• Cong Wang's avatar
    net_sched: avoid generating same handle for u32 filters · 7801db8a
    Cong Wang authored
    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: default avatarCong Wang <cwang@twopensource.com>
    Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
    Signed-off-by: default avatarJamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    7801db8a
cls_u32.c 17.4 KB