[U-Boot] [PATCH v3 02/21] net: Move MAC-seeded rand out of bootp.c

[Michael Walle]

[sorry for my first mail.. wasn't intented to be send]


Sorry for being too late on this.

Am Mittwoch 23 Mai 2012, 19:57:58 schrieb Joe Hershberger:
> Make the MAC-seeded random number generator available to /net in
> general.  MAC-seeded rand will be needed by link-local as well, so
> give it an interface.
> 
> Signed-off-by: Joe Hershberger <joe.hershberger at ni.com>
> Cc: Joe Hershberger <joe.hershberger at gmail.com>
> ---
> Changes for v3:
>   - Lowercase hex
>   - Add blank line
>   - Always include header, even when it isn't needed
>   - Add function comments
> 
>  net/Makefile   |    1 +
>  net/bootp.c    |   67
> ++++++++++--------------------------------------------- net/bootp.h    |  
>  3 --
>  net/net_rand.c |   68
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ net/net_rand.h | 
>  26 +++++++++++++++++++++
>  5 files changed, 107 insertions(+), 58 deletions(-)
>  create mode 100644 net/net_rand.c
>  create mode 100644 net/net_rand.h
> 
[..]

> diff --git a/net/bootp.h b/net/bootp.h
> index ce73734..bf4e875 100644
> --- a/net/bootp.h
> +++ b/net/bootp.h
> @@ -63,9 +63,6 @@ struct Bootp_t {
>  extern ulong	BootpID;		/* ID of cur BOOTP request	*/
>  extern char	BootFile[128];		/* Boot file name		*/
>  extern int	BootpTry;
> -#ifdef CONFIG_BOOTP_RANDOM_DELAY
> -extern ulong	seed1, seed2;		/* seed for random BOOTP delay	*/
> -#endif
> 
> 
>  /* Send a BOOTP request */
> diff --git a/net/net_rand.c b/net/net_rand.c
> new file mode 100644
> index 0000000..5387aba
> --- /dev/null
> +++ b/net/net_rand.c
> @@ -0,0 +1,68 @@
> +/*
> + *	Based on LiMon - BOOTP.
> + *
> + *	Copyright 1994, 1995, 2000 Neil Russell.
> + *	(See License)
> + *	Copyright 2000 Roland Borde
> + *	Copyright 2000 Paolo Scaffardi
> + *	Copyright 2000-2004 Wolfgang Denk, wd at denx.de
> + */
> +
> +#include <common.h>
> +#include <net.h>
> +#include "net_rand.h"
> +
> +static ulong seed1, seed2;
> +
> +void srand_mac(void)
> +{
> +	ulong tst1, tst2, m_mask;
> +	ulong m_value = 0;
> +	int reg;
> +	unsigned char bi_enetaddr[6];
> +
> +	/* get our mac */
> +	eth_getenv_enetaddr("ethaddr", bi_enetaddr);
> +
> +	debug("BootpRequest => Our Mac: ");
mh? this shouldn't be here anymore should it?

> +	for (reg = 0; reg < 6; reg++)
> +		debug("%x%c", bi_enetaddr[reg], reg == 5 ? '\n' : ':');
> +
> +	/* Mac-Manipulation 2 get seed1 */
> +	tst1 = 0;
> +	tst2 = 0;
> +	for (reg = 2; reg < 6; reg++) {
> +		tst1 = tst1 << 8;
> +		tst1 = tst1 | bi_enetaddr[reg];
> +	}
> +	for (reg = 0; reg < 2; reg++) {
> +		tst2 = tst2 | bi_enetaddr[reg];
> +		tst2 = tst2 << 8;
> +	}
> +
> +	seed1 = tst1^tst2;
> +
> +	/* Mirror seed1*/
> +	m_mask = 0x1;
> +	for (reg = 1; reg <= 32; reg++) {
> +		m_value |= (m_mask & seed1);
> +		seed1 = seed1 >> 1;
> +		m_value = m_value << 1;
> +	}
> +	seed1 = m_value;
> +	seed2 = 0xb78d0945;
> +}
> +
> +unsigned long rand(void)
> +{
> +	ulong sum;
> +
> +	/* Random Number Generator */
> +	sum = seed1 + seed2;
> +	if (sum < seed1 || sum < seed2)
> +		sum++;
> +	seed2 = seed1;
> +	seed1 = sum;
> +
> +	return sum;
> +}

is this really random? this conflicts with my patch (lib/rand.c) i'm trying to 
put into upstream.

> diff --git a/net/net_rand.h b/net/net_rand.h
> new file mode 100644
> index 0000000..c98db64
> --- /dev/null
> +++ b/net/net_rand.h
> @@ -0,0 +1,26 @@
> +/*
> + *	Copied from LiMon - BOOTP.
> + *
> + *	Copyright 1994, 1995, 2000 Neil Russell.
> + *	(See License)
> + *	Copyright 2000 Paolo Scaffardi
> + */
> +
> +#ifndef __NET_RAND_H__
> +#define __NET_RAND_H__
> +
> +#define RAND_MAX 0xffffffff
> +
> +/*
> + * Seed the random number generator using the eth0 MAC address
> + */
> +void srand_mac(void);
> +
> +/*
> + * Get a random number (after seeding with MAC address)
> + *
> + * @return random number
> + */
> +unsigned long rand(void);
> +
> +#endif /* __NET_RAND_H__ */

if this is unconditionally included, my patch fails because there are multiple 
declarations of rand().

Can we unify this with my patch, which is based on a paper about PRNGs? Eg. 
use the rand()/srand() from my patch and create an srand_mac() inline function 
which uses srand() from lib/rand.c ?

Joe, if that is ok, i'll put that into the next version of my "lsxl: add 
support for lschlv2 and lsxhl" patch series.

-- 
Michael