doc/vpp: update VPP integration docs

Detailed instructions for **simplified steps 1-3** below, can be found on

VPP [Quick Start Guide](https://wiki.fd.io/view/VPP).

*SPDK supports VPP version 18.01.1.*

*SPDK supports VPP version 19.01.1.*

#  1. Building VPP (optional) {#vpp_build}

Clone and checkout VPP

~~~

git clone https://gerrit.fd.io/r/vpp && cd vpp

git checkout v18.01.1

git checkout v19.01.1

git cherry-pick 97dcf5bd26ca6de580943f5d39681f0144782c3d

git cherry-pick f5dc9fbf814865b31b52b20f5bf959e9ff818b25

~~~

NOTE: Cherry-picks are required for better integration with SPDK. They are

already merged to VPP 19.04.

NOTE: We have noticed that VPP tries to close connections to the non existing,

already closed applications, after timeout. It causes intermittent VPP application

segfaults when few instances of VPP clients connects and disconnects several times.

The following workaround for this issue helps to create more stable environment

for VPP v19.01.1. This issue should be solved in the next release of VPP.

~~~

git apply test/common/config/patch/vpp/workaround-dont-notify-transport-closing.patch

~~~

Install VPP build dependencies

For more in depth instructions please see Building section in

[VPP documentation](https://wiki.fd.io/view/VPP/Pulling,_Building,_Running,_Hacking_and_Pushing_VPP_Code#Building)

*Please note: VPP 18.01.1 does not support OpenSSL 1.1. It is suggested to install a compatibility package

for compilation time.*

~~~

sudo dnf install -y --allowerasing compat-openssl10-devel

~~~

*Then reinstall latest OpenSSL devel package:*

~~~

sudo dnf install -y --allowerasing openssl-devel

~~~

# 2. Installing VPP {#vpp_install}

Packages can be installed from a distribution repository or built in previous step.

Alternatively, use `vpp` binary directly

~~~

sudo vpp unix {cli-listen /run/vpp/cli.sock}

sudo vpp unix {cli-listen /run/vpp/cli.sock} session { evt_qs_memfd_seg } socksvr { socket-name /run/vpp-api.sock }

~~~

# 4. Configure VPP {#vpp_config}

VPP can be configured using a VPP startup file and the `vppctl` command; By default, the VPP startup file is `/etc/vpp/startup.conf`, however, you can pass any file with the `-c` vpp command argument.

## Startup configuration

Some key values from iSCSI point of view includes:

CPU section (`cpu`):

- `main-core <lcore>` -- logical CPU core used for main thread.

- `corelist-workers <lcore list>` -- logical CPU cores where worker threads are running.

DPDK section (`dpdk`):

- `num-rx-queues <num>` -- number of receive queues.

- `num-tx-queues <num>` -- number of transmit queues.

- `dev <PCI address>` -- whitelisted device.

- `num-mbufs` -- numbers of allocated buffers. For the most of our scenarios this

parameter requires to be increased over default value.

Session section (`session`):

- `evt_qs_memfd_seg` -- uses a memfd segment for event queues. This is required for SPDK.

Socket server session (`socksvr`):

- `socket-name <path>` -- configure API socket filename (curently SPDK uses default path `/run/vpp-api.sock`).

Plugins section (`plugins`):

- `plugin <plugin name> { [enable|disable] }` -- enable or disable VPP plugin.

### Example:

~~~

unix {

	nodaemon

	cli-listen /run/vpp/cli.sock

}

cpu {

	main-core 1

}

dpdk {

	num-mbufs 128000

}

session {

	evt_qs_memfd_seg

}

socksvr {

	socket-name /run/vpp-api.sock

}

plugins {

	plugin default { disable }

	plugin dpdk_plugin.so { enable }

}

~~~

A usefull tool is `vppctl`, that allows to control running VPP instance.

Either by entering VPP configuration prompt

## vppctl command tool

The `vppctl` command tool allows users to control VPP at runtime via a command prompt

~~~

sudo vppctl

~~~

sudo vppctl show interface

~~~

Useful commands:

- `show interface` -- show interfaces settings, state and some basic statistics.

- `show interface address` -- show interfaces state and assigned addresses.

- `set interface ip address <VPP interface> <Address>` -- set interfaces IP address.

- `set interface state <VPP interface> [up|down]` -- bring interface up or down.

- `show errors` -- show error counts.

## Example: Configure two interfaces to be available via VPP

We want to configure two DPDK ports with PCI addresses 0000:09:00.1 and 0000:0b:00.1

to be used as portals 10.0.0.1/24 and 10.10.0.1/24.

In the VPP startup file (e.g. `/etc/vpp/startup.conf`), whitelist the interfaces

by specifying PCI addresses in section dpdk:

~~~

	dev 0000:09:00.1

	dev 0000:0b:00.1

~~~

Bind PCI NICs to UIO driver (`igb_uio` or `uio_pci_generic`).

Restart vpp and use vppctl tool to verify interfaces.

~~~

$ vppctl show interface

              Name               Idx    State  MTU (L3/IP4/IP6/MPLS)     Counter          Count

FortyGigabitEthernet9/0/1         1     down         9000/0/0/0

FortyGigabitEthernetb/0/1         2     down         9000/0/0/0

~~~

Set appropriate addresses and bring interfaces up:

~~~

$ vppctl set interface ip address FortyGigabitEthernet9/0/1 10.0.0.1/24

$ vppctl set interface state FortyGigabitEthernet9/0/1 up

$ vppctl set interface ip address FortyGigabitEthernetb/0/1 10.10.0.1/24

$ vppctl set interface state FortyGigabitEthernetb/0/1 up

~~~

Verify configuration:

~~~

$ vppctl show interface address

FortyGigabitEthernet9/0/1 (up):

  L3 10.0.0.1/24

FortyGigabitEthernetb/0/1 (up):

  L3 10.10.0.1/24

~~~

Now, both interfaces are ready to use. To verify conectivity you can ping

10.0.0.1 and 10.10.0.1 addresses from another machine.

## Example: Tap interfaces on single host

For functional test purposes a virtual tap interface can be created,

    ping 10.0.0.1

~~~

# 4. Building SPDK with VPP {#vpp_built_into_spdk}

# 5. Building SPDK with VPP {#vpp_built_into_spdk}

Support for VPP can be built into SPDK by using configuration option.

~~~

Alternatively, directory with built libraries can be pointed at

and will be used for compilation instead of installed packages.

~~~

configure --with-vpp=/path/to/vpp/repo/build-root/rpmbuild/vpp-18.01.1.0/build-root/install-vpp-native/vpp

~~~

Alternatively, in Debian/Ubuntu system, the vpp path is different.

~~~

configure --with-vpp=/path/to/vpp/repo/build-root/install-vpp-native/vpp

~~~

# 5. Running SPDK with VPP {#vpp_running_with_spdk}

# 6. Running SPDK with VPP {#vpp_running_with_spdk}

VPP application has to be started before SPDK application, in order to enable

usage of network interfaces. For example, if you use SPDK iSCSI target or