linux – Jan Taczanowski's tech blog

Linux box as an IPv6 router with SLAAC and DHCPv6-PD

03/05/2017 Jan Taczanowski 2 Comments

Some time ago I replaced my Mikrotik router with linux box which is working as a router for my home network and as a server for some services.
I had to spend some time to set up IPv6 on linux in such way, that everything was working automatically and without need to configuring anything in statically way. This post will be only about IPv6 part of router configurations.
I omit IPv4 part and configurations of network interfaces, because it is well documented in internet.

My router is running on linux openSUSE leap 42.2. The configurations are the same for other distros but file paths of config files may be different.

eth0 – wan interface of the router

eth1 – lan interface of the router
To make the router working, I had to:

change some sysctls to obtain IPv6 address on wan interface of my router by Stateless autoconfiguration (SLAAC).
I used wide-dhcpv6-client client to obtain IPv6 adresses pool (DHCPv6-PD) to redistribute addresses from pool on my devices in home network.
Redistributing addresses is done by dnsmasq.

First step – sysctls:
Part of my /etc/sysctl.conf confgured to obtain IPv6 address from Stateless autoconfiguration (SLAAC) on wan interface – eth0:

# Enable IPv6 forwarding
net.ipv6.conf.all.forwarding = 1

# Obtain IPv6 address on wan interface by Stateless autoconfiguration (SLAAC)
net.ipv6.conf.eth0.accept_ra = 2

# I want to have one IPv6 address on my wan interface, based on my mac address. 
# Without this my router will also have temporary, random IPv6 addresses which will be changing over time.
net.ipv6.conf.all.use_tempaddr = 0
net.ipv6.conf.default.use_tempaddr = 0

# Enable IPv6 forwarding

net.ipv6.conf.all.forwarding = 1

# Obtain IPv6 address on wan interface by Stateless autoconfiguration (SLAAC)

net.ipv6.conf.eth0.accept_ra = 2

# I want to have one IPv6 address on my wan interface, based on my mac address.

# Without this my router will also have temporary, random IPv6 addresses which will be changing over time.

net.ipv6.conf.all.use_tempaddr = 0

net.ipv6.conf.default.use_tempaddr = 0

After reboot I can see that my wan interface has public IPv6 address:

eth0      Link encap:Ethernet  HWaddr 00:4F:62:XX:XX:XX  
          inet addr:37.X.X.X  Bcast:37.X.X.X  Mask:255.255.254.0
          inet6 addr: fe80::24f:62ff:fe16:bd48/64 Scope:Link
          inet6 addr: 2a03:XXXX:0:252:24f:62ff:fe16:bd48/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:264107 errors:0 dropped:0 overruns:0 frame:0
          TX packets:38333 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:33499400 (31.9 Mb)  TX bytes:25331826 (24.1 Mb)

eth0 Link encap:Ethernet HWaddr 00:4F:62:XX:XX:XX

inet addr:37.X.X.X Bcast:37.X.X.X Mask:255.255.254.0

inet6 addr: fe80::24f:62ff:fe16:bd48/64 Scope:Link

inet6 addr: 2a03:XXXX:0:252:24f:62ff:fe16:bd48/64 Scope:Global

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:264107 errors:0 dropped:0 overruns:0 frame:0

TX packets:38333 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:33499400 (31.9 Mb) TX bytes:25331826 (24.1 Mb)

Second step – wide-dhcpv6-client:
Configuration of wide-dhcpv6-client which will be obtaining IPv6 address pool (DHCPv6-PD) for lan interface (eth1)

router:~ # cat /etc/wide-dhcpv6/dhcp6c.conf 
# eth0 is my wan interface
interface eth0 { 
# request a non-temporary address   
    # request prefix delegation address
    send ia-pd 1;
    request domain-name-servers;
    request domain-name;
};

id-assoc pd 1 {
        prefix ::/64 infinity;
        prefix-interface eth1 {
                sla-len 0;

