net/dsa/tag_dsa.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Regular and Ethertype DSA tagging
   4  * Copyright (c) 2008-2009 Marvell Semiconductor
   5  *
   6  * Regular DSA
   7  * -----------
   8
   9  * For untagged (in 802.1Q terms) packets, the switch will splice in
  10  * the tag between the SA and the ethertype of the original
  11  * packet. Tagged frames will instead have their outermost .1Q tag
  12  * converted to a DSA tag. It expects the same layout when receiving
  13  * packets from the CPU.
  14  *
  15  * Example:
  16  *
  17  *     .----.----.----.---------
  18  * Pu: | DA | SA | ET | Payload ...
  19  *     '----'----'----'---------
  20  *       6    6    2       N
  21  *     .----.----.--------.-----.----.---------
  22  * Pt: | DA | SA | 0x8100 | TCI | ET | Payload ...
  23  *     '----'----'--------'-----'----'---------
  24  *       6    6       2      2    2       N
  25  *     .----.----.-----.----.---------
  26  * Pd: | DA | SA | DSA | ET | Payload ...
  27  *     '----'----'-----'----'---------
  28  *       6    6     4    2       N
  29  *
  30  * No matter if a packet is received untagged (Pu) or tagged (Pt),
  31  * they will both have the same layout (Pd) when they are sent to the
  32  * CPU. This is done by ignoring 802.3, replacing the ethertype field
  33  * with more metadata, among which is a bit to signal if the original
  34  * packet was tagged or not.
  35  *
  36  * Ethertype DSA
  37  * -------------
  38  * Uses the exact same tag format as regular DSA, but also includes a
  39  * proper ethertype field (which the mv88e6xxx driver sets to
  40  * ETH_P_EDSA/0xdada) followed by two zero bytes:
  41  *
  42  * .----.----.--------.--------.-----.----.---------
  43  * | DA | SA | 0xdada | 0x0000 | DSA | ET | Payload ...
  44  * '----'----'--------'--------'-----'----'---------
  45  *   6    6       2        2      4    2       N
  46  */
  47
  48 #include <linux/etherdevice.h>
  49 #include <linux/list.h>
  50 #include <linux/slab.h>
  51
  52 #include "dsa_priv.h"
  53
  54 #define DSA_HLEN        4
  55
  56 /**
  57  * enum dsa_cmd - DSA Command
  58  * @DSA_CMD_TO_CPU: Set on packets that were trapped or mirrored to
  59  *     the CPU port. This is needed to implement control protocols,
  60  *     e.g. STP and LLDP, that must not allow those control packets to
  61  *     be switched according to the normal rules.
  62  * @DSA_CMD_FROM_CPU: Used by the CPU to send a packet to a specific
  63  *     port, ignoring all the barriers that the switch normally
  64  *     enforces (VLANs, STP port states etc.). No source address
  65  *     learning takes place. "sudo send packet"
  66  * @DSA_CMD_TO_SNIFFER: Set on the copies of packets that matched some
  67  *     user configured ingress or egress monitor criteria. These are
  68  *     forwarded by the switch tree to the user configured ingress or
  69  *     egress monitor port, which can be set to the CPU port or a
  70  *     regular port. If the destination is a regular port, the tag
  71  *     will be removed before egressing the port. If the destination
  72  *     is the CPU port, the tag will not be removed.
  73  * @DSA_CMD_FORWARD: This tag is used on all bulk traffic passing
  74  *     through the switch tree, including the flows that are directed
  75  *     towards the CPU. Its device/port tuple encodes the original
  76  *     source port on which the packet ingressed. It can also be used
  77  *     on transmit by the CPU to defer the forwarding decision to the
  78  *     hardware, based on the current config of PVT/VTU/ATU
  79  *     etc. Source address learning takes places if enabled on the
  80  *     receiving DSA/CPU port.
  81  */
  82 enum dsa_cmd {
  83         DSA_CMD_TO_CPU     = 0,
  84         DSA_CMD_FROM_CPU   = 1,
  85         DSA_CMD_TO_SNIFFER = 2,
  86         DSA_CMD_FORWARD    = 3
  87 };
  88
  89 /**
  90  * enum dsa_code - TO_CPU Code
  91  *
  92  * @DSA_CODE_MGMT_TRAP: DA was classified as a management
  93  *     address. Typical examples include STP BPDUs and LLDP.
  94  * @DSA_CODE_FRAME2REG: Response to a "remote management" request.
  95  * @DSA_CODE_IGMP_MLD_TRAP: IGMP/MLD signaling.
  96  * @DSA_CODE_POLICY_TRAP: Frame matched some policy configuration on
  97  *     the device. Typical examples are matching on DA/SA/VID and DHCP
  98  *     snooping.
  99  * @DSA_CODE_ARP_MIRROR: The name says it all really.
 100  * @DSA_CODE_POLICY_MIRROR: Same as @DSA_CODE_POLICY_TRAP, but the
 101  *     particular policy was set to trigger a mirror instead of a
 102  *     trap.
