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// SPDX-License-Identifier: GPL-2.0
/*
* Handler for Realtek 8 byte switch tags
*
* Copyright (C) 2021 Alvin Šipraga <alsi@bang-olufsen.dk>
*
* NOTE: Currently only supports protocol "4" found in the RTL8365MB, hence
* named tag_rtl8_4.
*
* This tag has the following format:
*
* 0 7|8 15
* |-----------------------------------+-----------------------------------|---
* | (16-bit) | ^
* | Realtek EtherType [0x8899] | |
* |-----------------------------------+-----------------------------------| 8
* | (8-bit) | (8-bit) |
* | Protocol [0x04] | REASON | b
* |-----------------------------------+-----------------------------------| y
* | (1) | (1) | (2) | (1) | (3) | (1) | (1) | (1) | (5) | t
* | FID_EN | X | FID | PRI_EN | PRI | KEEP | X | LEARN_DIS | X | e
* |-----------------------------------+-----------------------------------| s
* | (1) | (15-bit) | |
* | ALLOW | TX/RX | v
* |-----------------------------------+-----------------------------------|---
*
* With the following field descriptions:
*
* field | description
* ------------+-------------
* Realtek | 0x8899: indicates that this is a proprietary Realtek tag;
* EtherType | note that Realtek uses the same EtherType for
* | other incompatible tag formats (e.g. tag_rtl4_a.c)
* Protocol | 0x04: indicates that this tag conforms to this format
* X | reserved
* ------------+-------------
* REASON | reason for forwarding packet to CPU
* | 0: packet was forwarded or flooded to CPU
* | 80: packet was trapped to CPU
* FID_EN | 1: packet has an FID
* | 0: no FID
* FID | FID of packet (if FID_EN=1)
* PRI_EN | 1: force priority of packet
* | 0: don't force priority
* PRI | priority of packet (if PRI_EN=1)
* KEEP | preserve packet VLAN tag format
* LEARN_DIS | don't learn the source MAC address of the packet
* ALLOW | 1: treat TX/RX field as an allowance port mask, meaning the
* | packet may only be forwarded to ports specified in the
* | mask
* | 0: no allowance port mask, TX/RX field is the forwarding
* | port mask
* TX/RX | TX (switch->CPU): port number the packet was received on
* | RX (CPU->switch): forwarding port mask (if ALLOW=0)
* | allowance port mask (if ALLOW=1)
*
* The tag can be positioned before Ethertype, using tag "rtl8_4":
*
* +--------+--------+------------+------+-----
* | MAC DA | MAC SA | 8 byte tag | Type | ...
* +--------+--------+------------+------+-----
*
* The tag can also appear between the end of the payload and before the CRC,
* using tag "rtl8_4t":
*
* +--------+--------+------+-----+---------+------------+-----+
* | MAC DA | MAC SA | TYPE | ... | payload | 8-byte tag | CRC |
* +--------+--------+------+-----+---------+------------+-----+
*
* The added bytes after the payload will break most checksums, either in
* software or hardware. To avoid this issue, if the checksum is still pending,
* this tagger checksums the packet in software before adding the tag.
*
*/
#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/etherdevice.h>
#include "tag.h"
/* Protocols supported:
*
* 0x04 = RTL8365MB DSA protocol
*/
#define RTL8_4_NAME "rtl8_4"
#define RTL8_4T_NAME "rtl8_4t"
#define RTL8_4_TAG_LEN 8
#define RTL8_4_PROTOCOL GENMASK(15, 8)
#define RTL8_4_PROTOCOL_RTL8365MB 0x04
#define RTL8_4_REASON GENMASK(7, 0)
#define RTL8_4_REASON_FORWARD 0
#define RTL8_4_REASON_TRAP 80
#define RTL8_4_LEARN_DIS BIT(5)
#define RTL8_4_TX GENMASK(3, 0)
#define RTL8_4_RX GENMASK(10, 0)
static void rtl8_4_write_tag(struct sk_buff *skb, struct net_device *dev,
void *tag)
{
struct dsa_port *dp = dsa_user_to_port(dev);
__be16 tag16[RTL8_4_TAG_LEN / 2];
/* Set Realtek EtherType */
