[PATCH net-next v7 2/8] hsr: Use skb_clone() while adding the HSR header

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

hsr_create_tagged_frame() creates a new skb where the HSR header can be
prepended via __pskb_copy(). This does not copy the skb_shared_info part
of the original skb so any timestamp request is lost.

An alternative is to use skb_clone() where the skb_shared_info part is
shared and then skb_cow_head() to make the header part writeable. This
avoids touching manually the tx_flags and tskey members.
Using skb_clone() allows also return early (after the clone) in the
offloaded case so this can be unified a bit.

This is a prepartion for PTP handling where timestatmps are requested.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 net/hsr/hsr_forward.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index 7734a521a96c2..6c0b1f467940d 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -342,33 +342,41 @@ struct sk_buff *hsr_create_tagged_frame(struct hsr_frame_info *frame,
 		/* set the lane id properly */
 		hsr_set_path_id(frame, hsr_ethhdr, port);
 		return skb_clone(frame->skb_hsr, GFP_ATOMIC);
-	} else if (port->dev->features & NETIF_F_HW_HSR_TAG_INS) {
-		return skb_clone(frame->skb_std, GFP_ATOMIC);
 	}
 
-	/* Create the new skb with enough headroom to fit the HSR tag */
-	skb = __pskb_copy(frame->skb_std,
-			  skb_headroom(frame->skb_std) + HSR_HLEN, GFP_ATOMIC);
+	skb = skb_clone(frame->skb_std, GFP_ATOMIC);
 	if (!skb)
 		return NULL;
-	skb_reset_mac_header(skb);
 
-	if (skb->ip_summed == CHECKSUM_PARTIAL)
-		skb->csum_start += HSR_HLEN;
+	if (port->dev->features & NETIF_F_HW_HSR_TAG_INS)
+		return skb;
+
+	/* Ensure the cloned skb has enough headroom to fit the HSR tag */
+	if (skb_cow_head(skb, HSR_HLEN))
+		goto err;
 
 	movelen = ETH_HLEN;
 	if (frame->is_vlan)
 		movelen += VLAN_HLEN;
 
+	/* The entire header area needs to be linear */
+	if (!pskb_may_pull(skb, movelen))
+		goto err;
+
 	src = skb_mac_header(skb);
 	dst = skb_push(skb, HSR_HLEN);
 	memmove(dst, src, movelen);
+	skb_set_network_header(skb, HSR_HLEN + movelen);
 	skb_reset_mac_header(skb);
+	skb_reset_mac_len(skb);
 
 	/* skb_put_padto free skb on error and hsr_fill_tag returns NULL in
 	 * that case
 	 */
 	return hsr_fill_tag(skb, frame, port, port->hsr->prot_version);
+err:
+	kfree_skb(skb);
+	return NULL;
 }
 
 struct sk_buff *prp_create_tagged_frame(struct hsr_frame_info *frame,

-- 
2.55.0