net: macsec: add support for specifying offload upon link creation

This patch adds new netlink attribute to allow a user to (optionally)
specify the desired offload mode immediately upon MACSec link creation.

Separate iproute patch will be required to support this from user space.

Signed-off-by: Mark Starovoytov <[e-mail]>
Signed-off-by: Igor Russkikh <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/macsec.c

···
 	return dev;
 }
 
+static enum macsec_offload nla_get_offload(const struct nlattr *nla)
+{
+	return (__force enum macsec_offload)nla_get_u8(nla);
+}
+
 static sci_t nla_get_sci(const struct nlattr *nla)
 {
 	return (__force sci_t)nla_get_u64(nla);
···
 
 	macsec->real_dev = real_dev;
 
-	/* MACsec offloading is off by default */
-	macsec->offload = MACSEC_OFFLOAD_OFF;
+	if (data && data[IFLA_MACSEC_OFFLOAD])
+		macsec->offload = nla_get_offload(data[IFLA_MACSEC_OFFLOAD]);
+	else
+		/* MACsec offloading is off by default */
+		macsec->offload = MACSEC_OFFLOAD_OFF;
+
+	/* Check if the offloading mode is supported by the underlying layers */
+	if (macsec->offload != MACSEC_OFFLOAD_OFF &&
+	    !macsec_check_offload(macsec->offload, macsec))
+		return -EOPNOTSUPP;
 
 	if (data && data[IFLA_MACSEC_ICV_LEN])
 		icv_len = nla_get_u8(data[IFLA_MACSEC_ICV_LEN]);
···
 		err = macsec_changelink_common(dev, data);
 		if (err)
 			goto del_dev;
+	}
+
+	/* If h/w offloading is available, propagate to the device */
+	if (macsec_is_offloaded(macsec)) {
+		const struct macsec_ops *ops;
+		struct macsec_context ctx;
+
+		ops = macsec_get_ops(macsec, &ctx);
+		if (ops) {
+			ctx.secy = &macsec->secy;
+			err = macsec_offload(ops->mdo_add_secy, &ctx);
+			if (err)
+				goto del_dev;
+		}
 	}
 
 	err = register_macsec_dev(real_dev, dev);

include/uapi/linux/if_link.h

···
 	IFLA_MACSEC_REPLAY_PROTECT,
 	IFLA_MACSEC_VALIDATION,
 	IFLA_MACSEC_PAD,
+	IFLA_MACSEC_OFFLOAD,
 	__IFLA_MACSEC_MAX,
 };
 

tools/include/uapi/linux/if_link.h

···
 	IFLA_MACSEC_REPLAY_PROTECT,
 	IFLA_MACSEC_VALIDATION,
 	IFLA_MACSEC_PAD,
+	IFLA_MACSEC_OFFLOAD,
 	__IFLA_MACSEC_MAX,
 };