NFV services tutorial

This tutorial will cover using faucet with Network Function Virtualisation (NFV) style services.

NFV services that will be demonstrated in this tutorial are:

  • DHCP/DNS server

  • Zeek (formerly known as Bro) Intrusion Detection System (IDS)

This tutorial demonstrates how the previous topics in this tutorial series can be combined to run real world services on our network.

Prerequisites

  • A good understanding of the previous tutorial topics (ACL tutorial, VLAN tutorial, Routing tutorial)

  • Install Faucet - Package installation steps 1 & 2

  • Install Open vSwitch - Connect your first datapath steps 1 & 2

  • Useful Bash Functions - Copy and paste the following definitions into your bash terminal, or to make them persistent between sessions add them to the bottom of your .bashrc and run ‘source .bashrc’.

    # Run command inside network namespace
    as_ns () {
        NAME=$1
        NETNS=faucet-${NAME}
        shift
        sudo ip netns exec ${NETNS} [email protected]
    }
    
    # Create network namespace
    create_ns () {
        NAME=$1
        IP=$2
        NETNS=faucet-${NAME}
        sudo ip netns add ${NETNS}
        sudo ip link add dev veth-${NAME} type veth peer name veth0 netns ${NETNS}
        sudo ip link set dev veth-${NAME} up
        as_ns ${NAME} ip link set dev lo up
        [ -n "${IP}" ] && as_ns ${NAME} ip addr add dev veth0 ${IP}
        as_ns ${NAME} ip link set dev veth0 up
    }
    
    # Clean up namespaces, bridges and processes created during faucet tutorial
    cleanup () {
        for NETNS in $(sudo ip netns list | grep "faucet-" | awk '{print $1}'); do
            [ -n "${NETNS}" ] || continue
            NAME=${NETNS#faucet-}
            if [ -f "/run/dhclient-${NAME}.pid" ]; then
                # Stop dhclient
                sudo pkill -F "/run/dhclient-${NAME}.pid"
            fi
            if [ -f "/run/iperf3-${NAME}.pid" ]; then
                # Stop iperf3
                sudo pkill -F "/run/iperf3-${NAME}.pid"
            fi
            if [ -f "/run/bird-${NAME}.pid" ]; then
                # Stop bird
                sudo pkill -F "/run/bird-${NAME}.pid"
            fi
            # Remove netns and veth pair
            sudo ip link delete veth-${NAME}
            sudo ip netns delete ${NETNS}
        done
        for isl in $(ip -o link show | awk -F': ' '{print $2}' | grep -oE "^l-br[0-9](_[0-9]*)?-br[0-9](_[0-9]*)?"); do
            # Delete inter-switch links
            sudo ip link delete dev $isl 2>/dev/null || true
        done
        for DNSMASQ in /run/dnsmasq-vlan*.pid; do
            [ -e "${DNSMASQ}" ] || continue
            # Stop dnsmasq
            sudo pkill -F "${DNSMASQ}"
        done
        # Remove faucet dataplane connection
        sudo ip link delete veth-faucet 2>/dev/null || true
        # Remove openvswitch bridges
        sudo ovs-vsctl --if-exists del-br br0
        sudo ovs-vsctl --if-exists del-br br1
        sudo ovs-vsctl --if-exists del-br br2
        sudo ovs-vsctl --if-exists del-br br3
    }
    
    # Add tagged VLAN interface to network namespace
    add_tagged_interface () {
         NAME=$1
         VLAN=$2
         IP=$3
         NETNS=faucet-${NAME}
         as_ns ${NAME} ip link add link veth0 name veth0.${VLAN} type vlan id ${VLAN}
         [ -n "${IP}" ] && as_ns ${NAME} ip addr add dev veth0.${VLAN} ${IP}
         as_ns ${NAME} ip link set dev veth0.${VLAN} up
         as_ns ${NAME} ip addr flush dev veth0
    }
    
  • Run the cleanup script to remove old namespaces and switches:

    cleanup
    

Network setup

The network will be divided into three VLANs, two of which are client VLANs (200 & 300), with two clients in each and a DHCP/DNS server. There is also a separate VLAN 100 for the Zeek server which we will mirror traffic two from the other two VLANs.

NFV Network Diagram

To start, let’s create our hosts and dnsmasq namespaces.

