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Containers Tutorial

Walks through container networking and concepts step by step

Prerequisites

  1. Download Vagrant
  2. Download Virtualbox

Setup

Step 1: Get the Vagrantfile

Copy the contents into a file called Vagrantfile. It could be done using curl as follows

$ curl https://raw.githubusercontent.com/jainvipin/tutorial/master/Vagrantfile -o Vagrantfile
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  6731  100  6731    0     0   8424      0 --:--:-- --:--:-- --:--:--  8424

Note: On Windows the file may be downloaded with .txt extension. Rename the file if needed to remove the extension. Some steps are documented here.

Step 2: Create resolv.conf file in the current directory, where you have copied the Vagrantfile.

This is used by the VMs to access outside network for downloading docker images in rest of tuorial. The next steps will fail if this is not specified correctly. On Mac or Linux based systems you may copy /etc/resolv.conf to current directory.

$ cp /etc/resolv.conf .

$ cat resolv.conf
domain foobar.com
nameserver 171.70.168.183
nameserver 173.36.131.10

$ ls
Vagrantfile	resolv.conf

Step 3: Start a small two-node cluster

$ vagrant up
Bringing machine 'tutorial-node1' up with 'virtualbox' provider...
Bringing machine 'tutorial-node2' up with 'virtualbox' provider...
 < more output here when trying to bring up the two VMs>
==> tutorial-node2: ++ nohup /opt/bin/start-swarm.sh 192.168.2.11 slave
$

Step 4: Log into one of the VMs, confirm all looks good

Note:

  • On Windows, you will need a ssh client to be installed like putty, cygwin etc.
  • The username/password for the VMs is vagrant/vagrant
$ vagrant ssh tutorial-node1
vagrant@tutorial-node1:~$ docker info

The above command shows the node information, version, etc.

vagrant@tutorial-node1:~$ etcdctl cluster-health

etcdctl is a control utility to manipulate etcd, state store used by kubernetes/docker/contiv

vagrant@tutorial-node1:~$ ifconfig docker0
docker0   Link encap:Ethernet  HWaddr 02:42:fb:53:27:56  
          inet addr:172.17.0.1  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::42:fbff:fe53:2756/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3521 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3512 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:178318 (178.3 KB)  TX bytes:226978 (226.9 KB)

vagrant@tutorial-node1:~$ ifconfig eth1
eth1      Link encap:Ethernet  HWaddr 08:00:27:f7:17:75  
          inet addr:192.168.2.10  Bcast:0.0.0.0  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fef7:1775/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:219585 errors:0 dropped:0 overruns:0 frame:0
          TX packets:272864 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:21413163 (21.4 MB)  TX bytes:28556948 (28.5 MB)

vagrant@tutorial-node1:~$ ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 08:00:27:a2:bc:0d  
          inet addr:10.0.2.15  Bcast:10.0.2.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fea2:bc0d/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:28103 errors:0 dropped:0 overruns:0 frame:0
          TX packets:13491 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:36213596 (36.2 MB)  TX bytes:858264 (858.2 KB)

In the above output, you'll see:

  • docker0 interface corresponds to the linux bridge and its associated subnet 172.17.0.1/16. This is created by docker daemon automatically, and is the default network containers would belong to when an override network is not specified
  • eth0 in this VM is the management interface, on which we ssh into the VM
  • eth1 in this VM is the interface that connects to external network (if needed)
  • eth2 in this VM is the interface that carries vxlan and control (e.g. etcd) traffic
vagrant@tutorial-node1:~$ netctl version

netctl is a utility to create, update, read and modify contiv objects. It is a CLI wrapper on top of REST interface.

How to restart if VM is shut down, restarted or connectivity is lost

It is okay to restart the tutorial from where you left at the beginning of the chapter. The recommended way is to cleanup the setup using vagrant -f destroy, and then restarting them again using vagrant up

Chapter 1 - Introduction to Container Networking

There are two main container networking model discussed within the community.

Docker libnetwork - Container Network Model (CNM)

CNM (Container Network Model) is Docker's libnetwork network model for containers

  • An endpoint is container's interface into a network
  • A network is collection of arbitrary endpoints
  • A container can belong to multiple endpoints (and therefore multiple networks)
  • CNM allows for co-existence of multiple drivers, with a network managed by one driver
  • Provides Driver APIs for IPAM and Endpoint creation/deletion
  • IPAM Driver APIs: Create/Delete Pool, Allocate/Free IP Address
  • Network Driver APIs: Network Create/Delete, Endpoint Create/Delete/Join/Leave
  • Used by docker engine, docker swarm, and docker compose; and other schedulers that schedules regular docker containers e.g. Nomad or Mesos docker containerizer

CoreOS CNI - Container Network Interface (CNI)

