net: macsec: Verify that send_sci is on when setting Tx sci explicitly

When setting Tx sci explicit, the Rx side is expected to use this
sci and not recalculate it from the packet.However, in case of Tx sci
is explicit and send_sci is off, the receiver is wrongly recalculate
the sci from the source MAC address which most likely be different
than the explicit sci.

Fix by preventing such configuration when macsec newlink is established
and return EINVAL error code on such cases.

Fixes: c09440f7 ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: Lior Nahmanson <liorna@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Raed Salem <raeds@nvidia.com>
Link: https://lore.kernel.org/r/1643542672-29403-1-git-send-email-raeds@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/macsec.c

@@ -4018,6 +4018,15 @@ static int macsec_newlink(struct net *net, struct net_device *dev,
 	    !macsec_check_offload(macsec->offload, macsec))
 		return -EOPNOTSUPP;
 
+	/* send_sci must be set to true when transmit sci explicitly is set */
+	if ((data && data[IFLA_MACSEC_SCI]) &&
+	    (data && data[IFLA_MACSEC_INC_SCI])) {
+		u8 send_sci = !!nla_get_u8(data[IFLA_MACSEC_INC_SCI]);
+
+		if (!send_sci)
+			return -EINVAL;
+	}
+
 	if (data && data[IFLA_MACSEC_ICV_LEN])
 		icv_len = nla_get_u8(data[IFLA_MACSEC_ICV_LEN]);
 	mtu = real_dev->mtu - icv_len - macsec_extra_len(true);