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_ETHERTYPE 0x8899 27 #define RTL4_A_PROTOCOL_SHIFT 12 28 /* 29 * 0x1 = Realtek Remote Control protocol (RRCP) 30 * 0x2/0x3 seems to be used for loopback testing 31 * 0x9 = RTL8306 DSA protocol 32 * 0xa = RTL8366RB DSA protocol 33 */ 34 #define RTL4_A_PROTOCOL_RTL8366RB 0xa 35 36 static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, 37 struct net_device *dev) 38 { 39 struct dsa_port *dp = dsa_slave_to_port(dev); 40 __be16 *p; 41 u8 *tag; 42 u16 out; 43 44 /* Pad out to at least 60 bytes */ 45 if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false))) 46 return NULL; 47 48 netdev_dbg(dev, "add realtek tag to package to port %d\n", 49 dp->index); 50 skb_push(skb, RTL4_A_HDR_LEN); 51 52 dsa_alloc_etype_header(skb, RTL4_A_HDR_LEN); 53 tag = dsa_etype_header_pos_tx(skb); 54 55 /* Set Ethertype */ 56 p = (__be16 *)tag; 57 *p = htons(RTL4_A_ETHERTYPE); 58 59 out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT); 60 /* The lower bits indicate the port number */ 61 out |= BIT(dp->index); 62 63 p = (__be16 *)(tag + 2); 64 *p = htons(out); 65 66 return skb; 67 } 68 69 static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb, 70 struct net_device *dev) 71 { 72 u16 protport; 73 __be16 *p; 74 u16 etype; 75 u8 *tag; 76 u8 prot; 77 u8 port; 78 79 if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN))) 80 return NULL; 81 82 tag = dsa_etype_header_pos_rx(skb); 83 p = (__be16 *)tag; 84 etype = ntohs(*p); 85 if (etype != RTL4_A_ETHERTYPE) { 86 /* Not custom, just pass through */ 87 netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype); 88 return skb; 89 } 90 p = (__be16 *)(tag + 2); 91 protport = ntohs(*p); 92 /* The 4 upper bits are the protocol */ 93 prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f; 94 if (prot != RTL4_A_PROTOCOL_RTL8366RB) { 95 netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot); 96 return NULL; 97 } 98 port = protport & 0xff; 99 100 skb->dev = dsa_master_find_slave(dev, 0, port); 101 if (!skb->dev) { 102 netdev_dbg(dev, "could not find slave for port %d\n", port); 103 return NULL; 104 } 105 106 /* Remove RTL4 tag and recalculate checksum */ 107 skb_pull_rcsum(skb, RTL4_A_HDR_LEN); 108 109 dsa_strip_etype_header(skb, RTL4_A_HDR_LEN); 110 111 dsa_default_offload_fwd_mark(skb); 112 113 return skb; 114 } 115 116 static const struct dsa_device_ops rtl4a_netdev_ops = { 117 .name = RTL4_A_NAME, 118 .proto = DSA_TAG_PROTO_RTL4_A, 119 .xmit = rtl4a_tag_xmit, 120 .rcv = rtl4a_tag_rcv, 121 .needed_headroom = RTL4_A_HDR_LEN, 122 }; 123 module_dsa_tag_driver(rtl4a_netdev_ops); 124 125 MODULE_LICENSE("GPL"); 126 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A, RTL4_A_NAME); 127