CNI (Container Network Interface) CoreOS's network model for containers

  • Allows specifying container id (uuid) for which network interface is being created
  • Provide Container Create/Delete events
  • Provides access to network namespace to the driver to plumb networking
  • No separate IPAM Driver: Container Create returns the IAPM information along with other data
  • Used by Kubernetes and thus supported by various kubernet network plugins, including Contiv

Using Contiv with CNI/Kubernetes can be found here. The rest of the tutorial walks through the docker examples, which implements CNM APIs

Basic container networking

Let's examine the networking a container gets upon vanilla run

vagrant@tutorial-node1:~$ docker network ls
NETWORK ID          NAME                DRIVER
3c5ec5bc780a        none                null                
fb44f53e1e91        host                host                
6a63b892d974        bridge              bridge              

vagrant@tutorial-node1:~$ docker run -itd --name=vanilla-c alpine /bin/sh
Unable to find image 'alpine:latest' locally
latest: Pulling from library/alpine
b66121b7b9c0: Pull complete 
Digest: sha256:9cacb71397b640eca97488cf08582ae4e4068513101088e9f96c9814bfda95e0
Status: Downloaded newer image for alpine:latest
2cf083c0a4de1347d8fea449dada155b7ef1c99f1f0e684767ae73b3bbb6b533
 
vagrant@tutorial-node1:~$ ifconfig

In the ifconfig output, you will see that it would have created a veth virtual ethernet interface that could look like veth...... towards the end. More importantly it is allocated an IP address from default docker bridge docker0, likely 172.17.0.3 in this setup, and can be examined using

vagrant@tutorial-node1:~$ docker network inspect bridge
[
    {
        "Name": "bridge",
        "Id": "6a63b892d97413275ab32e8792d32498848ad32bfb78d3cfd74a82ce5cbc46c2",
        "Scope": "local",
        "Driver": "bridge",
        "IPAM": {
            "Driver": "default",
            "Config": [
                {
                    "Subnet": "172.17.0.1/16",
                    "Gateway": "172.17.0.1"
                }
            ]
        },
        "Containers": {
            "2cf083c0a4de1347d8fea449dada155b7ef1c99f1f0e684767ae73b3bbb6b533": {
                "EndpointID": "c0cebaaf691c3941fca1dae4a8d2b3a94c511027f15d4c27b40606f7fb937f24",
                "MacAddress": "02:42:ac:11:00:03",
                "IPv4Address": "172.17.0.3/16",
                "IPv6Address": ""
            },
            "ab353464b4e20b0267d6a078e872fd21730242235667724a9147fdf278a03220": {
                "EndpointID": "6259ca5d2267f02d139bbcf55cb15b4ad670edefb5f4308e47da399beb1dc62c",
                "MacAddress": "02:42:ac:11:00:02",
                "IPv4Address": "172.17.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        }
    }
]

vagrant@tutorial-node1:~$ docker inspect --format '{{.NetworkSettings.IPAddress}}' vanilla-c
172.17.0.3

The other pair of veth interface is put into the container with the name eth0

vagrant@tutorial-node1:~$ docker exec -it vanilla-c /bin/sh
/ # ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 02:42:AC:11:00:03  
          inet addr:172.17.0.3  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::42:acff:fe11:3%32577/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:648 (648.0 B)  TX bytes:648 (648.0 B)
/ # exit

All traffic to/from this container is Port-NATed to the host's IP (on eth0). The Port NATing on the host is done using iptables, which can be seen as a MASQUERADE rule for outbound traffic for 172.17.0.0/16

$ vagrant@tutorial-node1:~$ sudo iptables -t nat -L -n

Chapter 2: Multi-host networking

There are many solutions, like Contiv, Calico, Weave, Openshift, OpenContrail, Nuage, VMWare, Docker, Kubernetes, Openstack that provide solutions to multi-host container networking. In this section we examine Contiv and Docker overlay solutions.

Multi-host networking with Contiv

Let's use the same example as above to spin up two containers on the two different hosts

3#### 1. Create a multi-host network

vagrant@tutorial-node1:~$ netctl net create --subnet=10.1.2.0/24 contiv-net
vagrant@tutorial-node1:~$ netctl net ls
Tenant   Network     Nw Type  Encap type  Packet tag  Subnet       Gateway
------   -------     -------  ----------  ----------  -------      ------
default  contiv-net  data     vxlan       0           10.1.2.0/24  

vagrant@tutorial-node1:~$ docker network ls
NETWORK ID          NAME                DRIVER
22f79fe02239        overlay-net         overlay             
af2ed0437304        contiv-net          netplugin           
6a63b892d974        bridge              bridge              
3c5ec5bc780a        none                null                
fb44f53e1e91        host                host                
cf7ccff07b64        docker_gwbridge     bridge              

