ia64/linux-2.6.18-xen.hg

view net/netfilter/xt_limit.c @ 871:9cbcc9008446

xen/x86: don't initialize cpu_data[]'s apicid field on generic code

Afaict, this is not only redundant with the intialization done in
drivers/xen/core/smpboot.c, but actually results - at least for
secondary CPUs - in the Xen-specific value written to be later
overwritten with whatever the generic code determines (with no
guarantee that the two values are identical).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Thu May 14 10:09:15 2009 +0100 (2009-05-14)
parents 831230e53067
children
line source
1 /* Kernel module to control the rate
2 *
3 * 2 September 1999: Changed from the target RATE to the match
4 * `limit', removed logging. Did I mention that
5 * Alexey is a fucking genius?
6 * Rusty Russell (rusty@rustcorp.com.au). */
8 /* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr>
9 * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr>
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
14 */
16 #include <linux/module.h>
17 #include <linux/skbuff.h>
18 #include <linux/spinlock.h>
19 #include <linux/interrupt.h>
21 #include <linux/netfilter/x_tables.h>
22 #include <linux/netfilter/xt_limit.h>
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
26 MODULE_DESCRIPTION("iptables rate limit match");
27 MODULE_ALIAS("ipt_limit");
28 MODULE_ALIAS("ip6t_limit");
30 /* The algorithm used is the Simple Token Bucket Filter (TBF)
31 * see net/sched/sch_tbf.c in the linux source tree
32 */
34 static DEFINE_SPINLOCK(limit_lock);
36 /* Rusty: This is my (non-mathematically-inclined) understanding of
37 this algorithm. The `average rate' in jiffies becomes your initial
38 amount of credit `credit' and the most credit you can ever have
39 `credit_cap'. The `peak rate' becomes the cost of passing the
40 test, `cost'.
42 `prev' tracks the last packet hit: you gain one credit per jiffy.
43 If you get credit balance more than this, the extra credit is
44 discarded. Every time the match passes, you lose `cost' credits;
45 if you don't have that many, the test fails.
47 See Alexey's formal explanation in net/sched/sch_tbf.c.
49 To get the maxmum range, we multiply by this factor (ie. you get N
50 credits per jiffy). We want to allow a rate as low as 1 per day
51 (slowest userspace tool allows), which means
52 CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */
53 #define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
55 /* Repeated shift and or gives us all 1s, final shift and add 1 gives
56 * us the power of 2 below the theoretical max, so GCC simply does a
57 * shift. */
58 #define _POW2_BELOW2(x) ((x)|((x)>>1))
59 #define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
60 #define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
61 #define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
62 #define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
63 #define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
65 #define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
67 static int
68 ipt_limit_match(const struct sk_buff *skb,
69 const struct net_device *in,
70 const struct net_device *out,
71 const struct xt_match *match,
72 const void *matchinfo,
73 int offset,
74 unsigned int protoff,
75 int *hotdrop)
76 {
77 struct xt_rateinfo *r = ((struct xt_rateinfo *)matchinfo)->master;
78 unsigned long now = jiffies;
80 spin_lock_bh(&limit_lock);
81 r->credit += (now - xchg(&r->prev, now)) * CREDITS_PER_JIFFY;
82 if (r->credit > r->credit_cap)
83 r->credit = r->credit_cap;
85 if (r->credit >= r->cost) {
86 /* We're not limited. */
87 r->credit -= r->cost;
88 spin_unlock_bh(&limit_lock);
89 return 1;
90 }
92 spin_unlock_bh(&limit_lock);
93 return 0;
94 }
96 /* Precision saver. */
97 static u_int32_t
98 user2credits(u_int32_t user)
99 {
100 /* If multiplying would overflow... */
101 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
102 /* Divide first. */
103 return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
105 return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
106 }
108 static int
109 ipt_limit_checkentry(const char *tablename,
110 const void *inf,
111 const struct xt_match *match,
112 void *matchinfo,
113 unsigned int matchsize,
114 unsigned int hook_mask)
115 {
116 struct xt_rateinfo *r = matchinfo;
118 /* Check for overflow. */
119 if (r->burst == 0
120 || user2credits(r->avg * r->burst) < user2credits(r->avg)) {
121 printk("Overflow in xt_limit, try lower: %u/%u\n",
122 r->avg, r->burst);
123 return 0;
124 }
126 /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies *
127 128. */
128 r->prev = jiffies;
129 r->credit = user2credits(r->avg * r->burst); /* Credits full. */
130 r->credit_cap = user2credits(r->avg * r->burst); /* Credits full. */
131 r->cost = user2credits(r->avg);
133 /* For SMP, we only want to use one set of counters. */
134 r->master = r;
136 return 1;
137 }
139 static struct xt_match ipt_limit_reg = {
140 .name = "limit",
141 .match = ipt_limit_match,
142 .matchsize = sizeof(struct xt_rateinfo),
143 .checkentry = ipt_limit_checkentry,
144 .family = AF_INET,
145 .me = THIS_MODULE,
146 };
147 static struct xt_match limit6_reg = {
148 .name = "limit",
149 .match = ipt_limit_match,
150 .matchsize = sizeof(struct xt_rateinfo),
151 .checkentry = ipt_limit_checkentry,
152 .family = AF_INET6,
153 .me = THIS_MODULE,
154 };
156 static int __init xt_limit_init(void)
157 {
158 int ret;
160 ret = xt_register_match(&ipt_limit_reg);
161 if (ret)
162 return ret;
164 ret = xt_register_match(&limit6_reg);
165 if (ret)
166 xt_unregister_match(&ipt_limit_reg);
168 return ret;
169 }
171 static void __exit xt_limit_fini(void)
172 {
173 xt_unregister_match(&ipt_limit_reg);
174 xt_unregister_match(&limit6_reg);
175 }
177 module_init(xt_limit_init);
178 module_exit(xt_limit_fini);