                # elated with ia-pd to configure subnet on lan interface - eth1
                sla-id 1;

                # "postfix" of IPv6 address on lan interface. 
                # if not configured interface will has EUI-64 (mac based) address.
                # In this case, eth1 will get a IPv6 ending with ::1
                ifid 1;
        };
};

router:~ # cat /etc/wide-dhcpv6/dhcp6c.conf

# eth0 is my wan interface

interface eth0 {

# request a non-temporary address

# request prefix delegation address

send ia-pd 1;

request domain-name-servers;

request domain-name;

};

id-assoc pd 1 {

prefix ::/64 infinity;

prefix-interface eth1 {

sla-len 0;

# elated with ia-pd to configure subnet on lan interface - eth1

sla-id 1;

# "postfix" of IPv6 address on lan interface.

# if not configured interface will has EUI-64 (mac based) address.

# In this case, eth1 will get a IPv6 ending with ::1

ifid 1;

};

Unfortunately package of wide-dhcpv6-client does not provide configuration file for systemd. To start up wide-dhcpv6-client by systemd I created wide-dhcpv6.service entry:

router:~ # cat /usr/lib/systemd/system/wide-dhcpv6.service;
[Unit]
Description=wide-dhcpv6
Before=dnsmasq.service
After=network.target ypbind.service nfs.service nfsserver.service rpcbind.service SuSEfirewall2_init.service

[Service]
ExecStart=/usr/sbin/dhcp6c -c /etc/wide-dhcpv6/dhcp6c.conf -P default -d -D -f eth0
RemainAfterExit=true

[Install]
WantedBy=multi-user.target

router:~ # cat /usr/lib/systemd/system/wide-dhcpv6.service;

[Unit]

Description=wide-dhcpv6

Before=dnsmasq.service

After=network.target ypbind.service nfs.service nfsserver.service rpcbind.service SuSEfirewall2_init.service

[Service]

ExecStart=/usr/sbin/dhcp6c -c /etc/wide-dhcpv6/dhcp6c.conf -P default -d -D -f eth0

RemainAfterExit=true

[Install]

WantedBy=multi-user.target

Enable it on system startup:

router:~ # systemctl enable wide-dhcpv6.service
Created symlink from /etc/systemd/system/multi-user.target.wants/wide-dhcpv6.service to /usr/lib/systemd/system/wide-dhcpv6.service.

1 2	router:~ # systemctl enable wide-dhcpv6.service Created symlink from /etc/systemd/system/multi-user.target.wants/wide-dhcpv6.service to /usr/lib/systemd/system/wide-dhcpv6.service.

After reboot I can see that my lan interface (eth1) has assignment IPv6 address with prefix:

eth1      Link encap:Ethernet  HWaddr C0:3F:D5:6D:F4:5C  
          inet addr:192.168.51.1  Bcast:192.168.51.255  Mask:255.255.255.0
          inet6 addr: fe80::c23f:d5ff:fe6d:f45c/64 Scope:Link
          inet6 addr: 2a03:XXXX:252f:e900::1/56 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:361458 errors:0 dropped:0 overruns:0 frame:0
          TX packets:92615 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:61669608 (58.8 Mb)  TX bytes:31434041 (29.9 Mb)
          Interrupt:20 Memory:f7c00000-f7c20000

eth1 Link encap:Ethernet HWaddr C0:3F:D5:6D:F4:5C

inet addr:192.168.51.1 Bcast:192.168.51.255 Mask:255.255.255.0

inet6 addr: fe80::c23f:d5ff:fe6d:f45c/64 Scope:Link

inet6 addr: 2a03:XXXX:252f:e900::1/56 Scope:Global

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:361458 errors:0 dropped:0 overruns:0 frame:0

TX packets:92615 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:61669608 (58.8 Mb) TX bytes:31434041 (29.9 Mb)

Interrupt:20 Memory:f7c00000-f7c20000

Last step – dnsmasq:
Part of configuration of dnsmasq (/etc/dnsmasq.conf) to redistributing IPv6 addresses in home network. Dnsmasq will also work as dns cache. :

# don't listen to anything on eth0
except-interface=eth0

bogus-priv

# IPv6 Route Advertisements
enable-ra

# Create a IPv6 range from address on the interface. The ::1 is related to the ifid in /etc/wide-dhcpv6/dhcp6c.conf.
dhcp-range=tag:eth1,::1,constructor:eth1, ra-names, 12h

