net: uclass: Save generated ethernet MAC addresses to the environment

When a MAC address is randomly generated we currently only update the
appropriate data structure.  For consistency and to re-align with
historic usage, it should be also saved to the appropriate environment
variable as well.

Cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
[trini: Update Kconfig, handle legacy networking case as well]
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Ramon Fried <rfried.dev@gmail.com>
Link: https://lore.kernel.org/r/1a2518e3cc19c14a41875ef64c5acc1f16edc813.1641893287.git.michal.simek@xilinx.com

net/Kconfig

@@ -27,10 +27,11 @@ config BOOTP_SEND_HOSTNAME
 config NET_RANDOM_ETHADDR
 	bool "Random ethaddr if unset"
 	help
-	  Selecting this will allow the Ethernet interface to function
-	  even when the ethaddr variable for that interface is unset.
-	  A new MAC address will be generated on every boot and it will
-	  not be added to the environment.
+	  Selecting this will allow the Ethernet interface to function even
+	  when the ethaddr variable for that interface is unset.  In this case,
+	  a random MAC address in the locally administered address space is
+	  generated. It will be saved to the appropriate environment variable,
+	  too.
 
 config NETCONSOLE
 	bool "NetConsole support"

net/eth-uclass.c

@@ -583,6 +583,8 @@ static int eth_post_probe(struct udevice *dev)
 		net_random_ethaddr(pdata->enetaddr);
 		printf("\nWarning: %s (eth%d) using random MAC address - %pM\n",
 		       dev->name, dev_seq(dev), pdata->enetaddr);
+		eth_env_set_enetaddr_by_index("eth", dev_seq(dev),
+					      pdata->enetaddr);
 #else
 		printf("\nError: %s address not set.\n",
 		       dev->name);

net/eth_legacy.c

@@ -164,6 +164,8 @@ int eth_write_hwaddr(struct eth_device *dev, const char *base_name,
 		net_random_ethaddr(dev->enetaddr);
 		printf("\nWarning: %s (eth%d) using random MAC address - %pM\n",
 		       dev->name, eth_number, dev->enetaddr);
+		eth_env_set_enetaddr_by_index("eth", eth_number,
+					      dev->enetaddr);
 #else
 		printf("\nError: %s address not set.\n",
 		       dev->name);