net/dsa/tag_rtl8_4.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Handler for Realtek 8 byte switch tags
   4  *
   5  * Copyright (C) 2021 Alvin Šipraga <alsi@bang-olufsen.dk>
   6  *
   7  * NOTE: Currently only supports protocol "4" found in the RTL8365MB, hence
   8  * named tag_rtl8_4.
   9  *
  10  * This tag has the following format:
  11  *
  12  *  0                                  7|8                                 15
  13  *  |-----------------------------------+-----------------------------------|---
  14  *  |                               (16-bit)                                | ^
  15  *  |                       Realtek EtherType [0x8899]                      | |
  16  *  |-----------------------------------+-----------------------------------| 8
  17  *  |              (8-bit)              |              (8-bit)              |
  18  *  |          Protocol [0x04]          |              REASON               | b
  19  *  |-----------------------------------+-----------------------------------| y
  20  *  |   (1)  | (1) | (2) |   (1)  | (3) | (1)  | (1) |    (1)    |   (5)    | t
  21  *  | FID_EN |  X  | FID | PRI_EN | PRI | KEEP |  X  | LEARN_DIS |    X     | e
  22  *  |-----------------------------------+-----------------------------------| s
  23  *  |   (1)  |                       (15-bit)                               | |
  24  *  |  ALLOW |                        TX/RX                                 | v
  25  *  |-----------------------------------+-----------------------------------|---
  26  *
  27  * With the following field descriptions:
  28  *
  29  *    field      | description
  30  *   ------------+-------------
  31  *    Realtek    | 0x8899: indicates that this is a proprietary Realtek tag;
  32  *     EtherType |         note that Realtek uses the same EtherType for
  33  *               |         other incompatible tag formats (e.g. tag_rtl4_a.c)
  34  *    Protocol   | 0x04: indicates that this tag conforms to this format
  35  *    X          | reserved
  36  *   ------------+-------------
  37  *    REASON     | reason for forwarding packet to CPU
  38  *               | 0: packet was forwarded or flooded to CPU
  39  *               | 80: packet was trapped to CPU
  40  *    FID_EN     | 1: packet has an FID
  41  *               | 0: no FID
  42  *    FID        | FID of packet (if FID_EN=1)
  43  *    PRI_EN     | 1: force priority of packet
  44  *               | 0: don't force priority
  45  *    PRI        | priority of packet (if PRI_EN=1)
  46  *    KEEP       | preserve packet VLAN tag format
  47  *    LEARN_DIS  | don't learn the source MAC address of the packet
  48  *    ALLOW      | 1: treat TX/RX field as an allowance port mask, meaning the
  49  *               |    packet may only be forwarded to ports specified in the
  50  *               |    mask
  51  *               | 0: no allowance port mask, TX/RX field is the forwarding
  52  *               |    port mask
  53  *    TX/RX      | TX (switch->CPU): port number the packet was received on
  54  *               | RX (CPU->switch): forwarding port mask (if ALLOW=0)
  55  *               |                   allowance port mask (if ALLOW=1)
  56  *
  57  * The tag can be positioned before Ethertype, using tag "rtl8_4":
  58  *
  59  *  +--------+--------+------------+------+-----
  60  *  | MAC DA | MAC SA | 8 byte tag | Type | ...
  61  *  +--------+--------+------------+------+-----
  62  *
  63  * The tag can also appear between the end of the payload and before the CRC,
  64  * using tag "rtl8_4t":
  65  *
  66  * +--------+--------+------+-----+---------+------------+-----+
  67  * | MAC DA | MAC SA | TYPE | ... | payload | 8-byte tag | CRC |
  68  * +--------+--------+------+-----+---------+------------+-----+
  69  *
  70  * The added bytes after the payload will break most checksums, either in
  71  * software or hardware. To avoid this issue, if the checksum is still pending,
  72  * this tagger checksums the packet in software before adding the tag.
