[GitHub/mt8127/android_kernel_alcatel_ttab.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/slab.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>
5a0e3ad6	28	#include <linux/slab.h>
f5144854	29	#include <linux/wlp.h>
f5144854	30
bce83697	31	#include "wlp-internal.h"
f5144854	32
bce83697	33	/*
f5144854 RC	34	* Direct incoming association msg to correct parsing routine
	35	*
	36	* We only expect D1, E1, C1, C3 messages as new. All other incoming
	37	* association messages should form part of an established session that is
	38	* handled elsewhere.
	39	* The handling of these messages often require calling sleeping functions
	40	* - this cannot be done in interrupt context. We use the kernel's
	41	* workqueue to handle these messages.
	42	*/
	43	static
	44	void wlp_direct_assoc_frame(struct wlp wlp, struct sk_buff skb,
	45	struct uwb_dev_addr *src)
	46	{
	47	struct device *dev = &wlp->rc->uwb_dev.dev;
	48	struct wlp_frame_assoc assoc = (void ) skb->data;
	49	struct wlp_assoc_frame_ctx *frame_ctx;
bce83697	50
f5144854 RC	51	frame_ctx = kmalloc(sizeof(*frame_ctx), GFP_ATOMIC);
	52	if (frame_ctx == NULL) {
	53	dev_err(dev, "WLP: Unable to allocate memory for association "
	54	"frame handling.\n");
	55	kfree_skb(skb);
bce83697	56	return;
f5144854 RC	57	}
	58	frame_ctx->wlp = wlp;
	59	frame_ctx->skb = skb;
	60	frame_ctx->src = *src;
	61	switch (assoc->type) {
	62	case WLP_ASSOC_D1:
f5144854 RC	63	INIT_WORK(&frame_ctx->ws, wlp_handle_d1_frame);
	64	schedule_work(&frame_ctx->ws);
	65	break;
	66	case WLP_ASSOC_E1:
f5144854 RC	67	kfree_skb(skb); /* Temporary until we handle it */
	68	kfree(frame_ctx); /* Temporary until we handle it */
	69	break;
	70	case WLP_ASSOC_C1:
f5144854 RC	71	INIT_WORK(&frame_ctx->ws, wlp_handle_c1_frame);
	72	schedule_work(&frame_ctx->ws);
	73	break;
	74	case WLP_ASSOC_C3:
f5144854 RC	75	INIT_WORK(&frame_ctx->ws, wlp_handle_c3_frame);
	76	schedule_work(&frame_ctx->ws);
	77	break;
	78	default:
	79	dev_err(dev, "Received unexpected association frame. "
	80	"Type = %d \n", assoc->type);
	81	kfree_skb(skb);
	82	kfree(frame_ctx);
	83	break;
	84	}
f5144854 RC	85	}
f5144854 RC	86
bce83697	87	/*
f5144854 RC	88	* Process incoming association frame
	89	*
	90	* Although it could be possible to deal with some incoming association
	91	* messages without creating a new session we are keeping things simple. We
	92	* do not accept new association messages if there is a session in progress
	93	* and the messages do not belong to that session.
	94	*
	95	* If an association message arrives that causes the creation of a session
	96	* (WLP_ASSOC_E1) while we are in the process of creating a session then we
	97	* rely on the neighbor mutex to protect the data. That is, the new session
	98	* will not be started until the previous is completed.
	99	*/
	100	static
	101	void wlp_receive_assoc_frame(struct wlp wlp, struct sk_buff skb,
	102	struct uwb_dev_addr *src)
	103	{
	104	struct device *dev = &wlp->rc->uwb_dev.dev;
	105	struct wlp_frame_assoc assoc = (void ) skb->data;
	106	struct wlp_session *session = wlp->session;
	107	u8 version;
f5144854 RC	108
	109	if (wlp_get_version(wlp, &assoc->version, &version,
	110	sizeof(assoc->version)) < 0)
	111	goto error;
	112	if (version != WLP_VERSION) {
	113	dev_err(dev, "Unsupported WLP version in association "
	114	"message.\n");
	115	goto error;
	116	}
	117	if (session != NULL) {
	118	/* Function that created this session is still holding the
	119	* &wlp->mutex to protect this session. */
	120	if (assoc->type == session->exp_message \|\|
	121	assoc->type == WLP_ASSOC_F0) {
	122	if (!memcmp(&session->neighbor_addr, src,
	123	sizeof(*src))) {
	124	session->data = skb;
	125	(session->cb)(wlp);
	126	} else {
	127	dev_err(dev, "Received expected message from "
	128	"unexpected source. Expected message "
	129	"%d or F0 from %02x:%02x, but received "
	130	"it from %02x:%02x. Dropping.\n",
	131	session->exp_message,
	132	session->neighbor_addr.data[1],
	133	session->neighbor_addr.data[0],
	134	src->data[1], src->data[0]);
	135	goto error;
	136	}
	137	} else {
	138	dev_err(dev, "Association already in progress. "
	139	"Dropping.\n");
	140	goto error;
	141	}
	142	} else {
	143	wlp_direct_assoc_frame(wlp, skb, src);
	144	}
f5144854 RC	145	return;
	146	error:
	147	kfree_skb(skb);
f5144854 RC	148	}
f5144854 RC	149
bce83697	150	/*
f5144854 RC	151	* Verify incoming frame is from connected neighbor, prep to pass to WLP client
	152	*
	153	* Verification proceeds according to WLP 0.99 [7.3.1]. The source address
	154	* is used to determine which neighbor is sending the frame and the WSS tag
	155	* is used to know to which WSS the frame belongs (we only support one WSS
	156	* so this test is straight forward).
