Commit 54550c04 authored by Bilal Wasim's avatar Bilal Wasim Committed by Carles Cufi
Browse files

net: qemu: Adding support for User Networking 



Added support for Qemu User Networking and tested with
qemu_x86 model. The support is kept simple assuming that
the TAP interface will always be preferred for more
sophisticated / practical use cases.

QEMU User Networking is implemented using "slirp", which
provides a full TCP/IP stack within QEMU and uses that
stack to implement a virtual NAT'd network. As this
support is built into QEMU, it can be used with any model
and requires no admin privileges on the host machine,
unlike TAP.

Added documentation to facilitate the user.

Signed-off-by: default avatarBilal Wasim <bilalwasim676@gmail.com>
parent 46dc8a08

cmake/app/boilerplate.cmake

+13 −11
Original line number Diff line number Diff line
@@ -550,17 +550,19 @@ include(${BOARD_DIR}/board.cmake OPTIONAL) 
# The Qemu supported ethernet driver should define CONFIG_ETH_NIC_MODEL

# string that tells what nic model Qemu should use.

if(CONFIG_QEMU_TARGET)

  if(CONFIG_NET_QEMU_ETHERNET)

    if(CONFIG_ETH_NIC_MODEL)

      list(APPEND QEMU_FLAGS_${ARCH}

        -nic tap,model=${CONFIG_ETH_NIC_MODEL},script=no,downscript=no,ifname=${CONFIG_ETH_QEMU_IFACE_NAME}

      )

    else()

  if ((CONFIG_NET_QEMU_ETHERNET OR CONFIG_NET_QEMU_USER) AND NOT CONFIG_ETH_NIC_MODEL)

    message(FATAL_ERROR "

      No Qemu ethernet driver configured!

      Enable Qemu supported ethernet driver like e1000 at drivers/ethernet"

    )

    endif()

  elseif(CONFIG_NET_QEMU_ETHERNET)

    list(APPEND QEMU_FLAGS_${ARCH}

      -nic tap,model=${CONFIG_ETH_NIC_MODEL},script=no,downscript=no,ifname=${CONFIG_ETH_QEMU_IFACE_NAME}

    )

  elseif(CONFIG_NET_QEMU_USER)

    list(APPEND QEMU_FLAGS_${ARCH}

      -nic user,model=${CONFIG_ETH_NIC_MODEL},${CONFIG_NET_QEMU_USER_EXTRA_ARGS}

    )

  else()

    list(APPEND QEMU_FLAGS_${ARCH}

      -net none

doc/guides/networking/networking_with_host.rst

+10 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ Networking with the host system 
   qemu_eth_setup.rst

   qemu_setup.rst

   usbnet_setup.rst

   qemu_user_setup.rst



While developing networking software, it is usually necessary to connect and

exchange data with the host system like a Linux desktop computer.
@@ -30,6 +31,15 @@ possible: 
    in some cases, you might need to use the SLIP method for host connectivity.

    See :ref:`networking_with_eth_qemu` for details.



* QEMU using SLIRP (Qemu User Networking).



  * QEMU User Networking is implemented using "slirp", which provides a full TCP/IP

    stack within QEMU and uses that stack to implement a virtual NAT'd network. As

    this support is built into QEMU, it can be used with any model and requires no

    admin privileges on the host machine, unlike TAP. However, it has several

    limitations including performance which makes it less valuable for practical

    purposes. See :ref:`networking_with_user_qemu` for details.



* native_posix board.



  * The Zephyr instance can be executed as a user space process in the host

doc/guides/networking/qemu_user_setup.rst

0 → 100644
+87 −0
Original line number Diff line number Diff line 
.. _networking_with_user_qemu:



Networking with QEMU User

#############################



.. contents::

    :local:

    :depth: 2



This page is intended to serve as a starting point for anyone interested in

using QEMU SLIRP with Zephyr.



Introduction

*************



SLIRP is a network backend which provides the complete TCP/IP stack within

QEMU and uses that stack to implement a virtual NAT'd network. As there are

no dependencies on the host, SLIRP is simple to setup.



By default, QEMU uses the ``10.0.2.X/24`` network and runs a gateway at

``10.0.2.2``. All traffic intended for the host network has to travel through

this gateway, which will filter out packets based on the QEMU command line

parameters. This gateway also functions as a DHCP server for all GOS,

allowing them to be automatically assigned with an IP address starting from

``10.0.2.15``.



More details about User Networking can be obtained from here:

https://wiki.qemu.org/Documentation/Networking#User_Networking_.28SLIRP.29



Using SLIRP with Zephyr

************************



In order to use SLIRP with Zephyr, the user has to set the Kconfig option to

enable User Networking.



.. code-block:: console



   CONFIG_NET_QEMU_USER=y



Once this configuration option is enabled, all QEMU launches will use SLIRP.

In the default configuration, Zephyr only enables User Networking, and does

not pass any arguments to it. This means that the Guest will only be able to

communicate to the QEMU gateway, and any data intended for the host machine

will be dropped by QEMU.



In general, QEMU User Networking can take in a lot of arguments including,



* Information about host/guest port forwarding. This must be provided to

  create a communication channel between the guest and host.

* Information about network to use. This may be valuable if the user does

  not want to use the default ``10.0.2.X`` network.

* Tell QEMU to start DHCP server at user-defined IP address.

* ID and other information.



As this information varies with every use case, it is difficult to come up

with good defaults that work for all. Therefore, Zephyr Implementation

offloads this to the user, and expects that they will provide arguments

based on requirements. For this, there is a Kconfig string which can be

populated by the user.



.. code-block:: console



   CONFIG_NET_QEMU_USER_EXTRA_ARGS="net=192.168.0.0/24,hostfwd=tcp::8080-:8080"



This option is appended as-is to the QEMU command line. Therefore, any problems with

this command line will be reported by QEMU only. Here's what this particular

example will do,



* Make QEMU use the ``192.168.0.0/24`` network instead of the default.

* Enable forwarding of any TCP data received from port 8080 of host to port

  8080 of guest, and vice versa.



Limitations

*************



If the user does not have any specific networking requirements other than the

ability to access a web page from the guest, user networking (slirp) is a

good choice. However, it has several limitations



* There is a lot of overhead so the performance is poor.

* The guest is not directly accessible from the host or the external network.

* In general, ICMP traffic does not work (so you cannot use ping within a guest).

* As port mappings need to be defined before launching qemu, clients which use

  dynamically generated ports cannot communicate with external network.

* There is a bug in the SLIRP implementation which filters out all IPv6 packets

  from the guest. See https://bugs.launchpad.net/qemu/+bug/1724590 for details.

  Therefore, IPv6 will not work with User Networking.

subsys/net/ip/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -86,8 +86,24 @@ config NET_QEMU_ETHERNET 
	  Connect to host system via Qemu ethernet driver support. One such

	  driver that Zephyr supports is Intel e1000 ethernet driver.



config NET_QEMU_USER

	bool "SLIRP"

	help

	  Connect to host system via Qemu's built-in User Networking support. This

	  is implemented using "slirp", which provides a full TCP/IP stack within

	  QEMU and uses that stack to implement a virtual NAT'd network.



endchoice



config NET_QEMU_USER_EXTRA_ARGS

	string "Qemu User Networking Args"

	depends on NET_QEMU_USER

	default ""

	help

	  Extra arguments passed to QEMU when User Networking is enabled. This may

	  include host / guest port forwarding, device id, Network address

	  information etc. This string is appended to the QEMU "-net user" option.



config NET_INIT_PRIO

	int

	default 90

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