1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
4 * This module is not a complete tagger implementation. It only provides
5 * primitives for taggers that rely on 802.1Q VLAN tags to use. The
6 * dsa_8021q_netdev_ops is registered for API compliance and not used
9 #include <linux/if_bridge.h>
10 #include <linux/if_vlan.h>
14 /* Binary structure of the fake 12-bit VID field (when the TPID is
17 * | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
18 * +-----------+-----+-----------------+-----------+-----------------------+
19 * | DIR | RSV | SWITCH_ID | RSV | PORT |
20 * +-----------+-----+-----------------+-----------+-----------------------+
24 * * 1 (0b01) for RX VLAN,
25 * * 2 (0b10) for TX VLAN.
26 * These values make the special VIDs of 0, 1 and 4095 to be left
27 * unused by this coding scheme.
30 * To be used for further expansion of SWITCH_ID or for other purposes.
31 * Must be transmitted as zero and ignored on receive.
33 * SWITCH_ID - VID[8:6]:
34 * Index of switch within DSA tree. Must be between 0 and
35 * DSA_MAX_SWITCHES - 1.
38 * To be used for further expansion of PORT or for other purposes.
39 * Must be transmitted as zero and ignored on receive.
42 * Index of switch port. Must be between 0 and DSA_MAX_PORTS - 1.
45 #define DSA_8021Q_DIR_SHIFT 10
46 #define DSA_8021Q_DIR_MASK GENMASK(11, 10)
47 #define DSA_8021Q_DIR(x) (((x) << DSA_8021Q_DIR_SHIFT) & \
49 #define DSA_8021Q_DIR_RX DSA_8021Q_DIR(1)
50 #define DSA_8021Q_DIR_TX DSA_8021Q_DIR(2)
52 #define DSA_8021Q_SWITCH_ID_SHIFT 6
53 #define DSA_8021Q_SWITCH_ID_MASK GENMASK(8, 6)
54 #define DSA_8021Q_SWITCH_ID(x) (((x) << DSA_8021Q_SWITCH_ID_SHIFT) & \
55 DSA_8021Q_SWITCH_ID_MASK)
57 #define DSA_8021Q_PORT_SHIFT 0
58 #define DSA_8021Q_PORT_MASK GENMASK(3, 0)
59 #define DSA_8021Q_PORT(x) (((x) << DSA_8021Q_PORT_SHIFT) & \
62 /* Returns the VID to be inserted into the frame from xmit for switch steering
63 * instructions on egress. Encodes switch ID and port ID.
65 u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port)
67 return DSA_8021Q_DIR_TX | DSA_8021Q_SWITCH_ID(ds->index) |
70 EXPORT_SYMBOL_GPL(dsa_8021q_tx_vid);
72 /* Returns the VID that will be installed as pvid for this switch port, sent as
73 * tagged egress towards the CPU port and decoded by the rcv function.
75 u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
77 return DSA_8021Q_DIR_RX | DSA_8021Q_SWITCH_ID(ds->index) |
80 EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid);
82 /* Returns the decoded switch ID from the RX VID. */
83 int dsa_8021q_rx_switch_id(u16 vid)
85 return (vid & DSA_8021Q_SWITCH_ID_MASK) >> DSA_8021Q_SWITCH_ID_SHIFT;
87 EXPORT_SYMBOL_GPL(dsa_8021q_rx_switch_id);
89 /* Returns the decoded port ID from the RX VID. */
90 int dsa_8021q_rx_source_port(u16 vid)
92 return (vid & DSA_8021Q_PORT_MASK) >> DSA_8021Q_PORT_SHIFT;
94 EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);
96 /* RX VLAN tagging (left) and TX VLAN tagging (right) setup shown for a single
97 * front-panel switch port (here swp0).
99 * Port identification through VLAN (802.1Q) tags has different requirements
100 * for it to work effectively:
101 * - On RX (ingress from network): each front-panel port must have a pvid
102 * that uniquely identifies it, and the egress of this pvid must be tagged
103 * towards the CPU port, so that software can recover the source port based
104 * on the VID in the frame. But this would only work for standalone ports;
105 * if bridged, this VLAN setup would break autonomous forwarding and would
106 * force all switched traffic to pass through the CPU. So we must also make
107 * the other front-panel ports members of this VID we're adding, albeit
108 * we're not making it their PVID (they'll still have their own).
109 * By the way - just because we're installing the same VID in multiple
110 * switch ports doesn't mean that they'll start to talk to one another, even
111 * while not bridged: the final forwarding decision is still an AND between
112 * the L2 forwarding information (which is limiting forwarding in this case)
113 * and the VLAN-based restrictions (of which there are none in this case,
114 * since all ports are members).
115 * - On TX (ingress from CPU and towards network) we are faced with a problem.
116 * If we were to tag traffic (from within DSA) with the port's pvid, all
117 * would be well, assuming the switch ports were standalone. Frames would
118 * have no choice but to be directed towards the correct front-panel port.
119 * But because we also want the RX VLAN to not break bridging, then
120 * inevitably that means that we have to give them a choice (of what
121 * front-panel port to go out on), and therefore we cannot steer traffic
122 * based on the RX VID. So what we do is simply install one more VID on the
123 * front-panel and CPU ports, and profit off of the fact that steering will
124 * work just by virtue of the fact that there is only one other port that's
125 * a member of the VID we're tagging the traffic with - the desired one.
