• John Fastabend's avatar
    net: sched: cls_u32 changes to knode must appear atomic to readers · de5df632
    John Fastabend authored
    Changes to the cls_u32 classifier must appear atomic to the
    readers. Before this patch if a change is requested for both
    the exts and ifindex, first the ifindex is updated then the
    exts with tcf_exts_change(). This opens a small window where
    a reader can have a exts chain with an incorrect ifindex. This
    violates the the RCU semantics.
    
    Here we resolve this by always passing u32_set_parms() a copy
    of the tc_u_knode to work on and then inserting it into the hash
    table after the updates have been successfully applied.
    
    Tested with the following short script:
    
    #tc filter add dev p3p2 parent 8001:0 protocol ip prio 99 handle 1: \
    	       u32 divisor 256
    
    #tc filter add dev p3p2 parent 8001:0 protocol ip prio 99 \
    	       u32 link 1: hashkey mask ffffff00 at 12    \
    	       match ip src 192.168.8.0/2
    
    #tc filter add dev p3p2 parent 8001:0 protocol ip prio 102    \
    	       handle 1::10 u32 classid 1:2 ht 1: 	      \
    	       match ip src 192.168.8.0/8 match ip tos 0x0a 1e
    
    #tc filter change dev p3p2 parent 8001:0 protocol ip prio 102 \
    		 handle 1::10 u32 classid 1:2 ht 1:        \
    		 match ip src 1.1.0.0/8 match ip tos 0x0b 1e
    
    CC: Eric Dumazet <edumazet@google.com>
    CC: Jamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: default avatarJohn Fastabend <john.r.fastabend@intel.com>
    Acked-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    de5df632
cls_u32.c 23.3 KB