net/net_rand.h

   1 /*
   2  *      Copied from LiMon - BOOTP.
   3  *
   4  *      Copyright 1994, 1995, 2000 Neil Russell.
   5  *      (See License)
   6  *      Copyright 2000 Paolo Scaffardi
   7  */
   8
   9 #ifndef __NET_RAND_H__
  10 #define __NET_RAND_H__
  11
  12 #include <common.h>
  13
  14 /*
  15  * Return a seed for the PRNG derived from the eth0 MAC address.
  16  */
  17 static inline unsigned int seed_mac(void)
  18 {
  19         unsigned char enetaddr[ARP_HLEN];
  20         unsigned int seed;
  21
  22         /* get our mac */
  23         memcpy(enetaddr, eth_get_ethaddr(), ARP_HLEN);
  24
  25         seed = enetaddr[5];
  26         seed ^= enetaddr[4] << 8;
  27         seed ^= enetaddr[3] << 16;
  28         seed ^= enetaddr[2] << 24;
  29         seed ^= enetaddr[1];
  30         seed ^= enetaddr[0] << 8;
  31
  32         return seed;
  33 }
  34
  35 /*
  36  * Seed the random number generator using the eth0 MAC address.
  37  */
  38 static inline void srand_mac(void)
  39 {
  40         srand(seed_mac());
  41 }
  42
  43 #endif /* __NET_RAND_H__ */