// SPDX-License-Identifier: GPL-2.0
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/*
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* Handler for Realtek 4 byte DSA switch tags
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* Currently only supports protocol "A" found in RTL8366RB
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* Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org>
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*
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* This "proprietary tag" header looks like so:
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*
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* -------------------------------------------------
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* | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type |
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* -------------------------------------------------
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*
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* The 2 bytes tag form a 16 bit big endian word. The exact
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* meaning has been guessed from packet dumps from ingress
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* frames.
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*/
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#include <linux/etherdevice.h>
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#include <linux/bits.h>
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#include "dsa_priv.h"
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#define RTL4_A_HDR_LEN 4
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#define RTL4_A_ETHERTYPE 0x8899
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#define RTL4_A_PROTOCOL_SHIFT 12
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/*
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* 0x1 = Realtek Remote Control protocol (RRCP)
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* 0x2/0x3 seems to be used for loopback testing
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* 0x9 = RTL8306 DSA protocol
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* 0xa = RTL8366RB DSA protocol
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*/
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#define RTL4_A_PROTOCOL_RTL8366RB 0xa
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static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
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struct net_device *dev)
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{
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struct dsa_port *dp = dsa_slave_to_port(dev);
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__be16 *p;
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u8 *tag;
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u16 out;
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/* Pad out to at least 60 bytes */
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if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false)))
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return NULL;
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netdev_dbg(dev, "add realtek tag to package to port %d\n",
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dp->index);
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skb_push(skb, RTL4_A_HDR_LEN);
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memmove(skb->data, skb->data + RTL4_A_HDR_LEN, 2 * ETH_ALEN);
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tag = skb->data + 2 * ETH_ALEN;
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/* Set Ethertype */
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p = (__be16 *)tag;
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*p = htons(RTL4_A_ETHERTYPE);
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out = (RTL4_A_PROTOCOL_RTL8366RB << RTL4_A_PROTOCOL_SHIFT) | (2 << 8);
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/* The lower bits indicate the port number */
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out |= BIT(dp->index);
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p = (__be16 *)(tag + 2);
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*p = htons(out);
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return skb;
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}
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static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb,
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struct net_device *dev,
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struct packet_type *pt)
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{
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u16 protport;
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__be16 *p;
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u16 etype;
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u8 *tag;
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u8 prot;
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u8 port;
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if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN)))
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return NULL;
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/* The RTL4 header has its own custom Ethertype 0x8899 and that
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* starts right at the beginning of the packet, after the src
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* ethernet addr. Apparantly skb->data always points 2 bytes in,
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* behind the Ethertype.
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*/
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tag = skb->data - 2;
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p = (__be16 *)tag;
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etype = ntohs(*p);
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if (etype != RTL4_A_ETHERTYPE) {
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/* Not custom, just pass through */
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netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype);
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return skb;
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}
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p = (__be16 *)(tag + 2);
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protport = ntohs(*p);
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/* The 4 upper bits are the protocol */
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prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f;
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if (prot != RTL4_A_PROTOCOL_RTL8366RB) {
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netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot);
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return NULL;
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}
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port = protport & 0xff;
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skb->dev = dsa_master_find_slave(dev, 0, port);
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if (!skb->dev) {
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netdev_dbg(dev, "could not find slave for port %d\n", port);
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return NULL;
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}
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/* Remove RTL4 tag and recalculate checksum */
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skb_pull_rcsum(skb, RTL4_A_HDR_LEN);
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/* Move ethernet DA and SA in front of the data */
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memmove(skb->data - ETH_HLEN,
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skb->data - ETH_HLEN - RTL4_A_HDR_LEN,
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2 * ETH_ALEN);
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skb->offload_fwd_mark = 1;
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return skb;
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}
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static const struct dsa_device_ops rtl4a_netdev_ops = {
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.name = "rtl4a",
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.proto = DSA_TAG_PROTO_RTL4_A,
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.xmit = rtl4a_tag_xmit,
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.rcv = rtl4a_tag_rcv,
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.overhead = RTL4_A_HDR_LEN,
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};
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module_dsa_tag_driver(rtl4a_netdev_ops);
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A);
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