target/linux/generic/backport-5.4/757-v5.8-net-dsa-tag_rtl4_a-Implement-Realtek-4-byte-A-tag.patch

   1 From 078ced30af696b52a450a016a16eb47499d68117 Mon Sep 17 00:00:00 2001
   2 From: Linus Walleij <linus.walleij@linaro.org>
   3 Date: Wed, 8 Jul 2020 14:25:36 +0200
   4 Subject: [PATCH 2/5] net: dsa: tag_rtl4_a: Implement Realtek 4 byte A tag
   5
   6 This implements the known parts of the Realtek 4 byte
   7 tag protocol version 0xA, as found in the RTL8366RB
   8 DSA switch.
   9
  10 It is designated as protocol version 0xA as a
  11 different Realtek 4 byte tag format with protocol
  12 version 0x9 is known to exist in the Realtek RTL8306
  13 chips.
  14
  15 The tag and switch chip lacks public documentation, so
  16 the tag format has been reverse-engineered from
  17 packet dumps. As only ingress traffic has been available
  18 for analysis an egress tag has not been possible to
  19 develop (even using educated guesses about bit fields)
  20 so this is as far as it gets. It is not known if the
  21 switch even supports egress tagging.
  22
  23 Excessive attempts to figure out the egress tag format
  24 was made. When nothing else worked, I just tried all bit
  25 combinations with 0xannp where a is protocol and p is
  26 port. I looped through all values several times trying
  27 to get a response from ping, without any positive
  28 result.
  29
  30 Using just these ingress tags however, the switch
  31 functionality is vastly improved and the packets find
  32 their way into the destination port without any
  33 tricky VLAN configuration. On the D-Link DIR-685 the
  34 LAN ports now come up and respond to ping without
  35 any command line configuration so this is a real
  36 improvement for users.
  37
  38 Egress packets need to be restricted to the proper
  39 target ports using VLAN, which the RTL8366RB DSA
  40 switch driver already sets up.
  41
  42 Cc: DENG Qingfang <dqfext@gmail.com>
  43 Cc: Mauri Sandberg <sandberg@mailfence.com>
  44 Reviewed-by: Andrew Lunn <andrew@lunn.ch>
  45 Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
  46 Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
  47 Signed-off-by: David S. Miller <davem@davemloft.net>
  48 ---
  49  include/net/dsa.h    |   2 +
  50  net/dsa/Kconfig      |   7 +++
  51  net/dsa/Makefile     |   1 +
  52  net/dsa/tag_rtl4_a.c | 130 +++++++++++++++++++++++++++++++++++++++++++
  53  4 files changed, 140 insertions(+)
  54  create mode 100644 net/dsa/tag_rtl4_a.c
  55
  56 --- a/include/net/dsa.h
  57 +++ b/include/net/dsa.h
  58 @@ -42,6 +42,7 @@ struct phylink_link_state;
  59  #define DSA_TAG_PROTO_8021Q_VALUE              12
  60  #define DSA_TAG_PROTO_SJA1105_VALUE            13
  61  #define DSA_TAG_PROTO_KSZ8795_VALUE            14
  62 +#define DSA_TAG_PROTO_RTL4_A_VALUE             17
  63
  64  enum dsa_tag_protocol {
  65         DSA_TAG_PROTO_NONE              = DSA_TAG_PROTO_NONE_VALUE,
  66 @@ -59,6 +60,7 @@ enum dsa_tag_protocol {
  67         DSA_TAG_PROTO_8021Q             = DSA_TAG_PROTO_8021Q_VALUE,
  68         DSA_TAG_PROTO_SJA1105           = DSA_TAG_PROTO_SJA1105_VALUE,
  69         DSA_TAG_PROTO_KSZ8795           = DSA_TAG_PROTO_KSZ8795_VALUE,
  70 +       DSA_TAG_PROTO_RTL4_A            = DSA_TAG_PROTO_RTL4_A_VALUE,
  71  };
  72
  73  struct packet_type;
  74 --- a/net/dsa/Kconfig
  75 +++ b/net/dsa/Kconfig
  76 @@ -80,6 +80,13 @@ config NET_DSA_TAG_KSZ
  77           Say Y if you want to enable support for tagging frames for the
  78           Microchip 8795/9477/9893 families of switches.
  79
  80 +config NET_DSA_TAG_RTL4_A
  81 +       tristate "Tag driver for Realtek 4 byte protocol A tags"
  82 +       help
  83 +         Say Y or M if you want to enable support for tagging frames for the
  84 +         Realtek switches with 4 byte protocol A tags, sich as found in
  85 +         the Realtek RTL8366RB.
