net/dsa/tag_sja1105.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
  */
 #include <linux/if_vlan.h>
 #include <linux/dsa/sja1105.h>
 #include <linux/dsa/8021q.h>
 #include <linux/packing.h>
 #include "dsa_priv.h"

 /* Similar to is_link_local_ether_addr(hdr->h_dest) but also covers PTP */
 static inline bool sja1105_is_link_local(const struct sk_buff *skb)
 {
 	const struct ethhdr *hdr = eth_hdr(skb);
 	u64 dmac = ether_addr_to_u64(hdr->h_dest);

 	if (ntohs(hdr->h_proto) == ETH_P_SJA1105_META)
 		return false;
 	if ((dmac & SJA1105_LINKLOCAL_FILTER_A_MASK) ==
 		    SJA1105_LINKLOCAL_FILTER_A)
 		return true;
 	if ((dmac & SJA1105_LINKLOCAL_FILTER_B_MASK) ==
 		    SJA1105_LINKLOCAL_FILTER_B)
 		return true;
 	return false;
 }

 struct sja1105_meta {
 	u64 tstamp;
 	u64 dmac_byte_4;
 	u64 dmac_byte_3;
 	u64 source_port;
 	u64 switch_id;
 };

 static void sja1105_meta_unpack(const struct sk_buff *skb,
 				struct sja1105_meta *meta)
 {
 	u8 *buf = skb_mac_header(skb) + ETH_HLEN;

 	/* UM10944.pdf section 4.2.17 AVB Parameters:
 	 * Structure of the meta-data follow-up frame.
 	 * It is in network byte order, so there are no quirks
 	 * while unpacking the meta frame.
 	 *
 	 * Also SJA1105 E/T only populates bits 23:0 of the timestamp
 	 * whereas P/Q/R/S does 32 bits. Since the structure is the
 	 * same and the E/T puts zeroes in the high-order byte, use
 	 * a unified unpacking command for both device series.
 	 */
 	packing(buf,     &meta->tstamp,     31, 0, 4, UNPACK, 0);
 	packing(buf + 4, &meta->dmac_byte_4, 7, 0, 1, UNPACK, 0);
 	packing(buf + 5, &meta->dmac_byte_3, 7, 0, 1, UNPACK, 0);
 	packing(buf + 6, &meta->source_port, 7, 0, 1, UNPACK, 0);
 	packing(buf + 7, &meta->switch_id,   7, 0, 1, UNPACK, 0);
 }

 static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
 {
 	const struct ethhdr *hdr = eth_hdr(skb);
 	u64 smac = ether_addr_to_u64(hdr->h_source);
 	u64 dmac = ether_addr_to_u64(hdr->h_dest);

 	if (smac != SJA1105_META_SMAC)
 		return false;
 	if (dmac != SJA1105_META_DMAC)
 		return false;
 	if (ntohs(hdr->h_proto) != ETH_P_SJA1105_META)
 		return false;
 	return true;
 }

 static bool sja1105_can_use_vlan_as_tags(const struct sk_buff *skb)
 {
 	struct vlan_ethhdr *hdr = vlan_eth_hdr(skb);
 	u16 vlan_tci;

 	if (hdr->h_vlan_proto == htons(ETH_P_SJA1105))
 		return true;

 	if (hdr->h_vlan_proto != htons(ETH_P_8021Q) &&
 	    !skb_vlan_tag_present(skb))
 		return false;

 	if (skb_vlan_tag_present(skb))
 		vlan_tci = skb_vlan_tag_get(skb);
 	else
 		vlan_tci = ntohs(hdr->h_vlan_TCI);

 	return vid_is_dsa_8021q(vlan_tci & VLAN_VID_MASK);
 }

 /* This is the first time the tagger sees the frame on RX.
  * Figure out if we can decode it.
  */
 static bool sja1105_filter(const struct sk_buff *skb, struct net_device *dev)
 {
 	if (sja1105_can_use_vlan_as_tags(skb))
 		return true;
 	if (sja1105_is_link_local(skb))
 		return true;
 	if (sja1105_is_meta_frame(skb))
 		return true;
 	return false;
 }

