// SPDX-License-Identifier: GPL-2.0
  /* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
   *
   * This module is not a complete tagger implementation. It only provides
   * primitives for taggers that rely on 802.1Q VLAN tags to use. The
   * dsa_8021q_netdev_ops is registered for API compliance and not used
   * directly by callers.
   */
  #include <linux/if_bridge.h>
  #include <linux/if_vlan.h>
  
  #include "dsa_priv.h"

  /* Binary structure of the fake 12-bit VID field (when the TPID is
   * ETH_P_DSA_8021Q):
   *
   * | 11  | 10  |  9  |  8  |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
   * +-----------+-----+-----------------+-----------+-----------------------+
   * |    DIR    | RSV |    SWITCH_ID    |    RSV    |          PORT         |
   * +-----------+-----+-----------------+-----------+-----------------------+
   *
   * DIR - VID[11:10]:
   *	Direction flags.
   *	* 1 (0b01) for RX VLAN,
   *	* 2 (0b10) for TX VLAN.
   *	These values make the special VIDs of 0, 1 and 4095 to be left
   *	unused by this coding scheme.
   *
   * RSV - VID[9]:
   *	To be used for further expansion of SWITCH_ID or for other purposes.

   *	Must be transmitted as zero and ignored on receive.

   *
   * SWITCH_ID - VID[8:6]:

   *	Index of switch within DSA tree. Must be between 0 and 7.

   *
   * RSV - VID[5:4]:
   *	To be used for further expansion of PORT or for other purposes.

   *	Must be transmitted as zero and ignored on receive.

   *
   * PORT - VID[3:0]:

   *	Index of switch port. Must be between 0 and 15.

   */

  
  #define DSA_8021Q_DIR_SHIFT		10
  #define DSA_8021Q_DIR_MASK		GENMASK(11, 10)
  #define DSA_8021Q_DIR(x)		(((x) << DSA_8021Q_DIR_SHIFT) & \
  						 DSA_8021Q_DIR_MASK)
  #define DSA_8021Q_DIR_RX		DSA_8021Q_DIR(1)
  #define DSA_8021Q_DIR_TX		DSA_8021Q_DIR(2)
  
  #define DSA_8021Q_SWITCH_ID_SHIFT	6
  #define DSA_8021Q_SWITCH_ID_MASK	GENMASK(8, 6)
  #define DSA_8021Q_SWITCH_ID(x)		(((x) << DSA_8021Q_SWITCH_ID_SHIFT) & \
  						 DSA_8021Q_SWITCH_ID_MASK)
  
  #define DSA_8021Q_PORT_SHIFT		0
  #define DSA_8021Q_PORT_MASK		GENMASK(3, 0)
  #define DSA_8021Q_PORT(x)		(((x) << DSA_8021Q_PORT_SHIFT) & \
  						 DSA_8021Q_PORT_MASK)

  
  /* Returns the VID to be inserted into the frame from xmit for switch steering
   * instructions on egress. Encodes switch ID and port ID.
   */
  u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port)
  {

  	return DSA_8021Q_DIR_TX | DSA_8021Q_SWITCH_ID(ds->index) |
  	       DSA_8021Q_PORT(port);

  }
  EXPORT_SYMBOL_GPL(dsa_8021q_tx_vid);
  
  /* Returns the VID that will be installed as pvid for this switch port, sent as
   * tagged egress towards the CPU port and decoded by the rcv function.
   */
  u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
  {

  	return DSA_8021Q_DIR_RX | DSA_8021Q_SWITCH_ID(ds->index) |
  	       DSA_8021Q_PORT(port);

  }
  EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid);
  
  /* Returns the decoded switch ID from the RX VID. */
  int dsa_8021q_rx_switch_id(u16 vid)
  {

  	return (vid & DSA_8021Q_SWITCH_ID_MASK) >> DSA_8021Q_SWITCH_ID_SHIFT;

  }
  EXPORT_SYMBOL_GPL(dsa_8021q_rx_switch_id);
  
  /* Returns the decoded port ID from the RX VID. */
  int dsa_8021q_rx_source_port(u16 vid)
  {

  	return (vid & DSA_8021Q_PORT_MASK) >> DSA_8021Q_PORT_SHIFT;

  }
  EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);

  static int dsa_8021q_restore_pvid(struct dsa_switch *ds, int port)
  {
  	struct bridge_vlan_info vinfo;
  	struct net_device *slave;
  	u16 pvid;
  	int err;
  
  	if (!dsa_is_user_port(ds, port))
  		return 0;

  	slave = dsa_to_port(ds, port)->slave;

  
  	err = br_vlan_get_pvid(slave, &pvid);

  	if (!pvid || err < 0)

