xref: /linux/net/dsa/tag_dsa.c (revision 0ed6e952)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Regular and Ethertype DSA tagging
4  * Copyright (c) 2008-2009 Marvell Semiconductor
5  *
6  * Regular DSA
7  * -----------
8 
9  * For untagged (in 802.1Q terms) packets, the switch will splice in
10  * the tag between the SA and the ethertype of the original
11  * packet. Tagged frames will instead have their outermost .1Q tag
12  * converted to a DSA tag. It expects the same layout when receiving
13  * packets from the CPU.
14  *
15  * Example:
16  *
17  *     .----.----.----.---------
18  * Pu: | DA | SA | ET | Payload ...
19  *     '----'----'----'---------
20  *       6    6    2       N
21  *     .----.----.--------.-----.----.---------
22  * Pt: | DA | SA | 0x8100 | TCI | ET | Payload ...
23  *     '----'----'--------'-----'----'---------
24  *       6    6       2      2    2       N
25  *     .----.----.-----.----.---------
26  * Pd: | DA | SA | DSA | ET | Payload ...
27  *     '----'----'-----'----'---------
28  *       6    6     4    2       N
29  *
30  * No matter if a packet is received untagged (Pu) or tagged (Pt),
31  * they will both have the same layout (Pd) when they are sent to the
32  * CPU. This is done by ignoring 802.3, replacing the ethertype field
33  * with more metadata, among which is a bit to signal if the original
34  * packet was tagged or not.
35  *
36  * Ethertype DSA
37  * -------------
38  * Uses the exact same tag format as regular DSA, but also includes a
39  * proper ethertype field (which the mv88e6xxx driver sets to
40  * ETH_P_EDSA/0xdada) followed by two zero bytes:
41  *
42  * .----.----.--------.--------.-----.----.---------
43  * | DA | SA | 0xdada | 0x0000 | DSA | ET | Payload ...
44  * '----'----'--------'--------'-----'----'---------
45  *   6    6       2        2      4    2       N
46  */
47 
48 #include <linux/dsa/mv88e6xxx.h>
49 #include <linux/etherdevice.h>
50 #include <linux/list.h>
51 #include <linux/slab.h>
52 
53 #include "tag.h"
54 
55 #define DSA_NAME	"dsa"
56 #define EDSA_NAME	"edsa"
57 
58 #define DSA_HLEN	4
59 
60 /**
61  * enum dsa_cmd - DSA Command
62  * @DSA_CMD_TO_CPU: Set on packets that were trapped or mirrored to
63  *     the CPU port. This is needed to implement control protocols,
64  *     e.g. STP and LLDP, that must not allow those control packets to
65  *     be switched according to the normal rules.
66  * @DSA_CMD_FROM_CPU: Used by the CPU to send a packet to a specific
67  *     port, ignoring all the barriers that the switch normally
68  *     enforces (VLANs, STP port states etc.). No source address
69  *     learning takes place. "sudo send packet"
70  * @DSA_CMD_TO_SNIFFER: Set on the copies of packets that matched some
71  *     user configured ingress or egress monitor criteria. These are
72  *     forwarded by the switch tree to the user configured ingress or
73  *     egress monitor port, which can be set to the CPU port or a
74  *     regular port. If the destination is a regular port, the tag
75  *     will be removed before egressing the port. If the destination
76  *     is the CPU port, the tag will not be removed.
77  * @DSA_CMD_FORWARD: This tag is used on all bulk traffic passing
78  *     through the switch tree, including the flows that are directed
79  *     towards the CPU. Its device/port tuple encodes the original
80  *     source port on which the packet ingressed. It can also be used
81  *     on transmit by the CPU to defer the forwarding decision to the
82  *     hardware, based on the current config of PVT/VTU/ATU
83  *     etc. Source address learning takes places if enabled on the
84  *     receiving DSA/CPU port.
85  */
86 enum dsa_cmd {
87 	DSA_CMD_TO_CPU     = 0,
88 	DSA_CMD_FROM_CPU   = 1,
89 	DSA_CMD_TO_SNIFFER = 2,
90 	DSA_CMD_FORWARD    = 3
91 };
92 
93 /**
94  * enum dsa_code - TO_CPU Code
95  *
96  * @DSA_CODE_MGMT_TRAP: DA was classified as a management
97  *     address. Typical examples include STP BPDUs and LLDP.