# ra-names - it gives DNS names to IPv6 hosts
local=/home/

# don't listen to anything on eth0

except-interface=eth0

bogus-priv

# IPv6 Route Advertisements

enable-ra

# Create a IPv6 range from address on the interface. The ::1 is related to the ifid in /etc/wide-dhcpv6/dhcp6c.conf.

dhcp-range=tag:eth1,::1,constructor:eth1, ra-names, 12h

# ra-names - it gives DNS names to IPv6 hosts

local=/home/

Enable dnsmasq on system startup:

router:~ # systemctl enable dnsmasq.service
Created symlink from /etc/systemd/system/multi-user.target.wants/dnsmasq.service to /usr/lib/systemd/system/dnsmasq.service.

1 2	router:~ # systemctl enable dnsmasq.service Created symlink from /etc/systemd/system/multi-user.target.wants/dnsmasq.service to /usr/lib/systemd/system/dnsmasq.service.

After reboot, devices in home network should be able to use internet by IPv6 🙂

But now, devices in home network are avaible from outside. Each of device has own public IPv6 address which is awailable from outside (internet).

We have to secure it, by allowing only for connections which are initialized from our internal network. It can be done by ip6tables.

ip6tables -A FORWARD -m state --state NEW -i eth1 -o eth0 -j ACCEPT
ip6tables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
ip6tables -P FORWARD DROP

ip6tables -A FORWARD -m state --state NEW -i eth1 -o eth0 -j ACCEPT

ip6tables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

ip6tables -P FORWARD DROP

It’s all, described configuration works flawlessly for me for days 🙂

Securing ssh by iptables rules

16/04/2017 Jan Taczanowski 3 Comments

I secured my ssh server in simple way – with iptables rules which will be blocking attackers. I setup my iptables in such way, that it is allowing only one tcp syn packet to ssh port per minute from one ip address. With aditional configuration of sshd daemon the rules will allowing for once login attempt per hour.
iptables rules:

iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -I INPUT -i eth0 -m tcp -p tcp --dport 22 -m state --state NEW -m hashlimit \
--hashlimit-upto 1/hour --hashlimit-burst 1 --hashlimit-htable-expire 3600000 --hashlimit-mode srcip \
--hashlimit-name ssh -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 22 -j DROP

iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state ESTABLISHED,RELATED -j ACCEPT

iptables -I INPUT -i eth0 -m tcp -p tcp --dport 22 -m state --state NEW -m hashlimit \

--hashlimit-upto 1/hour --hashlimit-burst 1 --hashlimit-htable-expire 3600000 --hashlimit-mode srcip \

--hashlimit-name ssh -j ACCEPT

iptables -A INPUT -i eth0 -p tcp --dport 22 -j DROP

After we reaches this one new connection per hour, the hashlimit-htable-expire rule starts to counting 60 minutes (3600000ms). In this time you can not connect again to ssh.

MaxAuthTries in /etc/ssh/sshd_config – this is important, with this, sshd will be closing ssh connections after authentication failure, thus attacker will have to create new ssh connection (and tcp connection) to try again. This fact (new syn packet) will by noticed by iptables.

MaxAuthTries 3

1	MaxAuthTries 3

If you use only public key authentication, you can set MaxAuthTries to 1 because this is first authentication method provided by OpenSSH server, also ssh clients firstly tries authenticate through public key. Other authentication methods are on further places.

debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey

With MaxAuthTries set to 1 only fist authentication method will work – usually publickey.

You can check the blocked addresses:

router:~ # cat /proc/net/ipt_hashlimit/ssh
16 216.98.212.11:0->0.0.0.0:0 90670848 108000000 36000000
338 42.7.26.55:0->0.0.0.0:0 80364416 108000000 36000000
553 116.31.116.50:0->0.0.0.0:0 31482240 108000000 36000000
593 123.183.209.134:0->0.0.0.0:0 32435072 108000000 36000000

router:~ # cat /proc/net/ipt_hashlimit/ssh

16 216.98.212.11:0->0.0.0.0:0 90670848 108000000 36000000

338 42.7.26.55:0->0.0.0.0:0 80364416 108000000 36000000

553 116.31.116.50:0->0.0.0.0:0 31482240 108000000 36000000

593 123.183.209.134:0->0.0.0.0:0 32435072 108000000 36000000

This rules very limited strength of attacks on my ssh.

