root/net/dsa/tag_sja1105.c

DEFINITIONS

1. sja1105_is_link_local
2. sja1105_meta_unpack
3. sja1105_is_meta_frame
4. sja1105_filter
5. sja1105_xmit
6. sja1105_transfer_meta
7. sja1105_rcv_meta_state_machine
8. sja1105_rcv

   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         u16 queue_mapping = skb_get_queue_mapping(skb);
  93         u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);
  94 
  95         /* Transmitting management traffic does not rely upon switch tagging,
  96          * but instead SPI-installed management routes. Part 2 of this
  97          * is the .port_deferred_xmit driver callback.
  98          */
  99         if (unlikely(sja1105_is_link_local(skb)))
 100                 return dsa_defer_xmit(skb, netdev);
 101 
 102         /* If we are under a vlan_filtering bridge, IP termination on
 103          * switch ports based on 802.1Q tags is simply too brittle to
 104          * be passable. So just defer to the dsa_slave_notag_xmit
 105          * implementation.
 106          */
 107         if (dsa_port_is_vlan_filtering(dp))
 108                 return skb;
 109 
 110         return dsa_8021q_xmit(skb, netdev, ETH_P_SJA1105,
 111                              ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 112 }
 113 
 114 static void sja1105_transfer_meta(struct sk_buff *skb,
 115                                   const struct sja1105_meta *meta)
 116 {
 117         struct ethhdr *hdr = eth_hdr(skb);
 118 
 119         hdr->h_dest[3] = meta->dmac_byte_3;
 120         hdr->h_dest[4] = meta->dmac_byte_4;
 121         SJA1105_SKB_CB(skb)->meta_tstamp = meta->tstamp;
 122 }
 123 
 124 /* This is a simple state machine which follows the hardware mechanism of
 125  * generating RX timestamps:
 126  *
 127  * After each timestampable skb (all traffic for which send_meta1 and
 128  * send_meta0 is true, aka all MAC-filtered link-local traffic) a meta frame
 129  * containing a partial timestamp is immediately generated by the switch and
 130  * sent as a follow-up to the link-local frame on the CPU port.
 131  *
 132  * The meta frames have no unique identifier (such as sequence number) by which
 133  * one may pair them to the correct timestampable frame.
 134  * Instead, the switch has internal logic that ensures no frames are sent on
 135  * the CPU port between a link-local timestampable frame and its corresponding
 136  * meta follow-up. It also ensures strict ordering between ports (lower ports
 137  * have higher priority towards the CPU port). For this reason, a per-port
 138  * data structure is not needed/desirable.
 139  *
 140  * This function pairs the link-local frame with its partial timestamp from the
 141  * meta follow-up frame. The full timestamp will be reconstructed later in a
 142  * work queue.
 143  */
 144 static struct sk_buff
 145 *sja1105_rcv_meta_state_machine(struct sk_buff *skb,
 146                                 struct sja1105_meta *meta,
 147                                 bool is_link_local,
 148                                 bool is_meta)
 149 {
 150         struct sja1105_port *sp;
 151         struct dsa_port *dp;
 152 
 153         dp = dsa_slave_to_port(skb->dev);
 154         sp = dp->priv;
 155 
 156         /* Step 1: A timestampable frame was received.
 157          * Buffer it until we get its meta frame.
 158          */
 159         if (is_link_local) {
 160                 if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
 161                         /* Do normal processing. */
 162                         return skb;
 163 
 164                 spin_lock(&sp->data->meta_lock);
 165                 /* Was this a link-local frame instead of the meta
 166                  * that we were expecting?
 167                  */
 168                 if (sp->data->stampable_skb) {
 169                         dev_err_ratelimited(dp->ds->dev,
 170                                             "Expected meta frame, is %12llx "
 171                                             "in the DSA master multicast filter?\n",
 172                                             SJA1105_META_DMAC);
 173                         kfree_skb(sp->data->stampable_skb);
 174                 }
 175 
 176                 /* Hold a reference to avoid dsa_switch_rcv
 177                  * from freeing the skb.
 178                  */
 179                 sp->data->stampable_skb = skb_get(skb);
 180                 spin_unlock(&sp->data->meta_lock);
 181 
 182                 /* Tell DSA we got nothing */
 183                 return NULL;
 184 
 185         /* Step 2: The meta frame arrived.
 186          * Time to take the stampable skb out of the closet, annotate it
 187          * with the partial timestamp, and pretend that we received it
