[RFC PATCH net-next 4/4] net: dsa: create a helper for locating EtherType DSA headers on TX

[Vladimir Oltean <vladimir.oltean@nxp.com>]

Create a similar helper for locating the offset to the DSA header
relative to skb->data, and make the existing EtherType header taggers to
use it.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 net/dsa/dsa_priv.h    |  9 +++++++++
 net/dsa/tag_dsa.c     |  6 +++---
 net/dsa/tag_lan9303.c |  3 ++-
 net/dsa/tag_mtk.c     |  2 +-
 net/dsa/tag_qca.c     |  2 +-
 net/dsa/tag_rtl4_a.c  |  2 +-
 net/dsa/tag_sja1105.c | 16 ++++++----------
 7 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index ee194df68902..9ea637832ea9 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -521,6 +521,15 @@ static inline void *dsa_etype_header_pos_rx(struct sk_buff *skb)
 	return skb->data - 2;
 }
 
+/* On TX, skb->data points to skb_mac_header(skb), which means that EtherType
+ * header taggers start exactly where the EtherType is (the EtherType is
+ * treated as part of the DSA header).
+ */
+static inline void *dsa_etype_header_pos_tx(struct sk_buff *skb)
+{
+	return skb->data + 2 * ETH_ALEN;
+}
+
 /* switch.c */
 int dsa_switch_register_notifier(struct dsa_switch *ds);
 void dsa_switch_unregister_notifier(struct dsa_switch *ds);
diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c
index 2eeabab27078..77d0ce89ab77 100644
--- a/net/dsa/tag_dsa.c
+++ b/net/dsa/tag_dsa.c
@@ -170,7 +170,7 @@ static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 		}
 
 		/* Construct tagged DSA tag from 802.1Q tag. */
-		dsa_header = skb->data + 2 * ETH_ALEN + extra;
+		dsa_header = dsa_etype_header_pos_tx(skb) + extra;
 		dsa_header[0] = (cmd << 6) | 0x20 | tag_dev;
 		dsa_header[1] = tag_port << 3;
 
@@ -184,7 +184,7 @@ static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 		dsa_alloc_etype_header(skb, DSA_HLEN + extra);
 
 		/* Construct untagged DSA tag. */
-		dsa_header = skb->data + 2 * ETH_ALEN + extra;
+		dsa_header = dsa_etype_header_pos_tx(skb) + extra;
 
 		dsa_header[0] = (cmd << 6) | tag_dev;
 		dsa_header[1] = tag_port << 3;
@@ -360,7 +360,7 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (!skb)
 		return NULL;
 
-	edsa_header = skb->data + 2 * ETH_ALEN;
+	edsa_header = dsa_etype_header_pos_tx(skb);
 	edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 	edsa_header[1] = ETH_P_EDSA & 0xff;
 	edsa_header[2] = 0x00;
diff --git a/net/dsa/tag_lan9303.c b/net/dsa/tag_lan9303.c
index d06951273127..cb548188f813 100644
--- a/net/dsa/tag_lan9303.c
+++ b/net/dsa/tag_lan9303.c
@@ -64,7 +64,8 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
 	/* make room between MACs and Ether-Type */
 	dsa_alloc_etype_header(skb, LAN9303_TAG_LEN);
 
-	lan9303_tag = (__be16 *)(skb->data + 2 * ETH_ALEN);
+	lan9303_tag = dsa_etype_header_pos_tx(skb);
+
 	tag = lan9303_xmit_use_arl(dp, skb->data) ?
 		LAN9303_TAG_TX_USE_ALR :
 		dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
diff --git a/net/dsa/tag_mtk.c b/net/dsa/tag_mtk.c
index a75f99e5fbe3..415d8ece242a 100644
--- a/net/dsa/tag_mtk.c
+++ b/net/dsa/tag_mtk.c
@@ -44,7 +44,7 @@ static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 		dsa_alloc_etype_header(skb, MTK_HDR_LEN);
 	}
 
