diff mbox series

[net-next,v4,2/3] net: dsa: tag_rtl8_4: add rtl8_4t trailing variant

Message ID 20220227035920.19101-3-luizluca@gmail.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net: dsa: realtek: add rtl8_4t tag | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 18 this patch: 18
netdev/cc_maintainers success CCed 7 of 7 maintainers
netdev/build_clang success Errors and warnings before: 24 this patch: 24
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 23 this patch: 23
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns WARNING: line length of 88 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Luiz Angelo Daros de Luca Feb. 27, 2022, 3:59 a.m. UTC 
Realtek switches supports the same tag both before ethertype or between
payload and the CRC.

Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
---
 include/net/dsa.h    |   2 +
 net/dsa/tag_rtl8_4.c | 150 +++++++++++++++++++++++++++++++++----------
 2 files changed, 117 insertions(+), 35 deletions(-)

Comments

Alvin Šipraga Feb. 28, 2022, 12:13 p.m. UTC | #1 
Luiz Angelo Daros de Luca <luizluca@gmail.com> writes:

> Realtek switches supports the same tag both before ethertype or between
> payload and the CRC.
>
> Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
> Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>

Hi Luiz,

Please note that you should normally put my Reviewed-by after your
S-o-b. After your v1 (and assuming you remembered your S-o-b) it should
be treated as append-only. Gives some chronology to the review process.

Kind regards,
Alvin
Vladimir Oltean Feb. 28, 2022, 2:50 p.m. UTC | #2 
On Sun, Feb 27, 2022 at 12:59:19AM -0300, Luiz Angelo Daros de Luca wrote:
> Realtek switches supports the same tag both before ethertype or between
> payload and the CRC.
> 
> Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
> Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
> ---
>  include/net/dsa.h    |   2 +
>  net/dsa/tag_rtl8_4.c | 150 +++++++++++++++++++++++++++++++++----------
>  2 files changed, 117 insertions(+), 35 deletions(-)
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index fd1f62a6e0a8..b688ced04b0e 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -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,
> @@ -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;
> diff --git a/net/dsa/tag_rtl8_4.c b/net/dsa/tag_rtl8_4.c
> index 02686ad4045d..bf34b257b193 100644
> --- a/net/dsa/tag_rtl8_4.c
> +++ b/net/dsa/tag_rtl8_4.c
> @@ -9,11 +9,6 @@
>   *
>   * This tag header has the following format:

If you generalize the comments, then it is no longer a "header".

>   *
> - *  -------------------------------------------
> - *  | MAC DA | MAC SA | 8 byte tag | Type | ...
> - *  -------------------------------------------
> - *     _______________/            \______________________________________
> - *    /                                                                   \
>   *  0                                  7|8                                 15
>   *  |-----------------------------------+-----------------------------------|---
>   *  |                               (16-bit)                                | ^
> @@ -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 checksum the packet in software before adding the tag.

s/checksum/checksums/

> + *
>   */
>  
>  #include <linux/bitfield.h>
> @@ -84,87 +97,133 @@
>  #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 and hardware based checksum

"either" is typically used with "or", not with "and"

> +	 */
> +	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,
> @@ -172,7 +231,28 @@ static const struct dsa_device_ops rtl8_4_netdev_ops = {
>  	.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");
> -- 
> 2.35.1
>
Vladimir Oltean Feb. 28, 2022, 3:22 p.m. UTC | #3 
On Mon, Feb 28, 2022 at 12:13:28PM +0000, Alvin Šipraga wrote:
> Luiz Angelo Daros de Luca <luizluca@gmail.com> writes:
> 
> > Realtek switches supports the same tag both before ethertype or between
> > payload and the CRC.
> >
> > Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
> > Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
> 
> Hi Luiz,
> 
> Please note that you should normally put my Reviewed-by after your
> S-o-b. After your v1 (and assuming you remembered your S-o-b) it should
> be treated as append-only. Gives some chronology to the review process.

I don't know if this is a hard and fast rule, but it is also how I do
things, and how b4 applies the tags as well. But I've seen people do
otherwise too.
diff mbox series

Patch

diff --git a/include/net/dsa.h b/include/net/dsa.h
index fd1f62a6e0a8..b688ced04b0e 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -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,
@@ -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;
diff --git a/net/dsa/tag_rtl8_4.c b/net/dsa/tag_rtl8_4.c
index 02686ad4045d..bf34b257b193 100644
--- a/net/dsa/tag_rtl8_4.c
+++ b/net/dsa/tag_rtl8_4.c
@@ -9,11 +9,6 @@ 
  *
  * This tag header has the following format:
  *
- *  -------------------------------------------
- *  | MAC DA | MAC SA | 8 byte tag | Type | ...
- *  -------------------------------------------
- *     _______________/            \______________________________________
- *    /                                                                   \
  *  0                                  7|8                                 15
  *  |-----------------------------------+-----------------------------------|---
  *  |                               (16-bit)                                | ^
@@ -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 checksum the packet in software before adding the tag.
+ *
  */
 
 #include <linux/bitfield.h>
@@ -84,87 +97,133 @@ 
 #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 and 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,
@@ -172,7 +231,28 @@  static const struct dsa_device_ops rtl8_4_netdev_ops = {
 	.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");