Please test this first with another server access!

NanoPi NEO as remote SDR server for RTL2832u

17/02/2017 Jan Taczanowski No Comments

Hi!
Today I will show how to make remote SDR radio server for RTL2832u dongle with very small and cheap device such as NanoPi NEO.

The main purpose of this is that I want place the NanoPI with RTL dongle and antenna attached to it on remote location – on high building 250 meters far away from my home. I have wireless bridge connecting my home with this place.

Notice: Wireless have to be able to send about 16Mb/s of tcp trafic from NanoPi to PC.

On NanoPi I installed Armian Linux. After that I was set up rtl_tcp server:
900001 – this is lowest sample-rate which can be used, I used lowest because my wireless bridge wasn’t able to pass more traffic.

 apt-get install rtl-sdr; rtl_tcp -a 0.0.0.0 -s 900001

1	apt-get install rtl-sdr; rtl_tcp -a 0.0.0.0 -s 900001

 _   _                   ____  _   _   _            
| \ | | __ _ _ __   ___ |  _ \(_) | \ | | ___  ___  
|  \| |/ _` | '_ \ / _ \| |_) | | |  \| |/ _ \/ _ \ 
| |\  | (_| | | | | (_) |  __/| | | |\  |  __/ (_) |
|_| \_|\__,_|_| |_|\___/|_|   |_| |_| \_|\___|\___/ 
                                                    

Welcome to ARMBIAN 5.25 stable Ubuntu 16.04.1 LTS 4.9.4-sun8i   
System load:   0.44            	Up time:       7 days		
Memory usage:  4 % of 497Mb  	IP:            192.168.51.30
CPU temp:      34°C           	
Usage of /:    17% of 14G    	


[ 23 updates to install: apt-get upgrade ]

Last login: Fri Feb 17 00:16:31 2017 from 192.168.51.24

root@nanopineo:~# apt-get install rtl-sdr
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  rtl-sdr
0 upgraded, 1 newly installed, 0 to remove and 23 not upgraded.
Need to get 0 B/50.0 kB of archives.
After this operation, 159 kB of additional disk space will be used.
Selecting previously unselected package rtl-sdr.
(Reading database ... 75756 files and directories currently installed.)
Preparing to unpack .../rtl-sdr_0.5.3-5_armhf.deb ...
Unpacking rtl-sdr (0.5.3-5) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up rtl-sdr (0.5.3-5) ...

root@nanopineo:~# rtl_tcp -a 0.0.0.0 -s 900001
Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Lifeview LV5TDeluxe
Found Fitipower FC0013 tuner
Exact sample rate is: 900001.019241 Hz
Tuned to 100000000 Hz.
listening...
Use the device argument 'rtl_tcp=0.0.0.0:1234' in OsmoSDR (gr-osmosdr) source
to receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...).

_ _ ____ _ _ _

| \ | | __ _ _ __ ___ | _ \(_) | \ | | ___ ___

| \| |/ _` | '_ \ / _ \| |_) | | | \| |/ _ \/ _ \

| |\ | (_| | | | | (_) | __/| | | |\ | __/ (_) |

|_| \_|\__,_|_| |_|\___/|_| |_| |_| \_|\___|\___/

Welcome to ARMBIAN 5.25 stable Ubuntu 16.04.1 LTS 4.9.4-sun8i

System load: 0.44 Up time: 7 days

Memory usage: 4 % of 497Mb IP: 192.168.51.30

CPU temp: 34°C

Usage of /: 17% of 14G

[ 23 updates to install: apt-get upgrade ]

Last login: Fri Feb 17 00:16:31 2017 from 192.168.51.24

root@nanopineo:~# apt-get install rtl-sdr

Reading package lists... Done

Building dependency tree

Reading state information... Done

The following NEW packages will be installed:

rtl-sdr

0 upgraded, 1 newly installed, 0 to remove and 23 not upgraded.

Need to get 0 B/50.0 kB of archives.

After this operation, 159 kB of additional disk space will be used.

