iodine/man/iodine.8

.\" groff -man -Tascii iodine.8
.TH IODINE 8 "JUL 2008" "User Manuals"
.SH NAME
iodine, iodined \- tunnel IPv4 over DNS
.SH SYNOPSIS
.B iodine [-v]

.B iodine [-h]

.B iodine [-f] [-u
.I user
.B ] [-P
.I password
.B ] [-m
.I fragsize
.B ] [-t
.I chrootdir
.B ] [-d
.I device
.B ] [-m
.I fragsize
.B ] [-z
.I context
.B ]
.B [
.I nameserver
.B ]
.I topdomain

.B iodined [-v]

.B iodined [-h]

.B iodined [-c] [-s] [-f] [-D] [-u
.I user
.B ] [-t
.I chrootdir
.B ] [-d
.I device
.B ] [-m
.I mtu
.B ] [-l
.I listen_ip
.B ] [-p
.I port
.B ] [-n
.I external ip
.B ] [-b
.I dnsport
.B ] [-P
.I password
.B ] [-z
.I context
.B ]
.I tunnel_ip
.B [
.I /netmask
.B ]
.I topdomain
.SH DESCRIPTION
.B iodine
lets you tunnel IPv4 data through a DNS 
server. This can be useful in situations where Internet access is firewalled,
but DNS queries are allowed. It needs a TUN/TAP device to operate. The 
bandwidth is asymmetrical with limited upstream and up to 1 Mbit/s downstream.
.B iodine
is the client application,
.B iodined
is the server.
.SH OPTIONS
.SS Common Options:
.TP
.B -v
Print version info and exit.
.TP
.B -h
Print usage info and exit.
.TP
.B -f
Keep running in foreground.
.TP
.B -u user
Drop privileges and run as user 'user' after setting up tunnel.
.TP
.B -t chrootdir
Chroot to 'chrootdir' after setting up tunnel.
.TP
.B -d device
Use the TUN device 'device' instead of the normal one, which is dnsX on Linux
and otherwise tunX.
.TP
.B -P password
Use 'password' to authenticate. If not used, 
.B stdin
will be used as input. Only the first 32 characters will be used.
.TP
.B -z context
Apply SELinux 'context' after initialization.
.SS Client Options:
.TP
.B -m fragsize
Maximum downstream fragsize. Not setting this will cause the client to probe
the maximum accepted downstream packet size.
.SS Server Options:
.TP
.B -c
Disable checks on client IP on all incoming requests.
.TP
.B -s
Don't try to configure IP address or MTU. This should only be used if
you have already configured the device that will be used.
.TP
.B -D
Increase debug level. Level 1 prints info about each RX/TX packet.
.TP
.B -m mtu
Set 'mtu' as mtu size for the tunnel device. This will be sent to the client
on connect, and the client will use the same mtu.
.TP
.B -l listen_ip
Make the server listen only on 'listen_ip' instead of on 0.0.0.0 for incoming
connections.
.TP
.B -p port
Make the server listen on 'port' instead of 53 for traffic. 
.B Note:
You must make sure the dns requests are forwarded to this port yourself.
.TP
.B -n external ip
The IP address to return in NS responses. Default is to return the address used
as destination in the query.
.TP
.B -b dnsport
If this port is specified, all incoming requests not inside the tunnel domain
will be forwarded to this port on localhost, to be handled by a real dns.
.SS Client Arguments:
.TP
.B nameserver
The nameserver to use to relay the dns traffic. This can be any relaying
nameserver  or the ip number of the server running iodined if reachable.
This argument is optional, and if not specified a nameserver will be read
from the
.I /etc/resolv.conf
file.
.TP
.B topdomain
The dns traffic will be sent as querys of type NULL for subdomains under
\'topdomain'. This is normally a subdomain to a domain you own. Use a short
domain name to get better throughput. If 
.B nameserver
is the iodined server, then the topdomain can be chosen freely. This argument
must be the same on both the client and the server.
.SS Server Arguments:
.TP
.B tunnel_ip[/netmask]
This is the servers ip address on the tunnel interface. The client will be
given the next ip number in the range. It is recommended to use the 
10.0.0.0 or 172.16.0.0 ranges. The default netmask is /27, can be overriden
by specifying it here. Using a smaller network will limit the number of
concurrent users.
.TP
.B topdomain
The dns traffic will is expected to be sent as querys of type NULL for 
subdomains under 'topdomain'. This is normally a subdomain to a domain you 
own. Use a short domain name to get better throughput. This argument must be 
the same on both the client and the server.
.SH EXAMPLES
.SS Quickstart:
.TP
Try it out within your own LAN! Follow these simple steps:
.TP
- On your server, run: ./iodined \-f 10.0.0.1 test.asdf
(If you already use the 10.0.0.0 network, use another internal net like 
172.16.0.0)
.TP
- Enter a password
.TP
- On the client, run: ./iodine \-f 192.168.0.1 test.asdf
(Replace 192.168.0.1 with the server's ip address)
.TP
- Enter the same password
.TP
- Now the client has the tunnel ip 10.0.0.2 and the server has 10.0.0.1
.TP
- Try pinging each other through the tunnel
.TP
- Done! :)
.TP
To actually use it through a relaying nameserver, see below.
.SS Full setup:

.TP
.B Server side:
To use this tunnel, you need control over a real domain (like mytunnel.com),
and a server with a public IP number. If the server already runs a DNS
server, change the listening port and then use the \-b option to let
iodined forward the DNS requests. Then, delegate a subdomain 
(say, tunnel1.mytunnel.com) to the server. If you use BIND for the domain, 
add these lines to the zone file (replace 10.15.213.99 with your server ip):

.nf
tunnel1host	IN	A	10.15.213.99
tunnel1		IN	NS	tunnel1host.mytunnel.com.
.fi

Now any DNS querys for domains ending with tunnel1.mytunnnel.com will be sent
to your server. Start iodined on the server. The first argument is the tunnel
IP address (like 192.168.99.1) and the second is the assigned domain (in this
case tunnel1.mytunnel.com). The \-f argument will keep iodined running in the
foreground, which helps when testing. iodined will start a virtual interface,
and also start listening for DNS queries on UDP port 53. Either enter a
password on the commandline (\-P pass) or after the server has started. Now 
everything is ready for the client.
.TP
.B Client side: 
All the setup is done, just start iodine. It also takes two
arguments, the first is the local relaying DNS server and the second is the
domain used (tunnel1.mytunnnel.com). If DNS queries are allowed to any
computer, you can use the tunnel endpoint (example: 10.15.213.99 or
tunnel1host.mytunnel.com) as the first argument. The tunnel interface will get
an IP close to the servers (in this case 192.168.99.2) and a suitable MTU. 
Enter the same password as on the server either by argument or after the client
has started. Now you should be able to ping the other end of the tunnel from 
either side.  
.TP
.B Routing:
The normal case is to route all traffic through the DNS tunnel. To do this, first
add a route to the nameserver you use with the default gateway as gateway. Then
replace the default gateway with the servers IP address within the DNS tunnel,
and configure the server to do NAT.
.TP
.B Troubleshooting:
Use the \-D option on the server to show received and sent queries, or use a 
tool like Wireshark/tcpdump. The iodined server replies to NS requests sent for
subdomains of the tunnel domain. If your domain is tunnel.com, send a NS
request for foo.tunnel.com to see if the delegation works. dig is a good tool
for this: 
.nf
dig \-t NS foo123.tunnel.com
.fi
.TP
.B MTU issues:
These issues should be solved now, with automatic fragmentation of downstream 
packets. There should be no need to set the MTU explicitly on the server.
.SH BUGS
File bugs at http://dev.kryo.se/iodine/
.SH AUTHORS
Erik Ekman <yarrick@kryo.se> and Bjorn Andersson <flex@kryo.se>