--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0
+ * Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
+ */
+
+#ifndef _NET_DSA_8021Q_H
+#define _NET_DSA_8021Q_H
+
+#include <linux/types.h>
+
+struct dsa_switch;
+struct sk_buff;
+struct net_device;
+struct packet_type;
+
+#if IS_ENABLED(CONFIG_NET_DSA_TAG_8021Q)
+
+int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int index,
+ bool enabled);
+
+struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
+ u16 tpid, u16 tci);
+
+struct sk_buff *dsa_8021q_rcv(struct sk_buff *skb, struct net_device *netdev,
+ struct packet_type *pt, u16 *tpid, u16 *tci);
+
+u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port);
+
+u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port);
+
+int dsa_8021q_rx_switch_id(u16 vid);
+
+int dsa_8021q_rx_source_port(u16 vid);
+
+#else
+
+int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int index,
+ bool enabled)
+{
+ return 0;
+}
+
+struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
+ u16 tpid, u16 tci)
+{
+ return NULL;
+}
+
+struct sk_buff *dsa_8021q_rcv(struct sk_buff *skb, struct net_device *netdev,
+ struct packet_type *pt, u16 *tpid, u16 *tci)
+{
+ return NULL;
+}
+
+u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port)
+{
+ return 0;
+}
+
+u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
+{
+ return 0;
+}
+
+int dsa_8021q_rx_switch_id(u16 vid)
+{
+ return 0;
+}
+
+int dsa_8021q_rx_source_port(u16 vid)
+{
+ return 0;
+}
+
+#endif /* IS_ENABLED(CONFIG_NET_DSA_TAG_8021Q) */
+
+#endif /* _NET_DSA_8021Q_H */
--- /dev/null
+// 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"
+
+/* Allocating two VLAN tags per port - one for the RX VID and
+ * the other for the TX VID - see below
+ */
+#define DSA_8021Q_VID_RANGE (DSA_MAX_SWITCHES * DSA_MAX_PORTS)
+#define DSA_8021Q_VID_BASE (VLAN_N_VID - 2 * DSA_8021Q_VID_RANGE - 1)
+#define DSA_8021Q_RX_VID_BASE (DSA_8021Q_VID_BASE)
+#define DSA_8021Q_TX_VID_BASE (DSA_8021Q_VID_BASE + DSA_8021Q_VID_RANGE)
+
+/* 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_TX_VID_BASE + (DSA_MAX_PORTS * ds->index) + 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_RX_VID_BASE + (DSA_MAX_PORTS * ds->index) + 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_RX_VID_BASE) / DSA_MAX_PORTS);
+}
+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_RX_VID_BASE) % DSA_MAX_PORTS);
+}
+EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);
+
+/* 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);
+ struct dsa_port *dp = &ds->ports[port];
+ struct dsa_port *upstream_dp = &ds->ports[upstream];
+ 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++) {
+ struct dsa_port *other_dp = &ds->ports[i];
+ u16 flags;
+
+ if (i == upstream)
+ /* CPU port needs to see this port's RX VID
+ * as tagged egress.
+ */
+ flags = 0;
+ 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;
+
+ if (enabled)
+ err = dsa_port_vid_add(other_dp, rx_vid, flags);
+ else
+ err = dsa_port_vid_del(other_dp, rx_vid);
+ if (err) {
+ dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
+ rx_vid, port, err);
+ return err;
+ }
+ }
+ /* Finally apply the TX VID on this port and on the CPU port */
+ if (enabled)
+ err = dsa_port_vid_add(dp, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED);
+ else
+ err = dsa_port_vid_del(dp, tx_vid);
+ if (err) {
+ dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
+ tx_vid, port, err);
+ return err;
+ }
+ if (enabled)
+ err = dsa_port_vid_add(upstream_dp, tx_vid, 0);
+ else
+ err = dsa_port_vid_del(upstream_dp, tx_vid);
+ if (err) {
+ dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
+ tx_vid, upstream, err);
+ return err;
+ }
+
+ return 0;
+}
+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);
+
+struct sk_buff *dsa_8021q_rcv(struct sk_buff *skb, struct net_device *netdev,
+ struct packet_type *pt, u16 *tpid, u16 *tci)
+{
+ struct vlan_ethhdr *tag;
+
+ if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
+ return NULL;
+
+ tag = vlan_eth_hdr(skb);
+ *tpid = ntohs(tag->h_vlan_proto);
+ *tci = ntohs(tag->h_vlan_TCI);
+
+ /* 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_pull_rcsum(skb, VLAN_HLEN);
+
+ return skb;
+}
+EXPORT_SYMBOL_GPL(dsa_8021q_rcv);
+
+static const struct dsa_device_ops dsa_8021q_netdev_ops = {
+ .name = "8021q",
+ .proto = DSA_TAG_PROTO_8021Q,
+ .overhead = VLAN_HLEN,
+};
+
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_8021Q);
+
+module_dsa_tag_driver(dsa_8021q_netdev_ops);
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