	157	* With the WSS found we need to ensure that we are connected before
	158	* allowing the exchange of data frames.
	159	*/
	160	static
	161	int wlp_verify_prep_rx_frame(struct wlp wlp, struct sk_buff skb,
	162	struct uwb_dev_addr *src)
	163	{
	164	struct device *dev = &wlp->rc->uwb_dev.dev;
	165	int result = -EINVAL;
	166	struct wlp_eda_node eda_entry;
	167	struct wlp_frame_std_abbrv_hdr hdr = (void ) skb->data;
	168
f5144854 RC	169	/verify/
	170	result = wlp_copy_eda_node(&wlp->eda, src, &eda_entry);
	171	if (result < 0) {
	172	if (printk_ratelimit())
	173	dev_err(dev, "WLP: Incoming frame is from unknown "
	174	"neighbor %02x:%02x.\n", src->data[1],
	175	src->data[0]);
	176	goto out;
	177	}
	178	if (hdr->tag != eda_entry.tag) {
	179	if (printk_ratelimit())
	180	dev_err(dev, "WLP: Tag of incoming frame from "
	181	"%02x:%02x does not match expected tag. "
	182	"Received 0x%02x, expected 0x%02x. \n",
	183	src->data[1], src->data[0], hdr->tag,
	184	eda_entry.tag);
	185	result = -EINVAL;
	186	goto out;
	187	}
	188	if (eda_entry.state != WLP_WSS_CONNECTED) {
	189	if (printk_ratelimit())
	190	dev_err(dev, "WLP: Incoming frame from "
	191	"%02x:%02x does is not from connected WSS.\n",
	192	src->data[1], src->data[0]);
	193	result = -EINVAL;
	194	goto out;
	195	}
	196	/prep/
	197	skb_pull(skb, sizeof(*hdr));
	198	out:
f5144854 RC	199	return result;
	200	}
	201
bce83697	202	/*
f5144854 RC	203	* Receive a WLP frame from device
	204	*
	205	* @returns: 1 if calling function should free the skb
	206	* 0 if it successfully handled skb and freed it
	207	* 0 if error occured, will free skb in this case
	208	*/
	209	int wlp_receive_frame(struct device dev, struct wlp wlp, struct sk_buff *skb,
	210	struct uwb_dev_addr *src)
	211	{
	212	unsigned len = skb->len;
	213	void *ptr = skb->data;
	214	struct wlp_frame_hdr *hdr;
	215	int result = 0;
	216
f5144854 RC	217	if (len < sizeof(*hdr)) {
	218	dev_err(dev, "Not enough data to parse WLP header.\n");
	219	result = -EINVAL;
	220	goto out;
	221	}
	222	hdr = ptr;
f5144854 RC	223	if (le16_to_cpu(hdr->mux_hdr) != WLP_PROTOCOL_ID) {
	224	dev_err(dev, "Not a WLP frame type.\n");
	225	result = -EINVAL;
	226	goto out;
	227	}
	228	switch (hdr->type) {
	229	case WLP_FRAME_STANDARD:
	230	if (len < sizeof(struct wlp_frame_std_abbrv_hdr)) {
	231	dev_err(dev, "Not enough data to parse Standard "
	232	"WLP header.\n");
	233	goto out;
	234	}
	235	result = wlp_verify_prep_rx_frame(wlp, skb, src);
	236	if (result < 0) {
	237	if (printk_ratelimit())
	238	dev_err(dev, "WLP: Verification of frame "
	239	"from neighbor %02x:%02x failed.\n",
	240	src->data[1], src->data[0]);
	241	goto out;
	242	}
	243	result = 1;
	244	break;
	245	case WLP_FRAME_ABBREVIATED:
	246	dev_err(dev, "Abbreviated frame received. FIXME?\n");
	247	kfree_skb(skb);
	248	break;
	249	case WLP_FRAME_CONTROL:
	250	dev_err(dev, "Control frame received. FIXME?\n");
	251	kfree_skb(skb);
	252	break;
	253	case WLP_FRAME_ASSOCIATION:
	254	if (len < sizeof(struct wlp_frame_assoc)) {
	255	dev_err(dev, "Not enough data to parse Association "
	256	"WLP header.\n");
	257	goto out;
	258	}
f5144854 RC	259	wlp_receive_assoc_frame(wlp, skb, src);
	260	break;
	261	default:
	262	dev_err(dev, "Invalid frame received.\n");
	263	result = -EINVAL;
	264	break;
	265	}
	266	out:
	267	if (result < 0) {
	268	kfree_skb(skb);
	269	result = 0;
	270	}
f5144854 RC	271	return result;
	272	}
	273	EXPORT_SYMBOL_GPL(wlp_receive_frame);
	274
	275
bce83697	276	/*
f5144854 RC	277	* Verify frame from network stack, prepare for further transmission
	278	*
	279	* @skb: the socket buffer that needs to be prepared for transmission (it
	280	* is in need of a WLP header). If this is a broadcast frame we take
	281	* over the entire transmission.