vagrant@tutorial-node1:~$ docker network inspect contiv-net
[
    {
        "Name": "contiv-net",
        "Id": "af2ed043730432e383bbe7fc7716cdfee87246f96342a320ef5fa99f8cf60312",
        "Scope": "global",
        "Driver": "netplugin",
        "IPAM": {
            "Driver": "netplugin",
            "Config": [
                {
                    "Subnet": "10.1.2.0/24"
                }
            ]
        },
        "Containers": {
            "ab353464b4e20b0267d6a078e872fd21730242235667724a9147fdf278a03220": {
                "EndpointID": "5d1720e71e3a4c8da6a8ed361480c094aeb6a3cd3adfe0c7b185690bc64ddcd9",
                "MacAddress": "",
                "IPv4Address": "10.1.2.2/24",
                "IPv6Address": ""
            }
        },
        "Options": {
            "encap": "vxlan",
            "pkt-tag": "1",
            "tenant": "default"
        }
    }
]

We can now run a new container belonging to contiv-net network that we created just now

vagrant@tutorial-node1:~$ docker run -itd --name=contiv-c1 --net=contiv-net alpine /bin/sh
46e619b0b418107114e93f9814963d5c351835624e8da54100b0707582c69549

Let's ssh into the second node using vagrant ssh tutorial-node2, and spin up a new container on it and try to reach another container running on tutorial-node1

vagrant@tutorial-node2:~$ docker run -itd --name=contiv-c2 --net=contiv-net alpine /bin/sh
26b9f22b9790b55cdfc85f1c2779db5d5fc78c18fee1ea088b85ec0883361a72

vagrant@tutorial-node2:~$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                  PORTS               NAMES
26b9f22b9790        alpine              "/bin/sh"           2 seconds ago       Up Less than a second                       contiv-c2

vagrant@tutorial-node2:~$ docker exec -it contiv-c2 /bin/sh

/ # ping contiv-c1
PING contiv-c1 (10.1.2.3): 56 data bytes
64 bytes from 10.1.2.3: seq=0 ttl=64 time=6.596 ms
64 bytes from 10.1.2.3: seq=1 ttl=64 time=9.451 ms
^C
--- contiv-c1 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 6.596/8.023/9.451 ms

/ # exit

As you will see during the ping that, built in dns resolves the name overlay-c1 to the IP address of overlay-c1 container and be able to reach another container across using a vxlan overlay.

Docker Overlay multi-host networking

Docker engine has a built in overlay driver that can be use to connect containers across multiple nodes.

vagrant@tutorial-node1:~$ docker network create -d=overlay --subnet=10.1.1.0/24 overlay-net
22f79fe02239d3cbc2c8a4f7147f0e799dc13f3af6e46a69cc3adf8f299a7e56

vagrant@tutorial-node1:~$ docker network inspect overlay-net
[
    {
        "Name": "overlay-net",
        "Id": "22f79fe02239d3cbc2c8a4f7147f0e799dc13f3af6e46a69cc3adf8f299a7e56",
        "Scope": "global",
        "Driver": "overlay",
        "IPAM": {
            "Driver": "default",
            "Config": [
                {
                    "Subnet": "10.1.1.0/24"
                }
            ]
        },
        "Containers": {},
        "Options": {}
    }
]

Now, we can create a container that belongs to overlay-net

vagrant@tutorial-node1:~$ docker run -itd --name=overlay-c1 --net=overlay-net alpine /bin/sh
0ab717006962fb2fe936aa3c133dd27d68c347d5f239f473373c151ad4c77b28

vagrant@tutorial-node1:~$ docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' overlay-c1
10.1.1.2

And, we can run another container within the cluster, that belongs to the same network and make sure that they can reach each other.

vagrant@tutorial-node1:~$ docker run -itd --name=overlay-c2 --net=overlay-net alpine /bin/sh
0a6f43693361855ad56cda417b9ec63f504de4782ac82f0181fed92d803b4a30
vagrant@tutorial-node1:~$ docker ps
CONTAINER ID        IMAGE                          COMMAND             CREATED             STATUS              PORTS               NAMES
fb822eda9916        alpine                         "/bin/sh"           3 minutes ago       Up 3 minutes                            overlay-c2
0ab717006962        alpine                         "/bin/sh"           21 minutes ago      Up 21 minutes                           overlay-c1
2cf083c0a4de        alpine                         "/bin/sh"           28 minutes ago      Up 28 minutes                           vanilla-c
ab353464b4e2        skynetservices/skydns:latest   "/skydns"           33 minutes ago      Up 33 minutes       53/tcp, 53/udp      defaultdns

vagrant@tutorial-node2:~$ docker exec -it overlay-c2 /bin/sh
/ # ping overlay-c1
PING overlay-c1 (10.1.1.2): 56 data bytes
64 bytes from 10.1.1.2: seq=0 ttl=64 time=0.066 ms
64 bytes from 10.1.1.2: seq=1 ttl=64 time=0.092 ms
^C
--- overlay-c1 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.066/0.079/0.092 ms

/ # exit

Similar to contiv-networking, built in dns resolves the name overlay-c1 to the IP address of overlay-c1 container and be able to reach another container across using a vxlan overlay.

