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.
32 * SWITCH_ID - VID[8:6]:
33 * Index of switch within DSA tree. Must be between 0 and
34 * DSA_MAX_SWITCHES - 1.
37 * To be used for further expansion of PORT or for other purposes.
40 * Index of switch port. Must be between 0 and DSA_MAX_PORTS - 1.
43 #define DSA_8021Q_DIR_SHIFT 10
44 #define DSA_8021Q_DIR_MASK GENMASK(11, 10)
45 #define DSA_8021Q_DIR(x) (((x) << DSA_8021Q_DIR_SHIFT) & \
47 #define DSA_8021Q_DIR_RX DSA_8021Q_DIR(1)
48 #define DSA_8021Q_DIR_TX DSA_8021Q_DIR(2)
50 #define DSA_8021Q_SWITCH_ID_SHIFT 6
51 #define DSA_8021Q_SWITCH_ID_MASK GENMASK(8, 6)
52 #define DSA_8021Q_SWITCH_ID(x) (((x) << DSA_8021Q_SWITCH_ID_SHIFT) & \
53 DSA_8021Q_SWITCH_ID_MASK)
55 #define DSA_8021Q_PORT_SHIFT 0
56 #define DSA_8021Q_PORT_MASK GENMASK(3, 0)
57 #define DSA_8021Q_PORT(x) (((x) << DSA_8021Q_PORT_SHIFT) & \
60 /* Returns the VID to be inserted into the frame from xmit for switch steering
61 * instructions on egress. Encodes switch ID and port ID.
63 u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port)
65 return DSA_8021Q_DIR_TX | DSA_8021Q_SWITCH_ID(ds->index) |
68 EXPORT_SYMBOL_GPL(dsa_8021q_tx_vid);
70 /* Returns the VID that will be installed as pvid for this switch port, sent as
71 * tagged egress towards the CPU port and decoded by the rcv function.
73 u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
75 return DSA_8021Q_DIR_RX | DSA_8021Q_SWITCH_ID(ds->index) |
78 EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid);
80 /* Returns the decoded switch ID from the RX VID. */
81 int dsa_8021q_rx_switch_id(u16 vid)
83 return (vid & DSA_8021Q_SWITCH_ID_MASK) >> DSA_8021Q_SWITCH_ID_SHIFT;
85 EXPORT_SYMBOL_GPL(dsa_8021q_rx_switch_id);
87 /* Returns the decoded port ID from the RX VID. */
88 int dsa_8021q_rx_source_port(u16 vid)
90 return (vid & DSA_8021Q_PORT_MASK) >> DSA_8021Q_PORT_SHIFT;
92 EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);
94 /* RX VLAN tagging (left) and TX VLAN tagging (right) setup shown for a single
95 * front-panel switch port (here swp0).
97 * Port identification through VLAN (802.1Q) tags has different requirements
98 * for it to work effectively:
99 * - On RX (ingress from network): each front-panel port must have a pvid
100 * that uniquely identifies it, and the egress of this pvid must be tagged
101 * towards the CPU port, so that software can recover the source port based
102 * on the VID in the frame. But this would only work for standalone ports;
103 * if bridged, this VLAN setup would break autonomous forwarding and would
104 * force all switched traffic to pass through the CPU. So we must also make
105 * the other front-panel ports members of this VID we're adding, albeit
106 * we're not making it their PVID (they'll still have their own).
107 * By the way - just because we're installing the same VID in multiple
108 * switch ports doesn't mean that they'll start to talk to one another, even
109 * while not bridged: the final forwarding decision is still an AND between
110 * the L2 forwarding information (which is limiting forwarding in this case)
111 * and the VLAN-based restrictions (of which there are none in this case,
112 * since all ports are members).
113 * - On TX (ingress from CPU and towards network) we are faced with a problem.
114 * If we were to tag traffic (from within DSA) with the port's pvid, all
115 * would be well, assuming the switch ports were standalone. Frames would
116 * have no choice but to be directed towards the correct front-panel port.
117 * But because we also want the RX VLAN to not break bridging, then
118 * inevitably that means that we have to give them a choice (of what
119 * front-panel port to go out on), and therefore we cannot steer traffic
120 * based on the RX VID. So what we do is simply install one more VID on the
121 * front-panel and CPU ports, and profit off of the fact that steering will
122 * work just by virtue of the fact that there is only one other port that's
123 * a member of the VID we're tagging the traffic with - the desired one.
125 * So at the end, each front-panel port will have one RX VID (also the PVID),
126 * the RX VID of all other front-panel ports, and one TX VID. Whereas the CPU
127 * port will have the RX and TX VIDs of all front-panel ports, and on top of
128 * that, is also tagged-input and tagged-output (VLAN trunk).