 103  * @DSA_CODE_RESERVED_6: Unused on all devices up to at least 6393X.
 104  * @DSA_CODE_RESERVED_7: Unused on all devices up to at least 6393X.
 105  *
 106  * A 3-bit code is used to relay why a particular frame was sent to
 107  * the CPU. We only use this to determine if the packet was mirrored
 108  * or trapped, i.e. whether the packet has been forwarded by hardware
 109  * or not.
 110  *
 111  * This is the superset of all possible codes. Any particular device
 112  * may only implement a subset.
 113  */
 114 enum dsa_code {
 115         DSA_CODE_MGMT_TRAP     = 0,
 116         DSA_CODE_FRAME2REG     = 1,
 117         DSA_CODE_IGMP_MLD_TRAP = 2,
 118         DSA_CODE_POLICY_TRAP   = 3,
 119         DSA_CODE_ARP_MIRROR    = 4,
 120         DSA_CODE_POLICY_MIRROR = 5,
 121         DSA_CODE_RESERVED_6    = 6,
 122         DSA_CODE_RESERVED_7    = 7
 123 };
 124
 125 static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 126                                    u8 extra)
 127 {
 128         struct dsa_port *dp = dsa_slave_to_port(dev);
 129         u8 *dsa_header;
 130
 131         if (skb->protocol == htons(ETH_P_8021Q)) {
 132                 if (extra) {
 133                         skb_push(skb, extra);
 134                         memmove(skb->data, skb->data + extra, 2 * ETH_ALEN);
 135                 }
 136
 137                 /* Construct tagged FROM_CPU DSA tag from 802.1Q tag. */
 138                 dsa_header = skb->data + 2 * ETH_ALEN + extra;
 139                 dsa_header[0] = (DSA_CMD_FROM_CPU << 6) | 0x20 | dp->ds->index;
 140                 dsa_header[1] = dp->index << 3;
 141
 142                 /* Move CFI field from byte 2 to byte 1. */
 143                 if (dsa_header[2] & 0x10) {
 144                         dsa_header[1] |= 0x01;
 145                         dsa_header[2] &= ~0x10;
 146                 }
 147         } else {
 148                 skb_push(skb, DSA_HLEN + extra);
 149                 memmove(skb->data, skb->data + DSA_HLEN + extra, 2 * ETH_ALEN);
 150
 151                 /* Construct untagged FROM_CPU DSA tag. */
 152                 dsa_header = skb->data + 2 * ETH_ALEN + extra;
 153                 dsa_header[0] = (DSA_CMD_FROM_CPU << 6) | dp->ds->index;
 154                 dsa_header[1] = dp->index << 3;
 155                 dsa_header[2] = 0x00;
 156                 dsa_header[3] = 0x00;
 157         }
 158
 159         return skb;
 160 }
 161
 162 static struct sk_buff *dsa_rcv_ll(struct sk_buff *skb, struct net_device *dev,
 163                                   u8 extra)
 164 {
 165         int source_device, source_port;
 166         enum dsa_code code;
 167         enum dsa_cmd cmd;
 168         u8 *dsa_header;
 169
 170         /* The ethertype field is part of the DSA header. */
 171         dsa_header = skb->data - 2;
 172
 173         cmd = dsa_header[0] >> 6;
 174         switch (cmd) {
 175         case DSA_CMD_FORWARD:
 176                 skb->offload_fwd_mark = 1;
 177                 break;
 178
 179         case DSA_CMD_TO_CPU:
 180                 code = (dsa_header[1] & 0x6) | ((dsa_header[2] >> 4) & 1);
 181
 182                 switch (code) {
 183                 case DSA_CODE_FRAME2REG:
 184                         /* Remote management is not implemented yet,
 185                          * drop.
 186                          */
 187                         return NULL;
 188                 case DSA_CODE_ARP_MIRROR:
 189                 case DSA_CODE_POLICY_MIRROR:
 190                         /* Mark mirrored packets to notify any upper
 191                          * device (like a bridge) that forwarding has
 192                          * already been done by hardware.
 193                          */
 194                         skb->offload_fwd_mark = 1;
 195                         break;
 196                 case DSA_CODE_MGMT_TRAP:
 197                 case DSA_CODE_IGMP_MLD_TRAP:
 198                 case DSA_CODE_POLICY_TRAP:
 199                         /* Traps have, by definition, not been
 200                          * forwarded by hardware, so don't mark them.
 201                          */
 202                         break;
 203                 default:
 204                         /* Reserved code, this could be anything. Drop
 205                          * seems like the safest option.