98  * @DSA_CODE_FRAME2REG: Response to a "remote management" request.
99  * @DSA_CODE_IGMP_MLD_TRAP: IGMP/MLD signaling.
100  * @DSA_CODE_POLICY_TRAP: Frame matched some policy configuration on
101  *     the device. Typical examples are matching on DA/SA/VID and DHCP
102  *     snooping.
103  * @DSA_CODE_ARP_MIRROR: The name says it all really.
104  * @DSA_CODE_POLICY_MIRROR: Same as @DSA_CODE_POLICY_TRAP, but the
105  *     particular policy was set to trigger a mirror instead of a
106  *     trap.
107  * @DSA_CODE_RESERVED_6: Unused on all devices up to at least 6393X.
108  * @DSA_CODE_RESERVED_7: Unused on all devices up to at least 6393X.
109  *
110  * A 3-bit code is used to relay why a particular frame was sent to
111  * the CPU. We only use this to determine if the packet was mirrored
112  * or trapped, i.e. whether the packet has been forwarded by hardware
113  * or not.
114  *
115  * This is the superset of all possible codes. Any particular device
116  * may only implement a subset.
117  */
118 enum dsa_code {
119 	DSA_CODE_MGMT_TRAP     = 0,
120 	DSA_CODE_FRAME2REG     = 1,
121 	DSA_CODE_IGMP_MLD_TRAP = 2,
122 	DSA_CODE_POLICY_TRAP   = 3,
123 	DSA_CODE_ARP_MIRROR    = 4,
124 	DSA_CODE_POLICY_MIRROR = 5,
125 	DSA_CODE_RESERVED_6    = 6,
126 	DSA_CODE_RESERVED_7    = 7
127 };
128 
dsa_xmit_ll(struct sk_buff * skb,struct net_device * dev,u8 extra)129 static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
130 				   u8 extra)
131 {
132 	struct dsa_port *dp = dsa_user_to_port(dev);
133 	struct net_device *br_dev;
134 	u8 tag_dev, tag_port;
135 	enum dsa_cmd cmd;
136 	u8 *dsa_header;
137 
138 	if (skb->offload_fwd_mark) {
139 		unsigned int bridge_num = dsa_port_bridge_num_get(dp);
140 		struct dsa_switch_tree *dst = dp->ds->dst;
141 
142 		cmd = DSA_CMD_FORWARD;
143 
144 		/* When offloading forwarding for a bridge, inject FORWARD
145 		 * packets on behalf of a virtual switch device with an index
146 		 * past the physical switches.
147 		 */
148 		tag_dev = dst->last_switch + bridge_num;
149 		tag_port = 0;
150 	} else {
151 		cmd = DSA_CMD_FROM_CPU;
152 		tag_dev = dp->ds->index;
153 		tag_port = dp->index;
154 	}
155 
156 	br_dev = dsa_port_bridge_dev_get(dp);
157 
158 	/* If frame is already 802.1Q tagged, we can convert it to a DSA
159 	 * tag (avoiding a memmove), but only if the port is standalone
160 	 * (in which case we always send FROM_CPU) or if the port's
161 	 * bridge has VLAN filtering enabled (in which case the CPU port
162 	 * will be a member of the VLAN).