# DHCP/DNS server
create_ns dnsmasq 0.0.0.0
add_tagged_interface dnsmasq 200 192.168.2.1/24 # to serve VLAN 200
add_tagged_interface dnsmasq 300 192.168.3.1/24 # to serve VLAN 300

# VLAN 200 hosts
create_ns host1 0.0.0.0
create_ns host2 0.0.0.0
# VLAN 300 hosts
create_ns host3 0.0.0.0
create_ns host4 0.0.0.0

Then create an Open vSwitch bridge and connect all hosts to it.

sudo ovs-vsctl add-br br0 \
-- set bridge br0 other-config:datapath-id=0000000000000001 \
-- set bridge br0 other-config:disable-in-band=true \
-- set bridge br0 fail_mode=secure \
-- add-port br0 veth-host1 -- set interface veth-host1 ofport_request=1 \
-- add-port br0 veth-host2 -- set interface veth-host2 ofport_request=2 \
-- add-port br0 veth-host3 -- set interface veth-host3 ofport_request=3 \
-- add-port br0 veth-host4 -- set interface veth-host4 ofport_request=4 \
-- add-port br0 veth-dnsmasq -- set interface veth-dnsmasq ofport_request=5 \
-- set-controller br0 tcp:127.0.0.1:6653 tcp:127.0.0.1:6654

Dnsmasq setup

We will use dnsmasq to assign IP addresses to our host namespaces via the DHCP protocol. It will also serve as our DNS resolver for the hosts.

First install dnsmasq:

sudo apt-get install dnsmasq
sudo systemctl stop dnsmasq

Run the following two commands to start two dnsmasq instances inside the dnsmasq namespace. One instance will serve hosts on VLAN 200 and the other VLAN 300. We will be providing DHCP leases in the supplied ranges, the lease will set the gateway for each host to point at faucet’s virtual IP and set dnsmasq as the DNS resolver. We also provide a fake does.it.work DNS name which we will later use to demonstrate DNS is working as expected.

# 192.168.2.0/24 for VLAN 200
as_ns dnsmasq dnsmasq \
                   --dhcp-range=192.168.2.10,192.168.2.20 \
                   --dhcp-sequential-ip \
                   --dhcp-option=option:router,192.168.2.254 \
                   --no-resolv \
                   --txt-record=does.it.work,yes \
                   --bind-interfaces \
                   --except-interface=lo --interface=veth0.200 \
                   --dhcp-leasefile=/tmp/nfv-dhcp-vlan200.leases \
                   --log-facility=/tmp/nfv-dhcp-vlan200.log \
                   --pid-file=/run/dnsmasq-vlan200.pid \
                   --conf-file=

# 192.168.3.0/24 for VLAN 300
as_ns dnsmasq dnsmasq \
                   --dhcp-range=192.168.3.10,192.168.3.20 \
                   --dhcp-sequential-ip \
                   --dhcp-option=option:router,192.168.3.254 \
                   --no-resolv \
                   --txt-record=does.it.work,yes \
                   --bind-interfaces \
                   --except-interface=lo --interface=veth0.300 \
                   --dhcp-leasefile=/tmp/nfv-dhcp-vlan300.leases \
                   --log-facility=/tmp/nfv-dhcp-vlan300.log \
                   --pid-file=/run/dnsmasq-vlan300.pid \
                   --conf-file=

Now let’s configure faucet.yaml.

/etc/faucet/faucet.yaml
vlans:
    vlan200:
        vid: 200
        description: "192.168.2.0/24 network"
        faucet_vips: ["192.168.2.254/24"]
        faucet_mac: "00:00:00:00:00:22"
    vlan300:
        vid: 300
        description: "192.168.3.0/24 network"
        faucet_vips: ["192.168.3.254/24"]
        faucet_mac: "00:00:00:00:00:33"
dps:
    sw1:
        dp_id: 0x1
        hardware: "Open vSwitch"
        interfaces:
            1:
                name: "host1"
                description: "host1 network namespace"
                native_vlan: vlan200
            2:
                name: "host2"
                description: "host2 network namespace"
                native_vlan: vlan200
            3:
                name: "host3"
                description: "host3 network namespace"
                native_vlan: vlan300
            4:
                name: "host4"
                description: "host4 network namespace"
                native_vlan: vlan300
            5:
                name: "dnsmasq"
                description: "dnsmasq server network namespace"
                tagged_vlans: [vlan200, vlan300]

Now reload faucet configuration file.

sudo systemctl reload faucet

Use dhclient to configure host1 to host4 using DHCP (it may take a few seconds, but should return when successful).

as_ns host1 dhclient -v -pf /run/dhclient-host1.pid -lf /run/dhclient-host1.leases veth0
as_ns host2 dhclient -v -pf /run/dhclient-host2.pid -lf /run/dhclient-host2.leases veth0
as_ns host3 dhclient -v -pf /run/dhclient-host3.pid -lf /run/dhclient-host3.leases veth0
as_ns host4 dhclient -v -pf /run/dhclient-host4.pid -lf /run/dhclient-host4.leases veth0

If dhclient is unable to obtain an address you can check /tmp/nfv-dhcp-vlan<vlanid>.log (e.g /tmp/nfv-dhcp-vlan300.leases) to check the log messages from dnsmasq.