131 * +-------------+-----+-------------+ +-------------+-----+-------------+
132 * | RX VID | | | | TX VID | | |
133 * | of swp0 | | | | of swp0 | | |
134 * | +-----+ | | +-----+ |
135 * | ^ T | | | Tagged |
136 * | | | | | ingress |
137 * | +-------+---+---+-------+ | | +-----------+ |
138 * | | | | | | | | Untagged |
139 * | | U v U v U v | | v egress |
140 * | +-----+ +-----+ +-----+ +-----+ | | +-----+ +-----+ +-----+ +-----+ |
141 * | | | | | | | | | | | | | | | | | | | |
142 * | |PVID | | | | | | | | | | | | | | | | | |
143 * +-+-----+-+-----+-+-----+-+-----+-+ +-+-----+-+-----+-+-----+-+-----+-+
144 * swp0 swp1 swp2 swp3 swp0 swp1 swp2 swp3
146 int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
148 int upstream = dsa_upstream_port(ds, port);
149 struct dsa_port *dp = &ds->ports[port];
150 struct dsa_port *upstream_dp = &ds->ports[upstream];
151 u16 rx_vid = dsa_8021q_rx_vid(ds, port);
152 u16 tx_vid = dsa_8021q_tx_vid(ds, port);
155 /* The CPU port is implicitly configured by
156 * configuring the front-panel ports
158 if (!dsa_is_user_port(ds, port))
161 /* Add this user port's RX VID to the membership list of all others
162 * (including itself). This is so that bridging will not be hindered.
163 * L2 forwarding rules still take precedence when there are no VLAN
164 * restrictions, so there are no concerns about leaking traffic.
166 for (i = 0; i < ds->num_ports; i++) {
167 struct dsa_port *other_dp = &ds->ports[i];
173 /* The RX VID is pvid on this port */
174 flags = BRIDGE_VLAN_INFO_UNTAGGED |
175 BRIDGE_VLAN_INFO_PVID;
177 /* The RX VID is a regular VLAN on all others */
178 flags = BRIDGE_VLAN_INFO_UNTAGGED;
181 err = dsa_port_vid_add(other_dp, rx_vid, flags);
183 err = dsa_port_vid_del(other_dp, rx_vid);
185 dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
191 /* CPU port needs to see this port's RX VID
195 err = dsa_port_vid_add(upstream_dp, rx_vid, 0);
197 err = dsa_port_vid_del(upstream_dp, rx_vid);
199 dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
204 /* Finally apply the TX VID on this port and on the CPU port */
206 err = dsa_port_vid_add(dp, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED);
208 err = dsa_port_vid_del(dp, tx_vid);
210 dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
215 err = dsa_port_vid_add(upstream_dp, tx_vid, 0);
217 err = dsa_port_vid_del(upstream_dp, tx_vid);
219 dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
220 tx_vid, upstream, err);
226 EXPORT_SYMBOL_GPL(dsa_port_setup_8021q_tagging);
228 struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
231 /* skb->data points at skb_mac_header, which
232 * is fine for vlan_insert_tag.
234 return vlan_insert_tag(skb, htons(tpid), tci);
236 EXPORT_SYMBOL_GPL(dsa_8021q_xmit);
238 /* In the DSA packet_type handler, skb->data points in the middle of the VLAN
239 * tag, after tpid and before tci. This is because so far, ETH_HLEN
240 * (DMAC, SMAC, EtherType) bytes were pulled.
241 * There are 2 bytes of VLAN tag left in skb->data, and upper
242 * layers expect the 'real' EtherType to be consumed as well.
243 * Coincidentally, a VLAN header is also of the same size as
244 * the number of bytes that need to be pulled.
246 * skb_mac_header skb->data
249 * | | | | | | | | | | | | | | | | | | |
250 * +-----------------------+-----------------------+-------+-------+-------+
251 * | Destination MAC | Source MAC | TPID | TCI | EType |
252 * +-----------------------+-----------------------+-------+-------+-------+
254 * |<--VLAN_HLEN-->to <---VLAN_HLEN--->
257 * >>>>>>> | | | | | | | | | | | | | | |
258 * >>>>>>> +-----------------------+-----------------------+-------+
259 * >>>>>>> | Destination MAC | Source MAC | EType |
260 * +-----------------------+-----------------------+-------+
263 * skb->head) skb_mac_header skb->data
265 struct sk_buff *dsa_8021q_remove_header(struct sk_buff *skb)
267 u8 *from = skb_mac_header(skb);
268 u8 *dest = from + VLAN_HLEN;
270 memmove(dest, from, ETH_HLEN - VLAN_HLEN);
271 skb_pull(skb, VLAN_HLEN);
272 skb_push(skb, ETH_HLEN);
273 skb_reset_mac_header(skb);
274 skb_reset_mac_len(skb);
275 skb_pull_rcsum(skb, ETH_HLEN);
279 EXPORT_SYMBOL_GPL(dsa_8021q_remove_header);
281 static const struct dsa_device_ops dsa_8021q_netdev_ops = {
283 .proto = DSA_TAG_PROTO_8021Q,
284 .overhead = VLAN_HLEN,
287 MODULE_LICENSE("GPL v2");
288 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_8021Q);
290 module_dsa_tag_driver(dsa_8021q_netdev_ops);