 206                          */
 207                         return NULL;
 208                 }
 209
 210                 break;
 211
 212         default:
 213                 return NULL;
 214         }
 215
 216         source_device = dsa_header[0] & 0x1f;
 217         source_port = (dsa_header[1] >> 3) & 0x1f;
 218
 219         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
 220         if (!skb->dev)
 221                 return NULL;
 222
 223         /* If the 'tagged' bit is set; convert the DSA tag to a 802.1Q
 224          * tag, and delete the ethertype (extra) if applicable. If the
 225          * 'tagged' bit is cleared; delete the DSA tag, and ethertype
 226          * if applicable.
 227          */
 228         if (dsa_header[0] & 0x20) {
 229                 u8 new_header[4];
 230
 231                 /* Insert 802.1Q ethertype and copy the VLAN-related
 232                  * fields, but clear the bit that will hold CFI (since
 233                  * DSA uses that bit location for another purpose).
 234                  */
 235                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 236                 new_header[1] = ETH_P_8021Q & 0xff;
 237                 new_header[2] = dsa_header[2] & ~0x10;
 238                 new_header[3] = dsa_header[3];
 239
 240                 /* Move CFI bit from its place in the DSA header to
 241                  * its 802.1Q-designated place.
 242                  */
 243                 if (dsa_header[1] & 0x01)
 244                         new_header[2] |= 0x10;
 245
 246                 /* Update packet checksum if skb is CHECKSUM_COMPLETE. */
 247                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 248                         __wsum c = skb->csum;
 249                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 250                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
 251                         skb->csum = c;
 252                 }
 253
 254                 memcpy(dsa_header, new_header, DSA_HLEN);
 255
 256                 if (extra)
 257                         memmove(skb->data - ETH_HLEN,
 258                                 skb->data - ETH_HLEN - extra,
 259                                 2 * ETH_ALEN);
 260         } else {
 261                 skb_pull_rcsum(skb, DSA_HLEN);
 262                 memmove(skb->data - ETH_HLEN,
 263                         skb->data - ETH_HLEN - DSA_HLEN - extra,
 264                         2 * ETH_ALEN);
 265         }
 266
 267         return skb;
 268 }
 269
 270 #if IS_ENABLED(CONFIG_NET_DSA_TAG_DSA)
 271
 272 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 273 {
 274         return dsa_xmit_ll(skb, dev, 0);
 275 }
 276
 277 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 278                                struct packet_type *pt)
 279 {
 280         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
 281                 return NULL;
 282
 283         return dsa_rcv_ll(skb, dev, 0);
 284 }
 285
 286 static const struct dsa_device_ops dsa_netdev_ops = {
 287         .name     = "dsa",
 288         .proto    = DSA_TAG_PROTO_DSA,
 289         .xmit     = dsa_xmit,
 290         .rcv      = dsa_rcv,
 291         .overhead = DSA_HLEN,
 292 };
 293
 294 DSA_TAG_DRIVER(dsa_netdev_ops);
 295 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
 296 #endif  /* CONFIG_NET_DSA_TAG_DSA */
 297
 298 #if IS_ENABLED(CONFIG_NET_DSA_TAG_EDSA)
 299
 300 #define EDSA_HLEN 8
 301
 302 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 303 {
 304         u8 *edsa_header;
 305
 306         skb = dsa_xmit_ll(skb, dev, EDSA_HLEN - DSA_HLEN);
 307         if (!skb)
 308                 return NULL;
 309
 310         edsa_header = skb->data + 2 * ETH_ALEN;
 311         edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 312         edsa_header[1] = ETH_P_EDSA & 0xff;
 313         edsa_header[2] = 0x00;
 314         edsa_header[3] = 0x00;
 315         return skb;
 316 }
 317
 318 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 319                                 struct packet_type *pt)
 320 {
 321         if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
 322                 return NULL;
 323
 324         skb_pull_rcsum(skb, EDSA_HLEN - DSA_HLEN);
 325
 326         return dsa_rcv_ll(skb, dev, EDSA_HLEN - DSA_HLEN);
 327 }
 328
 329 static const struct dsa_device_ops edsa_netdev_ops = {
 330         .name     = "edsa",
 331         .proto    = DSA_TAG_PROTO_EDSA,
 332         .xmit     = edsa_xmit,
 333         .rcv      = edsa_rcv,
 334         .overhead = EDSA_HLEN,
 335 };
 336
 337 DSA_TAG_DRIVER(edsa_netdev_ops);
 338 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA);
 339 #endif  /* CONFIG_NET_DSA_TAG_EDSA */
 340
 341 static struct dsa_tag_driver *dsa_tag_drivers[] = {
 342 #if IS_ENABLED(CONFIG_NET_DSA_TAG_DSA)
 343         &DSA_TAG_DRIVER_NAME(dsa_netdev_ops),
 344 #endif
 345 #if IS_ENABLED(CONFIG_NET_DSA_TAG_EDSA)
 346         &DSA_TAG_DRIVER_NAME(edsa_netdev_ops),
 347 #endif
 348 };
 349
 350 module_dsa_tag_drivers(dsa_tag_drivers);
 351
 352 MODULE_LICENSE("GPL");