net/dsa/tag_sja1105.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
   3  */
   4 #include <linux/if_vlan.h>
   5 #include <linux/dsa/sja1105.h>
   6 #include <linux/dsa/8021q.h>
   7 #include <linux/packing.h>
   8 #include "dsa_priv.h"
   9
  10 /* Similar to is_link_local_ether_addr(hdr->h_dest) but also covers PTP */
  11 static inline bool sja1105_is_link_local(const struct sk_buff *skb)
  12 {
  13         const struct ethhdr *hdr = eth_hdr(skb);
  14         u64 dmac = ether_addr_to_u64(hdr->h_dest);
  15
  16         if (ntohs(hdr->h_proto) == ETH_P_SJA1105_META)
  17                 return false;
  18         if ((dmac & SJA1105_LINKLOCAL_FILTER_A_MASK) ==
  19                     SJA1105_LINKLOCAL_FILTER_A)
  20                 return true;
  21         if ((dmac & SJA1105_LINKLOCAL_FILTER_B_MASK) ==
  22                     SJA1105_LINKLOCAL_FILTER_B)
  23                 return true;
  24         return false;
  25 }
  26
  27 struct sja1105_meta {
  28         u64 tstamp;
  29         u64 dmac_byte_4;
  30         u64 dmac_byte_3;
  31         u64 source_port;
  32         u64 switch_id;
  33 };
  34
  35 static void sja1105_meta_unpack(const struct sk_buff *skb,
  36                                 struct sja1105_meta *meta)
  37 {
  38         u8 *buf = skb_mac_header(skb) + ETH_HLEN;
  39
  40         /* UM10944.pdf section 4.2.17 AVB Parameters:
  41          * Structure of the meta-data follow-up frame.
  42          * It is in network byte order, so there are no quirks
  43          * while unpacking the meta frame.
  44          *
  45          * Also SJA1105 E/T only populates bits 23:0 of the timestamp
  46          * whereas P/Q/R/S does 32 bits. Since the structure is the
  47          * same and the E/T puts zeroes in the high-order byte, use
  48          * a unified unpacking command for both device series.
  49          */
  50         packing(buf,     &meta->tstamp,     31, 0, 4, UNPACK, 0);
  51         packing(buf + 4, &meta->dmac_byte_4, 7, 0, 1, UNPACK, 0);
  52         packing(buf + 5, &meta->dmac_byte_3, 7, 0, 1, UNPACK, 0);
  53         packing(buf + 6, &meta->source_port, 7, 0, 1, UNPACK, 0);
  54         packing(buf + 7, &meta->switch_id,   7, 0, 1, UNPACK, 0);
  55 }
  56
  57 static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
  58 {
  59         const struct ethhdr *hdr = eth_hdr(skb);
  60         u64 smac = ether_addr_to_u64(hdr->h_source);
  61         u64 dmac = ether_addr_to_u64(hdr->h_dest);
  62
  63         if (smac != SJA1105_META_SMAC)
  64                 return false;
  65         if (dmac != SJA1105_META_DMAC)
  66                 return false;
  67         if (ntohs(hdr->h_proto) != ETH_P_SJA1105_META)
  68                 return false;
  69         return true;
  70 }
  71
  72 /* This is the first time the tagger sees the frame on RX.
  73  * Figure out if we can decode it.
  74  */
  75 static bool sja1105_filter(const struct sk_buff *skb, struct net_device *dev)
  76 {
  77         if (!dsa_port_is_vlan_filtering(dev->dsa_ptr))
  78                 return true;
  79         if (sja1105_is_link_local(skb))
  80                 return true;
  81         if (sja1105_is_meta_frame(skb))
  82                 return true;
  83         return false;
  84 }
  85
  86 static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
  87                                     struct net_device *netdev)
  88 {
  89         struct dsa_port *dp = dsa_slave_to_port(netdev);
  90         struct dsa_switch *ds = dp->ds;
  91         u16 tx_vid = dsa_8021q_tx_vid(ds, dp->index);
  92         u8 pcp = skb->priority;
  93
  94         /* Transmitting management traffic does not rely upon switch tagging,
  95          * but instead SPI-installed management routes. Part 2 of this
  96          * is the .port_deferred_xmit driver callback.