Chapter 3: Using multiple tenants with arbitrary IPs in the networks

First, let's create a new tenant space

vagrant@tutorial-node1:~$ netctl tenant create blue
INFO[0000] Creating tenant: blue                    

vagrant@tutorial-node1:~$ netctl tenant ls 
Name     
------   
default  
blue

After the tenant is created, we can create network within in tenant blue and run containers. Here we chose the same subnet and network name for it. the same subnet and same network name, that we used before

vagrant@tutorial-node1:~$ netctl net create -t blue --subnet=10.1.2.0/24 contiv-net
vagrant@tutorial-node1:~$ netctl net ls -t blue
Tenant  Network     Nw Type  Encap type  Packet tag  Subnet       Gateway
-/-----  -------     -------  ----------  ----------  -------      ------
blue    contiv-net  data     vxlan       0           10.1.2.0/24

Next, we can run containers belonging to this tenant

vagrant@tutorial-node1:~$ docker run -itd --name=contiv-blue-c1 --net=contiv-net/blue alpine /bin/sh
6c7d8c0b14ec6c2c9f52468faf50444e29c4b1fa61753b75c00f033564814515

vagrant@tutorial-node1:~$ docker ps
CONTAINER ID        IMAGE                          COMMAND             CREATED             STATUS              PORTS               NAMES
6c7d8c0b14ec        alpine                         "/bin/sh"           8 seconds ago       Up 6 seconds                            contiv-blue-c1
17afcd58b8fc        skynetservices/skydns:latest   "/skydns"           6 minutes ago       Up 6 minutes        53/tcp, 53/udp      bluedns
46e619b0b418        alpine                         "/bin/sh"           11 minutes ago      Up 11 minutes                           contiv-c1
fb822eda9916        alpine                         "/bin/sh"           23 minutes ago      Up 23 minutes                           overlay-c2
0ab717006962        alpine                         "/bin/sh"           41 minutes ago      Up 41 minutes                           overlay-c1
2cf083c0a4de        alpine                         "/bin/sh"           48 minutes ago      Up 48 minutes                           vanilla-c
ab353464b4e2        skynetservices/skydns:latest   "/skydns"           53 minutes ago      Up 53 minutes       53/udp, 53/tcp      defaultdns

Let us run a couple of more containers in the host tutorial-node2 that belong to the tenatn blue

vagrant@tutorial-node2:~$ docker run -itd --name=contiv-blue-c2 --net=contiv-net/blue alpine /bin/sh
521abe19d6b5b3557de6ee4654cc504af0c497a64683f737ffb6f8238ddd6454
vagrant@tutorial-node2:~$ docker run -itd --name=contiv-blue-c3 --net=contiv-net/blue alpine /bin/sh
0fd07b44d042f37069f9a2f7c901867e8fd01c0a5d4cb761123e54e510705c60
vagrant@tutorial-node2:~$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
0fd07b44d042        alpine              "/bin/sh"           7 seconds ago       Up 5 seconds                            contiv-blue-c3
521abe19d6b5        alpine              "/bin/sh"           23 seconds ago      Up 21 seconds                           contiv-blue-c2
26b9f22b9790        alpine              "/bin/sh"           13 minutes ago      Up 13 minutes                           contiv-c2

vagrant@tutorial-node2:~$ docker network inspect contiv-net/blue
[
    {
        "Name": "contiv-net/blue",
        "Id": "4b8448967b7908cab6b3788886aaccc2748bbd85251258de3d01f64e5ee7ae68",
        "Scope": "global",
        "Driver": "netplugin",
        "IPAM": {
            "Driver": "netplugin",
            "Config": [
                {
                    "Subnet": "10.1.2.0/24"
                }
            ]
        },
        "Containers": {
            "0fd07b44d042f37069f9a2f7c901867e8fd01c0a5d4cb761123e54e510705c60": {
                "EndpointID": "4688209bd46047f1e9ab016fadff7bdf7c012cbfa253ec6a3661742f84ca5feb",
                "MacAddress": "",
                "IPv4Address": "10.1.2.4/24",
                "IPv6Address": ""
            },
            "521abe19d6b5b3557de6ee4654cc504af0c497a64683f737ffb6f8238ddd6454": {
                "EndpointID": "4d9ca7047b8737b78f271a41db82bbf5c3004f297211d831af757f565fc0c691",
                "IPv4Address": "10.1.2.3/24",
                "IPv6Address": ""
            }
        },
        "Options": {
            "encap": "vxlan",
            "pkt-tag": "2",
            "tenant": "blue"
        }
    }
]

