Re: explanation and code for stream.c issues

From: Tim Yardley (yardleyat_private)
Date: Fri Jan 21 2000 - 09:42:24 PST

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    At 11:25 AM 1/21/2000, Tim Yardley wrote:
    >stream.c issues
    >
    >---------------------------------------------------
    >:: temp remedy (exec summary)
    >---------------------------------------------------
    >
    >If you use ipfilter...
    >
    >-- start rule set --
    >block in quick proto tcp from any to any head 100
    >pass in quick proto tcp from any to any flags S keep state group 100
    >pass in all
    >-- end rule set --
    >
    >That will help you "stop" the attack, although it will still use some CPU
    >though
    >
    >Note: If you use IPFW, there is no immediate way to solve this problem due
    >to the fact that it is a stateless firewall.  If you are getting attacked,
    >then temporarily use ipfilter to stop it.
    >
    >Otherwise, wait for vendor patches.
    >
    >FreeBSD "unofficial patch" by Alfred Perlstein:
    >http://www.freebsd.org/~alfred/tcp_fix.diff
    
    <snip>
    
    >-- start stream.c --
    
    <snip>
    
    >   packet.tcp.th_flags           = 0;
    
    change this to a little different effect:
    
    packet.tcp.th_flags             = TH_ACK;
    
    <snip>
    
    /tmy
    
    
    -- Diving into infinity my consciousness expands in inverse
        proportion to my distance from singularity
    
    +--------  -------  ------  -----  ---- --- -- ------ --------+
    |  Tim Yardley (yardleyat_private)	
    |  http://www.students.uiuc.edu/~yardley/
    +--------  -------  ------  -----  ---- --- -- ------ --------+
    



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