  		/* There is no pvid on the bridge for this port, which is
  		 * perfectly valid. Nothing to restore, bye-bye!
  		 */
  		return 0;
  
  	err = br_vlan_get_info(slave, pvid, &vinfo);
  	if (err < 0) {
  		dev_err(ds->dev, "Couldn't determine PVID attributes
  ");
  		return err;
  	}

  	return dsa_port_vid_add(dsa_to_port(ds, port), pvid, vinfo.flags);

  }
  
  /* If @enabled is true, installs @vid with @flags into the switch port's HW
   * filter.
   * If @enabled is false, deletes @vid (ignores @flags) from the port. Had the
   * user explicitly configured this @vid through the bridge core, then the @vid
   * is installed again, but this time with the flags from the bridge layer.
   */
  static int dsa_8021q_vid_apply(struct dsa_switch *ds, int port, u16 vid,
  			       u16 flags, bool enabled)
  {

  	struct dsa_port *dp = dsa_to_port(ds, port);

  	struct bridge_vlan_info vinfo;
  	int err;
  
  	if (enabled)
  		return dsa_port_vid_add(dp, vid, flags);
  
  	err = dsa_port_vid_del(dp, vid);
  	if (err < 0)
  		return err;
  
  	/* Nothing to restore from the bridge for a non-user port.
  	 * The CPU port VLANs are restored implicitly with the user ports,
  	 * similar to how the bridge does in dsa_slave_vlan_add and
  	 * dsa_slave_vlan_del.
  	 */
  	if (!dsa_is_user_port(ds, port))
  		return 0;
  
  	err = br_vlan_get_info(dp->slave, vid, &vinfo);
  	/* Couldn't determine bridge attributes for this vid,
  	 * it means the bridge had not configured it.
  	 */
  	if (err < 0)
  		return 0;
  
  	/* Restore the VID from the bridge */
  	err = dsa_port_vid_add(dp, vid, vinfo.flags);
  	if (err < 0)
  		return err;
  
  	vinfo.flags &= ~BRIDGE_VLAN_INFO_PVID;
  
  	return dsa_port_vid_add(dp->cpu_dp, vid, vinfo.flags);
  }

  /* RX VLAN tagging (left) and TX VLAN tagging (right) setup shown for a single
   * front-panel switch port (here swp0).
   *
   * Port identification through VLAN (802.1Q) tags has different requirements
   * for it to work effectively:
   *  - On RX (ingress from network): each front-panel port must have a pvid
   *    that uniquely identifies it, and the egress of this pvid must be tagged
   *    towards the CPU port, so that software can recover the source port based
   *    on the VID in the frame. But this would only work for standalone ports;
   *    if bridged, this VLAN setup would break autonomous forwarding and would
   *    force all switched traffic to pass through the CPU. So we must also make
   *    the other front-panel ports members of this VID we're adding, albeit
   *    we're not making it their PVID (they'll still have their own).
   *    By the way - just because we're installing the same VID in multiple
   *    switch ports doesn't mean that they'll start to talk to one another, even
   *    while not bridged: the final forwarding decision is still an AND between
   *    the L2 forwarding information (which is limiting forwarding in this case)
   *    and the VLAN-based restrictions (of which there are none in this case,
   *    since all ports are members).
   *  - On TX (ingress from CPU and towards network) we are faced with a problem.
   *    If we were to tag traffic (from within DSA) with the port's pvid, all
   *    would be well, assuming the switch ports were standalone. Frames would
   *    have no choice but to be directed towards the correct front-panel port.
   *    But because we also want the RX VLAN to not break bridging, then
   *    inevitably that means that we have to give them a choice (of what
   *    front-panel port to go out on), and therefore we cannot steer traffic
   *    based on the RX VID. So what we do is simply install one more VID on the
   *    front-panel and CPU ports, and profit off of the fact that steering will
   *    work just by virtue of the fact that there is only one other port that's
   *    a member of the VID we're tagging the traffic with - the desired one.
   *
   * So at the end, each front-panel port will have one RX VID (also the PVID),
   * the RX VID of all other front-panel ports, and one TX VID. Whereas the CPU
   * port will have the RX and TX VIDs of all front-panel ports, and on top of
   * that, is also tagged-input and tagged-output (VLAN trunk).
   *
   *               CPU port                               CPU port
   * +-------------+-----+-------------+    +-------------+-----+-------------+
   * |  RX VID     |     |             |    |  TX VID     |     |             |
   * |  of swp0    |     |             |    |  of swp0    |     |             |
   * |             +-----+             |    |             +-----+             |
   * |                ^ T              |    |                | Tagged         |
   * |                |                |    |                | ingress        |
   * |    +-------+---+---+-------+    |    |    +-----------+                |
   * |    |       |       |       |    |    |    | Untagged                   |
   * |    |     U v     U v     U v    |    |    v egress                     |
   * | +-----+ +-----+ +-----+ +-----+ |    | +-----+ +-----+ +-----+ +-----+ |
   * | |     | |     | |     | |     | |    | |     | |     | |     | |     | |
   * | |PVID | |     | |     | |     | |    | |     | |     | |     | |     | |
   * +-+-----+-+-----+-+-----+-+-----+-+    +-+-----+-+-----+-+-----+-+-----+-+
   *   swp0    swp1    swp2    swp3           swp0    swp1    swp2    swp3
   */
  int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
  {
  	int upstream = dsa_upstream_port(ds, port);

  	u16 rx_vid = dsa_8021q_rx_vid(ds, port);
  	u16 tx_vid = dsa_8021q_tx_vid(ds, port);
  	int i, err;
  
