net/dsa/tag_brcm.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Broadcom tag support
   4  *
   5  * Copyright (C) 2014 Broadcom Corporation
   6  */
   7
   8 #include <linux/etherdevice.h>
   9 #include <linux/list.h>
  10 #include <linux/slab.h>
  11
  12 #include "dsa_priv.h"
  13
  14 /* This tag length is 4 bytes, older ones were 6 bytes, we do not
  15  * handle them
  16  */
  17 #define BRCM_TAG_LEN    4
  18
  19 /* Tag is constructed and desconstructed using byte by byte access
  20  * because the tag is placed after the MAC Source Address, which does
  21  * not make it 4-bytes aligned, so this might cause unaligned accesses
  22  * on most systems where this is used.
  23  */
  24
  25 /* Ingress and egress opcodes */
  26 #define BRCM_OPCODE_SHIFT       5
  27 #define BRCM_OPCODE_MASK        0x7
  28
  29 /* Ingress fields */
  30 /* 1st byte in the tag */
  31 #define BRCM_IG_TC_SHIFT        2
  32 #define BRCM_IG_TC_MASK         0x7
  33 /* 2nd byte in the tag */
  34 #define BRCM_IG_TE_MASK         0x3
  35 #define BRCM_IG_TS_SHIFT        7
  36 /* 3rd byte in the tag */
  37 #define BRCM_IG_DSTMAP2_MASK    1
  38 #define BRCM_IG_DSTMAP1_MASK    0xff
  39
  40 /* Egress fields */
  41
  42 /* 2nd byte in the tag */
  43 #define BRCM_EG_CID_MASK        0xff
  44
  45 /* 3rd byte in the tag */
  46 #define BRCM_EG_RC_MASK         0xff
  47 #define  BRCM_EG_RC_RSVD        (3 << 6)
  48 #define  BRCM_EG_RC_EXCEPTION   (1 << 5)
  49 #define  BRCM_EG_RC_PROT_SNOOP  (1 << 4)
  50 #define  BRCM_EG_RC_PROT_TERM   (1 << 3)
  51 #define  BRCM_EG_RC_SWITCH      (1 << 2)
  52 #define  BRCM_EG_RC_MAC_LEARN   (1 << 1)
  53 #define  BRCM_EG_RC_MIRROR      (1 << 0)
  54 #define BRCM_EG_TC_SHIFT        5
  55 #define BRCM_EG_TC_MASK         0x7
  56 #define BRCM_EG_PID_MASK        0x1f
  57
  58 #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM) || \
  59         IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)
  60
  61 static struct sk_buff *brcm_tag_xmit_ll(struct sk_buff *skb,
  62                                         struct net_device *dev,
  63                                         unsigned int offset)
  64 {
  65         struct dsa_port *dp = dsa_slave_to_port(dev);
  66         u16 queue = skb_get_queue_mapping(skb);
  67         u8 *brcm_tag;
  68
  69         /* The Ethernet switch we are interfaced with needs packets to be at
  70          * least 64 bytes (including FCS) otherwise they will be discarded when
  71          * they enter the switch port logic. When Broadcom tags are enabled, we
  72          * need to make sure that packets are at least 68 bytes
  73          * (including FCS and tag) because the length verification is done after
  74          * the Broadcom tag is stripped off the ingress packet.
  75          *
  76          * Let dsa_slave_xmit() free the SKB
  77          */
  78         if (__skb_put_padto(skb, ETH_ZLEN + BRCM_TAG_LEN, false))
  79                 return NULL;
  80
  81         skb_push(skb, BRCM_TAG_LEN);
  82
  83         if (offset)
  84                 memmove(skb->data, skb->data + BRCM_TAG_LEN, offset);
  85
  86         brcm_tag = skb->data + offset;
  87
  88         /* Set the ingress opcode, traffic class, tag enforcment is
  89          * deprecated
  90          */
  91         brcm_tag[0] = (1 << BRCM_OPCODE_SHIFT) |
  92                        ((queue & BRCM_IG_TC_MASK) << BRCM_IG_TC_SHIFT);
  93         brcm_tag[1] = 0;
  94         brcm_tag[2] = 0;
  95         if (dp->index == 8)
  96                 brcm_tag[2] = BRCM_IG_DSTMAP2_MASK;
  97         brcm_tag[3] = (1 << dp->index) & BRCM_IG_DSTMAP1_MASK;
  98
  99         /* Now tell the master network device about the desired output queue
 100          * as well
 101          */
 102         skb_set_queue_mapping(skb, BRCM_TAG_SET_PORT_QUEUE(dp->index, queue));
 103
 104         return skb;
 105 }
 106
 107 /* Frames with this tag have one of these two layouts:
 108  * -----------------------------------
 109  * | MAC DA | MAC SA | 4b tag | Type | DSA_TAG_PROTO_BRCM
 110  * -----------------------------------
 111  * -----------------------------------
 112  * | 4b tag | MAC DA | MAC SA | Type | DSA_TAG_PROTO_BRCM_PREPEND
 113  * -----------------------------------
 114  * In both cases, at receive time, skb->data points 2 bytes before the actual
 115  * Ethernet type field and we have an offset of 4bytes between where skb->data
 116  * and where the payload starts. So the same low-level receive function can be
 117  * used.