 /* Calls sja1105_port_deferred_xmit in sja1105_main.c */
 static struct sk_buff *sja1105_defer_xmit(struct sja1105_port *sp,
 					  struct sk_buff *skb)
 {
 	/* Increase refcount so the kfree_skb in dsa_slave_xmit
 	 * won't really free the packet.
 	 */
 	skb_queue_tail(&sp->xmit_queue, skb_get(skb));
 	kthread_queue_work(sp->xmit_worker, &sp->xmit_work);

 	return NULL;
 }

 static u16 sja1105_xmit_tpid(struct sja1105_port *sp)
 {
 	return sp->xmit_tpid;
 }

 static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
 				    struct net_device *netdev)
 {
 	struct dsa_port *dp = dsa_slave_to_port(netdev);
 	u16 tx_vid = dsa_8021q_tx_vid(dp->ds, dp->index);
 	u16 queue_mapping = skb_get_queue_mapping(skb);
 	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);

 	/* Transmitting management traffic does not rely upon switch tagging,
 	 * but instead SPI-installed management routes. Part 2 of this
 	 * is the .port_deferred_xmit driver callback.
 	 */
 	if (unlikely(sja1105_is_link_local(skb)))
 		return sja1105_defer_xmit(dp->priv, skb);

 	return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv),
 			     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 }

 static void sja1105_transfer_meta(struct sk_buff *skb,
 				  const struct sja1105_meta *meta)
 {
 	struct ethhdr *hdr = eth_hdr(skb);

 	hdr->h_dest[3] = meta->dmac_byte_3;
 	hdr->h_dest[4] = meta->dmac_byte_4;
 	SJA1105_SKB_CB(skb)->meta_tstamp = meta->tstamp;
 }

 /* This is a simple state machine which follows the hardware mechanism of
  * generating RX timestamps:
  *
  * After each timestampable skb (all traffic for which send_meta1 and
  * send_meta0 is true, aka all MAC-filtered link-local traffic) a meta frame
  * containing a partial timestamp is immediately generated by the switch and
  * sent as a follow-up to the link-local frame on the CPU port.
  *
  * The meta frames have no unique identifier (such as sequence number) by which
  * one may pair them to the correct timestampable frame.
  * Instead, the switch has internal logic that ensures no frames are sent on
  * the CPU port between a link-local timestampable frame and its corresponding
  * meta follow-up. It also ensures strict ordering between ports (lower ports
  * have higher priority towards the CPU port). For this reason, a per-port
  * data structure is not needed/desirable.
  *
  * This function pairs the link-local frame with its partial timestamp from the
  * meta follow-up frame. The full timestamp will be reconstructed later in a
  * work queue.
  */
 static struct sk_buff
 *sja1105_rcv_meta_state_machine(struct sk_buff *skb,
 				struct sja1105_meta *meta,
 				bool is_link_local,
 				bool is_meta)
 {
 	struct sja1105_port *sp;
 	struct dsa_port *dp;

 	dp = dsa_slave_to_port(skb->dev);
 	sp = dp->priv;

 	/* Step 1: A timestampable frame was received.
 	 * Buffer it until we get its meta frame.
 	 */
 	if (is_link_local) {
 		if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
 			/* Do normal processing. */
 			return skb;

 		spin_lock(&sp->data->meta_lock);
 		/* Was this a link-local frame instead of the meta
 		 * that we were expecting?
 		 */
 		if (sp->data->stampable_skb) {
 			dev_err_ratelimited(dp->ds->dev,
 					    "Expected meta frame, is %12llx "
 					    "in the DSA master multicast filter?\n",
 					    SJA1105_META_DMAC);
 			kfree_skb(sp->data->stampable_skb);
 		}

 		/* Hold a reference to avoid dsa_switch_rcv
 		 * from freeing the skb.
 		 */
 		sp->data->stampable_skb = skb_get(skb);
 		spin_unlock(&sp->data->meta_lock);

 		/* Tell DSA we got nothing */
 		return NULL;

 	/* Step 2: The meta frame arrived.
 	 * Time to take the stampable skb out of the closet, annotate it
 	 * with the partial timestamp, and pretend that we received it
 	 * just now (basically masquerade the buffered frame as the meta
 	 * frame, which serves no further purpose).
 	 */
 	} else if (is_meta) {
 		struct sk_buff *stampable_skb;

 		/* Drop the meta frame if we're not in the right state
 		 * to process it.
 		 */
 		if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
 			return NULL;

 		spin_lock(&sp->data->meta_lock);

 		stampable_skb = sp->data->stampable_skb;
 		sp->data->stampable_skb = NULL;

