Verona, 29/07/2005

*Sorry, this document is in italian only, if you need it translated in english feel free to ask, I will try to find time to translate it :)*

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 dated June, 1991.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.

On Debian GNU/Linux systems, the complete text of the GNU General
Public License can be found in `/usr/share/common-licenses/GPL'.

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

NOTA: la prima parte indica come abilitare una singola subnet IPv6 tramite OpenVPN. Per poter avere piu' subnet e' necessario passare ai certificati ed al tunnel di tipo tap (tun non supporta IPv6 in modalita' server/multiclient).

PRIMA PARTE

Cosa: Questo breve documento illustra come abilitare un host IPv6 in una subnet assegnatavi, su una macchina remota tramite OpenVPN.
Come: Avremo bisogno di uno spazio di indirizzi IPv6 funzionante su un host, sul quale sia stata attivata anche una subnet. Io uso Sixxs <www.sixxs.net>.

Premessa

Abbiamo una macchina connessa ad Internet cui viene fatto puntare l'indirizzo IPv6 base del tunnel, che fara' da gateway per la subnet. Ovviamente se noi siamo connessi con un'altra macchina, diciamo attraverso una adsl, ecco che non facendo parte della rete del gateway non potremmo avere un indirizzo della subnet da usare a casa. Per ovviare a questo dovremo usare OpenVPN.

La prima cosa da fare, quindi, e' quella di attivare OpenVPN, avendo l'accortezza di usare l'opzione tun-ipv6.

Configurazione di OpenVPN lato gateway (con shared key):

[/etc/openvpn/static-jenny.conf]
#
# Sample OpenVPN configuration file for
# office using a pre-shared static key.
#
# '#' or ';' may be used to delimit comments.

# Use a dynamic tun device.
# For Linux 2.2 or non-Linux OSes,
# you may want to use an explicit
# unit number such as "tun1".
# OpenVPN also supports virtual
# ethernet "tap" devices.
dev tun
tun-ipv6

# 10.1.0.1 is our local VPN endpoint (office).
# 10.1.0.2 is our remote VPN endpoint (home).
ifconfig 192.168.2.1 192.168.2.2

# Our up script will establish routes
# once the VPN is alive.
up /etc/openvpn/jenny.up

# Our pre-shared static key
secret /etc/openvpn/static.key

# OpenVPN uses UDP port 1194 by default.
# Each OpenVPN tunnel must use
# a different port number.
# lport or rport can be used
# to denote different ports
# for local and remote.
; port 1194

# Downgrade UID and GID to
# "nobody" after initialization
# for extra security.
; user nobody
; group nobody

# If you built OpenVPN with
# LZO compression, uncomment
# out the following line.
; comp-lzo

# Send a UDP ping to remote once
# every 15 seconds to keep
# stateful firewall connection
# alive. Uncomment this
# out if you are using a stateful
# firewall.
; ping 15

# Uncomment this section for a more reliable detection when a system
# loses its connection. For example, dial-ups or laptops that
# travel to other locations.
; ping 15
; ping-restart 45
; ping-timer-rem
; persist-tun
; persist-key

# Verbosity level.
# 0 -- quiet except for fatal errors.
# 1 -- mostly quiet, but display non-fatal network errors.
# 3 -- medium output, good for normal operation.
# 9 -- verbose, good for troubleshooting
verb 3

[/etc/openvpn/jenny.up]
#!/bin/bash
route add -net 192.168.2.0 netmask 255.255.255.0 gw $5

Configurazione lato remoto (GATEWAYIPV4 e' l'indirizzo IPv4 del gateway)

[/etc/openvpn/static-remote.conf]
#
# Sample OpenVPN configuration file for
# home using a pre-shared static key.
#
# '#' or ';' may be used to delimit comments.

