Re: [PATCH net-next v2 1/4] net: hsr: add PRP interlink (RedBox) datapath and duplicate discard

A PRP RedBox proxies SANs that sit behind an interlink port: their frames
must reach the PRP network with the SAN source MAC preserved, and PRP
unicast must be steered between the LAN and the SAN segment correctly.

Add the PRP interlink forwarding rules to prp_drop_frame() and give RedBox
nodes a second duplicate-discard slot so the two LAN copies of a frame
destined to a SAN collapse to a single delivery out the interlink.

The destination classification (is the unicast DA a PRP-network node or a
proxied SAN) is resolved once per frame in fill_frame_info(), gated to PRP
RedBox devices, and cached in struct hsr_frame_info, so prp_drop_frame()
stays O(1) and does not walk the node tables for every candidate egress
port in the softIRQ path. HSR RedBox frame classification is untouched.

Factor the LAN A/B duplicate test into prp_is_lan_dup() so the new PRP
interlink rules do not change hsr_drop_frame() behaviour, including the
NETIF_F_HW_HSR_FWD path which keeps using the LAN-duplicate test only.

Publish the RedBox state before the first hsr_add_port(): the slave and
interlink rx handlers are live from hsr_add_port() on and rtnl does not
stop softirq processing, so a frame could otherwise be handled while
hsr->redbox is still false. hsr_add_node() sizes each node's per-port
sequence state from hsr->redbox; a node learned in that window would get
a single-port sequence block, breaking the interlink duplicate discard
(WARN_ON_ONCE plus duplicate delivery to the SAN) and letting the
supervision sequence-block merge read beyond the source node's allocated
sequence bitmap. Publishing the flag before any port exists makes the
per-node sizing uniform by construction. This is safe: the proxy
announce timer is only armed from hsr_check_announce() once the master
is running, the packet-path readers of hsr->redbox tolerate an empty
proxy node database and an absent interlink port, and the
prune_proxy_timer is still armed only after the interlink port has been
attached successfully.

Additionally bound the supervision sequence-block merge by the smaller
of the two nodes' seq_port_cnt as defense in depth against mismatched
node sizes.

Signed-off-by: Xin Xie <redacted>

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index 5555b71ab19b..5af491ed2b72 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c

@@ -768,6 +768,15 @@ int hsr_dev_finalize(struct net_device *hsr_dev, struct net_device *slave[2],
 	/* Make sure the 1st call to netif_carrier_on() gets through */
 	netif_carrier_off(hsr_dev);
 
+	/* Publish the RedBox state before any port is attached: the rx
+	 * handlers are live from hsr_add_port() on, and hsr_add_node()
+	 * sizes each node's per-port sequence state from hsr->redbox.
+	 */
+	if (interlink) {
+		hsr->redbox = true;
+		ether_addr_copy(hsr->macaddress_redbox, interlink->dev_addr);
+	}
+
 	res = hsr_add_port(hsr, hsr_dev, HSR_PT_MASTER, extack);
 	if (res)
 		goto err_add_master;

@@ -805,8 +814,6 @@ int hsr_dev_finalize(struct net_device *hsr_dev, struct net_device *slave[2],
 		if (res)
 			goto err_unregister;
 
-		hsr->redbox = true;
-		ether_addr_copy(hsr->macaddress_redbox, interlink->dev_addr);
 		mod_timer(&hsr->prune_proxy_timer,
 			  jiffies + msecs_to_jiffies(PRUNE_PROXY_PERIOD));
 	}

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index 0774981a65c1..efcd0acef38c 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c

@@ -440,12 +440,37 @@ static int hsr_xmit(struct sk_buff *skb, struct hsr_port *port,
 	return dev_queue_xmit(skb);
 }
 
+static bool prp_is_lan_dup(struct hsr_frame_info *frame,
+			   struct hsr_port *port)
+{
+	enum hsr_port_type rx = frame->port_rcv->type;
+
+	return (rx == HSR_PT_SLAVE_A && port->type == HSR_PT_SLAVE_B) ||
+	       (rx == HSR_PT_SLAVE_B && port->type == HSR_PT_SLAVE_A);
+}
+
 bool prp_drop_frame(struct hsr_frame_info *frame, struct hsr_port *port)
 {
-	return ((frame->port_rcv->type == HSR_PT_SLAVE_A &&
-		 port->type == HSR_PT_SLAVE_B) ||
-		(frame->port_rcv->type == HSR_PT_SLAVE_B &&
-		 port->type == HSR_PT_SLAVE_A));
+	enum hsr_port_type rx = frame->port_rcv->type;
+
+	/* Supervision frames are not delivered to a SAN on the interlink. */
+	if (frame->is_supervision && port->type == HSR_PT_INTERLINK)
+		return true;
+
+	if (prp_is_lan_dup(frame, port))
+		return true;

+
+	/* LAN to interlink: keep PRP-network unicast off the SAN segment. */
+	if ((rx == HSR_PT_SLAVE_A || rx == HSR_PT_SLAVE_B) &&
+	    port->type == HSR_PT_INTERLINK)
+		return frame->dst_in_node_db;
+
+	/* Interlink to LAN: keep SAN-to-SAN unicast local. */
+	if ((port->type == HSR_PT_SLAVE_A || port->type == HSR_PT_SLAVE_B) &&
+	    rx == HSR_PT_INTERLINK)
+		return frame->dst_in_proxy_node_db;
+
+	return false;
 }
 
 bool hsr_drop_frame(struct hsr_frame_info *frame, struct hsr_port *port)

@@ -453,7 +478,7 @@ bool hsr_drop_frame(struct hsr_frame_info *frame, struct hsr_port *port)
 	struct sk_buff *skb;
 
 	if (port->dev->features & NETIF_F_HW_HSR_FWD)
-		return prp_drop_frame(frame, port);
+		return prp_is_lan_dup(frame, port);