1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * net/dsa/tag_edsa.c - Ethertype DSA tagging
  4 * Copyright (c) 2008-2009 Marvell Semiconductor
  5 */
  6
  7#include <linux/etherdevice.h>
  8#include <linux/list.h>
  9#include <linux/slab.h>
 10
 11#include "dsa_priv.h"
 12
 13#define DSA_HLEN	4
 14#define EDSA_HLEN	8
 15
 16#define FRAME_TYPE_TO_CPU	0x00
 17#define FRAME_TYPE_FORWARD	0x03
 18
 19#define TO_CPU_CODE_MGMT_TRAP		0x00
 20#define TO_CPU_CODE_FRAME2REG		0x01
 21#define TO_CPU_CODE_IGMP_MLD_TRAP	0x02
 22#define TO_CPU_CODE_POLICY_TRAP		0x03
 23#define TO_CPU_CODE_ARP_MIRROR		0x04
 24#define TO_CPU_CODE_POLICY_MIRROR	0x05
 25
 26static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 27{
 28	struct dsa_port *dp = dsa_slave_to_port(dev);
 29	u8 *edsa_header;
 30
 31	/*
 32	 * Convert the outermost 802.1q tag to a DSA tag and prepend
 33	 * a DSA ethertype field is the packet is tagged, or insert
 34	 * a DSA ethertype plus DSA tag between the addresses and the
 35	 * current ethertype field if the packet is untagged.
 36	 */
 37	if (skb->protocol == htons(ETH_P_8021Q)) {
 38		if (skb_cow_head(skb, DSA_HLEN) < 0)
 39			return NULL;
 40		skb_push(skb, DSA_HLEN);
 41
 42		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 43
 44		/*
 45		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 46		 */
 47		edsa_header = skb->data + 2 * ETH_ALEN;
 48		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 49		edsa_header[1] = ETH_P_EDSA & 0xff;
 50		edsa_header[2] = 0x00;
 51		edsa_header[3] = 0x00;
 52		edsa_header[4] = 0x60 | dp->ds->index;
 53		edsa_header[5] = dp->index << 3;
 54
 55		/*
 56		 * Move CFI field from byte 6 to byte 5.
 57		 */
 58		if (edsa_header[6] & 0x10) {
 59			edsa_header[5] |= 0x01;
 60			edsa_header[6] &= ~0x10;
 61		}
 62	} else {
 63		if (skb_cow_head(skb, EDSA_HLEN) < 0)
 64			return NULL;
 65		skb_push(skb, EDSA_HLEN);
 66
 67		memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
 68
 69		/*
 70		 * Construct untagged FROM_CPU DSA tag.
 71		 */
 72		edsa_header = skb->data + 2 * ETH_ALEN;
 73		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 74		edsa_header[1] = ETH_P_EDSA & 0xff;
 75		edsa_header[2] = 0x00;
 76		edsa_header[3] = 0x00;
 77		edsa_header[4] = 0x40 | dp->ds->index;
 78		edsa_header[5] = dp->index << 3;
 79		edsa_header[6] = 0x00;
 80		edsa_header[7] = 0x00;
 81	}
 82
 83	return skb;
 84}
 85
 86static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 87				struct packet_type *pt)
 88{
 89	u8 *edsa_header;
 90	int frame_type;
 91	int code;
 92	int source_device;
 93	int source_port;
 94
 95	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
 96		return NULL;
 97
 98	/*
 99	 * Skip the two null bytes after the ethertype.
100	 */
101	edsa_header = skb->data + 2;
102
103	/*
104	 * Check that frame type is either TO_CPU or FORWARD.
105	 */
106	frame_type = edsa_header[0] >> 6;
107
108	switch (frame_type) {
109	case FRAME_TYPE_TO_CPU:
110		code = (edsa_header[1] & 0x6) | ((edsa_header[2] >> 4) & 1);
111
112		/*
113		 * Mark the frame to never egress on any port of the same switch
114		 * unless it's a trapped IGMP/MLD packet, in which case the
115		 * bridge might want to forward it.
116		 */
117		if (code != TO_CPU_CODE_IGMP_MLD_TRAP)
118			skb->offload_fwd_mark = 1;
119
120		break;
121
122	case FRAME_TYPE_FORWARD:
123		skb->offload_fwd_mark = 1;
124		break;
125
126	default:
127		return NULL;
128	}
129
130	/*
131	 * Determine source device and port.
132	 */
133	source_device = edsa_header[0] & 0x1f;
134	source_port = (edsa_header[1] >> 3) & 0x1f;
135
136	skb->dev = dsa_master_find_slave(dev, source_device, source_port);
137	if (!skb->dev)
138		return NULL;
139
140	/*
141	 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
142	 * tag and delete the ethertype part.  If the 'tagged' bit is
143	 * clear, delete the ethertype and the DSA tag parts.
144	 */
145	if (edsa_header[0] & 0x20) {
146		u8 new_header[4];
147
148		/*
149		 * Insert 802.1q ethertype and copy the VLAN-related
150		 * fields, but clear the bit that will hold CFI (since
151		 * DSA uses that bit location for another purpose).
152		 */
153		new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
154		new_header[1] = ETH_P_8021Q & 0xff;
155		new_header[2] = edsa_header[2] & ~0x10;
156		new_header[3] = edsa_header[3];
157
158		/*
159		 * Move CFI bit from its place in the DSA header to
160		 * its 802.1q-designated place.
161		 */
162		if (edsa_header[1] & 0x01)
163			new_header[2] |= 0x10;
164
165		skb_pull_rcsum(skb, DSA_HLEN);
166
167		/*
168		 * Update packet checksum if skb is CHECKSUM_COMPLETE.
169		 */
170		if (skb->ip_summed == CHECKSUM_COMPLETE) {
171			__wsum c = skb->csum;
172			c = csum_add(c, csum_partial(new_header + 2, 2, 0));
173			c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
174			skb->csum = c;
175		}
176
177		memcpy(edsa_header, new_header, DSA_HLEN);
178
179		memmove(skb->data - ETH_HLEN,
180			skb->data - ETH_HLEN - DSA_HLEN,
181			2 * ETH_ALEN);
182	} else {
183		/*
184		 * Remove DSA tag and update checksum.
185		 */
186		skb_pull_rcsum(skb, EDSA_HLEN);
187		memmove(skb->data - ETH_HLEN,
188			skb->data - ETH_HLEN - EDSA_HLEN,
189			2 * ETH_ALEN);
190	}
191
192	return skb;
193}
194
195static int edsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
196				 int *offset)
197{
198	*offset = 8;
199	*proto = ((__be16 *)skb->data)[3];
200	return 0;
201}
202
203static const struct dsa_device_ops edsa_netdev_ops = {
204	.name	= "edsa",
205	.proto	= DSA_TAG_PROTO_EDSA,
206	.xmit	= edsa_xmit,
207	.rcv	= edsa_rcv,
208	.flow_dissect   = edsa_tag_flow_dissect,
209	.overhead = EDSA_HLEN,
210};
211
212MODULE_LICENSE("GPL");
213MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA);
214
215module_dsa_tag_driver(edsa_netdev_ops);