  73  *
  74  */
  75
  76 #include <linux/bitfield.h>
  77 #include <linux/bits.h>
  78 #include <linux/etherdevice.h>
  79
  80 #include "tag.h"
  81
  82 /* Protocols supported:
  83  *
  84  * 0x04 = RTL8365MB DSA protocol
  85  */
  86
  87 #define RTL8_4_NAME                     "rtl8_4"
  88 #define RTL8_4T_NAME                    "rtl8_4t"
  89
  90 #define RTL8_4_TAG_LEN                  8
  91
  92 #define RTL8_4_PROTOCOL                 GENMASK(15, 8)
  93 #define   RTL8_4_PROTOCOL_RTL8365MB     0x04
  94 #define RTL8_4_REASON                   GENMASK(7, 0)
  95 #define   RTL8_4_REASON_FORWARD         0
  96 #define   RTL8_4_REASON_TRAP            80
  97
  98 #define RTL8_4_LEARN_DIS                BIT(5)
  99
 100 #define RTL8_4_TX                       GENMASK(3, 0)
 101 #define RTL8_4_RX                       GENMASK(10, 0)
 102
 103 static void rtl8_4_write_tag(struct sk_buff *skb, struct net_device *dev,
 104                              void *tag)
 105 {
 106         struct dsa_port *dp = dsa_user_to_port(dev);
 107         __be16 tag16[RTL8_4_TAG_LEN / 2];
 108
 109         /* Set Realtek EtherType */
 110         tag16[0] = htons(ETH_P_REALTEK);
 111
 112         /* Set Protocol; zero REASON */
 113         tag16[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));
 114
 115         /* Zero FID_EN, FID, PRI_EN, PRI, KEEP; set LEARN_DIS */
 116         tag16[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));
 117
 118         /* Zero ALLOW; set RX (CPU->switch) forwarding port mask */
 119         tag16[3] = htons(FIELD_PREP(RTL8_4_RX, BIT(dp->index)));
 120
 121         memcpy(tag, tag16, RTL8_4_TAG_LEN);
 122 }
 123
 124 static struct sk_buff *rtl8_4_tag_xmit(struct sk_buff *skb,
 125                                        struct net_device *dev)
 126 {
 127         skb_push(skb, RTL8_4_TAG_LEN);
 128
 129         dsa_alloc_etype_header(skb, RTL8_4_TAG_LEN);
 130
 131         rtl8_4_write_tag(skb, dev, dsa_etype_header_pos_tx(skb));
 132
 133         return skb;
 134 }
 135
 136 static struct sk_buff *rtl8_4t_tag_xmit(struct sk_buff *skb,
 137                                         struct net_device *dev)
 138 {
 139         /* Calculate the checksum here if not done yet as trailing tags will
 140          * break either software or hardware based checksum
 141          */
 142         if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
 143                 return NULL;
 144
 145         rtl8_4_write_tag(skb, dev, skb_put(skb, RTL8_4_TAG_LEN));
 146
 147         return skb;
 148 }
 149
 150 static int rtl8_4_read_tag(struct sk_buff *skb, struct net_device *dev,
 151                            void *tag)
 152 {
 153         __be16 tag16[RTL8_4_TAG_LEN / 2];
 154         u16 etype;
 155         u8 reason;
 156         u8 proto;
 157         u8 port;
 158
 159         memcpy(tag16, tag, RTL8_4_TAG_LEN);
 160
 161         /* Parse Realtek EtherType */
 162         etype = ntohs(tag16[0]);
 163         if (unlikely(etype != ETH_P_REALTEK)) {
 164                 dev_warn_ratelimited(&dev->dev,
 165                                      "non-realtek ethertype 0x%04x\n", etype);
 166                 return -EPROTO;
 167         }
 168
 169         /* Parse Protocol */