 118  */
 119 static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
 120                                        struct net_device *dev,
 121                                        struct packet_type *pt,
 122                                        unsigned int offset)
 123 {
 124         int source_port;
 125         u8 *brcm_tag;
 126
 127         if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
 128                 return NULL;
 129
 130         brcm_tag = skb->data - offset;
 131
 132         /* The opcode should never be different than 0b000 */
 133         if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
 134                 return NULL;
 135
 136         /* We should never see a reserved reason code without knowing how to
 137          * handle it
 138          */
 139         if (unlikely(brcm_tag[2] & BRCM_EG_RC_RSVD))
 140                 return NULL;
 141
 142         /* Locate which port this is coming from */
 143         source_port = brcm_tag[3] & BRCM_EG_PID_MASK;
 144
 145         skb->dev = dsa_master_find_slave(dev, 0, source_port);
 146         if (!skb->dev)
 147                 return NULL;
 148
 149         /* Remove Broadcom tag and update checksum */
 150         skb_pull_rcsum(skb, BRCM_TAG_LEN);
 151
 152         skb->offload_fwd_mark = 1;
 153
 154         return skb;
 155 }
 156 #endif
 157
 158 #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM)
 159 static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
 160                                      struct net_device *dev)
 161 {
 162         /* Build the tag after the MAC Source Address */
 163         return brcm_tag_xmit_ll(skb, dev, 2 * ETH_ALEN);
 164 }
 165
 166
 167 static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 168                                     struct packet_type *pt)
 169 {
 170         struct sk_buff *nskb;
 171
 172         /* skb->data points to the EtherType, the tag is right before it */
 173         nskb = brcm_tag_rcv_ll(skb, dev, pt, 2);
 174         if (!nskb)
 175                 return nskb;
 176
 177         /* Move the Ethernet DA and SA */
 178         memmove(nskb->data - ETH_HLEN,
 179                 nskb->data - ETH_HLEN - BRCM_TAG_LEN,
 180                 2 * ETH_ALEN);
 181
 182         return nskb;
 183 }
 184
 185 static const struct dsa_device_ops brcm_netdev_ops = {
 186         .name   = "brcm",
 187         .proto  = DSA_TAG_PROTO_BRCM,
 188         .xmit   = brcm_tag_xmit,
 189         .rcv    = brcm_tag_rcv,
 190         .overhead = BRCM_TAG_LEN,
 191 };
 192
 193 DSA_TAG_DRIVER(brcm_netdev_ops);
 194 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM);
 195 #endif
 196
 197 #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)
 198 static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb,
 199                                              struct net_device *dev)
 200 {
 201         /* tag is prepended to the packet */
 202         return brcm_tag_xmit_ll(skb, dev, 0);
 203 }
 204
 205 static struct sk_buff *brcm_tag_rcv_prepend(struct sk_buff *skb,
 206                                             struct net_device *dev,
 207                                             struct packet_type *pt)
 208 {
 209         /* tag is prepended to the packet */
 210         return brcm_tag_rcv_ll(skb, dev, pt, ETH_HLEN);
 211 }
 212
 213 static const struct dsa_device_ops brcm_prepend_netdev_ops = {
 214         .name   = "brcm-prepend",
 215         .proto  = DSA_TAG_PROTO_BRCM_PREPEND,
 216         .xmit   = brcm_tag_xmit_prepend,
 217         .rcv    = brcm_tag_rcv_prepend,
 218         .overhead = BRCM_TAG_LEN,
 219 };
 220
 221 DSA_TAG_DRIVER(brcm_prepend_netdev_ops);
 222 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM_PREPEND);
 223 #endif
 224
 225 static struct dsa_tag_driver *dsa_tag_driver_array[] =  {
 226 #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM)
 227         &DSA_TAG_DRIVER_NAME(brcm_netdev_ops),
 228 #endif
 229 #if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)
 230         &DSA_TAG_DRIVER_NAME(brcm_prepend_netdev_ops),
 231 #endif
 232 };
 233
 234 module_dsa_tag_drivers(dsa_tag_driver_array);
 235
 236 MODULE_LICENSE("GPL");