[JohnAmadis]

Summary

The STM32F746G Discovery board now resolves host names: the dns service starts at boot, and the Renode network test checks resolution end to end. The PR also fixes two causes of the red Renode pipeline.

configs/board/stm32f746g-disco/flash.dmd

dmdns service=dns.ini
nslookup

• dns.ini is a type=library unit from the dmdns package. It loads and enables the resolver once for the whole system, with no per-interface rule.
• Name servers come from the DHCP lease (option 6). dmdhcp ≥ 0.4 reports them through dmdns's dmdns_provide_servers DIF on every lookup, so the board needs no DNS configuration.
• nslookup lets you look names up from the shell.

scripts/test_renode_network.py

• The host DHCP server now also offers option 6 (DNS = 192.168.100.1).
• A new DnsServer thread listens on the TAP (UDP 53). It knows one name, dmod-boot.test → 192.168.100.77, and answers AAAA for it with NODATA. Every other name gets NXDOMAIN.
• After the telnet check, the test runs:
  1. nslookup -4 dmod-boot.test without a server argument → must print Address: 192.168.100.77. This checks the whole path: dns service → server from the DHCP lease through the DIF → UDP query → answer parsing.
  2. A check that the query really reached the host's DNS server from 192.168.100.2.
  3. nslookup -4 no-such-host.test → must report NXDOMAIN.

Fixes for the red Renode pipeline

1. dmlog ring too small for the emulation. monitor-gdb attaches only after the board has run for a while. With DNS added, the boot log up to the start of systemd is about 33 KB, so the 8 KiB ring had already overwritten DMOD-Boot started.
   • linker/common.ld now takes the ring size from __dmboot_logs_size__ when it is defined (default still 8192).
   • CMakeLists.txt sets it to 64 KiB for DMBOOT_EMULATION builds via DMBOOT_EMULATION_LOGS_SIZE.
   • Board builds are unchanged.
2. Unexpected GDB response: $ (master's failure after Board skill: always build and flash from build/, dmf-get's cache #117). This was a race in dmlog_monitor: a late stop reply from Renode arrived before the ack. It is fixed in Monitor: skip a stop reply that arrives before an ack dmlog#58 (merged), and lib/dmlog points at its merge commit.

Verification

• I ran the full scripts/run_renode_tests.sh locally with DMBOOT_TEST_NETWORK=1 (Renode 1.15.3, arm-none-eabi 10.3-2021.10, TAP). All 9 steps passed, including the DNS checks above.
• CI passed on 3c31ca4: all three builds and Test Renode Simulation.

Merge order

choco-technologies/dmdns#2 (adds nslookup to the manifest) before this PR.

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