net: macsec: add nla support for changing the offloading selection

MACsec offloading to underlying hardware devices is disabled by default
(the software implementation is used). This patch adds support for
changing this setting through the MACsec netlink interface. Many checks
are done when enabling offloading on a given MACsec interface as there
are limitations (it must be supported by the hardware, only a single
interface can be offloaded on a given physical device at a time, rules
can't be moved for now).

Signed-off-by: Antoine Tenart <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/macsec.c

···
 	[MACSEC_ATTR_IFINDEX] = { .type = NLA_U32 },
 	[MACSEC_ATTR_RXSC_CONFIG] = { .type = NLA_NESTED },
 	[MACSEC_ATTR_SA_CONFIG] = { .type = NLA_NESTED },
+	[MACSEC_ATTR_OFFLOAD] = { .type = NLA_NESTED },
 };
 
 static const struct nla_policy macsec_genl_rxsc_policy[NUM_MACSEC_RXSC_ATTR] = {
···
 				   .len = MACSEC_KEYID_LEN, },
 	[MACSEC_SA_ATTR_KEY] = { .type = NLA_BINARY,
 				 .len = MACSEC_MAX_KEY_LEN, },
+};
+
+static const struct nla_policy macsec_genl_offload_policy[NUM_MACSEC_OFFLOAD_ATTR] = {
+	[MACSEC_OFFLOAD_ATTR_TYPE] = { .type = NLA_U8 },
 };
 
 /* Offloads an operation to a device driver */
···
 	return ret;
 }
 
+static bool macsec_is_configured(struct macsec_dev *macsec)
+{
+	struct macsec_secy *secy = &macsec->secy;
+	struct macsec_tx_sc *tx_sc = &secy->tx_sc;
+	int i;
+
+	if (secy->n_rx_sc > 0)
+		return true;
+
+	for (i = 0; i < MACSEC_NUM_AN; i++)
+		if (tx_sc->sa[i])
+			return true;
+
+	return false;
+}
+
+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, *loop_dev;
+	const struct macsec_ops *ops;
+	struct macsec_context ctx;
+	struct macsec_dev *macsec;
+	struct net *loop_net;
+	int ret;
+
+	if (!attrs[MACSEC_ATTR_IFINDEX])
+		return -EINVAL;
+
+	if (!attrs[MACSEC_ATTR_OFFLOAD])
+		return -EINVAL;
+
+	if (nla_parse_nested_deprecated(tb_offload, MACSEC_OFFLOAD_ATTR_MAX,
+					attrs[MACSEC_ATTR_OFFLOAD],
+					macsec_genl_offload_policy, NULL))
+		return -EINVAL;
+
+	dev = get_dev_from_nl(genl_info_net(info), attrs);
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+	macsec = macsec_priv(dev);
+
+	offload = nla_get_u8(tb_offload[MACSEC_OFFLOAD_ATTR_TYPE]);
+	if (macsec->offload == offload)
+		return 0;
+
+	/* Check if the offloading mode is supported by the underlying layers */
+	if (offload != MACSEC_OFFLOAD_OFF &&
+	    !macsec_check_offload(offload, macsec))
+		return -EOPNOTSUPP;
+
+	if (offload == MACSEC_OFFLOAD_OFF)
+		goto skip_limitation;
+
+	/* Check the physical interface isn't offloading another interface
+	 * first.
+	 */
+	for_each_net(loop_net) {
+		for_each_netdev(loop_net, loop_dev) {
+			struct macsec_dev *priv;
+
+			if (!netif_is_macsec(loop_dev))
+				continue;
+
+			priv = macsec_priv(loop_dev);
+
+			if (priv->real_dev == macsec->real_dev &&
+			    priv->offload != MACSEC_OFFLOAD_OFF)
+				return -EBUSY;
+		}
+	}
+
+skip_limitation:
+	/* Check if the net device is busy. */
+	if (netif_running(dev))
+		return -EBUSY;
+
+	rtnl_lock();
+
+	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;
+
+	rtnl_unlock();
+	return ret;
+}
+
 static int copy_tx_sa_stats(struct sk_buff *skb,
 			    struct macsec_tx_sa_stats __percpu *pstats)
 {
···
 dump_secy(struct macsec_secy *secy, struct net_device *dev,
 	  struct sk_buff *skb, struct netlink_callback *cb)
 {
-	struct macsec_rx_sc *rx_sc;
+	struct macsec_dev *macsec = netdev_priv(dev);
 	struct macsec_tx_sc *tx_sc = &secy->tx_sc;
 	struct nlattr *txsa_list, *rxsc_list;
-	int i, j;
-	void *hdr;
+	struct macsec_rx_sc *rx_sc;
 	struct nlattr *attr;
+	void *hdr;
+	int i, j;
 
 	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
 			  &macsec_fam, NLM_F_MULTI, MACSEC_CMD_GET_TXSC);
···
 
 	if (nla_put_u32(skb, MACSEC_ATTR_IFINDEX, dev->ifindex))
 		goto nla_put_failure;
+
+	attr = nla_nest_start_noflag(skb, MACSEC_ATTR_OFFLOAD);
+	if (!attr)
+		goto nla_put_failure;
+	if (nla_put_u8(skb, MACSEC_OFFLOAD_ATTR_TYPE, macsec->offload))
+		goto nla_put_failure;
+	nla_nest_end(skb, attr);
 
 	if (nla_put_secy(secy, skb))
 		goto nla_put_failure;
···
 		.cmd = MACSEC_CMD_UPD_RXSA,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = macsec_upd_rxsa,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = MACSEC_CMD_UPD_OFFLOAD,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = macsec_upd_offload,
 		.flags = GENL_ADMIN_PERM,
 	},
 };

include/uapi/linux/if_macsec.h

···
 	MACSEC_ATTR_RXSC_LIST,   /* dump, nested, macsec_rxsc_attrs for each RXSC */
 	MACSEC_ATTR_TXSC_STATS,  /* dump, nested, macsec_txsc_stats_attr */
 	MACSEC_ATTR_SECY_STATS,  /* dump, nested, macsec_secy_stats_attr */
+	MACSEC_ATTR_OFFLOAD,     /* config, nested, macsec_offload_attrs */
 	__MACSEC_ATTR_END,
 	NUM_MACSEC_ATTR = __MACSEC_ATTR_END,
 	MACSEC_ATTR_MAX = __MACSEC_ATTR_END - 1,
···
 	MACSEC_SA_ATTR_MAX = __MACSEC_SA_ATTR_END - 1,
 };
 
+enum macsec_offload_attrs {
+	MACSEC_OFFLOAD_ATTR_UNSPEC,
+	MACSEC_OFFLOAD_ATTR_TYPE, /* config/dump, u8 0..2 */
+	MACSEC_OFFLOAD_ATTR_PAD,
+	__MACSEC_OFFLOAD_ATTR_END,
+	NUM_MACSEC_OFFLOAD_ATTR = __MACSEC_OFFLOAD_ATTR_END,
+	MACSEC_OFFLOAD_ATTR_MAX = __MACSEC_OFFLOAD_ATTR_END - 1,
+};
+
 enum macsec_nl_commands {
 	MACSEC_CMD_GET_TXSC,
 	MACSEC_CMD_ADD_RXSC,
···
 	MACSEC_CMD_ADD_RXSA,
 	MACSEC_CMD_DEL_RXSA,
 	MACSEC_CMD_UPD_RXSA,
+	MACSEC_CMD_UPD_OFFLOAD,
 };
 
 /* u64 per-RXSC stats */