  97          */
  98         if (unlikely(sja1105_is_link_local(skb)))
  99                 return dsa_defer_xmit(skb, netdev);
 100
 101         /* If we are under a vlan_filtering bridge, IP termination on
 102          * switch ports based on 802.1Q tags is simply too brittle to
 103          * be passable. So just defer to the dsa_slave_notag_xmit
 104          * implementation.
 105          */
 106         if (dsa_port_is_vlan_filtering(dp))
 107                 return skb;
 108
 109         return dsa_8021q_xmit(skb, netdev, ETH_P_SJA1105,
 110                              ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 111 }
 112
 113 static void sja1105_transfer_meta(struct sk_buff *skb,
 114                                   const struct sja1105_meta *meta)
 115 {
 116         struct ethhdr *hdr = eth_hdr(skb);
 117
 118         hdr->h_dest[3] = meta->dmac_byte_3;
 119         hdr->h_dest[4] = meta->dmac_byte_4;
 120         SJA1105_SKB_CB(skb)->meta_tstamp = meta->tstamp;
 121 }
 122
 123 /* This is a simple state machine which follows the hardware mechanism of
 124  * generating RX timestamps:
 125  *
 126  * After each timestampable skb (all traffic for which send_meta1 and
 127  * send_meta0 is true, aka all MAC-filtered link-local traffic) a meta frame
 128  * containing a partial timestamp is immediately generated by the switch and
 129  * sent as a follow-up to the link-local frame on the CPU port.
 130  *
 131  * The meta frames have no unique identifier (such as sequence number) by which
 132  * one may pair them to the correct timestampable frame.
 133  * Instead, the switch has internal logic that ensures no frames are sent on
 134  * the CPU port between a link-local timestampable frame and its corresponding
 135  * meta follow-up. It also ensures strict ordering between ports (lower ports
 136  * have higher priority towards the CPU port). For this reason, a per-port
 137  * data structure is not needed/desirable.
 138  *
 139  * This function pairs the link-local frame with its partial timestamp from the
 140  * meta follow-up frame. The full timestamp will be reconstructed later in a
 141  * work queue.
 142  */
 143 static struct sk_buff
 144 *sja1105_rcv_meta_state_machine(struct sk_buff *skb,
 145                                 struct sja1105_meta *meta,
 146                                 bool is_link_local,
 147                                 bool is_meta)
 148 {
 149         struct sja1105_port *sp;
 150         struct dsa_port *dp;
 151
 152         dp = dsa_slave_to_port(skb->dev);
 153         sp = dp->priv;
 154
 155         /* Step 1: A timestampable frame was received.
 156          * Buffer it until we get its meta frame.
 157          */
 158         if (is_link_local && sp->data->hwts_rx_en) {
 159                 spin_lock(&sp->data->meta_lock);
 160                 /* Was this a link-local frame instead of the meta
 161                  * that we were expecting?
 162                  */
 163                 if (sp->data->stampable_skb) {
 164                         dev_err_ratelimited(dp->ds->dev,
 165                                             "Expected meta frame, is %12llx "
 166                                             "in the DSA master multicast filter?\n",
 167                                             SJA1105_META_DMAC);
 168                         kfree_skb(sp->data->stampable_skb);
 169                 }
 170
 171                 /* Hold a reference to avoid dsa_switch_rcv
 172                  * from freeing the skb.
 173                  */
 174                 sp->data->stampable_skb = skb_get(skb);
 175                 spin_unlock(&sp->data->meta_lock);
 176
 177                 /* Tell DSA we got nothing */
 178                 return NULL;
 179
 180         /* Step 2: The meta frame arrived.
 181          * Time to take the stampable skb out of the closet, annotate it
 182          * with the partial timestamp, and pretend that we received it
 183          * just now (basically masquerade the buffered frame as the meta
 184          * frame, which serves no further purpose).