vagrant@tutorial-node2:~$ docker exec -it contiv-blue-c3 /bin/sh
/ # ping contiv-blue-c1
PING contiv-blue-c1 (10.1.2.2): 56 data bytes
64 bytes from 10.1.2.2: seq=0 ttl=64 time=60.414 ms
^C
--- contiv-blue-c1 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 60.414/60.414/60.414 ms
/ # ping contiv-blue-c2
PING contiv-blue-c2 (10.1.2.3): 56 data bytes
64 bytes from 10.1.2.3: seq=0 ttl=64 time=1.637 ms
^C
--- contiv-blue-c2 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 1.637/1.637/1.637 ms

/ # exit

Chapter 4: Connecting containers to external networks

In this chapter, we explore ways to connect containers to the external networks

1. External Connectivity using Host NATing

Docker uses the linux bridge (docker_gwbridge) based PNAT to reach out and port mappings for others to reach to the container

vagrant@tutorial-node1:~$ docker exec -it contiv-c1 /bin/sh
/ # ifconfig -a
eth0      Link encap:Ethernet  HWaddr 02:02:0A:01:02:03  
          inet addr:10.1.2.3  Bcast:0.0.0.0  Mask:255.255.255.0
          inet6 addr: fe80::2:aff:fe01:203%32627/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1
          RX packets:19 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1534 (1.4 KiB)  TX bytes:886 (886.0 B)

eth1      Link encap:Ethernet  HWaddr 02:42:AC:12:00:04  
          inet addr:172.18.0.4  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::42:acff:fe12:4%32627/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:32 errors:0 dropped:0 overruns:0 frame:0
          TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:5584 (5.4 KiB)  TX bytes:3344 (3.2 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1%32627/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

/ # ping contiv.com
PING contiv.com (216.239.34.21): 56 data bytes
64 bytes from 216.239.34.21: seq=0 ttl=61 time=35.941 ms
64 bytes from 216.239.34.21: seq=1 ttl=61 time=38.980 ms
^C
--- contiv.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 35.941/37.460/38.980 ms

/ # exit

What you see is that container has two interfaces belonging to it:

  • eth0 is reachability into the contiv-net
  • eth1 is reachability for container to the external world and outside traffic to be able to reach the container contiv-c1. This also relies on the host's dns resolv.conf as a default way to resolve non container IP resolution.

Similarly outside traffic can be exposed on specific ports using -p command. Before we do that, let us confirm that port 9099 is not reachable from the host tutorial-node1

vagrant@tutorial-node1:~$ nc -zvw 1 localhost 9099
nc: connect to localhost port 9099 (tcp) failed: Connection refused
nc: connect to localhost port 9099 (tcp) failed: Connection refused

Now we start a container that exposes tcp port 9099 out in the host.

vagrant@tutorial-node1:~$ docker run -itd -p 9099:9099 --name=contiv-exposed --net=contiv-net alpine /bin/sh

And if we re-run our nc utility, we'll see that 9099 is reachable.

vagrant@tutorial-node1:~$ nc -zvw 1 localhost 9099
Connection to localhost 9099 port [tcp/*] succeeded!

This happens because docker as soon as a port is exposed, a NAT rule is installed for the port to allow rest of the network to access the container on the specified/exposed port. The nat rules on the host can be seen by:

vagrant@tutorial-node1:~$ sudo iptables -t nat -L -n
iptables v1.4.21: can't initialize iptables table `nat': Permission denied (you must be root)
Perhaps iptables or your kernel needs to be upgraded.
vagrant@tutorial-node1:~$ sudo iptables -t nat -L -n
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         
DOCKER     all  --  0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type LOCAL

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
DOCKER     all  --  0.0.0.0/0           !127.0.0.0/8          ADDRTYPE match dst-type LOCAL

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
MASQUERADE  all  --  172.18.0.0/16        0.0.0.0/0           
MASQUERADE  all  --  172.17.0.0/16        0.0.0.0/0           
MASQUERADE  tcp  --  172.18.0.6           172.18.0.6           tcp dpt:9099

Chain DOCKER (2 references)
target     prot opt source               destination         
DNAT       tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:9099 to:172.18.0.6:9099

2. Natively connecting to the external networks

Remote drivers, like Contiv, can provide an easy way to connect to external layer2 or layer3 networks using BGP or standard L2 access into the network.