 		/* Was this a meta frame instead of the link-local
 		 * that we were expecting?
 		 */
 		if (!stampable_skb) {
 			dev_err_ratelimited(dp->ds->dev,
 					    "Unexpected meta frame\n");
 			spin_unlock(&sp->data->meta_lock);
 			return NULL;
 		}

 		if (stampable_skb->dev != skb->dev) {
 			dev_err_ratelimited(dp->ds->dev,
 					    "Meta frame on wrong port\n");
 			spin_unlock(&sp->data->meta_lock);
 			return NULL;
 		}

 		/* Free the meta frame and give DSA the buffered stampable_skb
 		 * for further processing up the network stack.
 		 */
 		kfree_skb(skb);
 		skb = stampable_skb;
 		sja1105_transfer_meta(skb, meta);

 		spin_unlock(&sp->data->meta_lock);
 	}

 	return skb;
 }

 static void sja1105_decode_subvlan(struct sk_buff *skb, u16 subvlan)
 {
 	struct dsa_port *dp = dsa_slave_to_port(skb->dev);
 	struct sja1105_port *sp = dp->priv;
 	u16 vid = sp->subvlan_map[subvlan];
 	u16 vlan_tci;

 	if (vid == VLAN_N_VID)
 		return;

 	vlan_tci = (skb->priority << VLAN_PRIO_SHIFT) | vid;
 	__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);
 }

 static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 				   struct net_device *netdev,
 				   struct packet_type *pt)
 {
 	struct sja1105_meta meta = {0};
 	int source_port, switch_id;
 	struct ethhdr *hdr;
 	u16 tpid, vid, tci;
 	bool is_link_local;
 	u16 subvlan = 0;
 	bool is_tagged;
 	bool is_meta;

 	hdr = eth_hdr(skb);
 	tpid = ntohs(hdr->h_proto);
 	is_tagged = (tpid == ETH_P_SJA1105 || tpid == ETH_P_8021Q ||
 		     skb_vlan_tag_present(skb));
 	is_link_local = sja1105_is_link_local(skb);
 	is_meta = sja1105_is_meta_frame(skb);

 	skb->offload_fwd_mark = 1;

 	if (is_tagged) {
 		/* Normal traffic path. */
 		skb_push_rcsum(skb, ETH_HLEN);
 		if (skb_vlan_tag_present(skb)) {
 			tci = skb_vlan_tag_get(skb);
 			__vlan_hwaccel_clear_tag(skb);
 		} else {
 			__skb_vlan_pop(skb, &tci);
 		}
 		skb_pull_rcsum(skb, ETH_HLEN);
 		skb_reset_network_header(skb);
 		skb_reset_transport_header(skb);

 		vid = tci & VLAN_VID_MASK;
 		source_port = dsa_8021q_rx_source_port(vid);
 		switch_id = dsa_8021q_rx_switch_id(vid);
 		skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
 		subvlan = dsa_8021q_rx_subvlan(vid);
 	} else if (is_link_local) {
 		/* Management traffic path. Switch embeds the switch ID and
 		 * port ID into bytes of the destination MAC, courtesy of
 		 * the incl_srcpt options.
 		 */
 		source_port = hdr->h_dest[3];
 		switch_id = hdr->h_dest[4];
 		/* Clear the DMAC bytes that were mangled by the switch */
 		hdr->h_dest[3] = 0;
 		hdr->h_dest[4] = 0;
 	} else if (is_meta) {
 		sja1105_meta_unpack(skb, &meta);
 		source_port = meta.source_port;
 		switch_id = meta.switch_id;
 	} else {
 		return NULL;
 	}

 	skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
 	if (!skb->dev) {
 		netdev_warn(netdev, "Couldn't decode source port\n");
 		return NULL;
 	}

 	if (subvlan)
 		sja1105_decode_subvlan(skb, subvlan);

 	return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
 					      is_meta);
 }

 static void sja1105_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 				 int *offset)
 {
 	/* No tag added for management frames, all ok */
 	if (unlikely(sja1105_is_link_local(skb)))
 		return;

 	dsa_tag_generic_flow_dissect(skb, proto, offset);
 }

 static const struct dsa_device_ops sja1105_netdev_ops = {
 	.name = "sja1105",
 	.proto = DSA_TAG_PROTO_SJA1105,
 	.xmit = sja1105_xmit,
 	.rcv = sja1105_rcv,
 	.filter = sja1105_filter,
 	.overhead = VLAN_HLEN,
 	.flow_dissect = sja1105_flow_dissect,
 	.promisc_on_master = true,
 };

