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Linux/net/dsa/tag_edsa.c

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  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 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 17 {
 18         struct dsa_port *dp = dsa_slave_to_port(dev);
 19         u8 *edsa_header;
 20 
 21         /*
 22          * Convert the outermost 802.1q tag to a DSA tag and prepend
 23          * a DSA ethertype field is the packet is tagged, or insert
 24          * a DSA ethertype plus DSA tag between the addresses and the
 25          * current ethertype field if the packet is untagged.
 26          */
 27         if (skb->protocol == htons(ETH_P_8021Q)) {
 28                 if (skb_cow_head(skb, DSA_HLEN) < 0)
 29                         return NULL;
 30                 skb_push(skb, DSA_HLEN);
 31 
 32                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 33 
 34                 /*
 35                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 36                  */
 37                 edsa_header = skb->data + 2 * ETH_ALEN;
 38                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 39                 edsa_header[1] = ETH_P_EDSA & 0xff;
 40                 edsa_header[2] = 0x00;
 41                 edsa_header[3] = 0x00;
 42                 edsa_header[4] = 0x60 | dp->ds->index;
 43                 edsa_header[5] = dp->index << 3;
 44 
 45                 /*
 46                  * Move CFI field from byte 6 to byte 5.
 47                  */
 48                 if (edsa_header[6] & 0x10) {
 49                         edsa_header[5] |= 0x01;
 50                         edsa_header[6] &= ~0x10;
 51                 }
 52         } else {
 53                 if (skb_cow_head(skb, EDSA_HLEN) < 0)
 54                         return NULL;
 55                 skb_push(skb, EDSA_HLEN);
 56 
 57                 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
 58 
 59                 /*
 60                  * Construct untagged FROM_CPU DSA tag.
 61                  */
 62                 edsa_header = skb->data + 2 * ETH_ALEN;
 63                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 64                 edsa_header[1] = ETH_P_EDSA & 0xff;
 65                 edsa_header[2] = 0x00;
 66                 edsa_header[3] = 0x00;
 67                 edsa_header[4] = 0x40 | dp->ds->index;
 68                 edsa_header[5] = dp->index << 3;
 69                 edsa_header[6] = 0x00;
 70                 edsa_header[7] = 0x00;
 71         }
 72 
 73         return skb;
 74 }
 75 
 76 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 77                                 struct packet_type *pt)
 78 {
 79         u8 *edsa_header;
 80         int source_device;
 81         int source_port;
 82 
 83         if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
 84                 return NULL;
 85 
 86         /*
 87          * Skip the two null bytes after the ethertype.
 88          */
 89         edsa_header = skb->data + 2;
 90 
 91         /*
 92          * Check that frame type is either TO_CPU or FORWARD.
 93          */
 94         if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
 95                 return NULL;
 96 
 97         /*
 98          * Determine source device and port.
 99          */
100         source_device = edsa_header[0] & 0x1f;
101         source_port = (edsa_header[1] >> 3) & 0x1f;
102 
103         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
104         if (!skb->dev)
105                 return NULL;
106 
107         /*
108          * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
109          * tag and delete the ethertype part.  If the 'tagged' bit is
110          * clear, delete the ethertype and the DSA tag parts.
111          */
112         if (edsa_header[0] & 0x20) {
113                 u8 new_header[4];
114 
115                 /*
116                  * Insert 802.1q ethertype and copy the VLAN-related
117                  * fields, but clear the bit that will hold CFI (since
118                  * DSA uses that bit location for another purpose).
119                  */
120                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
121                 new_header[1] = ETH_P_8021Q & 0xff;
122                 new_header[2] = edsa_header[2] & ~0x10;
123                 new_header[3] = edsa_header[3];
124 
125                 /*
126                  * Move CFI bit from its place in the DSA header to
127                  * its 802.1q-designated place.
128                  */
129                 if (edsa_header[1] & 0x01)
130                         new_header[2] |= 0x10;
131 
132                 skb_pull_rcsum(skb, DSA_HLEN);
133 
134                 /*
135                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
136                  */
137                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
138                         __wsum c = skb->csum;
139                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
140                         c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
141                         skb->csum = c;
142                 }
143 
144                 memcpy(edsa_header, new_header, DSA_HLEN);
145 
146                 memmove(skb->data - ETH_HLEN,
147                         skb->data - ETH_HLEN - DSA_HLEN,
148                         2 * ETH_ALEN);
149         } else {
150                 /*
151                  * Remove DSA tag and update checksum.
152                  */
153                 skb_pull_rcsum(skb, EDSA_HLEN);
154                 memmove(skb->data - ETH_HLEN,
155                         skb->data - ETH_HLEN - EDSA_HLEN,
156                         2 * ETH_ALEN);
157         }
158 
159         skb->offload_fwd_mark = 1;
160 
161         return skb;
162 }
163 
164 static int edsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
165                                  int *offset)
166 {
167         *offset = 8;
168         *proto = ((__be16 *)skb->data)[3];
169         return 0;
170 }
171 
172 static const struct dsa_device_ops edsa_netdev_ops = {
173         .name   = "edsa",
174         .proto  = DSA_TAG_PROTO_EDSA,
175         .xmit   = edsa_xmit,
176         .rcv    = edsa_rcv,
177         .flow_dissect   = edsa_tag_flow_dissect,
178         .overhead = EDSA_HLEN,
179 };
180 
181 MODULE_LICENSE("GPL");
182 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA);
183 
184 module_dsa_tag_driver(edsa_netdev_ops);
185 

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