Preferably using an BGP hand-off to the leaf/TOR, this can be done as in [https://github.com/contiv/demo/blob/master/net/Bgp.md], which describes how can you use BGP with Contiv to provide native container connectivity and reachability to rest of the network. However for this tutorial, since we don't have a real or simulated BGP router, we'll use some very simple native L2 connectivity to describe the power of native connectivity. This is done using vlan network, for example

vagrant@tutorial-node1:~$ netctl net create -p 112 -e vlan -s 10.1.3.0/24 contiv-vlan
vagrant@tutorial-node1:~$ netctl net ls
Tenant   Network         Nw Type  Encap type  Packet tag  Subnet       Gateway
------   -------         -------  ----------  ----------  -------      ------
default  contiv-net      data     vxlan       0           10.1.2.0/24  
default  contiv-vlan     data     vlan        112         10.1.3.0/24

The allocated vlan can be used to connect any workload in vlan 112 in the network infrstructure. The interface that connects to the outside network needs to be specified during netplugin start, for this VM configuration it is set as eth2

Let's run some containers to belong to this network, one on each node. Firs one on tutorial-node1

vagrant@tutorial-node1:~$ docker run -itd --name=contiv-vlan-c1 --net=contiv-vlan alpine /bin/sh
4bf58874c937e242b4fc2fd8bfd6896a7719fd10475af96e065a83a2e80e9e48

And another one on tutorial-node2

vagrant@tutorial-node2:~$ docker run -itd --name=contiv-vlan-c2 --net=contiv-vlan alpine /bin/sh
1c463ecad8295b112a7556d1eaf35f1a8152c6b8cfcef1356d40a7b015ae9d02

vagrant@tutorial-node2:~$ docker exec -it contiv-vlan-c2 /bin/sh

/ # ping contiv-vlan-c1
PING contiv-vlan-c1 (10.1.3.4): 56 data bytes
64 bytes from 10.1.3.4: seq=0 ttl=64 time=2.431 ms
64 bytes from 10.1.3.4: seq=1 ttl=64 time=1.080 ms
64 bytes from 10.1.3.4: seq=2 ttl=64 time=1.022 ms
64 bytes from 10.1.3.4: seq=3 ttl=64 time=1.048 ms
64 bytes from 10.1.3.4: seq=4 ttl=64 time=1.119 ms
. . .

While this is going on tutorial-node2, let's run run tcpdump on eth2 on tutorial-node and confirm how rx/tx packets look like on it

vagrant@tutorial-node1:~$ sudo tcpdump -e -i eth2 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth2, link-type EN10MB (Ethernet), capture size 262144 bytes
05:16:51.578066 02:02:0a:01:03:02 (oui Unknown) > 02:02:0a:01:03:04 (oui Unknown), ethertype 802.1Q (0x8100), length 102: vlan 112, p 0, ethertype IPv4, 10.1.3.2 > 10.1.3.4: ICMP echo request, id 2816, seq 294, length 64
05:16:52.588159 02:02:0a:01:03:02 (oui Unknown) > 02:02:0a:01:03:04 (oui Unknown), ethertype 802.1Q (0x8100), length 102: vlan 112, p 0, ethertype IPv4, 10.1.3.2 > 10.1.3.4: ICMP echo request, id 2816, seq 295, length 64
05:16:53.587408 02:02:0a:01:03:02 (oui Unknown) > 02:02:0a:01:03:04 (oui Unknown), ethertype 802.1Q (0x8100), length 102: vlan 112, p 0, ethertype IPv4, 10.1.3.2 > 10.1.3.4: ICMP echo request, id 2816, seq 296, length 64
05:16:54.587550 02:02:0a:01:03:02 (oui Unknown) > 02:02:0a:01:03:04 (oui Unknown), ethertype 802.1Q (0x8100), length 102: vlan 112, p 0, ethertype IPv4, 10.1.3.2 > 10.1.3.4: ICMP echo request, id 2816, seq 297, length 64
ç05:16:55.583786 02:02:0a:01:03:02 (oui Unknown) > 02:02:0a:01:03:04 (oui Unknown), ethertype 802.1Q (0x8100), length 102: vlan 112, p 0, ethertype IPv4, 10.1.3.2 > 10.1.3.4: ICMP echo request, id 2816, seq 298, length 64
^C
5 packets captured

Note that the vlan shown in tcpdump is same (i.e. 112) as what we configured in the VLAN. After verifying this, feel free to stop the ping that is still running on contiv-vlan-c2 container.

Chapter 5: Applying policies between containers with Contiv

Contiv provide a way to apply isolation policies between containers groups. For this, we create a simple policy called db-policy, and add some rules to which ports are allowed.

