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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_slave_priv *p = netdev_priv(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 | p->dp->ds->index;
 38                 dsa_header[1] = p->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 | p->dp->ds->index;
 59                 dsa_header[1] = p->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                                struct net_device *orig_dev)
 70 {
 71         struct dsa_switch_tree *dst = dev->dsa_ptr;
 72         struct dsa_switch *ds;
 73         u8 *dsa_header;
 74         int source_device;
 75         int source_port;
 76 
 77         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
 78                 return NULL;
 79 
 80         /*
 81          * The ethertype field is part of the DSA header.
 82          */
 83         dsa_header = skb->data - 2;
 84 
 85         /*
 86          * Check that frame type is either TO_CPU or FORWARD.
 87          */
 88         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
 89                 return NULL;
 90 
 91         /*
 92          * Determine source device and port.
 93          */
 94         source_device = dsa_header[0] & 0x1f;
 95         source_port = (dsa_header[1] >> 3) & 0x1f;
 96 
 97         /*
 98          * Check that the source device exists and that the source
 99          * port is a registered DSA port.
100          */
101         if (source_device >= DSA_MAX_SWITCHES)
102                 return NULL;
103 
104         ds = dst->ds[source_device];
105         if (!ds)
106                 return NULL;
107 
108         if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
109                 return NULL;
110 
111         /*
112          * Convert the DSA header to an 802.1q header if the 'tagged'
113          * bit in the DSA header is set.  If the 'tagged' bit is clear,
114          * delete the DSA header entirely.
115          */
116         if (dsa_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] = dsa_header[2] & ~0x10;
127                 new_header[3] = dsa_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 (dsa_header[1] & 0x01)
134                         new_header[2] |= 0x10;
135 
136                 /*
137                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
138                  */
139                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
140                         __wsum c = skb->csum;
141                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
142                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
143                         skb->csum = c;
144                 }
145 
146                 memcpy(dsa_header, new_header, DSA_HLEN);
147         } else {
148                 /*
149                  * Remove DSA tag and update checksum.
150                  */
151                 skb_pull_rcsum(skb, DSA_HLEN);
152                 memmove(skb->data - ETH_HLEN,
153                         skb->data - ETH_HLEN - DSA_HLEN,
154                         2 * ETH_ALEN);
155         }
156 
157         skb->dev = ds->ports[source_port].netdev;
158 
159         return skb;
160 }
161 
162 const struct dsa_device_ops dsa_netdev_ops = {
163         .xmit   = dsa_xmit,
164         .rcv    = dsa_rcv,
165 };
166 

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