net/dsa/tag_8021q.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
   3  *
   4  * This module is not a complete tagger implementation. It only provides
   5  * primitives for taggers that rely on 802.1Q VLAN tags to use. The
   6  * dsa_8021q_netdev_ops is registered for API compliance and not used
   7  * directly by callers.
   8  */
   9 #include <linux/if_bridge.h>
  10 #include <linux/if_vlan.h>
  11
  12 #include "dsa_priv.h"
  13
  14 /* Binary structure of the fake 12-bit VID field (when the TPID is
  15  * ETH_P_DSA_8021Q):
  16  *
  17  * | 11  | 10  |  9  |  8  |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
  18  * +-----------+-----+-----------------+-----------+-----------------------+
  19  * |    DIR    | RSV |    SWITCH_ID    |    RSV    |          PORT         |
  20  * +-----------+-----+-----------------+-----------+-----------------------+
  21  *
  22  * DIR - VID[11:10]:
  23  *      Direction flags.
  24  *      * 1 (0b01) for RX VLAN,
  25  *      * 2 (0b10) for TX VLAN.
  26  *      These values make the special VIDs of 0, 1 and 4095 to be left
  27  *      unused by this coding scheme.
  28  *
  29  * RSV - VID[9]:
  30  *      To be used for further expansion of SWITCH_ID or for other purposes.
  31  *      Must be transmitted as zero and ignored on receive.
  32  *
  33  * SWITCH_ID - VID[8:6]:
  34  *      Index of switch within DSA tree. Must be between 0 and 7.
  35  *
  36  * RSV - VID[5:4]:
  37  *      To be used for further expansion of PORT or for other purposes.
  38  *      Must be transmitted as zero and ignored on receive.
  39  *
  40  * PORT - VID[3:0]:
  41  *      Index of switch port. Must be between 0 and 15.
  42  */
  43
  44 #define DSA_8021Q_DIR_SHIFT             10
  45 #define DSA_8021Q_DIR_MASK              GENMASK(11, 10)
  46 #define DSA_8021Q_DIR(x)                (((x) << DSA_8021Q_DIR_SHIFT) & \
  47                                                  DSA_8021Q_DIR_MASK)
  48 #define DSA_8021Q_DIR_RX                DSA_8021Q_DIR(1)
  49 #define DSA_8021Q_DIR_TX                DSA_8021Q_DIR(2)
  50
  51 #define DSA_8021Q_SWITCH_ID_SHIFT       6
  52 #define DSA_8021Q_SWITCH_ID_MASK        GENMASK(8, 6)
  53 #define DSA_8021Q_SWITCH_ID(x)          (((x) << DSA_8021Q_SWITCH_ID_SHIFT) & \
  54                                                  DSA_8021Q_SWITCH_ID_MASK)
  55
  56 #define DSA_8021Q_PORT_SHIFT            0
  57 #define DSA_8021Q_PORT_MASK             GENMASK(3, 0)
  58 #define DSA_8021Q_PORT(x)               (((x) << DSA_8021Q_PORT_SHIFT) & \
  59                                                  DSA_8021Q_PORT_MASK)
  60
  61 /* Returns the VID to be inserted into the frame from xmit for switch steering
  62  * instructions on egress. Encodes switch ID and port ID.
  63  */
  64 u16 dsa_8021q_tx_vid(struct dsa_switch *ds, int port)
  65 {
  66         return DSA_8021Q_DIR_TX | DSA_8021Q_SWITCH_ID(ds->index) |
  67                DSA_8021Q_PORT(port);
  68 }
  69 EXPORT_SYMBOL_GPL(dsa_8021q_tx_vid);
  70
  71 /* Returns the VID that will be installed as pvid for this switch port, sent as
  72  * tagged egress towards the CPU port and decoded by the rcv function.
  73  */
  74 u16 dsa_8021q_rx_vid(struct dsa_switch *ds, int port)
  75 {
  76         return DSA_8021Q_DIR_RX | DSA_8021Q_SWITCH_ID(ds->index) |
  77                DSA_8021Q_PORT(port);
  78 }
  79 EXPORT_SYMBOL_GPL(dsa_8021q_rx_vid);
  80
  81 /* Returns the decoded switch ID from the RX VID. */
  82 int dsa_8021q_rx_switch_id(u16 vid)
  83 {
  84         return (vid & DSA_8021Q_SWITCH_ID_MASK) >> DSA_8021Q_SWITCH_ID_SHIFT;
  85 }
  86 EXPORT_SYMBOL_GPL(dsa_8021q_rx_switch_id);
  87
  88 /* Returns the decoded port ID from the RX VID. */
  89 int dsa_8021q_rx_source_port(u16 vid)
  90 {
  91         return (vid & DSA_8021Q_PORT_MASK) >> DSA_8021Q_PORT_SHIFT;
  92 }
  93 EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);
  94
  95 static int dsa_8021q_restore_pvid(struct dsa_switch *ds, int port)
  96 {
  97         struct bridge_vlan_info vinfo;
  98         struct net_device *slave;
  99         u16 pvid;
 100         int err;
 101
 102         if (!dsa_is_user_port(ds, port))
 103                 return 0;
 104
 105         slave = dsa_to_port(ds, port)->slave;
 106
 107         err = br_vlan_get_pvid(slave, &pvid);
 108         if (!pvid || err < 0)
 109                 /* There is no pvid on the bridge for this port, which is
 110                  * perfectly valid. Nothing to restore, bye-bye!
