diff options
Diffstat (limited to 'net/core/utils.c')
| -rw-r--r-- | net/core/utils.c | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/net/core/utils.c b/net/core/utils.c new file mode 100644 index 000000000..415926b8e --- /dev/null +++ b/net/core/utils.c @@ -0,0 +1,66 @@ +/* + * Generic address resultion entity + * + * Authors: + * net_random Alan Cox + * net_ratelimit Andy Kleen + * + * Created by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <asm/uaccess.h> +#include <asm/system.h> +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/string.h> +#include <linux/mm.h> + +static unsigned long net_rand_seed = 152L; + +unsigned long net_random(void) +{ + net_rand_seed=net_rand_seed*69069L+1; + return net_rand_seed^jiffies; +} + +void net_srandom(unsigned long entropy) +{ + net_rand_seed ^= entropy; + net_random(); +} + +int net_msg_cost = 5*HZ; +int net_msg_burst = 10*5*HZ; + +/* + * This enforces a rate limit: not more than one kernel message + * every 5secs to make a denial-of-service attack impossible. + * + * All warning printk()s should be guarded by this function. + */ +int net_ratelimit(void) +{ + static unsigned long toks = 10*5*HZ; + static unsigned long last_msg; + static int missed; + unsigned long now = jiffies; + + toks += now - xchg(&last_msg, now); + if (toks > net_msg_burst) + toks = net_msg_burst; + if (toks >= net_msg_cost) { + toks -= net_msg_cost; + if (missed) + printk(KERN_WARNING "NET: %d messages suppressed.\n", missed); + missed = 0; + return 1; + } + missed++; + return 0; +} |