Merge #19199 #19205 #19207

19199: sys/suit: Ensure previous thread is stopped before reusing its stack r=benpicco a=chrysn

### Contribution description

Closes: https://github.com/RIOT-OS/RIOT/issues/19195

If the thread has released the mutex but the thread has not terminated (which happens in the situation that would previously have overwritten a still active thread's state), then a warning is shown and the trigger is ignored.

### Testing procedure

This should work before and after:

* `make -C examples/suit_update BOARD=native all term`
* `aiocoap-client coap://'[fe80::3c63:beff:fe85:ca96%tapbr0]'/suit/trigger -m POST --payload 'coap://[2001:db8::]/foo'`
* In parallel, on the RIOT shell, run `suit fetch coap://[2001:db8::]/foo`
* After the first download fails, the second one starts right away ("suit_worker: update failed, hdr invalid" / "suit_worker: started").

Run again with the worker thread on low priority:

```patch
diff --git a/sys/suit/transport/worker.c b/sys/suit/transport/worker.c
index a54022fb28..e26701a64c 100644
--- a/sys/suit/transport/worker.c
+++ b/sys/suit/transport/worker.c
`@@` -70 +70 `@@`
-#define SUIT_COAP_WORKER_PRIO THREAD_PRIORITY_MAIN - 1
+#define SUIT_COAP_WORKER_PRIO THREAD_PRIORITY_MAIN + 1
```

Before, this runs the download once silently (no clue why it doesn't run it twice, but then again, I claim there's concurrent memory access from two thread, so who knows what happens). After, it runs a single download and shows an error message for the second one once the first is complete ("Ignoring SUIT trigger: worker is still busy.").

### Issues/PRs references

This may be made incrementally easier by https://github.com/RIOT-OS/RIOT/pull/19197 -- that PR as it is now would spare us the zombification (because returning would do that), and having a `wait` function would allow us to turn the new error case into a success.

19205: boards/common: add common timer config for GD32VF103 boards r=benpicco a=benpicco



19207: examples/gnrc_border_router: static: use router from advertisements by default r=benpicco a=benpicco




Co-authored-by: chrysn <chrysn@fsfe.org>
Co-authored-by: Benjamin Valentin <benjamin.valentin@bht-berlin.de>
Co-authored-by: Benjamin Valentin <benpicco@beuth-hochschule.de>

boards/common/gd32v/include/board_common.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2020 Koen Zandberg <koen@bergzand.net>
+ *               2023 Gunar Schorcht <gunar@schorcht.net>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_common_gd32v
+ * @{
+ *
+ * @file
+ * @brief       Common board definitions for GD32VF103 boards
+ *
+ * @author      Koen Zandberg <koen@bergzand.net>
+ * @author      Gunar Schorcht <gunar@schorcht.net>
+ */
+
+#ifndef BOARD_COMMON_H
+#define BOARD_COMMON_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    Xtimer configuration
+ * @{
+ */
+#define XTIMER_WIDTH                (16)
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BOARD_COMMON_H */
+/** @} */

boards/seeedstudio-gd32/include/board.h

@@ -21,6 +21,8 @@
 #ifndef BOARD_H
 #define BOARD_H
 
+#include "board_common.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif

boards/sipeed-longan-nano/include/board.h

@@ -20,6 +20,8 @@
 #ifndef BOARD_H
 #define BOARD_H
 
+#include "board_common.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif

examples/gnrc_border_router/Makefile

@@ -64,8 +64,14 @@ else ifeq (auto_subnets,$(PREFIX_CONF))
   USEMODULE += gnrc_ipv6_auto_subnets_simple
 else ifeq (static,$(PREFIX_CONF))
   IPV6_ADDR ?= 2001:db8:1::1
-  IPV6_DEFAULT_ROUTER ?= fe80::1
+# Only set this if the default router does not send router advertisements
+# IPV6_DEFAULT_ROUTER ?= fe80::1
   USEMODULE += gnrc_ipv6_static_addr
+
+  # configure static DNS server
+  ifneq (,$(filter sock_dns,$(USEMODULE)))
+    USEMODULE += auto_init_sock_dns
+  endif
 endif
 
 # Comment this out to disable code in RIOT that does safety checking

sys/net/gnrc/network_layer/ipv6/nib/_nib-router.c

@@ -155,7 +155,8 @@ static gnrc_pktsnip_t *_build_ext_opts(gnrc_netif_t *netif,
     uint32_t rdnss_ltime = _evtimer_lookup(&sock_dns_server,
                                            GNRC_IPV6_NIB_RDNSS_TIMEOUT);
 
-    if ((rdnss_ltime < UINT32_MAX) &&
+    /* with auto_init_sock_dns we always have a valid (static) DNS server */
+    if (((rdnss_ltime < UINT32_MAX) || IS_USED(MODULE_AUTO_INIT_SOCK_DNS)) &&
         (!ipv6_addr_is_link_local((ipv6_addr_t *)sock_dns_server.addr.ipv6))) {
         gnrc_pktsnip_t *rdnsso = gnrc_ndp_opt_rdnss_build(
                 rdnss_ltime * MS_PER_SEC,

sys/net/gnrc/network_layer/ipv6/static_addr/Kconfig

@@ -30,6 +30,5 @@ config GNRC_IPV6_STATIC_ADDR_DOWNSTREAM
 
 config GNRC_IPV6_STATIC_DEFAULT_ROUTER
     string "Static IPv6 address of the default router"
-    default "2001:db8::1"
 
 endif # KCONFIG_USEMODULE_GNRC_IPV6_STATIC_ADDR

sys/suit/transport/worker.c

@@ -79,6 +79,8 @@ static char _url[CONFIG_SOCK_URLPATH_MAXLEN];
 static uint8_t _manifest_buf[SUIT_MANIFEST_BUFSIZE];
 
 static mutex_t _worker_lock;
+/* PID of the worker thread, guarded by */
+static kernel_pid_t _worker_pid = KERNEL_PID_UNDEF;
 
 int suit_handle_url(const char *url)
 {
@@ -154,17 +156,27 @@ static void *_suit_worker_thread(void *arg)
     }
 
     mutex_unlock(&_worker_lock);
+    thread_zombify();
+    /* Actually unreachable, given we're in a thread */
     return NULL;
 }
 
 void suit_worker_trigger(const char *url, size_t len)
 {
     mutex_lock(&_worker_lock);
+    if (_worker_pid != KERNEL_PID_UNDEF) {
+        if (thread_kill_zombie(_worker_pid) != 1) {
+            /* This will only happen if the SUIT thread runs on a lower
+             * priority than the caller */
+            LOG_WARNING("Ignoring SUIT trigger: worker is still busy.\n");
+            return;
+        }
+    }
 
     memcpy(_url, url, len);
     _url[len] = '\0';
 
-    thread_create(_stack, SUIT_WORKER_STACKSIZE, SUIT_COAP_WORKER_PRIO,
+    _worker_pid = thread_create(_stack, SUIT_WORKER_STACKSIZE, SUIT_COAP_WORKER_PRIO,
                   THREAD_CREATE_STACKTEST,
                   _suit_worker_thread, NULL, "suit worker");
 }