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netfilter: xt_recent: add an entry reaper

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One of the problems with the way xt_recent is implemented is that
there is no efficient way to remove expired entries. Of course,
one can write a rule '-m recent --remove', but you have to know
beforehand which entry to delete. This commit adds reaper
logic which checks the head of the LRU list when a rule
is invoked that has a '--seconds' value and XT_RECENT_REAP set. If an
entry ceases to accumulate time stamps, then it will eventually bubble
to the top of the LRU list where it is then reaped.

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Tim Gardner 2010-03-16 19:53:13 +01:00 • committed by Patrick McHardy
parent 5be4a4f589
commit 0079c5aee3
2 changed files with 31 additions and 1 deletions
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4
include/linux/netfilter/xt_recent.h
View file

@ -9,6 +9,7 @@ enum {
XT_RECENT_UPDATE = 1 << 2, XT_RECENT_UPDATE = 1 << 2,
XT_RECENT_REMOVE = 1 << 3, XT_RECENT_REMOVE = 1 << 3,
XT_RECENT_TTL = 1 << 4, XT_RECENT_TTL = 1 << 4,
XT_RECENT_REAP = 1 << 5,
XT_RECENT_SOURCE = 0, XT_RECENT_SOURCE = 0,
XT_RECENT_DEST = 1, XT_RECENT_DEST = 1,
@ -16,6 +17,9 @@ enum {
XT_RECENT_NAME_LEN = 200, XT_RECENT_NAME_LEN = 200,
}; };
/* Only allowed with --rcheck and --update */
#define XT_RECENT_MODIFIERS (XT_RECENT_TTL|XT_RECENT_REAP)
struct xt_recent_mtinfo { struct xt_recent_mtinfo {
__u32 seconds; __u32 seconds;
__u32 hit_count; __u32 hit_count;

28
net/netfilter/xt_recent.c
View file

@ -143,6 +143,25 @@ static void recent_entry_remove(struct recent_table *t, struct recent_entry *e)
t->entries--; t->entries--;
} }
/*
* Drop entries with timestamps older then 'time'.
*/
static void recent_entry_reap(struct recent_table *t, unsigned long time)
{
struct recent_entry *e;
/*
* The head of the LRU list is always the oldest entry.
*/
e = list_entry(t->lru_list.next, struct recent_entry, lru_list);
/*
* The last time stamp is the most recent.
*/
if (time_after(time, e->stamps[e->index-1]))
recent_entry_remove(t, e);
}
static struct recent_entry * static struct recent_entry *
recent_entry_init(struct recent_table *t, const union nf_inet_addr *addr, recent_entry_init(struct recent_table *t, const union nf_inet_addr *addr,
u_int16_t family, u_int8_t ttl) u_int16_t family, u_int8_t ttl)
@ -269,6 +288,10 @@ recent_mt(const struct sk_buff *skb, const struct xt_match_param *par)
break; break;
} }
} }
/* info->seconds must be non-zero */
if (info->check_set & XT_RECENT_REAP)
recent_entry_reap(t, time);
} }
if (info->check_set & XT_RECENT_SET || if (info->check_set & XT_RECENT_SET ||
@ -301,7 +324,10 @@ static bool recent_mt_check(const struct xt_mtchk_param *par)
XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1) XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1)
return false; return false;
if ((info->check_set & (XT_RECENT_SET | XT_RECENT_REMOVE)) && if ((info->check_set & (XT_RECENT_SET | XT_RECENT_REMOVE)) &&
(info->seconds || info->hit_count)) (info->seconds || info->hit_count ||
(info->check_set & XT_RECENT_MODIFIERS)))
return false;
if ((info->check_set & XT_RECENT_REAP) && !info->seconds)
return false; return false;
if (info->hit_count > ip_pkt_list_tot) { if (info->hit_count > ip_pkt_list_tot) {
pr_info(KBUILD_MODNAME ": hitcount (%u) is larger than " pr_info(KBUILD_MODNAME ": hitcount (%u) is larger than "