 185          */
 186         } else if (is_meta) {
 187                 struct sk_buff *stampable_skb;
 188
 189                 spin_lock(&sp->data->meta_lock);
 190
 191                 stampable_skb = sp->data->stampable_skb;
 192                 sp->data->stampable_skb = NULL;
 193
 194                 /* Was this a meta frame instead of the link-local
 195                  * that we were expecting?
 196                  */
 197                 if (!stampable_skb) {
 198                         dev_err_ratelimited(dp->ds->dev,
 199                                             "Unexpected meta frame\n");
 200                         spin_unlock(&sp->data->meta_lock);
 201                         return NULL;
 202                 }
 203
 204                 if (stampable_skb->dev != skb->dev) {
 205                         dev_err_ratelimited(dp->ds->dev,
 206                                             "Meta frame on wrong port\n");
 207                         spin_unlock(&sp->data->meta_lock);
 208                         return NULL;
 209                 }
 210
 211                 /* Free the meta frame and give DSA the buffered stampable_skb
 212                  * for further processing up the network stack.
 213                  */
 214                 kfree_skb(skb);
 215                 skb = stampable_skb;
 216                 sja1105_transfer_meta(skb, meta);
 217
 218                 spin_unlock(&sp->data->meta_lock);
 219         }
 220
 221         return skb;
 222 }
 223
 224 static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 225                                    struct net_device *netdev,
 226                                    struct packet_type *pt)
 227 {
 228         struct sja1105_meta meta = {0};
 229         int source_port, switch_id;
 230         struct vlan_ethhdr *hdr;
 231         u16 tpid, vid, tci;
 232         bool is_link_local;
 233         bool is_tagged;
 234         bool is_meta;
 235
 236         hdr = vlan_eth_hdr(skb);
 237         tpid = ntohs(hdr->h_vlan_proto);
 238         is_tagged = (tpid == ETH_P_SJA1105);
 239         is_link_local = sja1105_is_link_local(skb);
 240         is_meta = sja1105_is_meta_frame(skb);
 241
 242         skb->offload_fwd_mark = 1;
 243
 244         if (is_tagged) {
 245                 /* Normal traffic path. */
 246                 tci = ntohs(hdr->h_vlan_TCI);
 247                 vid = tci & VLAN_VID_MASK;
 248                 source_port = dsa_8021q_rx_source_port(vid);
 249                 switch_id = dsa_8021q_rx_switch_id(vid);
 250                 skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
 251         } else if (is_link_local) {
 252                 /* Management traffic path. Switch embeds the switch ID and
 253                  * port ID into bytes of the destination MAC, courtesy of
 254                  * the incl_srcpt options.
 255                  */
 256                 source_port = hdr->h_dest[3];
 257                 switch_id = hdr->h_dest[4];
 258                 /* Clear the DMAC bytes that were mangled by the switch */
 259                 hdr->h_dest[3] = 0;
 260                 hdr->h_dest[4] = 0;
 261         } else if (is_meta) {
 262                 sja1105_meta_unpack(skb, &meta);
 263                 source_port = meta.source_port;
 264                 switch_id = meta.switch_id;
 265         } else {
 266                 return NULL;
 267         }
 268
 269         skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
 270         if (!skb->dev) {
 271                 netdev_warn(netdev, "Couldn't decode source port\n");
 272                 return NULL;
 273         }
 274
 275         /* Delete/overwrite fake VLAN header, DSA expects to not find
 276          * it there, see dsa_switch_rcv: skb_push(skb, ETH_HLEN).
 277          */
 278         if (is_tagged)
 279                 skb = dsa_8021q_remove_header(skb);
 280
 281         return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
 282                                               is_meta);
 283 }
 284
 285 static struct dsa_device_ops sja1105_netdev_ops = {
 286         .name = "sja1105",
 287         .proto = DSA_TAG_PROTO_SJA1105,
 288         .xmit = sja1105_xmit,
 289         .rcv = sja1105_rcv,
 290         .filter = sja1105_filter,
 291         .overhead = VLAN_HLEN,
 292 };
 293
 294 MODULE_LICENSE("GPL v2");
 295 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);
 296
 297 module_dsa_tag_driver(sja1105_netdev_ops);