tag16[0] = htons(ETH_P_REALTEK);
/* Set Protocol; zero REASON */
tag16[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));
/* Zero FID_EN, FID, PRI_EN, PRI, KEEP; set LEARN_DIS */
tag16[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));
/* Zero ALLOW; set RX (CPU->switch) forwarding port mask */
tag16[3] = htons(FIELD_PREP(RTL8_4_RX, BIT(dp->index)));
memcpy(tag, tag16, RTL8_4_TAG_LEN);
}
static struct sk_buff *rtl8_4_tag_xmit(struct sk_buff *skb,
struct net_device *dev)
{
skb_push(skb, RTL8_4_TAG_LEN);
dsa_alloc_etype_header(skb, RTL8_4_TAG_LEN);
rtl8_4_write_tag(skb, dev, dsa_etype_header_pos_tx(skb));
return skb;
}
static struct sk_buff *rtl8_4t_tag_xmit(struct sk_buff *skb,
struct net_device *dev)
{
/* Calculate the checksum here if not done yet as trailing tags will
* break either software or hardware based checksum
*/
if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
return NULL;
rtl8_4_write_tag(skb, dev, skb_put(skb, RTL8_4_TAG_LEN));
return skb;
}
static int rtl8_4_read_tag(struct sk_buff *skb, struct net_device *dev,
void *tag)
{
__be16 tag16[RTL8_4_TAG_LEN / 2];
u16 etype;
u8 reason;
u8 proto;
u8 port;
memcpy(tag16, tag, RTL8_4_TAG_LEN);
/* Parse Realtek EtherType */
etype = ntohs(tag16[0]);
if (unlikely(etype != ETH_P_REALTEK)) {
dev_warn_ratelimited(&dev->dev,
"non-realtek ethertype 0x%04x\n", etype);
return -EPROTO;
}
/* Parse Protocol */
proto = FIELD_GET(RTL8_4_PROTOCOL, ntohs(tag16[1]));
if (unlikely(proto != RTL8_4_PROTOCOL_RTL8365MB)) {
dev_warn_ratelimited(&dev->dev,
"unknown realtek protocol 0x%02x\n",
proto);
return -EPROTO;
}
/* Parse REASON */
reason = FIELD_GET(RTL8_4_REASON, ntohs(tag16[1]));
/* Parse TX (switch->CPU) */
port = FIELD_GET(RTL8_4_TX, ntohs(tag16[3]));
skb->dev = dsa_conduit_find_user(dev, 0, port);
if (!skb->dev) {
dev_warn_ratelimited(&dev->dev,
"could not find user for port %d\n",
port);
return -ENOENT;
}
if (reason != RTL8_4_REASON_TRAP)
dsa_default_offload_fwd_mark(skb);
return 0;
}
static struct sk_buff *rtl8_4_tag_rcv(struct sk_buff *skb,
struct net_device *dev)
{
if (unlikely(!pskb_may_pull(skb, RTL8_4_TAG_LEN)))
return NULL;
if (unlikely(rtl8_4_read_tag(skb, dev, dsa_etype_header_pos_rx(skb))))
return NULL;
/* Remove tag and recalculate checksum */
skb_pull_rcsum(skb, RTL8_4_TAG_LEN);
dsa_strip_etype_header(skb, RTL8_4_TAG_LEN);
return skb;
}
static struct sk_buff *rtl8_4t_tag_rcv(struct sk_buff *skb,
struct net_device *dev)
{
if (skb_linearize(skb))
return NULL;
if (unlikely(rtl8_4_read_tag(skb, dev, skb_tail_pointer(skb) - RTL8_4_TAG_LEN)))
return NULL;
if (pskb_trim_rcsum(skb, skb->len - RTL8_4_TAG_LEN))
return NULL;
return skb;
}
/* Ethertype version */
static const struct dsa_device_ops rtl8_4_netdev_ops = {
.name = "rtl8_4",
.proto = DSA_TAG_PROTO_RTL8_4,
.xmit = rtl8_4_tag_xmit,
.rcv = rtl8_4_tag_rcv,
.needed_headroom = RTL8_4_TAG_LEN,
};
DSA_TAG_DRIVER(rtl8_4_netdev_ops);
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4, RTL8_4_NAME);
/* Tail version */
static const struct dsa_device_ops rtl8_4t_netdev_ops = {
.name = "rtl8_4t",
.proto = DSA_TAG_PROTO_RTL8_4T,
.xmit = rtl8_4t_tag_xmit,
.rcv = rtl8_4t_tag_rcv,
.needed_tailroom = RTL8_4_TAG_LEN,
};
DSA_TAG_DRIVER(rtl8_4t_netdev_ops);
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4T, RTL8_4T_NAME);
static struct dsa_tag_driver *dsa_tag_drivers[] = {
&DSA_TAG_DRIVER_NAME(rtl8_4_netdev_ops),
&DSA_TAG_DRIVER_NAME(rtl8_4t_netdev_ops),
};
module_dsa_tag_drivers(dsa_tag_drivers);
MODULE_DESCRIPTION("DSA tag driver for Realtek 8 byte protocol 4 tags");
MODULE_LICENSE("GPL");
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