1 files changed, 30 insertions, 0 deletions

diff --git a/arch/um/drivers/net_user.c b/arch/um/drivers/net_user.c
index 107c5e43fa00..142bcb2c7c6a 100644
--- a/arch/um/drivers/net_user.c
+++ b/arch/um/drivers/net_user.c
@@ -12,6 +12,7 @@
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
+#include <sys/time.h>
 #include "user.h"
 #include "user_util.h"
 #include "kern_util.h"
@@ -258,3 +259,32 @@ char *split_if_spec(char *str, ...)
         va_end(ap);
         return str;
 }
+
+void random_mac(unsigned char *addr)
+{
+        struct timeval tv;
+        long n;
+        unsigned int seed;
+
+        gettimeofday(&tv, NULL);
+
+        /* Assume that 20 bits of microseconds and 12 bits of the pid are
+         * reasonably unpredictable.
+         */
+        seed = tv.tv_usec | (os_getpid() << 20);
+        srandom(seed);
+
+        /* Don't care about endianness here - switching endianness
+         * just rearranges what are hopefully random numbers.
+         *
+         * Assume that RAND_MAX > 65536, so random is called twice and
+         * we use 16 bits of the result.
+         */
+        n = random();
+        addr[2] = (n >> 8) & 255;
+        addr[3] = n % 255;
+
+        n = random();
+        addr[4] = (n >> 8) & 255;
+        addr[5] = n % 255;
+}