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