163 	 */
164 	if (skb->protocol == htons(ETH_P_8021Q) &&
165 	    (!br_dev || br_vlan_enabled(br_dev))) {
166 		if (extra) {
167 			skb_push(skb, extra);
168 			dsa_alloc_etype_header(skb, extra);
169 		}
170 
171 		/* Construct tagged DSA tag from 802.1Q tag. */
172 		dsa_header = dsa_etype_header_pos_tx(skb) + extra;
173 		dsa_header[0] = (cmd << 6) | 0x20 | tag_dev;
174 		dsa_header[1] = tag_port << 3;
175 
176 		/* Move CFI field from byte 2 to byte 1. */
177 		if (dsa_header[2] & 0x10) {
178 			dsa_header[1] |= 0x01;
179 			dsa_header[2] &= ~0x10;
180 		}
181 	} else {
182 		u16 vid;
183 
184 		vid = br_dev ? MV88E6XXX_VID_BRIDGED : MV88E6XXX_VID_STANDALONE;
185 
186 		skb_push(skb, DSA_HLEN + extra);
187 		dsa_alloc_etype_header(skb, DSA_HLEN + extra);
188 
189 		/* Construct DSA header from untagged frame. */
190 		dsa_header = dsa_etype_header_pos_tx(skb) + extra;
191 
192 		dsa_header[0] = (cmd << 6) | tag_dev;
193 		dsa_header[1] = tag_port << 3;
194 		dsa_header[2] = vid >> 8;
195 		dsa_header[3] = vid & 0xff;
196 	}
197 
198 	return skb;
199 }
200 
dsa_rcv_ll(struct sk_buff * skb,struct net_device * dev,u8 extra)201 static struct sk_buff *dsa_rcv_ll(struct sk_buff *skb, struct net_device *dev,
202 				  u8 extra)
203 {
204 	bool trap = false, trunk = false;
205 	int source_device, source_port;
206 	enum dsa_code code;
207 	enum dsa_cmd cmd;
208 	u8 *dsa_header;
209 
210 	/* The ethertype field is part of the DSA header. */
211 	dsa_header = dsa_etype_header_pos_rx(skb);
212 
213 	cmd = dsa_header[0] >> 6;
214 	switch (cmd) {
215 	case DSA_CMD_FORWARD:
216 		trunk = !!(dsa_header[1] & 4);
217 		break;
218 
219 	case DSA_CMD_TO_CPU:
220 		code = (dsa_header[1] & 0x6) | ((dsa_header[2] >> 4) & 1);
221 
222 		switch (code) {
223 		case DSA_CODE_FRAME2REG:
224 			/* Remote management is not implemented yet,
225 			 * drop.
226 			 */
227 			return NULL;
228 		case DSA_CODE_ARP_MIRROR:
229 		case DSA_CODE_POLICY_MIRROR:
230 			/* Mark mirrored packets to notify any upper
231 			 * device (like a bridge) that forwarding has
232 			 * already been done by hardware.
233 			 */
234 			break;
235 		case DSA_CODE_MGMT_TRAP:
236 		case DSA_CODE_IGMP_MLD_TRAP:
237 		case DSA_CODE_POLICY_TRAP:
238 			/* Traps have, by definition, not been
239 			 * forwarded by hardware, so don't mark them.
240 			 */
241 			trap = true;
242 			break;
243 		default:
244 			/* Reserved code, this could be anything. Drop
245 			 * seems like the safest option.
246 			 */
247 			return NULL;
248 		}
249 
250 		break;
251 
252 	default:
253 		return NULL;
254 	}
255 
256 	source_device = dsa_header[0] & 0x1f;
257 	source_port = (dsa_header[1] >> 3) & 0x1f;
258 
259 	if (trunk) {
260 		struct dsa_port *cpu_dp = dev->dsa_ptr;
261 		struct dsa_lag *lag;
262 
263 		/* The exact source port is not available in the tag,
264 		 * so we inject the frame directly on the upper
265 		 * team/bond.
266 		 */
267 		lag = dsa_lag_by_id(cpu_dp->dst, source_port + 1);
268 		skb->dev = lag ? lag->dev : NULL;
269 	} else {
270 		skb->dev = dsa_conduit_find_user(dev, source_device,
271 						 source_port);
272 	}
273 
274 	if (!skb->dev)
275 		return NULL;
276 
277 	/* When using LAG offload, skb->dev is not a DSA user interface,
278 	 * so we cannot call dsa_default_offload_fwd_mark and we need to
279 	 * special-case it.
280 	 */
281 	if (trunk)
282 		skb->offload_fwd_mark = true;
283 	else if (!trap)
284 		dsa_default_offload_fwd_mark(skb);
285 
286 	/* If the 'tagged' bit is set; convert the DSA tag to a 802.1Q
287 	 * tag, and delete the ethertype (extra) if applicable. If the
288 	 * 'tagged' bit is cleared; delete the DSA tag, and ethertype
289 	 * if applicable.
290 	 */
291 	if (dsa_header[0] & 0x20) {
292 		u8 new_header[4];
293 
294 		/* Insert 802.1Q ethertype and copy the VLAN-related
295 		 * fields, but clear the bit that will hold CFI (since
296 		 * DSA uses that bit location for another purpose).
297 		 */
298 		new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
299 		new_header[1] = ETH_P_8021Q & 0xff;
300 		new_header[2] = dsa_header[2] & ~0x10;
301 		new_header[3] = dsa_header[3];
302 
303 		/* Move CFI bit from its place in the DSA header to
304 		 * its 802.1Q-designated place.