To look up the address for each namespace we can run the following commands:

as_ns host1 ip address show dev veth0
as_ns host2 ip address show dev veth0
as_ns host3 ip address show dev veth0
as_ns host4 ip address show dev veth0

If the hosts have IPs then great our DHCP server works.

At the moment we should be able to ping inside VLAN 200 and VLAN 300:

as_ns host1 ping <ip of host2> # both in VLAN 200 should work
as_ns host3 ping <ip of host4> # both in VLAN 300 should work

Pinging between VLANs will not currently work as we didn’t turn on inter-VLAN routing in our faucet configuration.

DNS

We can use faucet to enforce where protocols such as DNS go on the network. In this section we will use a faucet ACL to rewrite DNS packets to allow our dnsmasq namespace to answer DNS queries for any IP address.

Firstly, we can see that our dnsmasq server is correctly responding to DNS requests by manually querying them:

as_ns host1 host -t txt does.it.work 192.168.2.1
as_ns host3 host -t txt does.it.work 192.168.3.1

Both commands should return:

does.it.work descriptive text "yes"

But if we tried to query say 8.8.8.8 we would see this fail:

as_ns host1 host -t txt does.it.work 8.8.8.8

To make this work we first need the MAC address of the dnsmasq container:

as_ns dnsmasq cat /sys/class/net/veth0/address

00:11:22:33:44:55

We now replace our previous faucet configuration with the configuration below which adds an ACL that rewrites the MAC address of all DNS packets from the host namespaces and sends these to our dnsmasq namespace. Make sure to update the example MAC address of 00:11:22:33:44:55 with the one you get from running the previous command.

/etc/faucet/faucet.yaml
vlans:
    vlan200:
        vid: 200
        description: "192.168.2.0/24 network"
        faucet_vips: ["192.168.2.254/24"]
        faucet_mac: "00:00:00:00:00:22"
    vlan300:
        vid: 300
        description: "192.168.3.0/24 network"
        faucet_vips: ["192.168.3.254/24"]
        faucet_mac: "00:00:00:00:00:33"
dps:
    sw1:
        dp_id: 0x1
        hardware: "Open vSwitch"
        interfaces:
            1:
                name: "host1"
                description: "host1 network namespace"
                native_vlan: vlan200
                acls_in: [nfv-dns, allow-all]
            2:
                name: "host2"
                description: "host2 network namespace"
                native_vlan: vlan200
                acls_in: [nfv-dns, allow-all]
            3:
                name: "host3"
                description: "host3 network namespace"
                native_vlan: vlan300
                acls_in: [nfv-dns, allow-all]
            4:
                name: "host4"
                description: "host4 network namespace"
                native_vlan: vlan300
                acls_in: [nfv-dns, allow-all]
            5:
                name: "dnsmasq"
                description: "dnsmasq server network namespace"
                tagged_vlans: [vlan200, vlan300]
acls:
    nfv-dns:
        # Force UDP DNS to our DNS server
        - rule:
            dl_type: 0x800      # ipv4
            nw_proto: 17        # udp
            udp_dst: 53         # dns
            actions:
                output:
                    set_fields:
                        - eth_dst: "00:11:22:33:44:55" # MAC address of dnsmasq namespace
                allow: True
        # Force TCP DNS to our DNS server
        - rule:
            dl_type: 0x800      # ipv4
            nw_proto: 6         # tcp
            tcp_dst: 53         # dns
            actions:
                output:
                    set_fields:
                        - eth_dst: "00:11:22:33:44:55" # MAC address of dnsmasq namespace
                allow: True
    allow-all:
        - rule:
            actions:
                allow: True

As usual reload faucet configuration file.

sudo systemctl reload faucet

The next step is to configure the namespace to be able to handle incoming DNS packets with any IP, this can be done by adding some rules to iptables that will NAT all DNS traffic to the IP address of the VLAN interface:

as_ns dnsmasq iptables -t nat -A PREROUTING -i veth0.200 -p udp --dport 53 -j DNAT --to-destination 192.168.2.1
as_ns dnsmasq iptables -t nat -A PREROUTING -i veth0.200 -p tcp --dport 53 -j DNAT --to-destination 192.168.2.1
as_ns dnsmasq iptables -t nat -A PREROUTING -i veth0.300 -p udp --dport 53 -j DNAT --to-destination 192.168.3.1
as_ns dnsmasq iptables -t nat -A PREROUTING -i veth0.300 -p tcp --dport 53 -j DNAT --to-destination 192.168.3.1

Now we should be able to query any IP address from the hosts and get a valid DNS response:

as_ns host1 host -t txt does.it.work 8.8.8.8
as_ns host2 host -t txt does.it.work 8.8.4.4

Zeek IDS

We will now add an IDS to our network on it’s on separate VLAN and use faucet to mirror packets from VLAN 200 and 300 to the IDS VLAN.

