[RFC net-next v2 3/3] bonding: use skb_vlan_push() for probe tags

[Xiang Mei (Microsoft)]

bond_handle_vlan() open-coded the VLAN stacking with
vlan_insert_tag_set_proto() for the inner tags and
__vlan_hwaccel_put_tag() for the outer one.  Now that the callers push
the link-layer header before tagging (arp_create() for ARP,
bond_ns_add_llhdr() for NS), the tags can be inserted with
skb_vlan_push(), which handles both the inline and the offloaded tag
and grows the headroom as needed.

Walk the tags from the innermost so each skb_vlan_push() moves the
previous tag into the frame, and free the skb on failure
(skb_vlan_push() does not).  Reset the MAC header in bond_arp_send()
so skb_vlan_push() finds skb->data at the Ethernet header.

Signed-off-by: Xiang Mei (Microsoft) <xmei5@xxxxxxx>
---
 drivers/net/bonding/bond_main.c | 38 ++++++++++++++-------------------
 1 file changed, 16 insertions(+), 22 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index d5a7a7dd1eb2..0da57e9bb47c 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2973,37 +2973,28 @@ static bool bond_handle_vlan(struct slave *slave, struct bond_vlan_tag *tags,
 {
 	struct net_device *bond_dev = slave->bond->dev;
 	struct net_device *slave_dev = slave->dev;
-	struct bond_vlan_tag *outer_tag = tags;
+	int i;
 
 	if (!tags || tags->vlan_proto == BOND_VLAN_PROTO_NONE)
 		return true;
 
-	tags++;
+	for (i = 0; tags[i].vlan_proto != BOND_VLAN_PROTO_NONE; i++)
+		;
 
-	/* Go through all the tags backwards and add them to the packet */
-	while (tags->vlan_proto != BOND_VLAN_PROTO_NONE) {
-		if (!tags->vlan_id) {
-			tags++;
+	/* tags[0] is the outermost tag; push inner-first so each skb_vlan_push()
+	 * moves the previous tag into the frame.
+	 */
+	while (i--) {
+		if (!tags[i].vlan_id)
 			continue;
-		}
 
-		slave_dbg(bond_dev, slave_dev, "inner tag: proto %X vid %X\n",
-			  ntohs(outer_tag->vlan_proto), tags->vlan_id);
-		skb = vlan_insert_tag_set_proto(skb, tags->vlan_proto,
-						tags->vlan_id);
-		if (!skb) {
-			net_err_ratelimited("failed to insert inner VLAN tag\n");
+		slave_dbg(bond_dev, slave_dev, "tag: proto %X vid %X\n",
+			  ntohs(tags[i].vlan_proto), tags[i].vlan_id);
+		if (skb_vlan_push(skb, tags[i].vlan_proto, tags[i].vlan_id)) {
+			net_err_ratelimited("failed to insert VLAN tag\n");
+			kfree_skb(skb);
 			return false;
 		}
-
-		tags++;
-	}
-	/* Set the outer tag */
-	if (outer_tag->vlan_id) {
-		slave_dbg(bond_dev, slave_dev, "outer tag: proto %X vid %X\n",
-			  ntohs(outer_tag->vlan_proto), outer_tag->vlan_id);
-		__vlan_hwaccel_put_tag(skb, outer_tag->vlan_proto,
-				       outer_tag->vlan_id);
 	}
 
 	return true;
@@ -3031,6 +3022,9 @@ static void bond_arp_send(struct slave *slave, int arp_op, __be32 dest_ip,
 		return;
 	}
 
+	/* arp_create() has already pushed the link-layer header */
+	skb_reset_mac_header(skb);
+
 	if (bond_handle_vlan(slave, tags, skb)) {
 		slave_update_last_tx(slave);
 		arp_xmit(skb);
-- 
2.43.0