Merge branch 'dsa-skb_mac_header'

Vladimir Oltean says:

====================
Remove skb_mac_header() dependency in DSA xmit path

Eric started working on removing skb_mac_header() assumptions from the
networking xmit path, and I offered to help for DSA:
https://lore.kernel.org/netdev/20230321164519.1286357-1-edumazet@google.com/

The majority of this patch set is a straightforward replacement of
skb_mac_header() with skb->data (hidden either behind skb_eth_hdr(), or
behind skb_vlan_eth_hdr()). The only patch which is more "interesting"
is 9/9.

Another potential caller of __skb_vlan_pop() on xmit (and therefore
also of skb_mac_header()) is tcf_vlan_act(), but I haven't had the time
to investigate that (enough to submit changes other than what's here).

v1->v2:
- 09/09: document the vlan_tci argument of vlan_remove_tag() in the kdoc

v1 at:
https://lore.kernel.org/netdev/20230322233823.1806736-1-vladimir.oltean@nxp.com/

Cc: Madalin Bucur <madalin.bucur@nxp.com>
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 33 insertions, 3 deletions

diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 6864b89ef868..0f40f379d75c 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -62,6 +62,14 @@ static inline struct vlan_ethhdr *vlan_eth_hdr(const struct sk_buff *skb)
 	return (struct vlan_ethhdr *)skb_mac_header(skb);
 }
 
+/* Prefer this version in TX path, instead of
+ * skb_reset_mac_header() + vlan_eth_hdr()
+ */
+static inline struct vlan_ethhdr *skb_vlan_eth_hdr(const struct sk_buff *skb)
+{
+	return (struct vlan_ethhdr *)skb->data;
+}
+
 #define VLAN_PRIO_MASK		0xe000 /* Priority Code Point */
 #define VLAN_PRIO_SHIFT		13
 #define VLAN_CFI_MASK		0x1000 /* Canonical Format Indicator / Drop Eligible Indicator */
@@ -351,7 +359,8 @@ static inline int __vlan_insert_inner_tag(struct sk_buff *skb,
 	/* Move the mac header sans proto to the beginning of the new header. */
 	if (likely(mac_len > ETH_TLEN))
 		memmove(skb->data, skb->data + VLAN_HLEN, mac_len - ETH_TLEN);
-	skb->mac_header -= VLAN_HLEN;
+	if (skb_mac_header_was_set(skb))
+		skb->mac_header -= VLAN_HLEN;
 
 	veth = (struct vlan_ethhdr *)(skb->data + mac_len - ETH_HLEN);
 
@@ -528,7 +537,7 @@ static inline void __vlan_hwaccel_put_tag(struct sk_buff *skb,
  */
 static inline int __vlan_get_tag(const struct sk_buff *skb, u16 *vlan_tci)
 {
-	struct vlan_ethhdr *veth = (struct vlan_ethhdr *)skb->data;
+	struct vlan_ethhdr *veth = skb_vlan_eth_hdr(skb);
 
 	if (!eth_type_vlan(veth->h_vlan_proto))
 		return -EINVAL;
@@ -677,6 +686,27 @@ static inline void vlan_set_encap_proto(struct sk_buff *skb,
 }
 
 /**
+ * vlan_remove_tag - remove outer VLAN tag from payload
+ * @skb: skbuff to remove tag from
+ * @vlan_tci: buffer to store value
+ *
+ * Expects the skb to contain a VLAN tag in the payload, and to have skb->data
+ * pointing at the MAC header.
+ *
+ * Returns a new pointer to skb->data, or NULL on failure to pull.
+ */
+static inline void *vlan_remove_tag(struct sk_buff *skb, u16 *vlan_tci)
+{
+	struct vlan_hdr *vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
+
+	*vlan_tci = ntohs(vhdr->h_vlan_TCI);
+
+	memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
+	vlan_set_encap_proto(skb, vhdr);
+	return __skb_pull(skb, VLAN_HLEN);
+}
+
+/**
  * skb_vlan_tagged - check if skb is vlan tagged.
  * @skb: skbuff to query
  *
@@ -712,7 +742,7 @@ static inline bool skb_vlan_tagged_multi(struct sk_buff *skb)
 		if (unlikely(!pskb_may_pull(skb, VLAN_ETH_HLEN)))
 			return false;
 
-		veh = (struct vlan_ethhdr *)skb->data;
+		veh = skb_vlan_eth_hdr(skb);
 		protocol = veh->h_vlan_encapsulated_proto;
 	}