	282	* If it is a unicast the WSS connection should already be established
	283	* and transmission will be done by the calling function.
	284	* @dst: On return this will contain the device address to which the
	285	* frame is destined.
af901ca1	286	* @returns: 0 on success no tx : WLP header successfully applied to skb buffer,
f5144854 RC	287	* calling function can proceed with tx
	288	* 1 on success with tx : WLP will take over transmission of this
	289	* frame
	290	* <0 on error
	291	*
	292	* The network stack (WLP client) is attempting to transmit a frame. We can
	293	* only transmit data if a local WSS is at least active (connection will be
	294	* done here if this is a broadcast frame and neighbor also has the WSS
	295	* active).
	296	*
	297	* The frame can be either broadcast or unicast. Broadcast in a WSS is
	298	* supported via multicast, but we don't support multicast yet (until
	299	* devices start to support MAB IEs). If a broadcast frame needs to be
	300	* transmitted it is treated as a unicast frame to each neighbor. In this
	301	* case the WLP takes over transmission of the skb and returns 1
	302	* to the caller to indicate so. Also, in this case, if a neighbor has the
	303	* same WSS activated but is not connected then the WSS connection will be
	304	* done at this time. The neighbor's virtual address will be learned at
	305	* this time.
	306	*
	307	* The destination address in a unicast frame is the virtual address of the
	308	* neighbor. This address only becomes known when a WSS connection is
	309	* established. We thus rely on a broadcast frame to trigger the setup of
	310	* WSS connections to all neighbors before we are able to send unicast
	311	* frames to them. This seems reasonable as IP would usually use ARP first
	312	* before any unicast frames are sent.
	313	*
	314	* If we are already connected to the neighbor (neighbor's virtual address
	315	* is known) we just prepare the WLP header and the caller will continue to
	316	* send the frame.
	317	*
	318	* A failure in this function usually indicates something that cannot be
	319	* fixed automatically. So, if this function fails (@return < 0) the calling
	320	* function should not retry to send the frame as it will very likely keep
	321	* failing.
	322	*
	323	*/
	324	int wlp_prepare_tx_frame(struct device dev, struct wlp wlp,
	325	struct sk_buff skb, struct uwb_dev_addr dst)
	326	{
	327	int result = -EINVAL;
	328	struct ethhdr eth_hdr = (void ) skb->data;
	329
b81c087f	330	if (is_multicast_ether_addr(eth_hdr->h_dest)) {
f5144854 RC	331	result = wlp_eda_for_each(&wlp->eda, wlp_wss_send_copy, skb);
	332	if (result < 0) {
	333	if (printk_ratelimit())
	334	dev_err(dev, "Unable to handle broadcast "
	335	"frame from WLP client.\n");
	336	goto out;
	337	}
	338	dev_kfree_skb_irq(skb);
	339	result = 1;
	340	/* Frame will be transmitted by WLP. */
	341	} else {
f5144854 RC	342	result = wlp_eda_for_virtual(&wlp->eda, eth_hdr->h_dest, dst,
	343	wlp_wss_prep_hdr, skb);
	344	if (unlikely(result < 0)) {
	345	if (printk_ratelimit())
	346	dev_err(dev, "Unable to prepare "
	347	"skb for transmission. \n");
	348	goto out;
	349	}
	350	}
	351	out:
f5144854 RC	352	return result;
	353	}
	354	EXPORT_SYMBOL_GPL(wlp_prepare_tx_frame);