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Linux/net/dsa/tag_dsa.c

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  1 /*
  2  * net/dsa/tag_dsa.c - (Non-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 
 19 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 20 {
 21         struct dsa_port *dp = dsa_slave_to_port(dev);
 22         u8 *dsa_header;
 23 
 24         /*
 25          * Convert the outermost 802.1q tag to a DSA tag for tagged
 26          * packets, or insert a DSA tag between the addresses and
 27          * the ethertype field for untagged packets.
 28          */
 29         if (skb->protocol == htons(ETH_P_8021Q)) {
 30                 if (skb_cow_head(skb, 0) < 0)
 31                         return NULL;
 32 
 33                 /*
 34                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 35                  */
 36                 dsa_header = skb->data + 2 * ETH_ALEN;
 37                 dsa_header[0] = 0x60 | dp->ds->index;
 38                 dsa_header[1] = dp->index << 3;
 39 
 40                 /*
 41                  * Move CFI field from byte 2 to byte 1.
 42                  */
 43                 if (dsa_header[2] & 0x10) {
 44                         dsa_header[1] |= 0x01;
 45                         dsa_header[2] &= ~0x10;
 46                 }
 47         } else {
 48                 if (skb_cow_head(skb, DSA_HLEN) < 0)
 49                         return NULL;
 50                 skb_push(skb, DSA_HLEN);
 51 
 52                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 53 
 54                 /*
 55                  * Construct untagged FROM_CPU DSA tag.
 56                  */
 57                 dsa_header = skb->data + 2 * ETH_ALEN;
 58                 dsa_header[0] = 0x40 | dp->ds->index;
 59                 dsa_header[1] = dp->index << 3;
 60                 dsa_header[2] = 0x00;
 61                 dsa_header[3] = 0x00;
 62         }
 63 
 64         return skb;
 65 }
 66 
 67 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 68                                struct packet_type *pt)
 69 {
 70         u8 *dsa_header;
 71         int source_device;
 72         int source_port;
 73 
 74         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
 75                 return NULL;
 76 
 77         /*
 78          * The ethertype field is part of the DSA header.
 79          */
 80         dsa_header = skb->data - 2;
 81 
 82         /*
 83          * Check that frame type is either TO_CPU or FORWARD.
 84          */
 85         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
 86                 return NULL;
 87 
 88         /*
 89          * Determine source device and port.
 90          */
 91         source_device = dsa_header[0] & 0x1f;
 92         source_port = (dsa_header[1] >> 3) & 0x1f;
 93 
 94         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
 95         if (!skb->dev)
 96                 return NULL;
 97 
 98         /*
 99          * Convert the DSA header to an 802.1q header if the 'tagged'
100          * bit in the DSA header is set.  If the 'tagged' bit is clear,
101          * delete the DSA header entirely.
102          */
103         if (dsa_header[0] & 0x20) {
104                 u8 new_header[4];
105 
106                 /*
107                  * Insert 802.1q ethertype and copy the VLAN-related
108                  * fields, but clear the bit that will hold CFI (since
109                  * DSA uses that bit location for another purpose).
110                  */
111                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
112                 new_header[1] = ETH_P_8021Q & 0xff;
113                 new_header[2] = dsa_header[2] & ~0x10;
114                 new_header[3] = dsa_header[3];
115 
116                 /*
117                  * Move CFI bit from its place in the DSA header to
118                  * its 802.1q-designated place.
119                  */
120                 if (dsa_header[1] & 0x01)
121                         new_header[2] |= 0x10;
122 
123                 /*
124                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
125                  */
126                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
127                         __wsum c = skb->csum;
128                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
129                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
130                         skb->csum = c;
131                 }
132 
133                 memcpy(dsa_header, new_header, DSA_HLEN);
134         } else {
135                 /*
136                  * Remove DSA tag and update checksum.
137                  */
138                 skb_pull_rcsum(skb, DSA_HLEN);
139                 memmove(skb->data - ETH_HLEN,
140                         skb->data - ETH_HLEN - DSA_HLEN,
141                         2 * ETH_ALEN);
142         }
143 
144         skb->offload_fwd_mark = 1;
145 
146         return skb;
147 }
148 
149 const struct dsa_device_ops dsa_netdev_ops = {
150         .xmit   = dsa_xmit,
151         .rcv    = dsa_rcv,
152 };
153 

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