Dynamic Rule Corpses of IPFW 2

Intron mag at intron.ac
Thu Aug 3 15:42:41 UTC 2006


I've set up a stateful IPFW rule to resist DoS attach. The rule is

     allow tcp from any to me tcpflags syn limit src-addr 10

But I found that there're many corpses in dynamic rules, which may
resist normal accesses. There isn't correspondence between those
corpses and existing TCP connections.

How to deal with those impedient corpses?

#ipfw -d show | grep myclient ; netstat -an | grep myclient
10010      4       192 (111s) LIMIT tcp myclient 50719 <-> myserver 443
10010      4       192 (80s) LIMIT tcp myclient 50700 <-> myserver 443
10010      4       192 (124s) LIMIT tcp myclient 50743 <-> myserver 443
10010      4       192 (119s) LIMIT tcp myclient 50735 <-> myserver 443
10010   3570    544131 (300s) LIMIT tcp myclient 50828 <-> myserver 22
10010      0         0 (3s) PARENT 10 tcp myclient 0 <-> 0.0.0.0 0
10010      4       192 (44s) LIMIT tcp myclient 50617 <-> myserver 443
10010      4       192 (59s) LIMIT tcp myclient 50652 <-> myserver 443
10010      4       192 (59s) LIMIT tcp myclient 50650 <-> myserver 443
10010      4       192 (57s) LIMIT tcp myclient 50645 <-> myserver 443
10010      2        96 (300s) LIMIT tcp myclient 50890 <-> myserver 443
tcp4       0      0  myserver.443     myclient.50817    TIME_WAIT
tcp4       0      0  myserver.443     myclient.50815    TIME_WAIT
tcp4       0      0  myserver.443     myclient.50813    TIME_WAIT
tcp4       0      0  myserver.443     myclient.50809    TIME_WAIT
tcp4       0    146  myserver.443     myclient.50706    ESTABLISHED
tcp4       0    146  myserver.443     myclient.50688    ESTABLISHED
tcp4       0    146  myserver.443     myclient.50679    ESTABLISHED
tcp4       0      0  myserver.443     myclient.50668    ESTABLISHED
tcp4       0      0  myserver.443     myclient.50618    ESTABLISHED
tcp4       0      0  myserver.443     myclient.50611    ESTABLISHED
tcp4       0    146  myserver.443     myclient.50493    FIN_WAIT_1
tcp4       0    146  myserver.443     myclient.50026    FIN_WAIT_1
tcp4       0      0  myserver.22      myclient.50828    ESTABLISHED

------------------------------------------------------------------------
                                                 From Beijing, China



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