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 "dsa_priv.h" 22 23 #define RTL4_A_HDR_LEN 4 24 #define RTL4_A_ETHERTYPE 0x8899 25 #define RTL4_A_PROTOCOL_SHIFT 12 26 /* 27 * 0x1 = Realtek Remote Control protocol (RRCP) 28 * 0x2/0x3 seems to be used for loopback testing 29 * 0x9 = RTL8306 DSA protocol 30 * 0xa = RTL8366RB DSA protocol 31 */ 32 #define RTL4_A_PROTOCOL_RTL8366RB 0xa 33 34 static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, 35 struct net_device *dev) 36 { 37 struct dsa_port *dp = dsa_slave_to_port(dev); 38 __be16 *p; 39 u8 *tag; 40 u16 out; 41 42 /* Pad out to at least 60 bytes */ 43 if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false))) 44 return NULL; 45 46 netdev_dbg(dev, "add realtek tag to package to port %d\n", 47 dp->index); 48 skb_push(skb, RTL4_A_HDR_LEN); 49 50 memmove(skb->data, skb->data + RTL4_A_HDR_LEN, 2 * ETH_ALEN); 51 tag = skb->data + 2 * ETH_ALEN; 52 53 /* Set Ethertype */ 54 p = (__be16 *)tag; 55 *p = htons(RTL4_A_ETHERTYPE); 56 57 out = (RTL4_A_PROTOCOL_RTL8366RB << 12) | (2 << 8); 58 /* The lower bits is the port number */ 59 out |= (u8)dp->index; 60 p = (__be16 *)(tag + 2); 61 *p = htons(out); 62 63 return skb; 64 } 65 66 static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb, 67 struct net_device *dev, 68 struct packet_type *pt) 69 { 70 u16 protport; 71 __be16 *p; 72 u16 etype; 73 u8 *tag; 74 u8 prot; 75 u8 port; 76 77 if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN))) 78 return NULL; 79 80 /* The RTL4 header has its own custom Ethertype 0x8899 and that 81 * starts right at the beginning of the packet, after the src 82 * ethernet addr. Apparently skb->data always points 2 bytes in, 83 * behind the Ethertype. 84 */ 85 tag = skb->data - 2; 86 p = (__be16 *)tag; 87 etype = ntohs(*p); 88 if (etype != RTL4_A_ETHERTYPE) { 89 /* Not custom, just pass through */ 90 netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype); 91 return skb; 92 } 93 p = (__be16 *)(tag + 2); 94 protport = ntohs(*p); 95 /* The 4 upper bits are the protocol */ 96 prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f; 97 if (prot != RTL4_A_PROTOCOL_RTL8366RB) { 98 netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot); 99 return NULL; 100 } 101 port = protport & 0xff; 102 103 skb->dev = dsa_master_find_slave(dev, 0, port); 104 if (!skb->dev) { 105 netdev_dbg(dev, "could not find slave for port %d\n", port); 106 return NULL; 107 } 108 109 /* Remove RTL4 tag and recalculate checksum */ 110 skb_pull_rcsum(skb, RTL4_A_HDR_LEN); 111 112 /* Move ethernet DA and SA in front of the data */ 113 memmove(skb->data - ETH_HLEN, 114 skb->data - ETH_HLEN - RTL4_A_HDR_LEN, 115 2 * ETH_ALEN); 116 117 skb->offload_fwd_mark = 1; 118 119 return skb; 120 } 121 122 static const struct dsa_device_ops rtl4a_netdev_ops = { 123 .name = "rtl4a", 124 .proto = DSA_TAG_PROTO_RTL4_A, 125 .xmit = rtl4a_tag_xmit, 126 .rcv = rtl4a_tag_rcv, 127 .overhead = RTL4_A_HDR_LEN, 128 }; 129 module_dsa_tag_driver(rtl4a_netdev_ops); 130 131 MODULE_LICENSE("GPL"); 132 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A); 133