[nrf fromtree] net: shell: Add random MAC address generation

Add option for setting a random MAC address to
the net iface set_mac command. With random option
a random MAC address can be assigned to an interface.
[SHEL-2352].

Signed-off-by: Kapil Bhatt <kapil.bhatt@nordicsemi.no>
(cherry picked from commit 8a52b64)

Author: kapbh

subsys/net/lib/shell/iface.c

@@ -6,6 +6,8 @@
  */
 
 #include <zephyr/logging/log.h>
+#include <zephyr/random/random.h>
+#include <strings.h>
 LOG_MODULE_DECLARE(net_shell);
 
 #if defined(CONFIG_NET_L2_ETHERNET)
@@ -20,6 +22,9 @@ LOG_MODULE_DECLARE(net_shell);
 
 #include "net_shell_private.h"
 
+#define UNICAST_MASK GENMASK(7, 1)
+#define LOCAL_BIT BIT(1)
+
 #if defined(CONFIG_NET_L2_ETHERNET) && defined(CONFIG_NET_NATIVE)
 struct ethernet_capabilities {
 	enum ethernet_hw_caps capability;
@@ -536,10 +541,15 @@ static int cmd_net_set_mac(const struct shell *sh, size_t argc, char *argv[])
 		goto err;
 	}
 
-	if ((net_bytes_from_str(mac_addr, sizeof(params.mac_address), argv[2]) < 0) ||
-	    !net_eth_is_addr_valid(&params.mac_address)) {
-		PR_WARNING("Invalid MAC address: %s\n", argv[2]);
-		goto err;
+	if (!strncasecmp(argv[2], "random", 6)) {
+		sys_rand_get(mac_addr, NET_ETH_ADDR_LEN);
+		mac_addr[0] = (mac_addr[0] & UNICAST_MASK) | LOCAL_BIT;
+	} else {
+		if ((net_bytes_from_str(mac_addr, sizeof(params.mac_address), argv[2]) < 0) ||
+		    !net_eth_is_addr_valid(&params.mac_address)) {
+			PR_WARNING("Invalid MAC address: %s\n", argv[2]);
+			goto err;
+		}
 	}
 
 	ret = net_mgmt(NET_REQUEST_ETHERNET_SET_MAC_ADDRESS, iface, &params, sizeof(params));