 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);

 module_dsa_tag_driver(sja1105_netdev_ops);
	// SPDX-License-Identifier: GPL-2.0
	/* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
	*/
	#include <linux/if_vlan.h>
	#include <linux/dsa/sja1105.h>
	#include <linux/dsa/8021q.h>
	#include <linux/packing.h>
	#include "dsa_priv.h"

	/* Similar to is_link_local_ether_addr(hdr->h_dest) but also covers PTP */
	static inline bool sja1105_is_link_local(const struct sk_buff *skb)
	{
	const struct ethhdr *hdr = eth_hdr(skb);
	u64 dmac = ether_addr_to_u64(hdr->h_dest);

	if (ntohs(hdr->h_proto) == ETH_P_SJA1105_META)
	return false;
	if ((dmac & SJA1105_LINKLOCAL_FILTER_A_MASK) ==
	SJA1105_LINKLOCAL_FILTER_A)
	return true;
	if ((dmac & SJA1105_LINKLOCAL_FILTER_B_MASK) ==
	SJA1105_LINKLOCAL_FILTER_B)
	return true;
	return false;
	}

	struct sja1105_meta {
	u64 tstamp;
	u64 dmac_byte_4;
	u64 dmac_byte_3;
	u64 source_port;
	u64 switch_id;
	};

	static void sja1105_meta_unpack(const struct sk_buff *skb,
	struct sja1105_meta *meta)
	{
	u8 *buf = skb_mac_header(skb) + ETH_HLEN;

	/* UM10944.pdf section 4.2.17 AVB Parameters:
	* Structure of the meta-data follow-up frame.
	* It is in network byte order, so there are no quirks
	* while unpacking the meta frame.
	*
	* Also SJA1105 E/T only populates bits 23:0 of the timestamp
	* whereas P/Q/R/S does 32 bits. Since the structure is the
	* same and the E/T puts zeroes in the high-order byte, use
	* a unified unpacking command for both device series.
	*/
	packing(buf, &meta->tstamp, 31, 0, 4, UNPACK, 0);
	packing(buf + 4, &meta->dmac_byte_4, 7, 0, 1, UNPACK, 0);
	packing(buf + 5, &meta->dmac_byte_3, 7, 0, 1, UNPACK, 0);
	packing(buf + 6, &meta->source_port, 7, 0, 1, UNPACK, 0);
	packing(buf + 7, &meta->switch_id, 7, 0, 1, UNPACK, 0);
	}

	static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
	{
	const struct ethhdr *hdr = eth_hdr(skb);
	u64 smac = ether_addr_to_u64(hdr->h_source);
	u64 dmac = ether_addr_to_u64(hdr->h_dest);

	if (smac != SJA1105_META_SMAC)
	return false;
	if (dmac != SJA1105_META_DMAC)
	return false;
	if (ntohs(hdr->h_proto) != ETH_P_SJA1105_META)
	return false;
	return true;
	}

	static bool sja1105_can_use_vlan_as_tags(const struct sk_buff *skb)
	{
	struct vlan_ethhdr *hdr = vlan_eth_hdr(skb);
	u16 vlan_tci;

	if (hdr->h_vlan_proto == htons(ETH_P_SJA1105))
	return true;

	if (hdr->h_vlan_proto != htons(ETH_P_8021Q) &&
	!skb_vlan_tag_present(skb))
	return false;

	if (skb_vlan_tag_present(skb))
	vlan_tci = skb_vlan_tag_get(skb);
	else
	vlan_tci = ntohs(hdr->h_vlan_TCI);

	return vid_is_dsa_8021q(vlan_tci & VLAN_VID_MASK);
	}

	/* This is the first time the tagger sees the frame on RX.
	* Figure out if we can decode it.
	*/
	static bool sja1105_filter(const struct sk_buff skb, struct net_device dev)
	{
	if (sja1105_can_use_vlan_as_tags(skb))
	return true;
	if (sja1105_is_link_local(skb))
	return true;
	if (sja1105_is_meta_frame(skb))
	return true;
	return false;
	}

