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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 #include "dsa_priv.h"
 15 
 16 #define DSA_HLEN        4
 17 
 18 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 19 {
 20         struct dsa_slave_priv *p = netdev_priv(dev);
 21         u8 *dsa_header;
 22 
 23         /*
 24          * Convert the outermost 802.1q tag to a DSA tag for tagged
 25          * packets, or insert a DSA tag between the addresses and
 26          * the ethertype field for untagged packets.
 27          */
 28         if (skb->protocol == htons(ETH_P_8021Q)) {
 29                 if (skb_cow_head(skb, 0) < 0)
 30                         goto out_free;
 31 
 32                 /*
 33                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 34                  */
 35                 dsa_header = skb->data + 2 * ETH_ALEN;
 36                 dsa_header[0] = 0x60 | p->parent->index;
 37                 dsa_header[1] = p->port << 3;
 38 
 39                 /*
 40                  * Move CFI field from byte 2 to byte 1.
 41                  */
 42                 if (dsa_header[2] & 0x10) {
 43                         dsa_header[1] |= 0x01;
 44                         dsa_header[2] &= ~0x10;
 45                 }
 46         } else {
 47                 if (skb_cow_head(skb, DSA_HLEN) < 0)
 48                         goto out_free;
 49                 skb_push(skb, DSA_HLEN);
 50 
 51                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 52 
 53                 /*
 54                  * Construct untagged FROM_CPU DSA tag.
 55                  */
 56                 dsa_header = skb->data + 2 * ETH_ALEN;
 57                 dsa_header[0] = 0x40 | p->parent->index;
 58                 dsa_header[1] = p->port << 3;
 59                 dsa_header[2] = 0x00;
 60                 dsa_header[3] = 0x00;
 61         }
 62 
 63         return skb;
 64 
 65 out_free:
 66         kfree_skb(skb);
 67         return NULL;
 68 }
 69 
 70 static int dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 71                    struct packet_type *pt, struct net_device *orig_dev)
 72 {
 73         struct dsa_switch_tree *dst = dev->dsa_ptr;
 74         struct dsa_switch *ds;
 75         u8 *dsa_header;
 76         int source_device;
 77         int source_port;
 78 
 79         if (unlikely(dst == NULL))
 80                 goto out_drop;
 81 
 82         skb = skb_unshare(skb, GFP_ATOMIC);
 83         if (skb == NULL)
 84                 goto out;
 85 
 86         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
 87                 goto out_drop;
 88 
 89         /*
 90          * The ethertype field is part of the DSA header.
 91          */
 92         dsa_header = skb->data - 2;
 93 
 94         /*
 95          * Check that frame type is either TO_CPU or FORWARD.
 96          */
 97         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
 98                 goto out_drop;
 99 
100         /*
101          * Determine source device and port.
102          */
103         source_device = dsa_header[0] & 0x1f;
104         source_port = (dsa_header[1] >> 3) & 0x1f;
105 
106         /*
107          * Check that the source device exists and that the source
108          * port is a registered DSA port.
109          */
110         if (source_device >= DSA_MAX_SWITCHES)
111                 goto out_drop;
112 
113         ds = dst->ds[source_device];
114         if (!ds)
115                 goto out_drop;
116 
117         if (source_port >= DSA_MAX_PORTS || !ds->ports[source_port].netdev)
118                 goto out_drop;
119 
120         /*
121          * Convert the DSA header to an 802.1q header if the 'tagged'
122          * bit in the DSA header is set.  If the 'tagged' bit is clear,
123          * delete the DSA header entirely.
124          */
125         if (dsa_header[0] & 0x20) {
126                 u8 new_header[4];
127 
128                 /*
129                  * Insert 802.1q ethertype and copy the VLAN-related
130                  * fields, but clear the bit that will hold CFI (since
131                  * DSA uses that bit location for another purpose).
132                  */
133                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
134                 new_header[1] = ETH_P_8021Q & 0xff;
135                 new_header[2] = dsa_header[2] & ~0x10;
136                 new_header[3] = dsa_header[3];
137 
138                 /*
139                  * Move CFI bit from its place in the DSA header to
140                  * its 802.1q-designated place.
141                  */
142                 if (dsa_header[1] & 0x01)
143                         new_header[2] |= 0x10;
144 
145                 /*
146                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
147                  */
148                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
149                         __wsum c = skb->csum;
150                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
151                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
152                         skb->csum = c;
153                 }
154 
155                 memcpy(dsa_header, new_header, DSA_HLEN);
156         } else {
157                 /*
158                  * Remove DSA tag and update checksum.
159                  */
160                 skb_pull_rcsum(skb, DSA_HLEN);
161                 memmove(skb->data - ETH_HLEN,
162                         skb->data - ETH_HLEN - DSA_HLEN,
163                         2 * ETH_ALEN);
164         }
165 
166         skb->dev = ds->ports[source_port].netdev;
167         skb_push(skb, ETH_HLEN);
168         skb->pkt_type = PACKET_HOST;
169         skb->protocol = eth_type_trans(skb, skb->dev);
170 
171         skb->dev->stats.rx_packets++;
172         skb->dev->stats.rx_bytes += skb->len;
173 
174         netif_receive_skb(skb);
175 
176         return 0;
177 
178 out_drop:
179         kfree_skb(skb);
180 out:
181         return 0;
182 }
183 
184 const struct dsa_device_ops dsa_netdev_ops = {
185         .xmit   = dsa_xmit,
186         .rcv    = dsa_rcv,
187 };
188 

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