On 21/9/2015 6:17 μμ, Jan Just Keijser wrote:
> Personally I'd use a simple file-based counter to figure out which
> source IP address to use:
I soon found out that we would need a slightly more sophisticated
file-based counter (to record which public address is used or released
and available, how many times a particular public address is used etc.)
So, I redesigned the whole process as follows, and I am already using
it, seemingly without problems in the time being.
It uses a simple file (scr/list1) -a primitive database- to record how
much a public address is currently (at any one time) used; Remember that
our pool of public addresses is: 194.xxx.xxx.150-155. I have structured
the file scr/list1 is as follows (fist col.: last octet of public addr
pool - second col.: number of times currently used):
----------------------------------------------------------------
scr/list1 file
----------------------------------------------------------------
150 0
151 0
152 0
153 0
154 0
155 0
----------------------------------------------------------------
The logic is: Always keep the above file sorted (first on col2, then on
col1) so as to have at the top the least used address (from lo to hi).
When a client connects, give the first available address -always the one
at the top- (here 150), increment 0 to 1 (and then sort the table). When
a client disconnects, find its public address, decrement it by one (and
sort the table). If all public addresses get used once, they will start
getting used for a second time and so forth.
We also store a file /var/log/openvpn_client_$real_client_ip with the
(last octet of the) public address assigned to the client, to read it
back in the disconnect script.
----------------------------------------------------------------
client-connect script
----------------------------------------------------------------
#!/bin/bash
listfile="/etc/openvpn/scr/list1"
count=`awk 'NR==1 {print $2}' <$listfile`
ip=`awk 'NR==1 {print $1}' <$listfile`
count1=$((count+1))
sed -i "/$ip/{s/\ $count/\ $count1/}" $listfile
sort -k2,2 -k1 -o $listfile <$listfile
virtual_client_ip=$ifconfig_pool_remote_ip
real_client_ip=$trusted_ip
/sbin/iptables -t nat -A POSTROUTING -s "$virtual_client_ip" -j SNAT
--to-source 194.xxx.xxx."$ip"
echo "$ip" > /var/log/openvpn_client_$real_client_ip
exit 0
----------------------------------------------------------------
client-disconnect script
----------------------------------------------------------------
#!/bin/bash
#
client_nat_scriptfile="/var/log/openvpn_client_$trusted_ip"
listfile="/etc/openvpn/scr/list1"
if [ -f $client_nat_scriptfile ]
then
ip=`awk 'NR==1 {print $1}' <$client_nat_scriptfile`
rm -f $client_nat_scriptfile
/sbin/iptables -t nat -D POSTROUTING -s $ifconfig_pool_remote_ip -j
SNAT --to-source 194.xxx.xxx.$ip
count=`awk -v myip=$ip '$1==myip {print $2;exit;}' <$listfile`
count1=$((count-1))
sed -i "/$ip/{s/\ $count/\ $count1/}" $listfile
sort -k2,2 -k1 -o $listfile <$listfile
fi
exit 0
----------------------------------------------------------------
At best, when we restart the server, a script should initialize the "db"
in its zero state. (I have not done that, at least yet.) I guess the
--up cmd would be the right place for such a script.
Any suggestions / improvements / additional ideas will be welcome.
Nick
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