tests: net: mdns: add test for external mDNS records

This commit adds a test for externally stored mDNS records for mDNS
responder.

Signed-off-by: Konrad Derda <konrad.derda@nordicsemi.no>

tests/net/lib/mdns_responder/CMakeLists.txt

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(dns_sd)
+
+target_include_directories(app PRIVATE
+        ${ZEPHYR_BASE}/subsys/net/lib/dns
+        ${ZEPHYR_BASE}/subsys/net/ip
+)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/net/lib/mdns_responder/prj.conf

@@ -0,0 +1,30 @@
+# Networking config
+CONFIG_NETWORKING=y
+CONFIG_NET_TEST=y
+CONFIG_NET_DRIVERS=y
+CONFIG_NET_LOOPBACK=y
+CONFIG_NET_IPV4=y
+CONFIG_NET_IPV6=y
+
+# Network driver config
+CONFIG_TEST_RANDOM_GENERATOR=y
+
+CONFIG_MDNS_RESPONDER=y
+CONFIG_NET_HOSTNAME_ENABLE=y
+CONFIG_DNS_SD=y
+CONFIG_DNS_SD_LOG_LEVEL_DBG=y
+
+CONFIG_ZTEST=y
+CONFIG_ZTEST_STACK_SIZE=2048
+
+# Maybe avoid stack overflow on mps2/an385?
+CONFIG_MAIN_STACK_SIZE=2048
+
+CONFIG_NET_MAX_CONTEXTS=8
+CONFIG_NET_L2_DUMMY=y
+CONFIG_NET_L2_ETHERNET=n
+CONFIG_NET_LOOPBACK=n
+CONFIG_NET_UDP=y
+CONFIG_NET_UDP_CHECKSUM=n
+CONFIG_NET_PKT_RX_COUNT=16
+CONFIG_NET_PKT_TX_COUNT=16