Commit 7801db8a authored Jul 17, 2014 by Cong Wang Committed by David S. Miller Jul 20, 2014

net_sched: avoid generating same handle for u32 filters



When kernel generates a handle for a u32 filter, it tries to start
from the max in the bucket. So when we have a filter with the max (fff)
handle, it will cause kernel always generates the same handle for new
filters. This can be shown by the following command:

	tc qdisc add dev eth0 ingress
	tc filter add dev eth0 parent ffff: protocol ip pref 770 handle 800::fff u32 match ip protocol 1 0xff
	tc filter add dev eth0 parent ffff: protocol ip pref 770 u32 match ip protocol 1 0xff
	...

we will get some u32 filters with same handle:

 # tc filter show dev eth0 parent ffff:
filter protocol ip pref 770 u32
filter protocol ip pref 770 u32 fh 800: ht divisor 1
filter protocol ip pref 770 u32 fh 800::fff order 4095 key ht 800 bkt 0
  match 00010000/00ff0000 at 8
filter protocol ip pref 770 u32 fh 800::fff order 4095 key ht 800 bkt 0
  match 00010000/00ff0000 at 8
filter protocol ip pref 770 u32 fh 800::fff order 4095 key ht 800 bkt 0
  match 00010000/00ff0000 at 8
filter protocol ip pref 770 u32 fh 800::fff order 4095 key ht 800 bkt 0
  match 00010000/00ff0000 at 8

handles should be unique. This patch fixes it by looking up a bitmap,
so that can guarantee the handle is as unique as possible. For compatibility,
we still start from 0x800.

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent c2a6c781

net/sched/cls_u32.c

+14 −5

Original line number	Diff line number	Diff line
		@@ -38,6 +38,7 @@
		#include <linux/errno.h>
		#include <linux/rtnetlink.h>
		#include <linux/skbuff.h>
		#include <linux/bitmap.h>
		#include <net/netlink.h>
		#include <net/act_api.h>
		#include <net/pkt_cls.h>
		@@ -460,17 +461,25 @@ static int u32_delete(struct tcf_proto *tp, unsigned long arg)
		return 0;
		}

		#define NR_U32_NODE (1<<12)
		static u32 gen_new_kid(struct tc_u_hnode *ht, u32 handle)
		{
		struct tc_u_knode *n;
		unsigned int i = 0x7FF;
		unsigned long i;
		unsigned long bitmap = kzalloc(BITS_TO_LONGS(NR_U32_NODE) sizeof(unsigned long),
		GFP_KERNEL);
		if (!bitmap)
		return handle \| 0xFFF;

		for (n = ht->ht[TC_U32_HASH(handle)]; n; n = n->next)
		if (i < TC_U32_NODE(n->handle))
		i = TC_U32_NODE(n->handle);
		i++;
		set_bit(TC_U32_NODE(n->handle), bitmap);

		return handle \| (i > 0xFFF ? 0xFFF : i);
		i = find_next_zero_bit(bitmap, NR_U32_NODE, 0x800);
		if (i >= NR_U32_NODE)
		i = find_next_zero_bit(bitmap, NR_U32_NODE, 1);

		kfree(bitmap);
		return handle \| (i >= NR_U32_NODE ? 0xFFF : i);
		}

		static const struct nla_policy u32_policy[TCA_U32_MAX + 1] = {

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