Zeek installation

We need first to install Zeek (formerly known as Bro).

sudo apt-get install bro broctl

Configure Zeek

In /etc/bro/node.cfg, set veth0 as the interface to monitor

/etc/bro/node.cfg
[bro]
type=standalone
host=localhost
interface=veth0

Comment out MailTo in /etc/bro/broctl.cfg

/etc/bro/broctl.cfg
# Recipient address for all emails sent out by bro and BroControl.
# MailTo = [email protected]

Run Zeek

Firstly, let’s create a namespace to run Zeek inside:

create_ns zeek 192.168.0.1
sudo ovs-vsctl add-port br0 veth-zeek -- set interface veth-zeek ofport_request=6

Since this is the first-time use of the Zeek command shell application, perform an initial installation of the BroControl configuration:

as_ns zeek broctl install

Then start Zeek instant

as_ns zeek broctl start

Check Zeek status

as_ns zeek broctl status

Name         Type       Host          Status    Pid    Started
bro          standalone localhost     running   15052  07 May 09:03:59

Now let’s add a mirror ACL so all VLAN 200 & VLAN 300 traffic is sent to Zeek.

We will use a VLAN ACLs similar to the previous VLAN tutorial. Copy and paste the entire configuration below into faucet.yaml.

/etc/faucet/faucet.yaml
acls:
    mirror-acl:
        - rule:
            actions:
                allow: true
                mirror: zeek
vlans:
    zeek-vlan:
        vid: 100
        description: "Zeek IDS network"
    vlan200:
        vid: 200
        description: "192.168.2.0/24 network"
        faucet_vips: ["192.168.2.254/24"]
        faucet_mac: "00:00:00:00:00:22"
        acls_in: [mirror-acl]
    vlan300:
        vid: 300
        description: "192.168.3.0/24 network"
        faucet_vips: ["192.168.3.254/24"]
        faucet_mac: "00:00:00:00:00:33"
        acls_in: [mirror-acl]
dps:
    sw1:
        dp_id: 0x1
        hardware: "Open vSwitch"
        interfaces:
            1:
                name: "host1"
                description: "host1 network namespace"
                native_vlan: vlan200
            2:
                name: "host2"
                description: "host2 network namespace"
                native_vlan: vlan200
            3:
                name: "host3"
                description: "host3 network namespace"
                native_vlan: vlan300
            4:
                name: "host4"
                description: "host4 network namespace"
                native_vlan: vlan300
            5:
                name: "dnsmasq"
                description: "dnsmasq server network namespace"
                tagged_vlans: [vlan200, vlan300]
            6:
                name: "zeek"
                description: "Zeek network namespace"
                native_vlan: zeek-vlan

As usual reload faucet configuration file.

sudo systemctl reload faucet

If we generate some DNS traffic on either of the hosts VLANs

as_ns host4 host -t txt does.it.work 192.168.3.1

Then if we inspect the Zeek logs for DNS /var/log/bro/current/dns.log, we should see that Zeek has seen the DNS queries and logged these.

/var/log/bro/current/dns.log
#separator \x09
#set_separator      ,
#empty_field        (empty)
#unset_field        -
#path       dns
#open       2019-01-17-17-43-56
#fields     ts      uid     id.orig_h       id.orig_p       id.resp_h       id.resp_p       proto   trans_id        rtt     query   qclass  qclass_name     qtype   qtype_name      rcode   rcode_name      AA      TC      RD      RA      Z       answers TTLs    rejected
#types      time    string  addr    port    addr    port    enum    count   interval        string  count   string  count   string  count   string  bool    bool    bool    bool    count   vector[string]  vector[interval]        bool
1547700236.794299   CsulWM1Px7fIyPpCVi      192.168.3.10    43428   192.168.3.1     53      udp     14288   0.006973does.it.work    1       C_INTERNET      16      TXT     0       NOERROR T       F       T       T       2       TXT 3 yes       0.000000        F
1547700379.311319   CZa11oBd3CgWBmgS8       192.168.3.11    45089   192.168.3.1     53      udp     64001   0.000336does.it.work    1       C_INTERNET      16      TXT     0       NOERROR T       F       T       T       0       TXT 3 yes       0.000000        F

You can also check if the traffic is being mirrored as expected using tcpdump in the zeek network namespace:

as_ns zeek sudo tcpdump -i veth0 -n -l

in one window, and then generating some more DNS traffic, eg:

as_ns host4 host -t txt does.it.work 192.168.3.1

then you should see something like:

zeek namespace tcpdump output
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on veth0, link-type EN10MB (Ethernet), capture size 262144 bytes
12:19:24.624244 IP 192.168.3.13.38174 > 192.168.3.1.53: 64571+ TXT? does.it.work. (30)
12:19:24.625109 IP 192.168.3.1.53 > 192.168.3.13.38174: 64571* 1/0/0 TXT "yes" (46)