# Our OpenVPN peer is the office gateway.
remote GATEWAYIPV4

# 10.1.0.2 is our local VPN endpoint (home).
# 10.1.0.1 is our remote VPN endpoint (office).
ifconfig 192.168.2.2 192.168.2.1

# Our up script will establish routes
# once the VPN is alive.
up /etc/openvpn/remote.up

# Our pre-shared static key
secret /etc/openvpn/static.key

# OpenVPN uses UDP port 1194 by default.
# Each OpenVPN tunnel must use
# a different port number.
# lport or rport can be used
# to denote different ports
# for local and remote.
; port 1194

# Downgrade UID and GID to
# "nobody" after initialization
# for extra security.
; user nobody
; group nobody

# If you built OpenVPN with
# LZO compression, uncomment
# out the following line.
; comp-lzo

# Send a UDP ping to remote once
# every 15 seconds to keep
# stateful firewall connection
# alive. Uncomment this
# out if you are using a stateful
# firewall.
; ping 15

[/etc/openvpn/remote.up]
#!/bin/bash
route add -net 192.168.2.0 netmask 255.255.255.0 gw $5

A questo punto facendo partire OpenVPN dovremmo avere la nostra connessione con il tunnel tun0 abilitato:

gateway: ifconfig
tun0 Link encap:UNSPEC HWaddr 38-30-3A-30-30-30-30-3A-00-00-00-00-00-00-00-00
inet addr:192.168.2.1 P-t-P:192.168.2.2 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1

remote: ifconfig
tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:192.168.2.2 P-t-P:192.168.2.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1

ed infatti dovremmo essere in grado di pingare i due lati della VPN:
remote: ping 192.168.2.1
PING 192.168.2.1 (192.168.2.1) 56(84) bytes of data.
64 bytes from 192.168.2.1: icmp_seq=1 ttl=64 time=122 ms

A questo punto dobbiamo iniziare a lavorare su IPv6

Per prima cosa modifichiamo lo script di avvio della VPN del gateway. Come indirizzo IPv6 con scope Link ho preso l'ho successivo a quello che ha eth0, sempre come scope link:
inet6 addr: fe80::201:2ff:fede:c1ab/64 Scope:Link -> inet6 addr: fe80::201:2ff:fede:c1ac/64 Scope:Link

Ora il file jenny.up sara':

#!/bin/bash
route add -net 192.168.2.0 netmask 255.255.255.0 gw $5

ip -6 addr add fe80::201:2ff:fede:c1ac/64 dev tun0 scope link >/dev/null 2>&1
ip -6 addr add 2001:1418:13c::1 dev tun0 >/dev/null 2>&1
ip -6 route add 2001:1418:13c::2 dev tun0 >/dev/null 2>&1

Il primo indirizzo aggiunto serve per fare andare radv (che vedremo) in quanto richiede un indirizzo con scope link, il secondo e' un indirizzo della subnet che ci e' stata assegnata da sixxs. il terzo comando fa ruotare i pacchetti IPv6 verso quella sottorete verso il tunnel tun0

Piu' o meno sul remote faremo cose simili, con l'accortezza di far ruotare anche il default verso il tunnel, ora remote.up sara':

#!/bin/bash
route add -net 192.168.2.0 netmask 255.255.255.0 gw $5

# IPv6
ip -6 route del fe80::/64 dev eth0 >/dev/null 2>&1
ip -6 route del ff00::/8 dev eth0 >/dev/null 2>&1
ip -6 addr add fe80::20e:a6ff:fe1f:26e2 dev tun0 scope link >/dev/null 2>&1
ip -6 addr add 2001:1418:13c::2 dev tun0 >/dev/null 2>&1
ip -6 route add fe80::/64 dev tun0 >/dev/null 2>&1
ip -6 route add ff00::/8 dev tun0 >/dev/null 2>&1
ip -6 route add 2001:1418:13c::1 dev tun0 >/dev/null 2>&1
ip -6 route add default via 2001:1418:13c::1 dev tun0 >/dev/null 2>&1

I primi due comandi tolgono a eth0 ilrouting di default che viene assegnato loro quando sono inizializzate, il terzo aggiunge al tunnel tun0 l'IP con scope Link, il quarto aggiunge sempre a tun0 l'IPv6 della subnet, poi vengono aggiunti alcuni routing richiesti, nonche' il default finale indicando come raggiungere il gateway per poi usarlo, appunto, come gateway IPv6

