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Old 03-03-2010, 07:37 PM
Tim Gardner
 
Default netfilter: xt_recent: Add an entry reaper

See discussion at http://www.spinics.net/lists/netfilter-devel/msg12072.html
This patch might land in 2.6.34, but more likely 2.6.35.

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>
---
include/linux/netfilter/xt_recent.h | 4 ++++
net/netfilter/xt_recent.c | 28 +++++++++++++++++++++++++++-
2 files changed, 31 insertions(+), 1 deletions(-)

diff --git a/include/linux/netfilter/xt_recent.h b/include/linux/netfilter/xt_recent.h
index d2c2766..bba990e 100644
--- a/include/linux/netfilter/xt_recent.h
+++ b/include/linux/netfilter/xt_recent.h
@@ -9,6 +9,7 @@ enum {
XT_RECENT_UPDATE = 1 << 2,
XT_RECENT_REMOVE = 1 << 3,
XT_RECENT_TTL = 1 << 4,
+ XT_RECENT_REAP = 1 << 5,

XT_RECENT_SOURCE = 0,
XT_RECENT_DEST = 1,
@@ -16,6 +17,9 @@ enum {
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 {
__u32 seconds;
__u32 hit_count;
diff --git a/net/netfilter/xt_recent.c b/net/netfilter/xt_recent.c
index 1a3b650..128ce2b 100644
--- a/net/netfilter/xt_recent.c
+++ b/net/netfilter/xt_recent.c
@@ -142,6 +142,25 @@ static void recent_entry_remove(struct recent_table *t, struct recent_entry *e)
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 *
recent_entry_init(struct recent_table *t, const union nf_inet_addr *addr,
u_int16_t family, u_int8_t ttl)
@@ -265,6 +284,10 @@ recent_mt(const struct sk_buff *skb, const struct xt_match_param *par)
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 ||
@@ -292,7 +315,10 @@ static bool recent_mt_check(const struct xt_mtchk_param *par)
XT_RECENT_CHECK | XT_RECENT_UPDATE)) != 1)
return false;
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;
if (info->hit_count > ip_pkt_list_tot)
return false;
--
1.7.0


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