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Linux/net/dsa/tag_edsa.c

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  1 /*
  2  * net/dsa/tag_edsa.c - Ethertype DSA tagging
  3  * Copyright (c) 2008-2009 Marvell Semiconductor
  4  *
  5  * This program is free software; you can redistribute it and/or modify
  6  * it under the terms of the GNU General Public License as published by
  7  * the Free Software Foundation; either version 2 of the License, or
  8  * (at your option) any later version.
  9  */
 10 
 11 #include <linux/etherdevice.h>
 12 #include <linux/list.h>
 13 #include <linux/slab.h>
 14 
 15 #include "dsa_priv.h"
 16 
 17 #define DSA_HLEN        4
 18 #define EDSA_HLEN       8
 19 
 20 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 21 {
 22         struct dsa_port *dp = dsa_slave_to_port(dev);
 23         u8 *edsa_header;
 24 
 25         /*
 26          * Convert the outermost 802.1q tag to a DSA tag and prepend
 27          * a DSA ethertype field is the packet is tagged, or insert
 28          * a DSA ethertype plus DSA tag between the addresses and the
 29          * current ethertype field if the packet is untagged.
 30          */
 31         if (skb->protocol == htons(ETH_P_8021Q)) {
 32                 if (skb_cow_head(skb, DSA_HLEN) < 0)
 33                         return NULL;
 34                 skb_push(skb, DSA_HLEN);
 35 
 36                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 37 
 38                 /*
 39                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 40                  */
 41                 edsa_header = skb->data + 2 * ETH_ALEN;
 42                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 43                 edsa_header[1] = ETH_P_EDSA & 0xff;
 44                 edsa_header[2] = 0x00;
 45                 edsa_header[3] = 0x00;
 46                 edsa_header[4] = 0x60 | dp->ds->index;
 47                 edsa_header[5] = dp->index << 3;
 48 
 49                 /*
 50                  * Move CFI field from byte 6 to byte 5.
 51                  */
 52                 if (edsa_header[6] & 0x10) {
 53                         edsa_header[5] |= 0x01;
 54                         edsa_header[6] &= ~0x10;
 55                 }
 56         } else {
 57                 if (skb_cow_head(skb, EDSA_HLEN) < 0)
 58                         return NULL;
 59                 skb_push(skb, EDSA_HLEN);
 60 
 61                 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
 62 
 63                 /*
 64                  * Construct untagged FROM_CPU DSA tag.
 65                  */
 66                 edsa_header = skb->data + 2 * ETH_ALEN;
 67                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 68                 edsa_header[1] = ETH_P_EDSA & 0xff;
 69                 edsa_header[2] = 0x00;
 70                 edsa_header[3] = 0x00;
 71                 edsa_header[4] = 0x40 | dp->ds->index;
 72                 edsa_header[5] = dp->index << 3;
 73                 edsa_header[6] = 0x00;
 74                 edsa_header[7] = 0x00;
 75         }
 76 
 77         return skb;
 78 }
 79 
 80 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 81                                 struct packet_type *pt)
 82 {
 83         u8 *edsa_header;
 84         int source_device;
 85         int source_port;
 86 
 87         if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
 88                 return NULL;
 89 
 90         /*
 91          * Skip the two null bytes after the ethertype.
 92          */
 93         edsa_header = skb->data + 2;
 94 
 95         /*
 96          * Check that frame type is either TO_CPU or FORWARD.
 97          */
 98         if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
 99                 return NULL;
100 
101         /*
102          * Determine source device and port.
103          */
104         source_device = edsa_header[0] & 0x1f;
105         source_port = (edsa_header[1] >> 3) & 0x1f;
106 
107         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
108         if (!skb->dev)
109                 return NULL;
110 
111         /*
112          * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
113          * tag and delete the ethertype part.  If the 'tagged' bit is
114          * clear, delete the ethertype and the DSA tag parts.
115          */
116         if (edsa_header[0] & 0x20) {
117                 u8 new_header[4];
118 
119                 /*
120                  * Insert 802.1q ethertype and copy the VLAN-related
121                  * fields, but clear the bit that will hold CFI (since
122                  * DSA uses that bit location for another purpose).
123                  */
124                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
125                 new_header[1] = ETH_P_8021Q & 0xff;
126                 new_header[2] = edsa_header[2] & ~0x10;
127                 new_header[3] = edsa_header[3];
128 
129                 /*
130                  * Move CFI bit from its place in the DSA header to
131                  * its 802.1q-designated place.
132                  */
133                 if (edsa_header[1] & 0x01)
134                         new_header[2] |= 0x10;
135 
136                 skb_pull_rcsum(skb, DSA_HLEN);
137 
138                 /*
139                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
140                  */
141                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
142                         __wsum c = skb->csum;
143                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
144                         c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
145                         skb->csum = c;
146                 }
147 
148                 memcpy(edsa_header, new_header, DSA_HLEN);
149 
150                 memmove(skb->data - ETH_HLEN,
151                         skb->data - ETH_HLEN - DSA_HLEN,
152                         2 * ETH_ALEN);
153         } else {
154                 /*
155                  * Remove DSA tag and update checksum.
156                  */
157                 skb_pull_rcsum(skb, EDSA_HLEN);
158                 memmove(skb->data - ETH_HLEN,
159                         skb->data - ETH_HLEN - EDSA_HLEN,
160                         2 * ETH_ALEN);
161         }
162 
163         skb->offload_fwd_mark = 1;
164 
165         return skb;
166 }
167 
168 const struct dsa_device_ops edsa_netdev_ops = {
169         .xmit   = edsa_xmit,
170         .rcv    = edsa_rcv,
171 };
172 

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