summaryrefslogtreecommitdiffstats
path: root/net/dsa/tag_8021q.c
blob: 65a35e976d7b67c5f5b97f74f1199f35a10e56f7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
// 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.
 *
 * SWITCH_ID - VID[8:6]:
 *	Index of switch within DSA tree. Must be between 0 and
 *	DSA_MAX_SWITCHES - 1.
 *
 * RSV - VID[5:4]:
 *	To be used for further expansion of PORT or for other purposes.
 *
 * PORT - VID[3:0]:
 *	Index of switch port. Must be between 0 and DSA_MAX_PORTS - 1.
 */

#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);

/* 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)
			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;

		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;
		}
	}

	/* CPU port needs to see this port's RX VID
	 * as tagged egress.
	 */
	if (enabled)
		err = dsa_port_vid_add(upstream_dp, rx_vid, 0);
	else
		err = dsa_port_vid_del(upstream_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);