Re: Syn+Fin (Setup) And TCP RST

From: Crist Clark (crist.clark@globalstar.com)
Date: 05/30/01 

Date: Tue, 29 May 2001 15:11:22 -0700
From: "Crist Clark" <crist.clark@globalstar.com>
To: Liran Dahan <lirandb@netvision.net.il>

Liran Dahan wrote:
>
> Yes, you right, i noticed it just now, i've changed the variable
> net.inet.tcp.restrict_rst to 1 and saw it took me ages till i got Connection
> timeout.. so what can be the problem.. why my firewall is not sending TCP
> RST when im doing ipfw add reset tcp from any to any ?

The output of,

  # ipfw show
  # tcpdump -nv 'host <host_you_telnet_from>'
  <do the telnet test from the testing host>
  # ipfw show

Yes, two 'ipfw show's to see if we can see the packets being counted in
another rule. Perhaps add some logging. We want to be _sure_ that the
connection attempts are actually triggering the rule with the 'reset'
action before jumping to conclusions about no RSTs.

I would be surprised if TCP_RESTRICT_RST is interfering with this. IIRC,
the code for "spoofing" these RSTs in the firewall lives in other parts
of the kernel from that generating "real" RSTs (where TCP_RESTRICT_RST
would have its effects). 

-- 
Crist J. Clark                                Network Security Engineer
crist.clark@globalstar.com                    Globalstar, L.P.
(408) 933-4387                                FAX: (408) 933-4926
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