Let's start with tutorial-node and create the contiv-net if you start this chapter afresh i.e. after vagrant up

vagrant@tutorial-node1:~$ netctl net create --subnet=10.1.2.0/24 contiv-net

Next we create a policy called db-policy to be applied to all db containers.

vagrant@tutorial-node1:~$ netctl policy create db-policy
INFO[0000] Creating policy default:db-policy
vagrant@tutorial-node1:~$ netctl policy ls
Tenant   Policy
------   ------
default  db-policy

Next we create some rules that are part of the policy

vagrant@tutorial-node1:~$ netctl policy rule-add db-policy 1 -direction=in -protocol=tcp -action=deny
vagrant@tutorial-node1:~$ netctl policy rule-add db-policy 2 -direction=in -protocol=tcp -port=8888 -action=allow -priority=10
vagrant@tutorial-node1:~$ netctl policy rule-ls db-policy
Incoming Rules:
Rule  Priority  From EndpointGroup  From Network  From IpAddress  Protocol  Port  Action
----  --------  ------------------  ------------  ---------       --------  ----  ------
1     1                                                           tcp       0     deny
2     10                                                          tcp       8888  allow
Outgoing Rules:
Rule  Priority  To EndpointGroup  To Network  To IpAddress  Protocol  Port  Action
----  --------  ----------------  ----------  ---------     --------  ----  ------

Finally, we associate the policy with a group (a group is an arbitrary collection of containers) and run some containers that belong to db group

vagrant@tutorial-node1:~$ netctl group create contiv-net db -policy=db-policy
vagrant@tutorial-node1:~$ netctl group ls
Tenant   Group  Network     Policies
------   -----  -------     --------
default  db     contiv-net  db-policy

vagrant@tutorial-node1:~$ docker run -itd --name=contiv-db --net=db.contiv-net alpine /bin/sh
27eedc376ef43e5a5f3f4ede01635d447b1a0c313cca4c2a640ba4d5dea3573a

Now let's verify this policy; in order to do so, we'll start netcat utility to listen an arbitrary port within a container that belongs to db group. Then, from another container we would scan a range of ports and confirm that only the one permitted i.e. port 8888 by db policy is accessible towards db container

vagrant@tutorial-node1:~$ docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' contiv-db
10.1.2.7

vagrant@tutorial-node1:~$ docker exec -it contiv-db /bin/sh
/ # nc -l 8888
<awaiting connection>

Switch over to tutorial-node2 window and run a web container and verify the policy.

vagrant@tutorial-node2:~$ docker run -itd --name=contiv-web --net=contiv-net alpine /bin/sh
54108c756699071d527a567f9b5d266284aaf5299b888d75cd19ba1a40a1135a
vagrant@tutorial-node2:~$ docker exec -it contiv-web /bin/sh

/ # nc -nzvw 1 10.1.2.7 8890
nc: 10.1.2.7 (10.1.2.7:8890): Operation timed out
/ # nc -nzvw 1 10.1.2.7 8889
nc: 10.1.2.7 (10.1.2.7:8889): Operation timed out
/ # nc -nzvw 1 10.1.2.7 8888
/ #

Note that the last scan on port 8888 using nc -nzvw 1 10.1.2.7 8888 returned without any Operation timed out message. At this point you can add/delete rules to the policy dynamically

Chapter 6: Running containers in a swarm cluster

We can bring in swarm scheduler by redirecting our requests to an already provision swarm cluster. To do so, we can set DOCKER_HOST as follows:

vagrant@tutorial-node1:~$ export DOCKER_HOST=tcp://192.168.2.10:2375

Let's look at the status of various hosts using docker info

vagrant@tutorial-node1:~$ docker info
Containers: 16
Images: 3
Role: primary
Strategy: spread
Filters: health, port, dependency, affinity, constraint
Nodes: 2
 tutorial-node1: 192.168.2.10:2385
  └ Containers: 10
  └ Reserved CPUs: 0 / 4
  └ Reserved Memory: 0 B / 2.051 GiB
  └ Labels: executiondriver=native-0.2, kernelversion=4.0.0-040000-generic, operatingsystem=Ubuntu 15.04, storagedriver=overlay
 tutorial-node2: 192.168.2.11:2385
  └ Containers: 6
  └ Reserved CPUs: 0 / 4
  └ Reserved Memory: 0 B / 2.051 GiB
  └ Labels: executiondriver=native-0.2, kernelversion=4.0.0-040000-generic, operatingsystem=Ubuntu 15.04, storagedriver=overlay
CPUs: 8
Total Memory: 4.103 GiB
Name: tutorial-node1
No Proxy: 192.168.2.10,192.168.2.11,127.0.0.1,localhost,netmaster

Above command would display the #nodes, #containers in the cluster, available cpu, memory and other relevant details.