	/* Calls sja1105_port_deferred_xmit in sja1105_main.c */
	static struct sk_buff sja1105_defer_xmit(struct sja1105_port sp,
	struct sk_buff *skb)
	{
	/* Increase refcount so the kfree_skb in dsa_slave_xmit
	* won't really free the packet.
	*/
	skb_queue_tail(&sp->xmit_queue, skb_get(skb));
	kthread_queue_work(sp->xmit_worker, &sp->xmit_work);

	return NULL;
	}

	static u16 sja1105_xmit_tpid(struct sja1105_port *sp)
	{
	return sp->xmit_tpid;
	}

	static struct sk_buff sja1105_xmit(struct sk_buff skb,
	struct net_device *netdev)
	{
	struct dsa_port *dp = dsa_slave_to_port(netdev);
	u16 tx_vid = dsa_8021q_tx_vid(dp->ds, dp->index);
	u16 queue_mapping = skb_get_queue_mapping(skb);
	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);

	/* Transmitting management traffic does not rely upon switch tagging,
	* but instead SPI-installed management routes. Part 2 of this
	* is the .port_deferred_xmit driver callback.
	*/
	if (unlikely(sja1105_is_link_local(skb)))
	return sja1105_defer_xmit(dp->priv, skb);

	return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv),
	((pcp << VLAN_PRIO_SHIFT) \| tx_vid));
	}

	static void sja1105_transfer_meta(struct sk_buff *skb,
	const struct sja1105_meta *meta)
	{
	struct ethhdr *hdr = eth_hdr(skb);

	hdr->h_dest[3] = meta->dmac_byte_3;
	hdr->h_dest[4] = meta->dmac_byte_4;
	SJA1105_SKB_CB(skb)->meta_tstamp = meta->tstamp;
	}

	/* This is a simple state machine which follows the hardware mechanism of
	* generating RX timestamps:
	*
	* After each timestampable skb (all traffic for which send_meta1 and
	* send_meta0 is true, aka all MAC-filtered link-local traffic) a meta frame
	* containing a partial timestamp is immediately generated by the switch and
	* sent as a follow-up to the link-local frame on the CPU port.
	*
	* The meta frames have no unique identifier (such as sequence number) by which
	* one may pair them to the correct timestampable frame.
	* Instead, the switch has internal logic that ensures no frames are sent on
	* the CPU port between a link-local timestampable frame and its corresponding
	* meta follow-up. It also ensures strict ordering between ports (lower ports
	* have higher priority towards the CPU port). For this reason, a per-port
	* data structure is not needed/desirable.
	*
	* This function pairs the link-local frame with its partial timestamp from the
	* meta follow-up frame. The full timestamp will be reconstructed later in a
	* work queue.
	*/
	static struct sk_buff
	sja1105_rcv_meta_state_machine(struct sk_buff skb,
	struct sja1105_meta *meta,
	bool is_link_local,
	bool is_meta)
	{
	struct sja1105_port *sp;
	struct dsa_port *dp;

	dp = dsa_slave_to_port(skb->dev);
	sp = dp->priv;

	/* Step 1: A timestampable frame was received.
	* Buffer it until we get its meta frame.
	*/
	if (is_link_local) {
	if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
	/* Do normal processing. */
	return skb;

	spin_lock(&sp->data->meta_lock);
	/* Was this a link-local frame instead of the meta
	* that we were expecting?
	*/
	if (sp->data->stampable_skb) {
	dev_err_ratelimited(dp->ds->dev,
	"Expected meta frame, is %12llx "
	"in the DSA master multicast filter?\n",
	SJA1105_META_DMAC);
	kfree_skb(sp->data->stampable_skb);
	}

	/* Hold a reference to avoid dsa_switch_rcv
	* from freeing the skb.
	*/
	sp->data->stampable_skb = skb_get(skb);
	spin_unlock(&sp->data->meta_lock);

	/* Tell DSA we got nothing */
	return NULL;

	/* Step 2: The meta frame arrived.
	* Time to take the stampable skb out of the closet, annotate it
	* with the partial timestamp, and pretend that we received it
	* just now (basically masquerade the buffered frame as the meta
	* frame, which serves no further purpose).
	*/
	} else if (is_meta) {
	struct sk_buff *stampable_skb;

	/* Drop the meta frame if we're not in the right state
	* to process it.
	*/
	if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
	return NULL;

	spin_lock(&sp->data->meta_lock);

	stampable_skb = sp->data->stampable_skb;
	sp->data->stampable_skb = NULL;

