1# Create NAT and routing for Zephyr native network on Linux 2 3This page describes how you can set up a networking rules that allows you to run Zephyr applications 4build to native_posix or QEMU targets and get them to access public Internet. 5 6 7 8 9 10Zephyr applications, when build on native_posix or various qemu targets, 11run simulated Ethernet driver that attaches itself to a network interface called zeth. 12This is Linux TAP interface so it can send and receive Ethernet frames. 13 14In order to have networking with Zephyr, you need to configure IP address on linux kernel side, 15set up the routing and have NAT (Network Address Translation / IP masquerading) for outbound 16traffic. 17 18Optionally, having dnsmasq to serve as small stand-alone DHCP and DNS server helps. 19When running dnsmasq, it must bind into the zeth interface, so it does not serve any 20requests coming from outside network. 21 22## Building the Zephyr application for native networking 23 24At minimun, you need following Kconfig settings for your *native_posix* application to have 25working network 26 27``` 28# General network requirements 29CONFIG_NETWORKING=y 30CONFIG_NET_IPV4=y 31CONFIG_NET_TCP=y 32CONFIG_NET_UDP=y 33CONFIG_NET_SOCKETS=y 34 35# Native posix requirements 36CONFIG_ENTROPY_GENERATOR=y 37CONFIG_TEST_RANDOM_GENERATOR=y 38 39CONFIG_NET_L2_ETHERNET=y 40CONFIG_ETH_NATIVE_POSIX=y 41CONFIG_ETH_NATIVE_POSIX_RANDOM_MAC=y 42 43# IPv4 config 44CONFIG_NET_CONFIG_SETTINGS=y 45CONFIG_NET_CONFIG_NEED_IPV4=y 46CONFIG_NET_CONFIG_MY_IPV4_ADDR="192.0.2.1" 47CONFIG_NET_CONFIG_MY_IPV4_GW="192.0.2.2" 48CONFIG_DNS_RESOLVER=y 49CONFIG_DNS_RESOLVER_MAX_SERVERS=1 50CONFIG_DNS_SERVER_IP_ADDRESSES=y 51CONFIG_DNS_SERVER1="192.0.2.2" 52``` 53 54## Running the native_posix app 55 56You can test your configuration for example in `zephyr/samples/net/sockets/http_get` by creating 57a file called `boards/native_posix.conf` with the content from the sample above. 58 59```sh 60cd zephyr/samples/net/sockets/http_get 61# create boards/native_posix.conf 62 63# Building the application 64west build -b native_posix -- -DOVERLAY_CONFIG=overlay-tls.conf 65 66# Run the application 67# Note that you need to run it realtime (-rt) so responses don't timeout, 68# otherwise it would run faster. 69# Also any TLS/DTLS traffic needs proper seed or random generator, 70# $RANDOM is adequate enough for testing purposes, not secure though, 71./build/zephyr/zephyr.elf -rt -seed=$RANDOM 72 73# Run application that use shell, for example lwm2m_client 74# These spawn the shell and logs into a virtual serial port on /dev/pts/X 75# it is easier to open a x-terminal to this serial port when you start the application 76./build/zephyr/zephyr.elf -rt -seed=$RANDOM -attach_uart 77``` 78 79You might need to supply also `-attach_uart_cmd` parameter, in case default X-terminal is not 80installed. For example `-attach_uart_cmd='x-terminal-emulator -e screen %s &'` works. 81