 188          * just now (basically masquerade the buffered frame as the meta
 189          * frame, which serves no further purpose).
 190          */
 191         } else if (is_meta) {
 192                 struct sk_buff *stampable_skb;
 193 
 194                 /* Drop the meta frame if we're not in the right state
 195                  * to process it.
 196                  */
 197                 if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
 198                         return NULL;
 199 
 200                 spin_lock(&sp->data->meta_lock);
 201 
 202                 stampable_skb = sp->data->stampable_skb;
 203                 sp->data->stampable_skb = NULL;
 204 
 205                 /* Was this a meta frame instead of the link-local
 206                  * that we were expecting?
 207                  */
 208                 if (!stampable_skb) {
 209                         dev_err_ratelimited(dp->ds->dev,
 210                                             "Unexpected meta frame\n");
 211                         spin_unlock(&sp->data->meta_lock);
 212                         return NULL;
 213                 }
 214 
 215                 if (stampable_skb->dev != skb->dev) {
 216                         dev_err_ratelimited(dp->ds->dev,
 217                                             "Meta frame on wrong port\n");
 218                         spin_unlock(&sp->data->meta_lock);
 219                         return NULL;
 220                 }
 221 
 222                 /* Free the meta frame and give DSA the buffered stampable_skb
 223                  * for further processing up the network stack.
 224                  */
 225                 kfree_skb(skb);
 226                 skb = stampable_skb;
 227                 sja1105_transfer_meta(skb, meta);
 228 
 229                 spin_unlock(&sp->data->meta_lock);
 230         }
 231 
 232         return skb;
 233 }
 234 
 235 static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
 236                                    struct net_device *netdev,
 237                                    struct packet_type *pt)
 238 {
 239         struct sja1105_meta meta = {0};
 240         int source_port, switch_id;
 241         struct ethhdr *hdr;
 242         u16 tpid, vid, tci;
 243         bool is_link_local;
 244         bool is_tagged;
 245         bool is_meta;
 246 
 247         hdr = eth_hdr(skb);
 248         tpid = ntohs(hdr->h_proto);
 249         is_tagged = (tpid == ETH_P_SJA1105);
 250         is_link_local = sja1105_is_link_local(skb);
 251         is_meta = sja1105_is_meta_frame(skb);
 252 
 253         skb->offload_fwd_mark = 1;
 254 
 255         if (is_tagged) {
 256                 /* Normal traffic path. */
 257                 skb_push_rcsum(skb, ETH_HLEN);
 258                 __skb_vlan_pop(skb, &tci);
 259                 skb_pull_rcsum(skb, ETH_HLEN);
 260                 skb_reset_network_header(skb);
 261                 skb_reset_transport_header(skb);
 262 
 263                 vid = tci & VLAN_VID_MASK;
 264                 source_port = dsa_8021q_rx_source_port(vid);
 265                 switch_id = dsa_8021q_rx_switch_id(vid);
 266                 skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
 267         } else if (is_link_local) {
 268                 /* Management traffic path. Switch embeds the switch ID and
 269                  * port ID into bytes of the destination MAC, courtesy of
 270                  * the incl_srcpt options.
 271                  */
 272                 source_port = hdr->h_dest[3];
 273                 switch_id = hdr->h_dest[4];
 274                 /* Clear the DMAC bytes that were mangled by the switch */
 275                 hdr->h_dest[3] = 0;
 276                 hdr->h_dest[4] = 0;
 277         } else if (is_meta) {
 278                 sja1105_meta_unpack(skb, &meta);
 279                 source_port = meta.source_port;
 280                 switch_id = meta.switch_id;
 281         } else {
 282                 return NULL;
 283         }
 284 
 285         skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
 286         if (!skb->dev) {
 287                 netdev_warn(netdev, "Couldn't decode source port\n");
 288                 return NULL;
 289         }
 290 
 291         return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
 292                                               is_meta);
 293 }
 294 
 295 static struct dsa_device_ops sja1105_netdev_ops = {
 296         .name = "sja1105",
 297         .proto = DSA_TAG_PROTO_SJA1105,
 298         .xmit = sja1105_xmit,
 299         .rcv = sja1105_rcv,
 300         .filter = sja1105_filter,
 301         .overhead = VLAN_HLEN,
 302 };
 303 
 304 MODULE_LICENSE("GPL v2");
 305 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);
 306 
 307 module_dsa_tag_driver(sja1105_netdev_ops);