1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Handler for Realtek 4 byte DSA switch tags |
4 | * Currently only supports protocol "A" found in RTL8366RB |
5 | * Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org> |
6 | * |
7 | * This "proprietary tag" header looks like so: |
8 | * |
9 | * ------------------------------------------------- |
10 | * | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type | |
11 | * ------------------------------------------------- |
12 | * |
13 | * The 2 bytes tag form a 16 bit big endian word. The exact |
14 | * meaning has been guessed from packet dumps from ingress |
15 | * frames. |
16 | */ |
17 | |
18 | #include <linux/etherdevice.h> |
19 | #include <linux/bits.h> |
20 | |
21 | #include "tag.h" |
22 | |
23 | #define RTL4_A_NAME "rtl4a" |
24 | |
25 | #define RTL4_A_HDR_LEN 4 |
26 | #define RTL4_A_PROTOCOL_SHIFT 12 |
27 | /* |
28 | * 0x1 = Realtek Remote Control protocol (RRCP) |
29 | * 0x2/0x3 seems to be used for loopback testing |
30 | * 0x9 = RTL8306 DSA protocol |
31 | * 0xa = RTL8366RB DSA protocol |
32 | */ |
33 | #define RTL4_A_PROTOCOL_RTL8366RB 0xa |
34 | |
35 | static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, |
36 | struct net_device *dev) |
37 | { |
38 | struct dsa_port *dp = dsa_user_to_port(dev); |
39 | __be16 *p; |
40 | u8 *tag; |
41 | u16 out; |
42 | |
43 | /* Pad out to at least 60 bytes */ |
44 | if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false))) |
45 | return NULL; |
46 | |
47 | netdev_dbg(dev, "add realtek tag to package to port %d\n" , |
48 | dp->index); |
49 | skb_push(skb, RTL4_A_HDR_LEN); |
50 | |
51 | dsa_alloc_etype_header(skb, RTL4_A_HDR_LEN); |
52 | tag = dsa_etype_header_pos_tx(skb); |
53 | |
54 | /* Set Ethertype */ |
55 | p = (__be16 *)tag; |
56 | *p = htons(ETH_P_REALTEK); |
57 | |
58 | out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT); |
59 | /* The lower bits indicate the port number */ |
60 | out |= BIT(dp->index); |
61 | |
62 | p = (__be16 *)(tag + 2); |
63 | *p = htons(out); |
64 | |
65 | return skb; |
66 | } |
67 | |
68 | static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb, |
69 | struct net_device *dev) |
70 | { |
71 | u16 protport; |
72 | __be16 *p; |
73 | u16 etype; |
74 | u8 *tag; |
75 | u8 prot; |
76 | u8 port; |
77 | |
78 | if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN))) |
79 | return NULL; |
80 | |
81 | tag = dsa_etype_header_pos_rx(skb); |
82 | p = (__be16 *)tag; |
83 | etype = ntohs(*p); |
84 | if (etype != ETH_P_REALTEK) { |
85 | /* Not custom, just pass through */ |
86 | netdev_dbg(dev, "non-realtek ethertype 0x%04x\n" , etype); |
87 | return skb; |
88 | } |
89 | p = (__be16 *)(tag + 2); |
90 | protport = ntohs(*p); |
91 | /* The 4 upper bits are the protocol */ |
92 | prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f; |
93 | if (prot != RTL4_A_PROTOCOL_RTL8366RB) { |
94 | netdev_err(dev, format: "unknown realtek protocol 0x%01x\n" , prot); |
95 | return NULL; |
96 | } |
97 | port = protport & 0xff; |
98 | |
99 | skb->dev = dsa_conduit_find_user(dev, device: 0, port); |
100 | if (!skb->dev) { |
101 | netdev_dbg(dev, "could not find user for port %d\n" , port); |
102 | return NULL; |
103 | } |
104 | |
105 | /* Remove RTL4 tag and recalculate checksum */ |
106 | skb_pull_rcsum(skb, RTL4_A_HDR_LEN); |
107 | |
108 | dsa_strip_etype_header(skb, RTL4_A_HDR_LEN); |
109 | |
110 | dsa_default_offload_fwd_mark(skb); |
111 | |
112 | return skb; |
113 | } |
114 | |
115 | static const struct dsa_device_ops rtl4a_netdev_ops = { |
116 | .name = RTL4_A_NAME, |
117 | .proto = DSA_TAG_PROTO_RTL4_A, |
118 | .xmit = rtl4a_tag_xmit, |
119 | .rcv = rtl4a_tag_rcv, |
120 | .needed_headroom = RTL4_A_HDR_LEN, |
121 | }; |
122 | module_dsa_tag_driver(rtl4a_netdev_ops); |
123 | |
124 | MODULE_DESCRIPTION("DSA tag driver for Realtek 4 byte protocol A tags" ); |
125 | MODULE_LICENSE("GPL" ); |
126 | MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A, RTL4_A_NAME); |
127 | |