Re: How would I do this? (expert tricks) OT

[Jan Engelhardt <jengelh@computergmbh.de>]

On Jun 19 2007 10:14, Marc Perkel wrote:
>> 
>> tcpdump -lni any port 25
>> iptables -p tcp --dport 25 -j NFQUEUE
>> ...
>> 
>
>Thanks Jan, but I'm not sure it answers my question.

There's more than one way to do it.

One is...
	tcpdump -lni eth0 tcp [extra operands to match SYN packets] |
	myprogram

a longer one is to write your own netfilter userspace program
that receives the TCP SYNs (by means of -j NFQUEUE) and does
take action.

Another one is to use -j LOG and let your program parse
down /var/log/firewall. Like

	iptables -A INPUT -p tcp --dport 25 --syn -j LOG --log-prefix "[evil]"
	tail -f /var/log/firewall | grep '^\[evil\]' | myscript

myscript:
#!/usr/bin/perl

while (defined(my $line = <>)) {
	my($ip) = ($line =~ /SRC=(\S+)/);
	# Do something
}

>I want to run a script every time a connection attempt is made in real time

The scripts runs constantly, preferably.

>with the IP address as a parameter to the script. How would I do that? Suppose
>my script is:
>
>iplog <ipaddress>
>
>
>
>
>       
>____________________________________________________________________________________
>Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos & more. 
>http://mobile.yahoo.com/go?refer=1GNXIC
>

	Jan
-- 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/