[PATCH 2/2] net: Use NDRNG device in srand_mac()

[Torsten Duwe]

On Wed, 16 Dec 2020 11:41:17 +0100
matthias.bgg at kernel.org wrote:

> From: Matthias Brugger <mbrugger at suse.com>
> 
> When calling srand_mac we use a weak seed dependent on the
> mac address. If present, use a RNG device instead to incerase entropy.
> 
> Signed-off-by: Matthias Brugger <mbrugger at suse.com>
> 
> ---
> 
>  net/net_rand.h | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/net/net_rand.h b/net/net_rand.h
> index 4bf9bd817e..600c3d825e 100644
> --- a/net/net_rand.h
> +++ b/net/net_rand.h
> @@ -10,6 +10,7 @@
>  #define __NET_RAND_H__
>  
>  #include <common.h>
> +#include <rng.h>
>  
>  /*
>   * Return a seed for the PRNG derived from the eth0 MAC address.
> @@ -37,7 +38,22 @@ static inline unsigned int seed_mac(void)
>   */
>  static inline void srand_mac(void)
>  {
> -	srand(seed_mac());
> +#if defined(CONFIG_DM_RNG)
> +	int ret;
> +	struct udevice *devp;
> +	u32 randv = 0;
> +
> +	ret = uclass_get_device(UCLASS_RNG, 0, &devp);
> +	if (ret) {
> +		ret = dm_rng_read(dev, randv, sizeof(randv));
Haven't tested this (yet), but shouldn't this be
		ret = dm_rng_read(devp, &randv, sizeof(randv));
		                     ^  ^ ?
> +		if (ret < 0)
> +			randv = 0;
> +	}
> +	if (randv)
> +		srand(randv);
> +	else
> +#endif
> +		srand(seed_mac());
>  }
>  
>  #endif /* __NET_RAND_H__ */