macsec: add support for IFLA_MACSEC_OFFLOAD in macsec_changelink

Add support for changing Macsec offload selection through the
netlink layer by implementing the relevant changes in
macsec_changelink.

Since the handling in macsec_changelink is similar to macsec_upd_offload,
update macsec_upd_offload to use a common helper function to avoid
duplication.

Example for setting offload for a macsec device:
    ip link set macsec0 type macsec offload mac
Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/macsec.c

@@ -2583,16 +2583,56 @@ static bool macsec_is_configured(struct macsec_dev *macsec)
 	return false;
 }
 
+static int macsec_update_offload(struct net_device *dev, enum macsec_offload offload)
+{
+	enum macsec_offload prev_offload;
+	const struct macsec_ops *ops;
+	struct macsec_context ctx;
+	struct macsec_dev *macsec;
+	int ret = 0;
+
+	macsec = macsec_priv(dev);
+
+	/* Check if the offloading mode is supported by the underlying layers */
+	if (offload != MACSEC_OFFLOAD_OFF &&
+	    !macsec_check_offload(offload, macsec))
+		return -EOPNOTSUPP;
+
+	/* Check if the net device is busy. */
+	if (netif_running(dev))
+		return -EBUSY;
+
+	/* Check if the device already has rules configured: we do not support
+	 * rules migration.
+	 */
+	if (macsec_is_configured(macsec))
+		return -EBUSY;
+
+	prev_offload = macsec->offload;
+
+	ops = __macsec_get_ops(offload == MACSEC_OFFLOAD_OFF ? prev_offload : offload,
+			       macsec, &ctx);
+	if (!ops)
+		return -EOPNOTSUPP;
+
+	macsec->offload = offload;
+
+	ctx.secy = &macsec->secy;
+	ret = offload == MACSEC_OFFLOAD_OFF ? macsec_offload(ops->mdo_del_secy, &ctx)
+					    : macsec_offload(ops->mdo_add_secy, &ctx);
+	if (ret)
+		macsec->offload = prev_offload;
+
+	return ret;
+}
+
 static int macsec_upd_offload(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr *tb_offload[MACSEC_OFFLOAD_ATTR_MAX + 1];
-	enum macsec_offload offload, prev_offload;
-	int (*func)(struct macsec_context *ctx);
 	struct nlattr **attrs = info->attrs;
-	struct net_device *dev;
-	const struct macsec_ops *ops;
-	struct macsec_context ctx;
+	enum macsec_offload offload;
 	struct macsec_dev *macsec;
+	struct net_device *dev;
 	int ret = 0;
 
 	if (!attrs[MACSEC_ATTR_IFINDEX])
@@ -2621,55 +2661,9 @@ static int macsec_upd_offload(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	offload = nla_get_u8(tb_offload[MACSEC_OFFLOAD_ATTR_TYPE]);
-	if (macsec->offload == offload)
-		goto out;
-
-	/* Check if the offloading mode is supported by the underlying layers */
-	if (offload != MACSEC_OFFLOAD_OFF &&
-	    !macsec_check_offload(offload, macsec)) {
-		ret = -EOPNOTSUPP;
-		goto out;
-	}
 
-	/* Check if the net device is busy. */
-	if (netif_running(dev)) {
-		ret = -EBUSY;
-		goto out;
-	}
-
-	prev_offload = macsec->offload;
-	macsec->offload = offload;
-
-	/* Check if the device already has rules configured: we do not support
-	 * rules migration.
-	 */
-	if (macsec_is_configured(macsec)) {
-		ret = -EBUSY;
-		goto rollback;
-	}
-
-	ops = __macsec_get_ops(offload == MACSEC_OFFLOAD_OFF ? prev_offload : offload,
-			       macsec, &ctx);
-	if (!ops) {
-		ret = -EOPNOTSUPP;
-		goto rollback;
-	}
-
-	if (prev_offload == MACSEC_OFFLOAD_OFF)
-		func = ops->mdo_add_secy;
-	else
-		func = ops->mdo_del_secy;
-
-	ctx.secy = &macsec->secy;
-	ret = macsec_offload(func, &ctx);
-	if (ret)
-		goto rollback;
-
-	rtnl_unlock();
-	return 0;
-
-rollback:
-	macsec->offload = prev_offload;
+	if (macsec->offload != offload)
+		ret = macsec_update_offload(dev, offload);
 out:
 	rtnl_unlock();
 	return ret;
@@ -3817,6 +3811,8 @@ static int macsec_changelink(struct net_device *dev, struct nlattr *tb[],
 			     struct netlink_ext_ack *extack)
 {
 	struct macsec_dev *macsec = macsec_priv(dev);
+	bool macsec_offload_state_change = false;
+	enum macsec_offload offload;
 	struct macsec_tx_sc tx_sc;
 	struct macsec_secy secy;
 	int ret;
@@ -3840,8 +3836,18 @@ static int macsec_changelink(struct net_device *dev, struct nlattr *tb[],
 	if (ret)
 		goto cleanup;
 
+	if (data[IFLA_MACSEC_OFFLOAD]) {
+		offload = nla_get_u8(data[IFLA_MACSEC_OFFLOAD]);
+		if (macsec->offload != offload) {
+			macsec_offload_state_change = true;
+			ret = macsec_update_offload(dev, offload);
+			if (ret)
+				goto cleanup;
+		}
+	}
+
 	/* If h/w offloading is available, propagate to the device */
-	if (macsec_is_offloaded(macsec)) {
+	if (!macsec_offload_state_change && macsec_is_offloaded(macsec)) {
 		const struct macsec_ops *ops;
 		struct macsec_context ctx;