4. Connecting two network namespaces (ns1, ns2) - with two veth pairs and a distributed OVS switch (openvswitch)

======================================================================================================================
 [1] NET namespace - Connecting two network namespaces (ns1, ns2) - with two veth pairs and
                     distribuovaneho prepinaca OVS (openvswitch)
======================================================================================================================

     +------------------+                 +-------------------------------+                 +------------------+
     | ns1        veth1 |======kabel======| veth1-ovs   ovs0    veth2-ovs |======kabel======| veth2        ns2 |
     +------------------+                 +-------------------------------+                 +------------------+
       namespace "ns1"                     hostitelsky system (openvswitch)                    namespace "ns2"

    Prvy  ethernet kabel (medzi mennym priestorom "ns1" a OVS prepinacom "ovs0"): veth1====veth1-ovs
    The second Ethernet cable (between namespace "ns2" and the OVS switch "ovs0"): veth2====veth2-ovs

    These test scenarios use RedHat Linux 7.3, which does carry the kernel module for Openvswitch, but
    no longer carries the user tools that administer openvswitch (ovs-vsctl). Those user tools are
    carried in other Redhat products such as Red Hat Openstack Platform. At this point what we
    there is nothing for it but to install Openvswitch from source, see [1.0.X].

    [1.0.1] Installing the distributed switch Openvswitch successfully needs the tools to compile it and
            kniznice, ktore Openvswitch vyuziva.
    ----------------------------------------------------------------------------------------------------------------
    # yum install gcc make python-devel openssl-devel kernel-devel graphviz kernel-debug-devel autoconf automake \
      rpm-build redhat-rpm-config libtool checkpolicy selinux-policy-devel python-six
    ----------------------------------------------------------------------------------------------------------------

    [1.0.2] - Create a directory to build the RPM package from source in, and download the current source package
              pre Openvswitch.
    ----------------------------------------------------------------------------------------------------------------
    # mkdir -p /root/rpmbuild/SOURCES
    # cd /root/rpmbuild/SOURCES
    # wget http://openvswitch.org/releases/openvswitch-2.6.1.tar.gz
    ----------------------------------------------------------------------------------------------------------------

    [1.0.3] - Unpack the source package, compile it and build the RPM package
              The RPM packages for Openvswitch appear in "/root/rpmbuild/RPMS/x86_64/"
    ----------------------------------------------------------------------------------------------------------------
    # cd /root/rpmbuild/SOURCES/
    # tar -xvf ./openvswitch-2.6.1.tar.gz
    # sed 's/openvswitch-kmod, //g' openvswitch-2.6.1/rhel/openvswitch.spec > openvswitch-2.6.1/rhel/openvswitch_no_kmod.spec
    # rpmbuild -bb --nocheck openvswitch-2.6.1/rhel/openvswitch_no_kmod.spec
    ----------------------------------------------------------------------------------------------------------------

    [1.0.4] - Nainstalujeme RPM balicek s Openvswitch
    ----------------------------------------------------------------------------------------------------------------
    # cd /root/rpmbuild/RPMS/x86_64/
    # yum localinstall ./openvswitch-2.6.1-1.x86_64.rpm
    ----------------------------------------------------------------------------------------------------------------

    [1.1] - Odstranime (ak existuju) sietove menne priestory "ns1" a "ns2".
    [1.2] - Create two network (NET) namespaces, "ns1" and "ns2".
    ----------------------------------------------------------------------------------------------------------------
    [1.1]# ip netns del ns1 &>/dev/null
    [1.1]# ip netns del ns2 &>/dev/null
    [1.2]# ip netns add ns1
    [1.2]# ip netns add ns2
    ----------------------------------------------------------------------------------------------------------------

    [1.3] - V hostitelskom systeme spustime Openvswitch a
    [1.3] - vytvorime distribuovany (openvswitch) ethernet prepinac/bridge s menom "ovs0".
    ----------------------------------------------------------------------------------------------------------------
    [1.3]# /etc/init.d/openvswitch start
    [1.3]# ovs-vsctl add-br ovs0
    ----------------------------------------------------------------------------------------------------------------

    [1.4]TERM1 - In network namespace "ns1", exec the command "bash".
    [1.5]TERM2 - In network namespace "ns2", exec the command "bash".
    ----------------------------------------------------------------------------------------------------------------
    [1.4]TERM1# ip netns exec ns1 bash
    [1.5]TERM2# ip netns exec ns2 bash
    ----------------------------------------------------------------------------------------------------------------

    [1.6]  - Create a pair of virtual Ethernet devices, which stand for a network cable with two RJ45
             koncovkami, pricom nasledne jednu stranu (veth1) umiestnime do menneho priestoru "ns1" a druhu stranu
             (veth1-ovs) umiestnime do distribuovaneho ethernet prepinaca "ovs0".
    [1.7]  - Virtualny ethernet adapter "veth1" umiestnime do sietoveho menneho priestoru "ns1".
    [1.8]  - Virtualny ethernet adapter "veth1-ovs" pripojime do distribuovaneho ethernet prepinaca "ovs0".

    [1.9]  - Create a pair of virtual Ethernet devices, which stand for a network cable with two RJ45
             koncovkami, pricom nasledne jednu stranu (veth2) umiestnime do menneho priestoru "ns2" a druhu stranu
             (veth2-ovs) umiestnime do distribuovaneho ethernet prepinaca "ovs0".
    [1.10] - Virtualny ethernet adapter "veth2" umiestnime do sietoveho menneho priestoru "ns2".
    [1.11] - Virtualny ethernet adapter "veth2-ovs" pripojime do distribuovaneho ethernet prepinaca "ovs0".
    ----------------------------------------------------------------------------------------------------------------
    [1.6] # ip link add veth1 type veth peer name veth1-ovs
    [1.7] # ip link set veth1 netns ns1
    [1.8] # ovs-vsctl add-port ovs0 veth1-ovs

    [1.9] # ip link add veth2 type veth peer name veth2-ovs
    [1.10]# ip link set veth2 netns ns2
    [1.11]# ovs-vsctl add-port ovs0 veth2-ovs
    ----------------------------------------------------------------------------------------------------------------

    [1.12] - Bring the network adapter "veth1" up in namespace "ns1" and give it the address "10.0.0.1".
    [1.13] - Zapneme sietovy adapter/port "veth1-ovs" na distribuovanom prepinaci "ovs0".

    [1.14] - Bring the network adapter "veth2" up in namespace "ns2" and give it the address "10.0.0.2".
    [1.15] - Zapneme sietovy adapter/port "veth2-ovs" na distribuovanom prepinaci "ovs0".

    [1.16] - From network namespace "ns1", test that namespace "ns2" answers.
    [1.17] - From network namespace "ns2", test that namespace "ns1" answers.
    -------------------------------------------------------------------------
    [1.12]# ip netns exec ns1 ifconfig veth1 10.0.0.1/24 up
    [1.13]# ip link set dev veth1-ovs up

    [1.14]# ip netns exec ns2 ifconfig veth2 10.0.0.2/24 up
    [1.15]# ip link set dev veth2-ovs up

    [1.16]# ip netns exec ns1 ping 10.0.0.2
    [1.17]# ip netns exec ns2 ping 10.0.0.1
    ----------------------------------------------------------------------------------------------------------------