88 lines
3.5 KiB
ReStructuredText
88 lines
3.5 KiB
ReStructuredText
.. _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.
|