At this point if we run some containers, they will get schedule dynamically across the cluster, which is two nodes tutorial-node1 and tutorial-node2 for us. To see the node on where the containers get scheduled, we can use docker ps command

vagrant@tutorial-node1:~$ docker run -itd --name=contiv-cluster-c1 --net=contiv-net alpine /bin/sh
f8fa35c0aa0ecd692a31e3d5249f5c158bd18902926978265acb3b38a9ed1c0d
vagrant@tutorial-node1:~$ docker run -itd --name=contiv-cluster-c2 --net=contiv-net alpine /bin/sh
bfc750736007c307827ae5012755085ca6591f3ac3ac0b707d2befd00e5d1621

After running two containers, scheduler will schedule these containers using the scheduling algorithm bin-packing or spread, and if they are not placed on different nodes, feel free to start more containers to see the distribution.

vagrant@tutorial-node1:~$ docker ps
CONTAINER ID        IMAGE                          COMMAND             CREATED             STATUS                  PORTS                         NAMES
bfc750736007        alpine                         "/bin/sh"           5 seconds ago       Up Less than a second                                 tutorial-node2/contiv-cluster-c2
f8fa35c0aa0e        alpine                         "/bin/sh"           22 seconds ago      Up 16 seconds                                         tutorial-node2/contiv-cluster-c1
54108c756699        alpine                         "/bin/sh"           14 minutes ago      Up 14 minutes                                         tutorial-node2/contiv-web
27eedc376ef4        alpine                         "/bin/sh"           25 minutes ago      Up 25 minutes                                         tutorial-node1/contiv-db
1c463ecad829        alpine                         "/bin/sh"           39 minutes ago      Up 39 minutes                                         tutorial-node2/contiv-vlan-c2
4bf58874c937        alpine                         "/bin/sh"           40 minutes ago      Up 40 minutes                                         tutorial-node1/contiv-vlan-c1
52bfcc02c362        alpine                         "/bin/sh"           About an hour ago   Up About an hour        192.168.2.10:9099->9099/tcp   tutorial-node1/contiv-exposed
0fd07b44d042        alpine                         "/bin/sh"           About an hour ago   Up About an hour                                      tutorial-node2/contiv-blue-c3
521abe19d6b5        alpine                         "/bin/sh"           About an hour ago   Up About an hour                                      tutorial-node2/contiv-blue-c2
6c7d8c0b14ec        alpine                         "/bin/sh"           2 hours ago         Up 2 hours                                            tutorial-node1/contiv-blue-c1
17afcd58b8fc        skynetservices/skydns:latest   "/skydns"           2 hours ago         Up 2 hours              53/tcp, 53/udp                tutorial-node1/bluedns
26b9f22b9790        alpine                         "/bin/sh"           2 hours ago         Up 2 hours                                            tutorial-node2/contiv-c2
46e619b0b418        alpine                         "/bin/sh"           2 hours ago         Up 2 hours                                            tutorial-node1/contiv-c1
fb822eda9916        alpine                         "/bin/sh"           2 hours ago         Up 2 hours                                            tutorial-node1/overlay-c2
0ab717006962        alpine                         "/bin/sh"           2 hours ago         Up 2 hours                                            tutorial-node1/overlay-c1
2cf083c0a4de        alpine                         "/bin/sh"           2 hours ago         Up 2 hours                                            tutorial-node1/vanilla-c
ab353464b4e2        skynetservices/skydns:latest   "/skydns"           2 hours ago         Up 2 hours              53/tcp, 53/udp                tutorial-node1/defaultdns

Let us conclude this section by checking the inter-container connectivity and external connectivity for the containers scheduled across multiple hosts

agrant@tutorial-node1:~$ docker exec -it contiv-cluster-c1 /bin/sh
/ # 
/ # 
/ # 
/ # ping contiv-cluster-c2
PING contiv-cluster-c2 (10.1.2.7): 56 data bytes
64 bytes from 10.1.2.7: seq=0 ttl=64 time=8.440 ms
64 bytes from 10.1.2.7: seq=1 ttl=64 time=1.479 ms
^C
--- contiv-cluster-c2 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 1.479/4.959/8.440 ms
/ # ping contiv.com
PING contiv.com (216.239.36.21): 56 data bytes
64 bytes from 216.239.36.21: seq=0 ttl=61 time=43.537 ms
64 bytes from 216.239.36.21: seq=1 ttl=61 time=38.867 ms
^C
--- contiv.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 38.867/41.202/43.537 ms

Cleanup: after all play is done

To cleanup the setup, after doing all the experiments, exit the VM destroy VMs

$ vagrant destroy -f
==> tutorial-node2: Forcing shutdown of VM...
==> tutorial-node2: Destroying VM and associated drives...
==> tutorial-node1: Forcing shutdown of VM...
==> tutorial-node1: Destroying VM and associated drives...

References

  1. CNI Specification
  2. CNM Design
  3. Contiv User Guide
  4. Contiv Networking Code

Improvements or Comments

This tutorial was developed by Contiv engineers. Thank you for trying out this tutorial. Please file a github issue if you see an issue with the tutorial, or if you prefer improving some text, feel free to send a pull request.

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