Ora le cose non funzionano ancora, serve un demone che gestisca il routing, e questo e' radv (apt-get install radvd). La configurazione e' piuttosto semplice.
Lato gateway:
[/etc/radvd.conf]
interface tun0
{
AdvSendAdvert on;
UnicastOnly on;
prefix 2001:1418:13c::/64
{
};
};

Lato remote:
[/etc/radvd.conf]
interface tun0
{
AdvSendAdvert on;
UnicastOnly on;
prefix 2001:1418:13c::/64
{
};
};

Ora facendo partire radvd con [/etc/init.d/radvd start] la nostra macchina dovrebbe avere una connessione IPv6 all'indirizzo 2001:1418:13c::2, proviamo a pingare il gateway:
remote: ping6 2001:1418:13c::1
64 bytes from 2001:1418:13c::1: icmp_seq=1 ttl=64 time=121 ms

proviamo un traceroute verso un host IPv6:
remote: traceroute6 www.linux.it
traceroute to picard.linux.it (2001:1418:13:2::1) from 2001:1418:13c::2, 30 hops max, 16 byte packets
1 2001:1418:13c::1 (2001:1418:13c::1) 122.57 ms 120.716 ms 122.371 ms
2 gw-15.trn-01.it.sixxs.net (2001:1418:100:e::1) 157.771 ms 157.89 ms 158.811 ms
3 if-1-12.charleston.CBQ.TRN.ipv6.ITgate.net (2001:1418:10:2::1) 158.129 ms 157.942 ms 153.751 ms
4 if-0-0.hula.core.TRN.ipv6.ITgate.net (2001:1418:1:101::17) 153.164 ms 155.912 ms 154.571 ms
5 picard.linux.it (2001:1418:13:2::1) 169.895 ms 166.016 ms 166.25 ms

Ottimo, se ora proviamo ad andare su www.sixxs.net vedremo basso a:

Not logged in.
non-SSL IPv6 connection from 2001:1418:13c::2

Oppure su www.kame.net vedremo la tartaruga animata, indicante che IPv6 funziona.

SECONDA PARTE

OpenVPN nella versione attuale non supporta, tramite il tipo di interfaccia tun, IPv6, per cui dobbiamo per forza passare alla versione tap (per le differenze guardate la documentazione ufficiale, in sostanza tun e' un collegamento punto-punto mentre tap simula una scheda di rete separata).
Cogliamo quindi l'occasione per abbandonare l'autenticazione shared key per passare a quella, piu' sicura, dei certificati. Facciamo sempre riferimento alla documentazione sul sito di openvpn per vedere come si implementa l'autenticazione mediante certificati, ecco alcuni miei file di configurazione. Consideriamo che voglio configurare 2 subnet remote, 2001:1418:13c:2::1/64 e 2001:1418:13c:3::1/64.

Lato server:

/etc/openvpn/server.conf

#################################################
# Sample OpenVPN 2.0 config file for #
# multi-client server. #
# #
# This file is for the server side #
# of a many-clients <-> one-server #
# OpenVPN configuration. #
# #
# OpenVPN also supports #
# single-machine <-> single-machine #
# configurations (See the Examples page #
# on the web site for more info). #
# #
# This config should work on Windows #
# or Linux/BSD systems. Remember on #
# Windows to quote pathnames and use #
# double backslashes, e.g.: #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
# #
# Comments are preceded with '#' or ';' #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one. You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap" if you are ethernet bridging.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
dev tap
;dev tun
#tun-ipv6

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one. On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key). Each client
# and the server must have their own cert and
# key file. The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys. Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).

# Kevin
ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/server.crt
key /etc/openvpn/easy-rsa/keys/server.key # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
# openssl dhparam -out dh1024.pem 1024
# Substitute 2048 for 1024 if you are using
# 2048 bit keys.

# Kevin
dh /etc/openvpn/easy-rsa/keys/dh1024.pem

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.