Selecting previously unselected package rtl-sdr.

(Reading database ... 75756 files and directories currently installed.)

Preparing to unpack .../rtl-sdr_0.5.3-5_armhf.deb ...

Unpacking rtl-sdr (0.5.3-5) ...

Processing triggers for man-db (2.7.5-1) ...

Setting up rtl-sdr (0.5.3-5) ...

root@nanopineo:~# rtl_tcp -a 0.0.0.0 -s 900001

Found 1 device(s):

0: Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Lifeview LV5TDeluxe

Found Fitipower FC0013 tuner

Exact sample rate is: 900001.019241 Hz

Tuned to 100000000 Hz.

listening...

Use the device argument 'rtl_tcp=0.0.0.0:1234' in OsmoSDR (gr-osmosdr) source

to receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...).

The next step was to setup and start gqrx on my home computer:
Notice: Input rate must be the same as set on rtl_tcp server. 192.168.51.30 – this is IP address of my NanoPi.

And now, we can hear everything around us 🙂

Raspberry Pi 2b as a home router with Cisco switch and VLANs

28/02/2016 Jan Taczanowski 5 Comments

Hi!

Some time ago I configured my Raspberry Pi as a home router. Below, in short brief is shown my configuration.
raspberry_cisco_switch

On the Cisco switch, I have created two vlans:
vlan10 – WAN (Internet connection)
vlan20 – LAN (Home network)

The first port of the Cisco switch is connected to the the Internet, and is configured as access port for vlan10. The second port is connected to the Raspberry Pi as trunk port – traffic from vlan10 and vlan20 is tagged on this port. Third port is in access mode and is connected to the home access point.

interface FastEthernet0/3
 switchport access vlan 20
!
interface FastEthernet0/2
 switchport mode trunk
!
interface FastEthernet0/1
 switchport access vlan 10
!
interface Vlan20
 ip address 192.168.50.2 255.255.255.0

interface FastEthernet0/3

switchport access vlan 20

interface FastEthernet0/2

switchport mode trunk

interface FastEthernet0/1

switchport access vlan 10

interface Vlan20

ip address 192.168.50.2 255.255.255.0

Switch#show vlan brief 

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/4
10   INTERNET                         active    Fa0/1
20   LAN                              active    Fa0/3

Switch#show vlan brief

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

1 default active Fa0/4

10 INTERNET active Fa0/1

20 LAN active Fa0/3

Network configuration on Raspberry Pi looks as follows:

root@raspberrypi:/home/pi# cat /etc/network/interfaces 
auto lo

iface lo inet loopback
# Management
iface eth0 inet static
        address 192.168.100.1
        netmask 255.255.255.0
        post-up ifup vlan10
        post-up ifup vlan20

# Internet
auto vlan10
iface vlan10 inet dhcp
        hwaddress ether 00:12:2a:a7:f7:c0
        vlan-raw-device eth0
# Home network
auto vlan20
iface vlan20 inet static
        address 192.168.50.1
        netmask 255.255.255.0
        vlan-raw-device eth0

root@raspberrypi:/home/pi# cat /etc/network/interfaces

auto lo

iface lo inet loopback

# Management

iface eth0 inet static

address 192.168.100.1

netmask 255.255.255.0

post-up ifup vlan10

post-up ifup vlan20

# Internet

auto vlan10

iface vlan10 inet dhcp

hwaddress ether 00:12:2a:a7:f7:c0

vlan-raw-device eth0

# Home network

auto vlan20

iface vlan20 inet static

address 192.168.50.1

netmask 255.255.255.0

vlan-raw-device eth0

On eth0 interface I have set 192.168.100.1 address for management purpose in case of problems with access to the Raspberry Pi from vlan’s side. On vlan10 interface I have to set the custom mac address to obtain IP address from my internet provider. Vlan20 with addresses 192.168.50.1/24 is for my home network.
The rest of my configuration like NAT, dhcp, dns is pretty standard and will not be posted about it here. If you have questions, I will be happy to answer in the comments 🙂

How Raspberry Pi performs as a router on my 100/50 Mb/s internet connection? Quite nicely for a network card supported by USB – which has Raspberry.
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