 111                  */
 112                 return 0;
 113
 114         err = br_vlan_get_info(slave, pvid, &vinfo);
 115         if (err < 0) {
 116                 dev_err(ds->dev, "Couldn't determine PVID attributes\n");
 117                 return err;
 118         }
 119
 120         return dsa_port_vid_add(dsa_to_port(ds, port), pvid, vinfo.flags);
 121 }
 122
 123 /* If @enabled is true, installs @vid with @flags into the switch port's HW
 124  * filter.
 125  * If @enabled is false, deletes @vid (ignores @flags) from the port. Had the
 126  * user explicitly configured this @vid through the bridge core, then the @vid
 127  * is installed again, but this time with the flags from the bridge layer.
 128  */
 129 static int dsa_8021q_vid_apply(struct dsa_switch *ds, int port, u16 vid,
 130                                u16 flags, bool enabled)
 131 {
 132         struct dsa_port *dp = dsa_to_port(ds, port);
 133         struct bridge_vlan_info vinfo;
 134         int err;
 135
 136         if (enabled)
 137                 return dsa_port_vid_add(dp, vid, flags);
 138
 139         err = dsa_port_vid_del(dp, vid);
 140         if (err < 0)
 141                 return err;
 142
 143         /* Nothing to restore from the bridge for a non-user port.
 144          * The CPU port VLANs are restored implicitly with the user ports,
 145          * similar to how the bridge does in dsa_slave_vlan_add and
 146          * dsa_slave_vlan_del.
 147          */
 148         if (!dsa_is_user_port(ds, port))
 149                 return 0;
 150
 151         err = br_vlan_get_info(dp->slave, vid, &vinfo);
 152         /* Couldn't determine bridge attributes for this vid,
 153          * it means the bridge had not configured it.
 154          */
 155         if (err < 0)
 156                 return 0;
 157
 158         /* Restore the VID from the bridge */
 159         err = dsa_port_vid_add(dp, vid, vinfo.flags);
 160         if (err < 0)
 161                 return err;
 162
 163         vinfo.flags &= ~BRIDGE_VLAN_INFO_PVID;
 164
 165         return dsa_port_vid_add(dp->cpu_dp, vid, vinfo.flags);
 166 }
 167
 168 /* RX VLAN tagging (left) and TX VLAN tagging (right) setup shown for a single
 169  * front-panel switch port (here swp0).
 170  *
 171  * Port identification through VLAN (802.1Q) tags has different requirements
 172  * for it to work effectively:
 173  *  - On RX (ingress from network): each front-panel port must have a pvid
 174  *    that uniquely identifies it, and the egress of this pvid must be tagged
 175  *    towards the CPU port, so that software can recover the source port based
 176  *    on the VID in the frame. But this would only work for standalone ports;
 177  *    if bridged, this VLAN setup would break autonomous forwarding and would
 178  *    force all switched traffic to pass through the CPU. So we must also make
 179  *    the other front-panel ports members of this VID we're adding, albeit
 180  *    we're not making it their PVID (they'll still have their own).
 181  *    By the way - just because we're installing the same VID in multiple
 182  *    switch ports doesn't mean that they'll start to talk to one another, even
 183  *    while not bridged: the final forwarding decision is still an AND between
 184  *    the L2 forwarding information (which is limiting forwarding in this case)
 185  *    and the VLAN-based restrictions (of which there are none in this case,
 186  *    since all ports are members).
 187  *  - On TX (ingress from CPU and towards network) we are faced with a problem.
 188  *    If we were to tag traffic (from within DSA) with the port's pvid, all
 189  *    would be well, assuming the switch ports were standalone. Frames would
 190  *    have no choice but to be directed towards the correct front-panel port.
 191  *    But because we also want the RX VLAN to not break bridging, then
 192  *    inevitably that means that we have to give them a choice (of what
 193  *    front-panel port to go out on), and therefore we cannot steer traffic
 194  *    based on the RX VID. So what we do is simply install one more VID on the
 195  *    front-panel and CPU ports, and profit off of the fact that steering will
 196  *    work just by virtue of the fact that there is only one other port that's
 197  *    a member of the VID we're tagging the traffic with - the desired one.