# Kevin
server 192.168.2.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file. If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
#ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface. Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0. Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients. Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Push routes to the client to allow it
# to reach other private subnets behind
# the server. Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
# iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN. This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
client-config-dir ccd
route 192.168.2.0 255.255.255.252
# Then add this line to ccd/Thelonious:
# ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients. There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
# group, and firewall the TUN/TAP interface
# for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
# modify the firewall in response to access
# from different clients. See man
# page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# the TUN/TAP interface to the internet in
# order for this to work properly).
# CAVEAT: May break client's network config if
# client's local DHCP server packets get routed
# through the tunnel. Solution: make sure
# client's local DHCP server is reachable via
# a more specific route than the default route
# of 0.0.0.0/0.0.0.0.
;push "redirect-gateway"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses. CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
;push "dhcp-option DNS 10.8.0.1"
;push "dhcp-option WINS 10.8.0.1"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names. This is recommended
# only for testing purposes. For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
# openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
;tls-auth ta.key 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC # Blowfish (default)
;cipher AES-128-CBC # AES
;cipher DES-EDE3-CBC # Triple-DES

# Enable compression on the VPN link.
# If you enable it here, you must also
# enable it in the client config file.
comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
user nobody
group nogroup

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it. Use one
# or the other (but not both).

# Kevin
log openvpn.log
log-append openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages. At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

# Kevin
#client-connect /etc/openvpn/scripts/client.up
route-gateway 192.168.2.1

Come vedete il server e' configurato per usare come indirizzamento IPv4 della VPN la classe 192.168.2.0/24.

Configurazione di un client:

/etc/openvpn/client3.conf

##############################################
# Sample client-side OpenVPN 2.0 config file #
# for connecting to multi-client server. #
# #
# This configuration can be used by multiple #
# clients, however each client should have #
# its own cert and key files. #
# #
# On Windows, you might want to rename this #
# file so it has a .ovpn extension #
##############################################

# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
client

# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
dev tap
;dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one. On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
;dev-node MyTap

# Are we connecting to a TCP or
# UDP server? Use the same setting as
# on the server.
;proto tcp
proto udp

# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote jenny.bestkevin.com 1194
;remote my-server-2 1194

# Choose a random host from the remote
# list for load-balancing. Otherwise
# try hosts in the order specified.
;remote-random

# Keep trying indefinitely to resolve the
# host name of the OpenVPN server. Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
resolv-retry infinite

# Most clients don't need to bind to
# a specific local port number.
nobind

# Downgrade privileges after initialization (non-Windows only)
user nobody
group nogroup

# Try to preserve some state across restarts.
persist-key
persist-tun

# If you are connecting through an
# HTTP proxy to reach the actual OpenVPN
# server, put the proxy server/IP and
# port number here. See the man page
# if your proxy server requires
# authentication.
;http-proxy-retry # retry on connection failures
;http-proxy [proxy server] [proxy port #]

# Wireless networks often produce a lot
# of duplicate packets. Set this flag
# to silence duplicate packet warnings.
;mute-replay-warnings

# SSL/TLS parms.
# See the server config file for more
# description. It's best to use
# a separate .crt/.key file pair
# for each client. A single ca
# file can be used for all clients.
ca /etc/openvpn/ca.crt
cert /etc/openvpn/client3.crt
key /etc/openvpn/client3.key

# Verify server certificate by checking
# that the certicate has the nsCertType
# field set to "server". This is an
# important precaution to protect against
# a potential attack discussed here:
# http://openvpn.net/howto.html#mitm
#
# To use this feature, you will need to generate
# your server certificates with the nsCertType
# field set to "server". The build-key-server
# script in the easy-rsa folder will do this.
;ns-cert-type server

# If a tls-auth key is used on the server
# then every client must also have the key.
;tls-auth ta.key 1

# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
;cipher x

# Enable compression on the VPN link.
# Don't enable this unless it is also
# enabled in the server config file.
comp-lzo

# Set log file verbosity.
verb 3

# Silence repeating messages
;mute 20

up /etc/openvpn/IPv6

L'ultima riga e' importante perche' lancia lo script seguente che si occupa di configurare il routing:

/etc/openvpn/IPv6

#!/bin/bash

# IPv6
ip -6 route del fe80::/64 dev eth0 # >/dev/null 2>&1
ip -6 route del ff00::/8 dev eth0 # >/dev/null 2>&1
ip -6 addr add 2001:1418:13c:0004::2/64 dev tap0 # >/dev/null 2>&1
ip -6 addr add fe80::20e:a6ff:fe1f:26e2 dev tap0 scope link # >/dev/null 2>&1
ip -6 route add 2001:1418:13c:0004::1/64 dev tap0 # >/dev/null 2>&1
ip -6 route add default via 2001:1418:13c:0004::1 dev tap0 # >/dev/null 2>&1

A questo punto dovreste riuscire a portare a termine con successo i test indicati in precedenza.

Troubleshooting

Se avete problemi, la cosa migliore e' sempre usare tcpdump, ricordandovi di analizzare tun0 ed eventualmente, se avete altro traffico ipv4, selezionare il proto 41:

tcpdump -n -i tun0 proto 41

sia lato gateway che lato remoto.

Risoluzione DNS con bind

Con sixxs.net viene delegato anche la risoluzione inversa degli indirizzi IP, il che e' molto comodo...vediamo alcuni file di configurazione:

Diretta:

$TTL 86400
@ IN SOA isn1.infosysnet.net. root.isn1.infosysnet.net. (
2005071300 ; serial number yymm.dd[0-9][0-9]
86400 ; refresh time
1800 ; retry
2592000 ; expire
86400 ; minimum
)

...
...

jenny6 IN AAAA 2001:1418:13c:1::1
www IN AAAA 2001:1418:13c:1::1

...
...

Il campo AAAA serve proprio per dare ad un host un indirizzo IPv6. Testiamolo:

dig AAAA jenny6.bestkevin.com

;; ANSWER SECTION:
jenny6.bestkevin.com. 84899 IN AAAA 2001:1418:13c:1::1

Vediamo ora il reverse. Nel file named.conf inseriamo le segg. righe:

zone "c.3.1.0.8.1.4.1.1.0.0.2.ip6.arpa" {
// 2001:1418:13c::/48
type master;
file "/etc/bind/db.ipv6";
};

notare che la zona e' scritta al rovescio con i punti, e che sono aggiunti gli 0 che di solito sono omessi (per cui :13c: diventa :013c: e quindi, rovesciata, c.3.1.0).
Nel file /etc/bind/db.ipv6 inseriamo ora la risoluzione vera e propria:

$TTL 604800
@ IN SOA isn1.infosysnet.net. hostmaster.infosysnet.net. (
2005072903 ; Serial
10800 ; Refresh
3600 ; Retry
2419200 ; Expire
604800 ) ; Default TTL

NS isn1.infosysnet.net.
TXT "2001:1418:13c::/64 Example IPv6 reverse"

;2001:1418:13c:1::1
;$ORIGIN c.3.1.0.8.1.4.1.1.0.0.2.ip6.arpa.
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0 IN PTR jenny6.bestkevin.com.

Anche qui, nulla di nuovo, considerate che al nome che avevamo indicato in precedenza per la zona nel named.conf viene aggiunto il pezzo indicato qui, per cui:

da:
zone "c.3.1.0.8.1.4.1.1.0.0.2.ip6.arpa" {
otteniamo
c.3.1.0.8.1.4.1.1.0.0.2
mentre da:

1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0 IN PTR jenny6.bestkevin.com.
otteniamo:
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0
per cui il nome definitivo da risolvere in inverso e':
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.c.3.1.0.8.1.4.1.1.0.0.2
che e' il nostro indirizzo IPv6.

Testiamolo:
dig -x 2001:1418:13c:1::1 @dnsserver
;; ANSWER SECTION:
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.c.3.1.0.8.1.4.1.1.0.0.2.ip6.arpa. 604800 IN PTR jenny6.bestkevin.com.

That's all folks...

Ogni commento e' benvenuto