	/* Was this a meta frame instead of the link-local
	* that we were expecting?
	*/
	if (!stampable_skb) {
	dev_err_ratelimited(dp->ds->dev,
	"Unexpected meta frame\n");
	spin_unlock(&sp->data->meta_lock);
	return NULL;
	}

	if (stampable_skb->dev != skb->dev) {
	dev_err_ratelimited(dp->ds->dev,
	"Meta frame on wrong port\n");
	spin_unlock(&sp->data->meta_lock);
	return NULL;
	}

	/* Free the meta frame and give DSA the buffered stampable_skb
	* for further processing up the network stack.
	*/
	kfree_skb(skb);
	skb = stampable_skb;
	sja1105_transfer_meta(skb, meta);

	spin_unlock(&sp->data->meta_lock);
	}

	return skb;
	}

	static void sja1105_decode_subvlan(struct sk_buff *skb, u16 subvlan)
	{
	struct dsa_port *dp = dsa_slave_to_port(skb->dev);
	struct sja1105_port *sp = dp->priv;
	u16 vid = sp->subvlan_map[subvlan];
	u16 vlan_tci;

	if (vid == VLAN_N_VID)
	return;

	vlan_tci = (skb->priority << VLAN_PRIO_SHIFT) \| vid;
	__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);
	}

	static struct sk_buff sja1105_rcv(struct sk_buff skb,
	struct net_device *netdev,
	struct packet_type *pt)
	{
	struct sja1105_meta meta = {0};
	int source_port, switch_id;
	struct ethhdr *hdr;
	u16 tpid, vid, tci;
	bool is_link_local;
	u16 subvlan = 0;
	bool is_tagged;
	bool is_meta;

	hdr = eth_hdr(skb);
	tpid = ntohs(hdr->h_proto);
	is_tagged = (tpid == ETH_P_SJA1105 \|\| tpid == ETH_P_8021Q \|\|
	skb_vlan_tag_present(skb));
	is_link_local = sja1105_is_link_local(skb);
	is_meta = sja1105_is_meta_frame(skb);

	skb->offload_fwd_mark = 1;

	if (is_tagged) {
	/* Normal traffic path. */
	skb_push_rcsum(skb, ETH_HLEN);
	if (skb_vlan_tag_present(skb)) {
	tci = skb_vlan_tag_get(skb);
	__vlan_hwaccel_clear_tag(skb);
	} else {
	__skb_vlan_pop(skb, &tci);
	}
	skb_pull_rcsum(skb, ETH_HLEN);
	skb_reset_network_header(skb);
	skb_reset_transport_header(skb);

	vid = tci & VLAN_VID_MASK;
	source_port = dsa_8021q_rx_source_port(vid);
	switch_id = dsa_8021q_rx_switch_id(vid);
	skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
	subvlan = dsa_8021q_rx_subvlan(vid);
	} else if (is_link_local) {
	/* Management traffic path. Switch embeds the switch ID and
	* port ID into bytes of the destination MAC, courtesy of
	* the incl_srcpt options.
	*/
	source_port = hdr->h_dest[3];
	switch_id = hdr->h_dest[4];
	/* Clear the DMAC bytes that were mangled by the switch */
	hdr->h_dest[3] = 0;
	hdr->h_dest[4] = 0;
	} else if (is_meta) {
	sja1105_meta_unpack(skb, &meta);
	source_port = meta.source_port;
	switch_id = meta.switch_id;
	} else {
	return NULL;
	}

	skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
	if (!skb->dev) {
	netdev_warn(netdev, "Couldn't decode source port\n");
	return NULL;
	}

	if (subvlan)
	sja1105_decode_subvlan(skb, subvlan);

	return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
	is_meta);
	}

	static void sja1105_flow_dissect(const struct sk_buff skb, __be16 proto,
	int *offset)
	{
	/* No tag added for management frames, all ok */
	if (unlikely(sja1105_is_link_local(skb)))
	return;

	dsa_tag_generic_flow_dissect(skb, proto, offset);
	}

	static const struct dsa_device_ops sja1105_netdev_ops = {
	.name = "sja1105",
	.proto = DSA_TAG_PROTO_SJA1105,
	.xmit = sja1105_xmit,
	.rcv = sja1105_rcv,
	.filter = sja1105_filter,
	.overhead = VLAN_HLEN,
	.flow_dissect = sja1105_flow_dissect,
	.promisc_on_master = true,
	};

	MODULE_LICENSE("GPL v2");
	MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);

	module_dsa_tag_driver(sja1105_netdev_ops);