  	/* The CPU port is implicitly configured by
  	 * configuring the front-panel ports
  	 */
  	if (!dsa_is_user_port(ds, port))
  		return 0;
  
  	/* Add this user port's RX VID to the membership list of all others
  	 * (including itself). This is so that bridging will not be hindered.
  	 * L2 forwarding rules still take precedence when there are no VLAN
  	 * restrictions, so there are no concerns about leaking traffic.
  	 */
  	for (i = 0; i < ds->num_ports; i++) {

  		u16 flags;
  
  		if (i == upstream)

  			continue;

  		else if (i == port)
  			/* The RX VID is pvid on this port */
  			flags = BRIDGE_VLAN_INFO_UNTAGGED |
  				BRIDGE_VLAN_INFO_PVID;
  		else
  			/* The RX VID is a regular VLAN on all others */
  			flags = BRIDGE_VLAN_INFO_UNTAGGED;

  		err = dsa_8021q_vid_apply(ds, i, rx_vid, flags, enabled);

  		if (err) {
  			dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d
  ",
  				rx_vid, port, err);
  			return err;
  		}
  	}

  
  	/* CPU port needs to see this port's RX VID
  	 * as tagged egress.
  	 */

  	err = dsa_8021q_vid_apply(ds, upstream, rx_vid, 0, enabled);

  	if (err) {
  		dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d
  ",
  			rx_vid, port, err);
  		return err;
  	}

  	/* Finally apply the TX VID on this port and on the CPU port */

  	err = dsa_8021q_vid_apply(ds, port, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED,
  				  enabled);

  	if (err) {
  		dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d
  ",
  			tx_vid, port, err);
  		return err;
  	}

  	err = dsa_8021q_vid_apply(ds, upstream, tx_vid, 0, enabled);

  	if (err) {
  		dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d
  ",
  			tx_vid, upstream, err);
  		return err;
  	}

  	if (!enabled)
  		err = dsa_8021q_restore_pvid(ds, port);
  
  	return err;

  }
  EXPORT_SYMBOL_GPL(dsa_port_setup_8021q_tagging);
  
  struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
  			       u16 tpid, u16 tci)
  {
  	/* skb->data points at skb_mac_header, which
  	 * is fine for vlan_insert_tag.
  	 */
  	return vlan_insert_tag(skb, htons(tpid), tci);
  }
  EXPORT_SYMBOL_GPL(dsa_8021q_xmit);

  /* In the DSA packet_type handler, skb->data points in the middle of the VLAN
   * tag, after tpid and before tci. This is because so far, ETH_HLEN
   * (DMAC, SMAC, EtherType) bytes were pulled.
   * There are 2 bytes of VLAN tag left in skb->data, and upper
   * layers expect the 'real' EtherType to be consumed as well.
   * Coincidentally, a VLAN header is also of the same size as
   * the number of bytes that need to be pulled.
   *
   * skb_mac_header                                      skb->data
   * |                                                       |
   * v                                                       v
   * |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
   * +-----------------------+-----------------------+-------+-------+-------+
   * |    Destination MAC    |      Source MAC       |  TPID |  TCI  | EType |
   * +-----------------------+-----------------------+-------+-------+-------+
   * ^                                               |               |
   * |<--VLAN_HLEN-->to                              <---VLAN_HLEN--->
   * from            |
   *       >>>>>>>   v
   *       >>>>>>>   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
   *       >>>>>>>   +-----------------------+-----------------------+-------+
   *       >>>>>>>   |    Destination MAC    |      Source MAC       | EType |
   *                 +-----------------------+-----------------------+-------+
   *                 ^                                                       ^
   * (now part of    |                                                       |
   *  skb->head)     skb_mac_header                                  skb->data
   */
  struct sk_buff *dsa_8021q_remove_header(struct sk_buff *skb)

  {

  	u8 *from = skb_mac_header(skb);
  	u8 *dest = from + VLAN_HLEN;

  	memmove(dest, from, ETH_HLEN - VLAN_HLEN);
  	skb_pull(skb, VLAN_HLEN);
  	skb_push(skb, ETH_HLEN);
  	skb_reset_mac_header(skb);
  	skb_reset_mac_len(skb);
  	skb_pull_rcsum(skb, ETH_HLEN);

  
  	return skb;
  }

  EXPORT_SYMBOL_GPL(dsa_8021q_remove_header);

  MODULE_LICENSE("GPL v2");