 170         proto = FIELD_GET(RTL8_4_PROTOCOL, ntohs(tag16[1]));
 171         if (unlikely(proto != RTL8_4_PROTOCOL_RTL8365MB)) {
 172                 dev_warn_ratelimited(&dev->dev,
 173                                      "unknown realtek protocol 0x%02x\n",
 174                                      proto);
 175                 return -EPROTO;
 176         }
 177
 178         /* Parse REASON */
 179         reason = FIELD_GET(RTL8_4_REASON, ntohs(tag16[1]));
 180
 181         /* Parse TX (switch->CPU) */
 182         port = FIELD_GET(RTL8_4_TX, ntohs(tag16[3]));
 183         skb->dev = dsa_conduit_find_user(dev, 0, port);
 184         if (!skb->dev) {
 185                 dev_warn_ratelimited(&dev->dev,
 186                                      "could not find user for port %d\n",
 187                                      port);
 188                 return -ENOENT;
 189         }
 190
 191         if (reason != RTL8_4_REASON_TRAP)
 192                 dsa_default_offload_fwd_mark(skb);
 193
 194         return 0;
 195 }
 196
 197 static struct sk_buff *rtl8_4_tag_rcv(struct sk_buff *skb,
 198                                       struct net_device *dev)
 199 {
 200         if (unlikely(!pskb_may_pull(skb, RTL8_4_TAG_LEN)))
 201                 return NULL;
 202
 203         if (unlikely(rtl8_4_read_tag(skb, dev, dsa_etype_header_pos_rx(skb))))
 204                 return NULL;
 205
 206         /* Remove tag and recalculate checksum */
 207         skb_pull_rcsum(skb, RTL8_4_TAG_LEN);
 208
 209         dsa_strip_etype_header(skb, RTL8_4_TAG_LEN);
 210
 211         return skb;
 212 }
 213
 214 static struct sk_buff *rtl8_4t_tag_rcv(struct sk_buff *skb,
 215                                        struct net_device *dev)
 216 {
 217         if (skb_linearize(skb))
 218                 return NULL;
 219
 220         if (unlikely(rtl8_4_read_tag(skb, dev, skb_tail_pointer(skb) - RTL8_4_TAG_LEN)))
 221                 return NULL;
 222
 223         if (pskb_trim_rcsum(skb, skb->len - RTL8_4_TAG_LEN))
 224                 return NULL;
 225
 226         return skb;
 227 }
 228
 229 /* Ethertype version */
 230 static const struct dsa_device_ops rtl8_4_netdev_ops = {
 231         .name = "rtl8_4",
 232         .proto = DSA_TAG_PROTO_RTL8_4,
 233         .xmit = rtl8_4_tag_xmit,
 234         .rcv = rtl8_4_tag_rcv,
 235         .needed_headroom = RTL8_4_TAG_LEN,
 236 };
 237
 238 DSA_TAG_DRIVER(rtl8_4_netdev_ops);
 239
 240 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4, RTL8_4_NAME);
 241
 242 /* Tail version */
 243 static const struct dsa_device_ops rtl8_4t_netdev_ops = {
 244         .name = "rtl8_4t",
 245         .proto = DSA_TAG_PROTO_RTL8_4T,
 246         .xmit = rtl8_4t_tag_xmit,
 247         .rcv = rtl8_4t_tag_rcv,
 248         .needed_tailroom = RTL8_4_TAG_LEN,
 249 };
 250
 251 DSA_TAG_DRIVER(rtl8_4t_netdev_ops);
 252
 253 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4T, RTL8_4T_NAME);
 254
 255 static struct dsa_tag_driver *dsa_tag_drivers[] = {
 256         &DSA_TAG_DRIVER_NAME(rtl8_4_netdev_ops),
 257         &DSA_TAG_DRIVER_NAME(rtl8_4t_netdev_ops),
 258 };
 259 module_dsa_tag_drivers(dsa_tag_drivers);
 260
 261 MODULE_DESCRIPTION("DSA tag driver for Realtek 8 byte protocol 4 tags");
 262 MODULE_LICENSE("GPL");