-	mtk_tag = skb->data + 2 * ETH_ALEN;
+	mtk_tag = dsa_etype_header_pos_tx(skb);
 
 	/* Mark tag attribute on special tag insertion to notify hardware
 	 * whether that's a combined special tag with 802.1Q header.
diff --git a/net/dsa/tag_qca.c b/net/dsa/tag_qca.c
index 79a81569d7ec..1ea9401b8ace 100644
--- a/net/dsa/tag_qca.c
+++ b/net/dsa/tag_qca.c
@@ -37,7 +37,7 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 	skb_push(skb, QCA_HDR_LEN);
 
 	dsa_alloc_etype_header(skb, QCA_HDR_LEN);
-	phdr = (__be16 *)(skb->data + 2 * ETH_ALEN);
+	phdr = dsa_etype_header_pos_tx(skb);
 
 	/* Set the version field, and set destination port information */
 	hdr = QCA_HDR_VERSION << QCA_HDR_XMIT_VERSION_S |
diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c
index 947247d2124e..40811bab4d09 100644
--- a/net/dsa/tag_rtl4_a.c
+++ b/net/dsa/tag_rtl4_a.c
@@ -48,7 +48,7 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
 	skb_push(skb, RTL4_A_HDR_LEN);
 
 	dsa_alloc_etype_header(skb, RTL4_A_HDR_LEN);
-	tag = skb->data + 2 * ETH_ALEN;
+	tag = dsa_etype_header_pos_tx(skb);
 
 	/* Set Ethertype */
 	p = (__be16 *)tag;
diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 34f3212a6703..0ed379a28ab6 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -223,7 +223,6 @@ static struct sk_buff *sja1110_xmit(struct sk_buff *skb,
 	u16 tx_vid = dsa_8021q_tx_vid(dp->ds, dp->index);
 	u16 queue_mapping = skb_get_queue_mapping(skb);
 	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);
-	struct ethhdr *eth_hdr;
 	__be32 *tx_trailer;
 	__be16 *tx_header;
 	int trailer_pos;
@@ -249,23 +248,20 @@ static struct sk_buff *sja1110_xmit(struct sk_buff *skb,
 
 	trailer_pos = skb->len;
 
-	/* On TX, skb->data points to skb_mac_header(skb) */
-	eth_hdr = (struct ethhdr *)skb->data;
-	tx_header = (__be16 *)(eth_hdr + 1);
+	tx_header = dsa_etype_header_pos_tx(skb);
 	tx_trailer = skb_put(skb, SJA1110_TX_TRAILER_LEN);
 
-	eth_hdr->h_proto = htons(ETH_P_SJA1110);
-
-	*tx_header = htons(SJA1110_HEADER_HOST_TO_SWITCH |
-			   SJA1110_TX_HEADER_HAS_TRAILER |
-			   SJA1110_TX_HEADER_TRAILER_POS(trailer_pos));
+	tx_header[0] = htons(ETH_P_SJA1110);
+	tx_header[1] = htons(SJA1110_HEADER_HOST_TO_SWITCH |
+			     SJA1110_TX_HEADER_HAS_TRAILER |
+			     SJA1110_TX_HEADER_TRAILER_POS(trailer_pos));
 	*tx_trailer = cpu_to_be32(SJA1110_TX_TRAILER_PRIO(pcp) |
 				  SJA1110_TX_TRAILER_SWITCHID(dp->ds->index) |
 				  SJA1110_TX_TRAILER_DESTPORTS(BIT(dp->index)));
 	if (clone) {
 		u8 ts_id = SJA1105_SKB_CB(clone)->ts_id;
 
-		*tx_header |= htons(SJA1110_TX_HEADER_TAKE_TS);
+		tx_header[1] |= htons(SJA1110_TX_HEADER_TAKE_TS);
 		*tx_trailer |= cpu_to_be32(SJA1110_TX_TRAILER_TSTAMP_ID(ts_id));
 	}
 
-- 
2.25.1