Revert "net: macsec: update SCI upon MAC address change."

This reverts commit 6fc498b.

Commit 6fc498b states:

    SCI should be updated, because it contains MAC in its first 6
    octets.

That's not entirely correct. The SCI can be based on the MAC address,
but doesn't have to be. We can also use any 64-bit number as the
SCI. When the SCI based on the MAC address, it uses a 16-bit "port
number" provided by userspace, which commit 6fc498b overwrites
with 1.

In addition, changing the SCI after macsec has been setup can just
confuse the receiver. If we configure the RXSC on the peer based on
the original SCI, we should keep the same SCI on TX.

When the macsec device is being managed by a userspace key negotiation
daemon such as wpa_supplicant, commit 6fc498b would also
overwrite the SCI defined by userspace.

Fixes: 6fc498b ("net: macsec: update SCI upon MAC address change.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/9b1a9d28327e7eb54550a92eebda45d25e54dd0d.1660667033.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/macsec.c

@@ -462,11 +462,6 @@ static struct macsec_eth_header *macsec_ethhdr(struct sk_buff *skb)
 	return (struct macsec_eth_header *)skb_mac_header(skb);
 }
 
-static sci_t dev_to_sci(struct net_device *dev, __be16 port)
-{
-	return make_sci(dev->dev_addr, port);
-}
-
 static void __macsec_pn_wrapped(struct macsec_secy *secy,
 				struct macsec_tx_sa *tx_sa)
 {
@@ -3661,7 +3656,6 @@ static int macsec_set_mac_address(struct net_device *dev, void *p)
 
 out:
 	eth_hw_addr_set(dev, addr->sa_data);
-	macsec->secy.sci = dev_to_sci(dev, MACSEC_PORT_ES);
 
 	/* If h/w offloading is available, propagate to the device */
 	if (macsec_is_offloaded(macsec)) {
@@ -4000,6 +3994,11 @@ static bool sci_exists(struct net_device *dev, sci_t sci)
 	return false;
 }
 
+static sci_t dev_to_sci(struct net_device *dev, __be16 port)
+{
+	return make_sci(dev->dev_addr, port);
+}
+
 static int macsec_add_dev(struct net_device *dev, sci_t sci, u8 icv_len)
 {
 	struct macsec_dev *macsec = macsec_priv(dev);