net: add helper to generate random mac address

Add new function eth_random_enetaddr() to generate a locally administered
ethernet address.

Signed-off-by: Michael Walle <michael@walle.cc>
Acked-by: Joe Hershberger <joe.hershberger@gmail.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/net/eth.c b/net/eth.c
index d9a643073d..d526264fa6 100644
--- a/net/eth.c
+++ b/net/eth.c
@@ -70,6 +70,28 @@ static int eth_mac_skip(int index)
         return ((skip_state = getenv(enetvar)) != NULL);
 }
 
+#ifdef CONFIG_RANDOM_MACADDR
+void eth_random_enetaddr(uchar *enetaddr)
+{
+        uint32_t rval;
+
+        srand(get_timer(0));
+
+        rval = rand();
+        enetaddr[0] = rval & 0xff;
+        enetaddr[1] = (rval >> 8) & 0xff;
+        enetaddr[2] = (rval >> 16) & 0xff;
+
+        rval = rand();
+        enetaddr[3] = rval & 0xff;
+        enetaddr[4] = (rval >> 8) & 0xff;
+        enetaddr[5] = (rval >> 16) & 0xff;
+
+        /* make sure it's local and unicast */
+        enetaddr[0] = (enetaddr[0] | 0x02) & ~0x01;
+}
+#endif
+
 /*
  * CPU and board-specific Ethernet initializations.  Aliased function
  * signals caller to move on