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net: dsa: tag_rtl8_4: add rtl8_4t trailing variant
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Realtek switches supports the same tag both before ethertype or between
payload and the CRC.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Luiz Angelo Daros de Luca authored and David S. Miller committed Mar 5, 2022
1 parent 617c3cc commit cd87fec
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Showing 2 changed files with 118 additions and 36 deletions.
2 changes: 2 additions & 0 deletions include/net/dsa.h
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,7 @@ struct phylink_link_state;
#define DSA_TAG_PROTO_BRCM_LEGACY_VALUE 22
#define DSA_TAG_PROTO_SJA1110_VALUE 23
#define DSA_TAG_PROTO_RTL8_4_VALUE 24
#define DSA_TAG_PROTO_RTL8_4T_VALUE 25

enum dsa_tag_protocol {
DSA_TAG_PROTO_NONE = DSA_TAG_PROTO_NONE_VALUE,
Expand Down Expand Up @@ -79,6 +80,7 @@ enum dsa_tag_protocol {
DSA_TAG_PROTO_SEVILLE = DSA_TAG_PROTO_SEVILLE_VALUE,
DSA_TAG_PROTO_SJA1110 = DSA_TAG_PROTO_SJA1110_VALUE,
DSA_TAG_PROTO_RTL8_4 = DSA_TAG_PROTO_RTL8_4_VALUE,
DSA_TAG_PROTO_RTL8_4T = DSA_TAG_PROTO_RTL8_4T_VALUE,
};

struct dsa_switch;
Expand Down
152 changes: 116 additions & 36 deletions net/dsa/tag_rtl8_4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7,13 +7,8 @@
* NOTE: Currently only supports protocol "4" found in the RTL8365MB, hence
* named tag_rtl8_4.
*
* This tag header has the following format:
* This tag has the following format:
*
* -------------------------------------------
* | MAC DA | MAC SA | 8 byte tag | Type | ...
* -------------------------------------------
* _______________/ \______________________________________
* / \
* 0 7|8 15
* |-----------------------------------+-----------------------------------|---
* | (16-bit) | ^
Expand Down Expand Up @@ -58,6 +53,24 @@
* 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>
Expand All @@ -84,95 +97,162 @@
#define RTL8_4_TX GENMASK(3, 0)
#define RTL8_4_RX GENMASK(10, 0)

static struct sk_buff *rtl8_4_tag_xmit(struct sk_buff *skb,
struct net_device *dev)
static void rtl8_4_write_tag(struct sk_buff *skb, struct net_device *dev,
void *tag)
{
struct dsa_port *dp = dsa_slave_to_port(dev);
__be16 *tag;

skb_push(skb, RTL8_4_TAG_LEN);

dsa_alloc_etype_header(skb, RTL8_4_TAG_LEN);
tag = dsa_etype_header_pos_tx(skb);
__be16 tag16[RTL8_4_TAG_LEN / 2];

/* Set Realtek EtherType */
tag[0] = htons(ETH_P_REALTEK);
tag16[0] = htons(ETH_P_REALTEK);

/* Set Protocol; zero REASON */
tag[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));
tag16[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));

/* Zero FID_EN, FID, PRI_EN, PRI, KEEP; set LEARN_DIS */
tag[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));
tag16[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));

/* Zero ALLOW; set RX (CPU->switch) forwarding port mask */
tag[3] = htons(FIELD_PREP(RTL8_4_RX, BIT(dp->index)));
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_4_tag_rcv(struct sk_buff *skb,
struct net_device *dev)
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 *tag;
__be16 tag16[RTL8_4_TAG_LEN / 2];
u16 etype;
u8 reason;
u8 proto;
u8 port;

if (unlikely(!pskb_may_pull(skb, RTL8_4_TAG_LEN)))
return NULL;

tag = dsa_etype_header_pos_rx(skb);
memcpy(tag16, tag, RTL8_4_TAG_LEN);

/* Parse Realtek EtherType */
etype = ntohs(tag[0]);
etype = ntohs(tag16[0]);
if (unlikely(etype != ETH_P_REALTEK)) {
dev_warn_ratelimited(&dev->dev,
"non-realtek ethertype 0x%04x\n", etype);
return NULL;
return -EPROTO;
}

/* Parse Protocol */
proto = FIELD_GET(RTL8_4_PROTOCOL, ntohs(tag[1]));
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 NULL;
return -EPROTO;
}

/* Parse REASON */
reason = FIELD_GET(RTL8_4_REASON, ntohs(tag[1]));
reason = FIELD_GET(RTL8_4_REASON, ntohs(tag16[1]));

/* Parse TX (switch->CPU) */
port = FIELD_GET(RTL8_4_TX, ntohs(tag[3]));
port = FIELD_GET(RTL8_4_TX, ntohs(tag16[3]));
skb->dev = dsa_master_find_slave(dev, 0, port);
if (!skb->dev) {
dev_warn_ratelimited(&dev->dev,
"could not find slave for port %d\n",
port);
return NULL;
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);

if (reason != RTL8_4_REASON_TRAP)
dsa_default_offload_fwd_mark(skb);
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,
};
module_dsa_tag_driver(rtl8_4_netdev_ops);

MODULE_LICENSE("GPL");
DSA_TAG_DRIVER(rtl8_4_netdev_ops);

MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8_4);

/* 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_4L);

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_LICENSE("GPL");

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