machine hangs on occasion - correlated with ssh break-in attempts

security security at
Thu Aug 21 21:37:34 UTC 2008

Mikhail Teterin wrote:
> Neil Neely написав(ла):
>> I haven't explored this issue enough to speak with any authority - 
>> but once upon a time I had an app doing tons of ipfw rule add/removes 
>> all the time and we had no end of performance and stability problems 
>> on that box (this would have been in 4.x or so timeline I expect).  
>> As that approach wasn't really critical we abandoned it without 
>> really digging into the details.
>> Years later a need for lots of rapid firewall changes came up again 
>> and I drilled into it and found the use of tables was excellent for 
>> doing this and it does the job very well.  This is approach is on a 
>> FreeBSD 6.3 box.
>> ipfw add 00550 deny ip from 'table(1)' to any
>> Then just add remove entries to table 1 via:
>> ipfw table 1 add
>> ipfw table 1 delete
>> show all entries in table 1 with:
>> ipfw table 1 list
>> Clear out the whole of table 1
>> ipfw table 1 flush
>> I can't be sure if this relates to your particular issue, but I would 
>> recommend trying it out.
> Thanks! I was not even aware of this functionality... Yes, I'll try 
> that -- maybe, a bug in ipfw only hits once per 1000 invocations :-)
>    -mi
blocksshd uses pf and a table to contain the addresses.  you might want 
to check it out

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