[U-Boot] [PATCH v2] net: make net_random_ethaddr() more random

The net_random_ethaddr() tries to get some entropy from different startup times of a board. The seed is initialized with get_timer() which has only a granularity of milliseconds. We can do better if we use get_ticks() which returns the raw timer ticks. Using this we have a higher chance of getting different values at startup.
Signed-off-by: Michael Walle michael@walle.cc --- since v1: - Removed the and-mask. Since there were no more comments I did some tests and apparently there are no compiler warnings.
include/net.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net.h b/include/net.h index a54d5eeac5..75a16e4c8f 100644 --- a/include/net.h +++ b/include/net.h @@ -816,7 +816,7 @@ static inline int is_valid_ethaddr(const u8 *addr) static inline void net_random_ethaddr(uchar *addr) { int i; - unsigned int seed = get_timer(0); + unsigned int seed = get_ticks();
for (i = 0; i < 6; i++) addr[i] = rand_r(&seed);

On Tue, Aug 27, 2019 at 4:14 PM Michael Walle michael@walle.cc wrote:
The net_random_ethaddr() tries to get some entropy from different startup times of a board. The seed is initialized with get_timer() which has only a granularity of milliseconds. We can do better if we use get_ticks() which returns the raw timer ticks. Using this we have a higher chance of getting different values at startup.
Signed-off-by: Michael Walle michael@walle.cc
since v1:
- Removed the and-mask. Since there were no more comments I did some tests and apparently there are no compiler warnings.
include/net.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Bin Meng bmeng.cn@gmail.com

On Tue, Aug 27, 2019 at 3:14 AM Michael Walle michael@walle.cc wrote:
The net_random_ethaddr() tries to get some entropy from different startup times of a board. The seed is initialized with get_timer() which has only a granularity of milliseconds. We can do better if we use get_ticks() which returns the raw timer ticks. Using this we have a higher chance of getting different values at startup.
Signed-off-by: Michael Walle michael@walle.cc
Acked-by: Joe Hershberger joe.hershberger@ni.com

Hi Michael,
https://patchwork.ozlabs.org/patch/1153632/ was applied to http://git.denx.de/?p=u-boot/u-boot-net.git
Thanks! -Joe
participants (3)
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Bin Meng
-
Joe Hershberger
-
Michael Walle