DNS resolve
Overview
This application will setup IP address for the device, and then try to resolve various hostnames according to how the user has configured the system.
If IPv4 is enabled, then A record for
www.zephyrproject.orgis resolved.If IPv6 is enabled, then AAAA record for
www.zephyrproject.orgis resolved.If mDNS is enabled, then
zephyr.localname is resolved.
Requirements
screen terminal emulator or equivalent.
For most boards without ethernet, the ENC28J60 Ethernet module is required.
dnsmasq application. The dnsmasq version used in this sample is:
dnsmasq -v
Dnsmasq version 2.76 Copyright (c) 2000-2016 Simon Kelley
Building and Running
Network Configuration
Open the project configuration file for your platform, for example:
prj_frdm_k64f.conf is the configuration file for the
NXP FRDM-K64F board.
In this sample application, both static or DHCPv4 IP addresses are supported. Static IP addresses are specified in the project configuration file, for example:
CONFIG_NET_CONFIG_MY_IPV6_ADDR="2001:db8::1"
CONFIG_NET_CONFIG_PEER_IPV6_ADDR="2001:db8::2"
are the IPv6 addresses for the DNS client running Zephyr and the DNS server, respectively.
DNS server
The dnsmasq tool may be used for testing purposes. On a Zephyr project default installation, the sample dnsmasq start script can be found in the net-tools project or downloaded from https://github.com/zephyrproject-rtos/net-tools.
Open a terminal window and type:
$ cd net-tools
$ sudo ./dnsmasq.sh
The default project configurations settings for this sample uses the public Google DNS servers. In order to use the local dnsmasq server, please edit the appropriate ‘prj.conf’ file and update the DNS server addresses. For instance, if using the usual IP addresses assigned to testing, update them to the following values:
CONFIG_DNS_SERVER1="192.0.2.2:5353"
CONFIG_DNS_SERVER2="[2001:db8::2]:5353"
Note
DNS uses port 53 by default, but the dnsmasq.conf file provided by net-tools uses port 5353 to allow executing the daemon without superuser privileges.
If dnsmasq fails to start with an error like this:
dnsmasq: failed to create listening socket for port 5353: Address already in use
Open a terminal window and type:
$ killall -s KILL dnsmasq
Try to launch the dnsmasq application again.
For testing mDNS, use Avahi script in net-tools project:
$ cd net-tools
$ ./avahi-daemon.sh
LLMNR Responder
If you want Zephyr to respond to a LLMNR DNS request that Windows host is sending, then following config options could be set:
CONFIG_NET_HOSTNAME_ENABLE=y
CONFIG_NET_HOSTNAME="zephyr-device"
CONFIG_DNS_RESOLVER=y
CONFIG_LLMNR_RESPONDER=y
A Zephyr host needs a hostname assigned to it so that it can respond to a DNS query. Note that the hostname should not have any dots in it.
QEMU x86
To use QEMU for testing, follow the Networking with QEMU guide.
FRDM K64F
Open a terminal window and type:
west build -b frdm_k64f samples/net/dns_resolve
west flash
See Freedom-K64F board documentation for more information about this board.
Open a terminal window and type:
$ screen /dev/ttyACM0 115200
Use ‘dmesg’ to find the right USB device.
Once the binary is loaded into the FRDM board, press the RESET button.
Wi-Fi
The IPv4 Wi-Fi support can be enabled in the sample with Wi-Fi snippet.