  86 +
  87  config NET_DSA_TAG_QCA
  88         tristate "Tag driver for Qualcomm Atheros QCA8K switches"
  89         help
  90 --- a/net/dsa/Makefile
  91 +++ b/net/dsa/Makefile
  92 @@ -10,6 +10,7 @@ obj-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa
  93  obj-$(CONFIG_NET_DSA_TAG_EDSA) += tag_edsa.o
  94  obj-$(CONFIG_NET_DSA_TAG_GSWIP) += tag_gswip.o
  95  obj-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o
  96 +obj-$(CONFIG_NET_DSA_TAG_RTL4_A) += tag_rtl4_a.o
  97  obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
  98  obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o
  99  obj-$(CONFIG_NET_DSA_TAG_QCA) += tag_qca.o
 100 --- /dev/null
 101 +++ b/net/dsa/tag_rtl4_a.c
 102 @@ -0,0 +1,130 @@
 103 +// SPDX-License-Identifier: GPL-2.0
 104 +/*
 105 + * Handler for Realtek 4 byte DSA switch tags
 106 + * Currently only supports protocol "A" found in RTL8366RB
 107 + * Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org>
 108 + *
 109 + * This "proprietary tag" header looks like so:
 110 + *
 111 + * -------------------------------------------------
 112 + * | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type |
 113 + * -------------------------------------------------
 114 + *
 115 + * The 2 bytes tag form a 16 bit big endian word. The exact
 116 + * meaning has been guessed from packet dumps from ingress
 117 + * frames, as no working egress traffic has been available
 118 + * we do not know the format of the egress tags or if they
 119 + * are even supported.
 120 + */
 121 +
 122 +#include <linux/etherdevice.h>
 123 +#include <linux/bits.h>
 124 +
 125 +#include "dsa_priv.h"
 126 +
 127 +#define RTL4_A_HDR_LEN         4
 128 +#define RTL4_A_ETHERTYPE       0x8899
 129 +#define RTL4_A_PROTOCOL_SHIFT  12
 130 +/*
 131 + * 0x1 = Realtek Remote Control protocol (RRCP)
 132 + * 0x2/0x3 seems to be used for loopback testing
 133 + * 0x9 = RTL8306 DSA protocol
 134 + * 0xa = RTL8366RB DSA protocol
 135 + */
 136 +#define RTL4_A_PROTOCOL_RTL8366RB      0xa
 137 +
 138 +static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
 139 +                                     struct net_device *dev)
 140 +{
 141 +       /*
 142 +        * Just let it pass thru, we don't know if it is possible
 143 +        * to tag a frame with the 0x8899 ethertype and direct it
 144 +        * to a specific port, all attempts at reverse-engineering have
 145 +        * ended up with the frames getting dropped.
 146 +        *
 147 +        * The VLAN set-up needs to restrict the frames to the right port.
 148 +        *
 149 +        * If you have documentation on the tagging format for RTL8366RB
 150 +        * (tag type A) then please contribute.
 151 +        */
 152 +       return skb;
 153 +}
 154 +
 155 +static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb,
 156 +                                    struct net_device *dev,
 157 +                                    struct packet_type *pt)
 158 +{
 159 +       u16 protport;
 160 +       __be16 *p;
 161 +       u16 etype;
 162 +       u8 *tag;
 163 +       u8 prot;
 164 +       u8 port;
 165 +
 166 +       if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN)))
 167 +               return NULL;
 168 +
 169 +       /* The RTL4 header has its own custom Ethertype 0x8899 and that
 170 +        * starts right at the beginning of the packet, after the src
 171 +        * ethernet addr. Apparantly skb->data always points 2 bytes in,
 172 +        * behind the Ethertype.
 173 +        */
 174 +       tag = skb->data - 2;
 175 +       p = (__be16 *)tag;
 176 +       etype = ntohs(*p);
 177 +       if (etype != RTL4_A_ETHERTYPE) {
 178 +               /* Not custom, just pass through */
 179 +               netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype);
 180 +               return skb;
 181 +       }
 182 +       p = (__be16 *)(tag + 2);
 183 +       protport = ntohs(*p);
 184 +       /* The 4 upper bits are the protocol */
 185 +       prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f;
 186 +       if (prot != RTL4_A_PROTOCOL_RTL8366RB) {
 187 +               netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot);
 188 +               return NULL;
 189 +       }
 190 +       port = protport & 0xff;
 191 +
 192 +       skb->dev = dsa_master_find_slave(dev, 0, port);
 193 +       if (!skb->dev) {
 194 +               netdev_dbg(dev, "could not find slave for port %d\n", port);
 195 +               return NULL;
 196 +       }
 197 +
 198 +       /* Remove RTL4 tag and recalculate checksum */
 199 +       skb_pull_rcsum(skb, RTL4_A_HDR_LEN);
 200 +
 201 +       /* Move ethernet DA and SA in front of the data */
 202 +       memmove(skb->data - ETH_HLEN,
 203 +               skb->data - ETH_HLEN - RTL4_A_HDR_LEN,
 204 +               2 * ETH_ALEN);
 205 +
 206 +       skb->offload_fwd_mark = 1;
 207 +
 208 +       return skb;
 209 +}
 210 +
 211 +static int rtl4a_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 212 +                                 int *offset)
 213 +{
 214 +       *offset = RTL4_A_HDR_LEN;
 215 +       /* Skip past the tag and fetch the encapsulated Ethertype */
 216 +       *proto = ((__be16 *)skb->data)[1];
 217 +
 218 +       return 0;
 219 +}
 220 +
 221 +static const struct dsa_device_ops rtl4a_netdev_ops = {
 222 +       .name   = "rtl4a",
 223 +       .proto  = DSA_TAG_PROTO_RTL4_A,
 224 +       .xmit   = rtl4a_tag_xmit,
 225 +       .rcv    = rtl4a_tag_rcv,
 226 +       .flow_dissect = rtl4a_tag_flow_dissect,
 227 +       .overhead = RTL4_A_HDR_LEN,
 228 +};
 229 +module_dsa_tag_driver(rtl4a_netdev_ops);
 230 +
 231 +MODULE_LICENSE("GPL");
 232 +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A);