305 		 */
306 		if (dsa_header[1] & 0x01)
307 			new_header[2] |= 0x10;
308 
309 		/* Update packet checksum if skb is CHECKSUM_COMPLETE. */
310 		if (skb->ip_summed == CHECKSUM_COMPLETE) {
311 			__wsum c = skb->csum;
312 			c = csum_add(c, csum_partial(new_header + 2, 2, 0));
313 			c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
314 			skb->csum = c;
315 		}
316 
317 		memcpy(dsa_header, new_header, DSA_HLEN);
318 
319 		if (extra)
320 			dsa_strip_etype_header(skb, extra);
321 	} else {
322 		skb_pull_rcsum(skb, DSA_HLEN);
323 		dsa_strip_etype_header(skb, DSA_HLEN + extra);
324 	}
325 
326 	return skb;
327 }
328 
329 #if IS_ENABLED(CONFIG_NET_DSA_TAG_DSA)
330 
dsa_xmit(struct sk_buff * skb,struct net_device * dev)331 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
332 {
333 	return dsa_xmit_ll(skb, dev, 0);
334 }
335 
dsa_rcv(struct sk_buff * skb,struct net_device * dev)336 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev)
337 {
338 	if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
339 		return NULL;
340 
341 	return dsa_rcv_ll(skb, dev, 0);
342 }
343 
344 static const struct dsa_device_ops dsa_netdev_ops = {
345 	.name	  = DSA_NAME,
346 	.proto	  = DSA_TAG_PROTO_DSA,
347 	.xmit	  = dsa_xmit,
348 	.rcv	  = dsa_rcv,
349 	.needed_headroom = DSA_HLEN,
350 };
351 
352 DSA_TAG_DRIVER(dsa_netdev_ops);
353 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA, DSA_NAME);
354 #endif	/* CONFIG_NET_DSA_TAG_DSA */
355 
356 #if IS_ENABLED(CONFIG_NET_DSA_TAG_EDSA)
357 
358 #define EDSA_HLEN 8
359 
edsa_xmit(struct sk_buff * skb,struct net_device * dev)360 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
361 {
362 	u8 *edsa_header;
363 
364 	skb = dsa_xmit_ll(skb, dev, EDSA_HLEN - DSA_HLEN);
365 	if (!skb)
366 		return NULL;
367 
368 	edsa_header = dsa_etype_header_pos_tx(skb);
369 	edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
370 	edsa_header[1] = ETH_P_EDSA & 0xff;
371 	edsa_header[2] = 0x00;
372 	edsa_header[3] = 0x00;
373 	return skb;
374 }
375 
edsa_rcv(struct sk_buff * skb,struct net_device * dev)376 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev)
377 {
378 	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
379 		return NULL;
380 
381 	skb_pull_rcsum(skb, EDSA_HLEN - DSA_HLEN);
382 
383 	return dsa_rcv_ll(skb, dev, EDSA_HLEN - DSA_HLEN);
384 }
385 
386 static const struct dsa_device_ops edsa_netdev_ops = {
387 	.name	  = EDSA_NAME,
388 	.proto	  = DSA_TAG_PROTO_EDSA,
389 	.xmit	  = edsa_xmit,
390 	.rcv	  = edsa_rcv,
391 	.needed_headroom = EDSA_HLEN,
392 };
393 
394 DSA_TAG_DRIVER(edsa_netdev_ops);
395 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA, EDSA_NAME);
396 #endif	/* CONFIG_NET_DSA_TAG_EDSA */
397 
398 static struct dsa_tag_driver *dsa_tag_drivers[] = {
399 #if IS_ENABLED(CONFIG_NET_DSA_TAG_DSA)
400 	&DSA_TAG_DRIVER_NAME(dsa_netdev_ops),
401 #endif
402 #if IS_ENABLED(CONFIG_NET_DSA_TAG_EDSA)
403 	&DSA_TAG_DRIVER_NAME(edsa_netdev_ops),
404 #endif
405 };
406 
407 module_dsa_tag_drivers(dsa_tag_drivers);
408 
409 MODULE_DESCRIPTION("DSA tag driver for Marvell switches using DSA headers");
410 MODULE_LICENSE("GPL");
411