127 * So at the end, each front-panel port will have one RX VID (also the PVID),
128 * the RX VID of all other front-panel ports, and one TX VID. Whereas the CPU
129 * port will have the RX and TX VIDs of all front-panel ports, and on top of
130 * that, is also tagged-input and tagged-output (VLAN trunk).
133 * +-------------+-----+-------------+ +-------------+-----+-------------+
134 * | RX VID | | | | TX VID | | |
135 * | of swp0 | | | | of swp0 | | |
136 * | +-----+ | | +-----+ |
137 * | ^ T | | | Tagged |
138 * | | | | | ingress |
139 * | +-------+---+---+-------+ | | +-----------+ |
140 * | | | | | | | | Untagged |
141 * | | U v U v U v | | v egress |
142 * | +-----+ +-----+ +-----+ +-----+ | | +-----+ +-----+ +-----+ +-----+ |
143 * | | | | | | | | | | | | | | | | | | | |
144 * | |PVID | | | | | | | | | | | | | | | | | |
145 * +-+-----+-+-----+-+-----+-+-----+-+ +-+-----+-+-----+-+-----+-+-----+-+
146 * swp0 swp1 swp2 swp3 swp0 swp1 swp2 swp3
148 int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
150 int upstream = dsa_upstream_port(ds, port);
151 struct dsa_port *dp = &ds->ports[port];
152 struct dsa_port *upstream_dp = &ds->ports[upstream];
153 u16 rx_vid = dsa_8021q_rx_vid(ds, port);
154 u16 tx_vid = dsa_8021q_tx_vid(ds, port);
157 /* The CPU port is implicitly configured by
158 * configuring the front-panel ports
160 if (!dsa_is_user_port(ds, port))
163 /* Add this user port's RX VID to the membership list of all others
164 * (including itself). This is so that bridging will not be hindered.
165 * L2 forwarding rules still take precedence when there are no VLAN
166 * restrictions, so there are no concerns about leaking traffic.
168 for (i = 0; i < ds->num_ports; i++) {
169 struct dsa_port *other_dp = &ds->ports[i];
175 /* The RX VID is pvid on this port */
176 flags = BRIDGE_VLAN_INFO_UNTAGGED |
177 BRIDGE_VLAN_INFO_PVID;
179 /* The RX VID is a regular VLAN on all others */
180 flags = BRIDGE_VLAN_INFO_UNTAGGED;
183 err = dsa_port_vid_add(other_dp, rx_vid, flags);
185 err = dsa_port_vid_del(other_dp, rx_vid);
187 dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
193 /* CPU port needs to see this port's RX VID
197 err = dsa_port_vid_add(upstream_dp, rx_vid, 0);
199 err = dsa_port_vid_del(upstream_dp, rx_vid);
201 dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
206 /* Finally apply the TX VID on this port and on the CPU port */
208 err = dsa_port_vid_add(dp, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED);
210 err = dsa_port_vid_del(dp, tx_vid);
212 dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
217 err = dsa_port_vid_add(upstream_dp, tx_vid, 0);
219 err = dsa_port_vid_del(upstream_dp, tx_vid);
221 dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
222 tx_vid, upstream, err);
228 EXPORT_SYMBOL_GPL(dsa_port_setup_8021q_tagging);
230 struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
233 /* skb->data points at skb_mac_header, which
234 * is fine for vlan_insert_tag.
236 return vlan_insert_tag(skb, htons(tpid), tci);
238 EXPORT_SYMBOL_GPL(dsa_8021q_xmit);
240 /* In the DSA packet_type handler, skb->data points in the middle of the VLAN
241 * tag, after tpid and before tci. This is because so far, ETH_HLEN
242 * (DMAC, SMAC, EtherType) bytes were pulled.
243 * There are 2 bytes of VLAN tag left in skb->data, and upper
244 * layers expect the 'real' EtherType to be consumed as well.
245 * Coincidentally, a VLAN header is also of the same size as
246 * the number of bytes that need to be pulled.
248 * skb_mac_header skb->data
251 * | | | | | | | | | | | | | | | | | | |
252 * +-----------------------+-----------------------+-------+-------+-------+
253 * | Destination MAC | Source MAC | TPID | TCI | EType |
254 * +-----------------------+-----------------------+-------+-------+-------+
256 * |<--VLAN_HLEN-->to <---VLAN_HLEN--->
259 * >>>>>>> | | | | | | | | | | | | | | |
260 * >>>>>>> +-----------------------+-----------------------+-------+
261 * >>>>>>> | Destination MAC | Source MAC | EType |
262 * +-----------------------+-----------------------+-------+
265 * skb->head) skb_mac_header skb->data
267 struct sk_buff *dsa_8021q_remove_header(struct sk_buff *skb)
269 u8 *from = skb_mac_header(skb);
270 u8 *dest = from + VLAN_HLEN;
272 memmove(dest, from, ETH_HLEN - VLAN_HLEN);
273 skb_pull(skb, VLAN_HLEN);
274 skb_push(skb, ETH_HLEN);
275 skb_reset_mac_header(skb);
276 skb_reset_mac_len(skb);
277 skb_pull_rcsum(skb, ETH_HLEN);
281 EXPORT_SYMBOL_GPL(dsa_8021q_remove_header);
283 static const struct dsa_device_ops dsa_8021q_netdev_ops = {
285 .proto = DSA_TAG_PROTO_8021Q,
286 .overhead = VLAN_HLEN,
289 MODULE_LICENSE("GPL v2");
290 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_8021Q);
292 module_dsa_tag_driver(dsa_8021q_netdev_ops);