linux-kernel - [PATCH net v2] macsec: MACsec SCI assignment for ES = 0

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Message-ID: <20250604113213.2595524-1-carlos.fernandez@technica-engineering.de>
Date: Wed,  4 Jun 2025 13:31:54 +0200
From: carlos.fernandez@...hnica-engineering.de
To: andreu.montiel@...hnica-engineering.de
Cc: carlos.fernandez@...hnica-engineering.de,
	Andreu Montiel <Andreu.Montiel@...hnica-engineering.de>,
	Sabrina Dubroca <sd@...asysnail.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net v2] macsec: MACsec SCI assignment for ES = 0

From: Carlos Fernandez <carlos.fernandez@...hnica-engineering.de>

According to 802.1AE standard, when ES and SC flags in TCI are zero,
used SCI should be the current active SC_RX. Current code uses the
header MAC address. Without this patch, when ES flag is 0 (using a
bridge or switch), header MAC will not fit the SCI and MACSec frames
will be discarted.

Fixes: c09440f7dcb3 ("macsec: introduce IEEE 802.1AE driver")

Co-developed-by: Andreu Montiel <Andreu.Montiel@...hnica-engineering.de>
Signed-off-by: Andreu Montiel <Andreu.Montiel@...hnica-engineering.de>
Signed-off-by: Carlos Fernandez <carlos.fernandez@...hnica-engineering.de>
---
v2: 
* Active sci lookup logic in a separate helper.
* Unnecessary loops avoided. 
* Check RXSC is exactly one for lower device.
* Drops frame in case of error.

v1: https://patchwork.kernel.org/project/netdevbpf/patch/20250529124455.2761783-1-carlos.fernandez@technica-engineering.de/#26409053

 drivers/net/macsec.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 3d315e30ee47..976927e715fd 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -247,15 +247,38 @@ static sci_t make_sci(const u8 *addr, __be16 port)
 	return sci;
 }
 
-static sci_t macsec_frame_sci(struct macsec_eth_header *hdr, bool sci_present)
+static sci_t macsec_active_sci(struct macsec_secy *secy)
 {
-	sci_t sci;
+	struct macsec_rx_sc *rx_sc = rcu_dereference_bh(secy->rx_sc);
+
+	/* Case single RX SC */
+	if (rx_sc && !rcu_dereference_bh(rx_sc->next))
+		return (rx_sc->active) ? rx_sc->sci : 0;
+	/* Case no RX SC or multiple */
+	else
+		return 0;
+}
+
+static sci_t macsec_frame_sci(struct macsec_eth_header *hdr, bool sci_present,
+			      struct macsec_rxh_data *rxd)
+{
+	struct macsec_dev *macsec;
+	sci_t sci = 0;
 
-	if (sci_present)
+	/* SC = 1 */
+	if (sci_present) {
 		memcpy(&sci, hdr->secure_channel_id,
 		       sizeof(hdr->secure_channel_id));
-	else
+	/* SC = 0; ES = 0 */
+	} else if ((!(hdr->tci_an & (MACSEC_TCI_ES | MACSEC_TCI_SC))) &&
+		   (list_is_singular(&rxd->secys))) {
+		/* Only one SECY should exist on this scenario */
+		macsec = list_first_or_null_rcu(&rxd->secys, struct macsec_dev, secys);
+		if (macsec)
+			return macsec_active_sci(&macsec->secy);
+	} else {
 		sci = make_sci(hdr->eth.h_source, MACSEC_PORT_ES);
+	}
 
 	return sci;
 }
@@ -1156,11 +1179,14 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 
 	macsec_skb_cb(skb)->has_sci = !!(hdr->tci_an & MACSEC_TCI_SC);
 	macsec_skb_cb(skb)->assoc_num = hdr->tci_an & MACSEC_AN_MASK;
-	sci = macsec_frame_sci(hdr, macsec_skb_cb(skb)->has_sci);
 
 	rcu_read_lock();
 	rxd = macsec_data_rcu(skb->dev);
 
+	sci = macsec_frame_sci(hdr, macsec_skb_cb(skb)->has_sci, rxd);
+	if (!sci)
+		goto drop;
+
 	list_for_each_entry_rcu(macsec, &rxd->secys, secys) {
 		struct macsec_rx_sc *sc = find_rx_sc(&macsec->secy, sci);
 
-- 
2.43.0