Hi Joe,
Am Dienstag 29 Mai 2012, 20:08:26 schrieb Joe Hershberger:
Hi Michael,
On Mon, May 28, 2012 at 5:03 PM, Michael Walle michael@walle.cc wrote:
[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@ni.com Cc: Joe Hershberger joe.hershberger@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/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@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?
Yes... It's not very appropriate any longer.
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?
It was the implementation used for bootp delays. It is some form of PRNG... just not the same as what you've implemented.
this conflicts with my patch (lib/rand.c) i'm trying to put into upstream.
True.
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 ?
If you can verify that the functionality of the CONFIG_BOOTP_RANDOM_DELAY and CONFIG_CMD_LINK_LOCAL are uneffected, then I'm OK with it.
One thing to note is that the link-local implementation needs to use a MAC seeded random number. That means we can't have other things coming in and seeding it with a time. It is nice that it is separate for that reason. Can you solve that and integrate it with your PRNG?
I'm in a hurry, short answer for now: I thought of sth like this:
static inline void srand_mac(void) { unsigned char enetaddr[6]; unsigned int seed;
/* get our mac */ eth_getenv_enetaddr("ethaddr", enetaddr);
seed = enetaddr[5]; seed |= enetaddr[4] << 8; seed |= enetaddr[3] << 16; seed |= enetaddr[2] << 24;
srand(seed); }