 198  *
 199  * So at the end, each front-panel port will have one RX VID (also the PVID),
 200  * the RX VID of all other front-panel ports, and one TX VID. Whereas the CPU
 201  * port will have the RX and TX VIDs of all front-panel ports, and on top of
 202  * that, is also tagged-input and tagged-output (VLAN trunk).
 203  *
 204  *               CPU port                               CPU port
 205  * +-------------+-----+-------------+    +-------------+-----+-------------+
 206  * |  RX VID     |     |             |    |  TX VID     |     |             |
 207  * |  of swp0    |     |             |    |  of swp0    |     |             |
 208  * |             +-----+             |    |             +-----+             |
 209  * |                ^ T              |    |                | Tagged         |
 210  * |                |                |    |                | ingress        |
 211  * |    +-------+---+---+-------+    |    |    +-----------+                |
 212  * |    |       |       |       |    |    |    | Untagged                   |
 213  * |    |     U v     U v     U v    |    |    v egress                     |
 214  * | +-----+ +-----+ +-----+ +-----+ |    | +-----+ +-----+ +-----+ +-----+ |
 215  * | |     | |     | |     | |     | |    | |     | |     | |     | |     | |
 216  * | |PVID | |     | |     | |     | |    | |     | |     | |     | |     | |
 217  * +-+-----+-+-----+-+-----+-+-----+-+    +-+-----+-+-----+-+-----+-+-----+-+
 218  *   swp0    swp1    swp2    swp3           swp0    swp1    swp2    swp3
 219  */
 220 int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
 221 {
 222         int upstream = dsa_upstream_port(ds, port);
 223         u16 rx_vid = dsa_8021q_rx_vid(ds, port);
 224         u16 tx_vid = dsa_8021q_tx_vid(ds, port);
 225         int i, err;
 226
 227         /* The CPU port is implicitly configured by
 228          * configuring the front-panel ports
 229          */
 230         if (!dsa_is_user_port(ds, port))
 231                 return 0;
 232
 233         /* Add this user port's RX VID to the membership list of all others
 234          * (including itself). This is so that bridging will not be hindered.
 235          * L2 forwarding rules still take precedence when there are no VLAN
 236          * restrictions, so there are no concerns about leaking traffic.
 237          */
 238         for (i = 0; i < ds->num_ports; i++) {
 239                 u16 flags;
 240
 241                 if (i == upstream)
 242                         continue;
 243                 else if (i == port)
 244                         /* The RX VID is pvid on this port */
 245                         flags = BRIDGE_VLAN_INFO_UNTAGGED |
 246                                 BRIDGE_VLAN_INFO_PVID;
 247                 else
 248                         /* The RX VID is a regular VLAN on all others */
 249                         flags = BRIDGE_VLAN_INFO_UNTAGGED;
 250
 251                 err = dsa_8021q_vid_apply(ds, i, rx_vid, flags, enabled);
 252                 if (err) {
 253                         dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
 254                                 rx_vid, port, err);
 255                         return err;
 256                 }
 257         }
 258
 259         /* CPU port needs to see this port's RX VID
 260          * as tagged egress.
 261          */
 262         err = dsa_8021q_vid_apply(ds, upstream, rx_vid, 0, enabled);
 263         if (err) {
 264                 dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
 265                         rx_vid, port, err);
 266                 return err;
 267         }
 268
 269         /* Finally apply the TX VID on this port and on the CPU port */
 270         err = dsa_8021q_vid_apply(ds, port, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED,
 271                                   enabled);
 272         if (err) {
 273                 dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
 274                         tx_vid, port, err);
 275                 return err;
 276         }
 277         err = dsa_8021q_vid_apply(ds, upstream, tx_vid, 0, enabled);
 278         if (err) {
 279                 dev_err(ds->dev, "Failed to apply TX VID %d on port %d: %d\n",
 280                         tx_vid, upstream, err);
 281                 return err;
 282         }
 283
 284         if (!enabled)
 285                 err = dsa_8021q_restore_pvid(ds, port);
 286
 287         return err;
 288 }
 289 EXPORT_SYMBOL_GPL(dsa_port_setup_8021q_tagging);
 290
 291 struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,
 292                                u16 tpid, u16 tci)
 293 {
 294         /* skb->data points at skb_mac_header, which
 295          * is fine for vlan_insert_tag.
 296          */
 297         return vlan_insert_tag(skb, htons(tpid), tci);
 298 }
 299 EXPORT_SYMBOL_GPL(dsa_8021q_xmit);
 300
 301 MODULE_LICENSE("GPL v2");