, src);
	259	break;
	260	default:
	261	dev_err(dev, "Invalid frame received.\n");
	262	result = -EINVAL;
	263	break;
	264	}
	265	out:
	266	if (result < 0) {
	267	kfree_skb(skb);
	268	result = 0;
	269	}
f5144854 RC	270	return result;
	271	}
	272	EXPORT_SYMBOL_GPL(wlp_receive_frame);
	273
	274
bce83697	275	/*
f5144854 RC	276	* Verify frame from network stack, prepare for further transmission
	277	*
	278	* @skb: the socket buffer that needs to be prepared for transmission (it
	279	* is in need of a WLP header). If this is a broadcast frame we take
	280	* over the entire transmission.
	281	* If it is a unicast the WSS connection should already be established
	282	* and transmission will be done by the calling function.
	283	* @dst: On return this will contain the device address to which the
	284	* frame is destined.
af901ca1	285	* @returns: 0 on success no tx : WLP header successfully applied to skb buffer,
f5144854 RC	286	* calling function can proceed with tx
	287	* 1 on success with tx : WLP will take over transmission of this
	288	* frame
	289	* <0 on error
	290	*
	291	* The network stack (WLP client) is attempting to transmit a frame. We can
	292	* only transmit data if a local WSS is at least active (connection will be
	293	* done here if this is a broadcast frame and neighbor also has the WSS
	294	* active).
	295	*
	296	* The frame can be either broadcast or unicast. Broadcast in a WSS is
	297	* supported via multicast, but we don't support multicast yet (until
	298	* devices start to support MAB IEs). If a broadcast frame needs to be
	299	* transmitted it is treated as a unicast frame to each neighbor. In this
	300	* case the WLP takes over transmission of the skb and returns 1
	301	* to the caller to indicate so. Also, in this case, if a neighbor has the
	302	* same WSS activated but is not connected then the WSS connection will be
	303	* done at this time. The neighbor's virtual address will be learned at
	304	* this time.
	305	*
	306	* The destination address in a unicast frame is the virtual address of the
	307	* neighbor. This address only becomes known when a WSS connection is
	308	* established. We thus rely on a broadcast frame to trigger the setup of
	309	* WSS connections to all neighbors before we are able to send unicast
	310	* frames to them. This seems reasonable as IP would usually use ARP first
	311	* before any unicast frames are sent.
	312	*
	313	* If we are already connected to the neighbor (neighbor's virtual address
	314	* is known) we just prepare the WLP header and the caller will continue to
	315	* send the frame.
	316	*
	317	* A failure in this function usually indicates something that cannot be
	318	* fixed automatically. So, if this function fails (@return < 0) the calling
	319	* function should not retry to send the frame as it will very likely keep
	320	* failing.
	321	*
	322	*/
	323	int wlp_prepare_tx_frame(struct device dev, struct wlp wlp,
	324	struct sk_buff skb, struct uwb_dev_addr dst)
	325	{
	326	int result = -EINVAL;
	327	struct ethhdr eth_hdr = (void ) skb->data;
	328
b81c087f	329	if (is_multicast_ether_addr(eth_hdr->h_dest)) {
f5144854 RC	330	result = wlp_eda_for_each(&wlp->eda, wlp_wss_send_copy, skb);
	331	if (result < 0) {
	332	if (printk_ratelimit())
	333	dev_err(dev, "Unable to handle broadcast "
	334	"frame from WLP client.\n");
	335	goto out;
	336	}
	337	dev_kfree_skb_irq(skb);
	338	result = 1;
	339	/* Frame will be transmitted by WLP. */
	340	} else {
f5144854 RC	341	result = wlp_eda_for_virtual(&wlp->eda, eth_hdr->h_dest, dst,
	342	wlp_wss_prep_hdr, skb);
	343	if (unlikely(result < 0)) {
	344	if (printk_ratelimit())
	345	dev_err(dev, "Unable to prepare "
	346	"skb for transmission. \n");
	347	goto out;
	348	}
	349	}
	350	out:
f5144854 RC	351	return result;
	352	}
	353	EXPORT_SYMBOL_GPL(wlp_prepare_tx_frame);