DD-WRT
DD-WRT is an opensource linux based firmware for Linksys WRT54G and similar 802.11g wireless routers.
Wiviz, an open source GPL project, allows you to use your WRT to see other networks. It scans for networks and then shows signal strength and effects of antenna adjustment in real time.
Let DD-WRT redirect SMTP traffic to a valid SMTP server so everyone on your net can send mail no matter what SMTP server their mail program uses
DD-WRT has an feature thet let's everyone on your network be able to send mail, no matter what SMTP server their mail program is set up to use.
- Select the Services Tab
- In the Services Tab select the Hotspot Tab
- Under SMTP Redirect select Enabled
- Set SMTP Destination IP to the ip address of your SMTP server
- Set SMTP Source Network to your source network. You find the source network address by making a bitwise AND between your routers LAN address and your LAN's subnet mask.
If your router ha address 192.168.10.1 and your subnet mask is 255.255.255.0 your SMTP Source Network is 192.168.10.0. You can find your routers ip and subnet mask in the Setup tab.
The only restriction is that the SMTP server the mail clients are pointing at actually exists, and can be looked up with on a DNS server. This will normally be the case unless they have entered some random name (so remember to use a real server name if you want to verify it is working after configuring the router).
How DD-WRT routes traffic
To get a better understanding on how DD-WRT routes traffic, you can read:
- [http://iptables-tutorial.frozentux.net/iptables-tutorial.html Oskar Andreasson's Iptables Tutorial 1.2.2
If you are interested it tells how to show routing information:
To list your currently active rule-set: iptables -L
This command should list your currently active rule-set, and translate everything possible to a more readable form. For example, it will translate all the different ports according to the /etc/services file as well as DNS all the IP addresses to get DNS records instead. The latter can be a bit of a problem though. For example, it will try to resolve LAN IP addresses, i.e. 192.168.1.1, to something useful. 192.168.0.0/16 is a private range though and should not resolve to anything and the command will seem to hang while resolving the IP. To get around this problem we would do something like the following:
iptables -L -n
Another thing that might be interesting is to see a few statistics about each policy, rule and chain. We could get this by adding the verbose flag. It would then look something like this:
iptables -L -n -v
Don't forget that it is also possible to list the nat and mangle tables. This is done with the -t switch, like this:
iptables -L -t nat
There are also a few files that might be interesting to look at in the /proc file system. For example, it might be interesting to know what connections are currently in the conntrack table. This table contains all the different connections currently tracked and serves as a basic table so we always know what state a connection currently is in. This table can't be edited and even if it was possible, it would be a bad idea. To see the table you can run the following command:
cat /proc/net/ip_conntrack | less
The above command will show all currently tracked connections even though it might be a bit hard to understand everything.