net: hsr: generate supervision frame without HSR/PRP tag

For a switch to offload insertion of HSR/PRP tags, frames must not be
sent to the CPU facing switch port with a tag. Generate supervision frames
(eth type ETH_P_PRP) without HSR v1 (ETH_P_HSR)/PRP tag and rely on
create_tagged_frame which inserts it later. This will allow skipping the
tag insertion for all outgoing frames in the future which is required for
HSR v1/PRP tag insertions to be offloaded.

HSR v0 supervision frames always contain tag information so insertion of
the tag can't be offloaded. IEC 62439-3 Ed.2.0 (HSR v1) specifically
notes that this was changed since v0 to allow offloading.

Signed-off-by: George McCollister <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Tested-by: Vladimir Oltean <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/hsr/hsr_device.c

···
 	.parse	 = eth_header_parse,
 };
 
-static struct sk_buff *hsr_init_skb(struct hsr_port *master, u16 proto)
+static struct sk_buff *hsr_init_skb(struct hsr_port *master)
 {
 	struct hsr_priv *hsr = master->hsr;
 	struct sk_buff *skb;
···
 	 * being, for PRP it is a trailer and for HSR it is a
 	 * header
 	 */
-	skb = dev_alloc_skb(sizeof(struct hsr_tag) +
-			    sizeof(struct hsr_sup_tag) +
+	skb = dev_alloc_skb(sizeof(struct hsr_sup_tag) +
 			    sizeof(struct hsr_sup_payload) + hlen + tlen);
 
 	if (!skb)
···
 
 	skb_reserve(skb, hlen);
 	skb->dev = master->dev;
-	skb->protocol = htons(proto);
 	skb->priority = TC_PRIO_CONTROL;
 
-	if (dev_hard_header(skb, skb->dev, proto,
+	if (dev_hard_header(skb, skb->dev, ETH_P_PRP,
 			    hsr->sup_multicast_addr,
 			    skb->dev->dev_addr, skb->len) <= 0)
 		goto out;
···
 {
 	struct hsr_priv *hsr = master->hsr;
 	__u8 type = HSR_TLV_LIFE_CHECK;
-	struct hsr_tag *hsr_tag = NULL;
 	struct hsr_sup_payload *hsr_sp;
 	struct hsr_sup_tag *hsr_stag;
 	unsigned long irqflags;
 	struct sk_buff *skb;
-	u16 proto;
 
 	*interval = msecs_to_jiffies(HSR_LIFE_CHECK_INTERVAL);
 	if (hsr->announce_count < 3 && hsr->prot_version == 0) {
···
 		hsr->announce_count++;
 	}
 
-	if (!hsr->prot_version)
-		proto = ETH_P_PRP;
-	else
-		proto = ETH_P_HSR;
-
-	skb = hsr_init_skb(master, proto);
+	skb = hsr_init_skb(master);
 	if (!skb) {
 		WARN_ONCE(1, "HSR: Could not send supervision frame\n");
 		return;
-	}
-
-	if (hsr->prot_version > 0) {
-		hsr_tag = skb_put(skb, sizeof(struct hsr_tag));
-		hsr_tag->encap_proto = htons(ETH_P_PRP);
-		set_hsr_tag_LSDU_size(hsr_tag, HSR_V1_SUP_LSDUSIZE);
 	}
 
 	hsr_stag = skb_put(skb, sizeof(struct hsr_sup_tag));
···
 	if (hsr->prot_version > 0) {
 		hsr_stag->sequence_nr = htons(hsr->sup_sequence_nr);
 		hsr->sup_sequence_nr++;
-		hsr_tag->sequence_nr = htons(hsr->sequence_nr);
-		hsr->sequence_nr++;
 	} else {
 		hsr_stag->sequence_nr = htons(hsr->sequence_nr);
 		hsr->sequence_nr++;
···
 	hsr_sp = skb_put(skb, sizeof(struct hsr_sup_payload));
 	ether_addr_copy(hsr_sp->macaddress_A, master->dev->dev_addr);
 
-	if (skb_put_padto(skb, ETH_ZLEN + HSR_HLEN))
+	if (skb_put_padto(skb, ETH_ZLEN))
 		return;
 
 	hsr_forward_skb(skb, master);
···
 	struct hsr_sup_tag *hsr_stag;
 	unsigned long irqflags;
 	struct sk_buff *skb;
-	struct prp_rct *rct;
-	u8 *tail;
 
-	skb = hsr_init_skb(master, ETH_P_PRP);
+	skb = hsr_init_skb(master);
 	if (!skb) {
 		WARN_ONCE(1, "PRP: Could not send supervision frame\n");
 		return;
···
 	hsr_sp = skb_put(skb, sizeof(struct hsr_sup_payload));
 	ether_addr_copy(hsr_sp->macaddress_A, master->dev->dev_addr);
 
-	if (skb_put_padto(skb, ETH_ZLEN + HSR_HLEN)) {
+	if (skb_put_padto(skb, ETH_ZLEN)) {
 		spin_unlock_irqrestore(&master->hsr->seqnr_lock, irqflags);
 		return;
 	}
 
-	tail = skb_tail_pointer(skb) - HSR_HLEN;
-	rct = (struct prp_rct *)tail;
-	rct->PRP_suffix = htons(ETH_P_PRP);
-	set_prp_LSDU_size(rct, HSR_V1_SUP_LSDUSIZE);
-	rct->sequence_nr = htons(hsr->sequence_nr);
-	hsr->sequence_nr++;
 	spin_unlock_irqrestore(&master->hsr->seqnr_lock, irqflags);
 
 	hsr_forward_skb(skb, master);

net/hsr/hsr_forward.c

···
 	set_prp_LSDU_size(trailer, lsdu_size);
 	trailer->sequence_nr = htons(frame->sequence_nr);
 	trailer->PRP_suffix = htons(ETH_P_PRP);
+	skb->protocol = eth_hdr(skb)->h_proto;
 
 	return skb;
 }
···
 	hsr_ethhdr->hsr_tag.encap_proto = hsr_ethhdr->ethhdr.h_proto;
 	hsr_ethhdr->ethhdr.h_proto = htons(proto_version ?
 			ETH_P_HSR : ETH_P_PRP);
+	skb->protocol = hsr_ethhdr->ethhdr.h_proto;
 
 	return skb;
 }
···
 void hsr_fill_frame_info(__be16 proto, struct sk_buff *skb,
 			 struct hsr_frame_info *frame)
 {
-	if (proto == htons(ETH_P_PRP) ||
+	struct hsr_port *port = frame->port_rcv;
+	struct hsr_priv *hsr = port->hsr;
+
+	/* HSRv0 supervisory frames double as a tag so treat them as tagged. */
+	if ((!hsr->prot_version && proto == htons(ETH_P_PRP)) ||
 	    proto == htons(ETH_P_HSR)) {
 		/* HSR tagged frame :- Data or Supervision */
 		frame->skb_std = NULL;