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Linux/net/dsa/tag_dsa.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * net/dsa/tag_dsa.c - (Non-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 
 15 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 16 {
 17         struct dsa_port *dp = dsa_slave_to_port(dev);
 18         u8 *dsa_header;
 19 
 20         /*
 21          * Convert the outermost 802.1q tag to a DSA tag for tagged
 22          * packets, or insert a DSA tag between the addresses and
 23          * the ethertype field for untagged packets.
 24          */
 25         if (skb->protocol == htons(ETH_P_8021Q)) {
 26                 if (skb_cow_head(skb, 0) < 0)
 27                         return NULL;
 28 
 29                 /*
 30                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 31                  */
 32                 dsa_header = skb->data + 2 * ETH_ALEN;
 33                 dsa_header[0] = 0x60 | dp->ds->index;
 34                 dsa_header[1] = dp->index << 3;
 35 
 36                 /*
 37                  * Move CFI field from byte 2 to byte 1.
 38                  */
 39                 if (dsa_header[2] & 0x10) {
 40                         dsa_header[1] |= 0x01;
 41                         dsa_header[2] &= ~0x10;
 42                 }
 43         } else {
 44                 if (skb_cow_head(skb, DSA_HLEN) < 0)
 45                         return NULL;
 46                 skb_push(skb, DSA_HLEN);
 47 
 48                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 49 
 50                 /*
 51                  * Construct untagged FROM_CPU DSA tag.
 52                  */
 53                 dsa_header = skb->data + 2 * ETH_ALEN;
 54                 dsa_header[0] = 0x40 | dp->ds->index;
 55                 dsa_header[1] = dp->index << 3;
 56                 dsa_header[2] = 0x00;
 57                 dsa_header[3] = 0x00;
 58         }
 59 
 60         return skb;
 61 }
 62 
 63 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 64                                struct packet_type *pt)
 65 {
 66         u8 *dsa_header;
 67         int source_device;
 68         int source_port;
 69 
 70         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
 71                 return NULL;
 72 
 73         /*
 74          * The ethertype field is part of the DSA header.
 75          */
 76         dsa_header = skb->data - 2;
 77 
 78         /*
 79          * Check that frame type is either TO_CPU or FORWARD.
 80          */
 81         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
 82                 return NULL;
 83 
 84         /*
 85          * Determine source device and port.
 86          */
 87         source_device = dsa_header[0] & 0x1f;
 88         source_port = (dsa_header[1] >> 3) & 0x1f;
 89 
 90         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
 91         if (!skb->dev)
 92                 return NULL;
 93 
 94         /*
 95          * Convert the DSA header to an 802.1q header if the 'tagged'
 96          * bit in the DSA header is set.  If the 'tagged' bit is clear,
 97          * delete the DSA header entirely.
 98          */
 99         if (dsa_header[0] & 0x20) {
100                 u8 new_header[4];
101 
102                 /*
103                  * Insert 802.1q ethertype and copy the VLAN-related
104                  * fields, but clear the bit that will hold CFI (since
105                  * DSA uses that bit location for another purpose).
106                  */
107                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
108                 new_header[1] = ETH_P_8021Q & 0xff;
109                 new_header[2] = dsa_header[2] & ~0x10;
110                 new_header[3] = dsa_header[3];
111 
112                 /*
113                  * Move CFI bit from its place in the DSA header to
114                  * its 802.1q-designated place.
115                  */
116                 if (dsa_header[1] & 0x01)
117                         new_header[2] |= 0x10;
118 
119                 /*
120                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
121                  */
122                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
123                         __wsum c = skb->csum;
124                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
125                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
126                         skb->csum = c;
127                 }
128 
129                 memcpy(dsa_header, new_header, DSA_HLEN);
130         } else {
131                 /*
132                  * Remove DSA tag and update checksum.
133                  */
134                 skb_pull_rcsum(skb, DSA_HLEN);
135                 memmove(skb->data - ETH_HLEN,
136                         skb->data - ETH_HLEN - DSA_HLEN,
137                         2 * ETH_ALEN);
138         }
139 
140         skb->offload_fwd_mark = 1;
141 
142         return skb;
143 }
144 
145 static int dsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
146                                 int *offset)
147 {
148         *offset = 4;
149         *proto = ((__be16 *)skb->data)[1];
150         return 0;
151 }
152 
153 static const struct dsa_device_ops dsa_netdev_ops = {
154         .name   = "dsa",
155         .proto  = DSA_TAG_PROTO_DSA,
156         .xmit   = dsa_xmit,
157         .rcv    = dsa_rcv,
158         .flow_dissect   = dsa_tag_flow_dissect,
159         .overhead = DSA_HLEN,
160 };
161 
162 MODULE_LICENSE("GPL");
163 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
164 
165 module_dsa_tag_driver(dsa_netdev_ops);
166 

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