statd, show: fix several operational data reporting bugs

Three bugs found while testing modem support on hardware:

ietf_system.py: "interface": null written to DNS server entries when
  no interface is associated, causing LY_EVALID in the ietf-system
  schema validator.  Only include the key when the interface name is
  non-empty.

ietf_system.py: empty list inserts (user [], server [], options [],
  search []) overwrote configured data in the operational store instead
  of leaving it intact.  Guard each insert so operational data only
  shadows configured data when there is something to report.

show system: CPU temperature reported only the first sensor named
  exactly "cpu", "soc", or "core".  Platforms with multiple thermal
  zones (e.g. BPI-R4 exposes cpu and cpu1) always showed only one
  reading.  Collect all sensors whose name matches a CPU/SoC prefix
  and report the maximum.

statd.c: yanger parse errors logged without model name or libyang
  error string, making failures hard to diagnose.  Include both.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/bin/show/__init__.py

@@ -558,8 +558,9 @@ def system(args: List[str]) -> None:
     runtime = {}
 
     # Extract CPU temperature and fan speed from hardware components
-    cpu_temp = None
+    cpu_temps = []
     fan_rpm = None
+    _cpu_prefixes = ("cpu", "soc", "core")
     if hardware_data and "ietf-hardware:hardware" in hardware_data:
         components = hardware_data.get("ietf-hardware:hardware", {}).get("component", [])
         for component in components:
@@ -570,18 +571,16 @@ def system(args: List[str]) -> None:
             name = component.get("name", "")
             value_type = sensor_data.get("value-type")
 
-            # Only capture CPU/SoC temperature (ignore phy, sfp, etc.)
-            # Different platforms use different names: cpu, soc, core, etc.
-            if value_type == "celsius" and name in ("cpu", "soc", "core") and cpu_temp is None:
-                temp_millidegrees = sensor_data.get("value", 0)
-                cpu_temp = temp_millidegrees / 1000.0
+            # Capture all CPU/SoC temperatures (handles cpu, cpu1, soc, core0, etc.)
+            if value_type == "celsius" and any(name == p or name.startswith(p) for p in _cpu_prefixes):
+                cpu_temps.append(sensor_data.get("value", 0) / 1000.0)
 
             # Capture fan speed if available
             elif value_type == "rpm" and fan_rpm is None:
                 fan_rpm = sensor_data.get("value", 0)
 
-    if cpu_temp is not None:
-        runtime["cpu_temp"] = cpu_temp
+    if cpu_temps:
+        runtime["cpu_temp"] = max(cpu_temps)
     if fan_rpm is not None:
         runtime["fan_rpm"] = fan_rpm
 

src/statd/python/yanger/ietf_system.py

@@ -134,11 +134,10 @@ def add_dns(out):
 
             try:
                 ipaddress.ip_address(ip)
-                servers.append({
-                    "address": ip,
-                    "origin": "dhcp",
-                    "interface": iface
-                })
+                entry = {"address": ip, "origin": "dhcp"}
+                if iface:
+                    entry["interface"] = iface
+                servers.append(entry)
             except ValueError:
                 continue
 
@@ -146,9 +145,12 @@ def add_dns(out):
             parts = line.split('#', 1)
             search.extend(parts[0].split()[1:])
 
-    insert(out, "infix-system:dns-resolver", "options", options)
-    insert(out, "infix-system:dns-resolver", "server", servers)
-    insert(out, "infix-system:dns-resolver", "search", search)
+    if options:
+        insert(out, "infix-system:dns-resolver", "options", options)
+    if servers:
+        insert(out, "infix-system:dns-resolver", "server", servers)
+    if search:
+        insert(out, "infix-system:dns-resolver", "search", search)
 
 def add_software_slots(out, data):
     slots = []
@@ -357,7 +359,8 @@ def add_users(out):
 
         users.append(user)
 
-    insert(out, "authentication", "user", users)
+    if users:
+        insert(out, "authentication", "user", users)
 
 def add_clock(out):
     clock = {}

src/statd/statd.c

@@ -112,7 +112,8 @@ static int ly_add_yanger_data(const struct ly_ctx *ctx, struct lyd_node **parent
 
 	err = lyd_parse_data_fd(ctx, fd, LYD_JSON, LYD_PARSE_ONLY, 0, parent);
 	if (err)
-		ERROR("Error, parsing yanger data (%d): %s", err, ly_errmsg(ctx));
+		ERROR("Error, parsing yanger data (%d) for model '%s': %s", err,
+		      yanger_args[1] ?: "?", ly_errmsg(ctx));
 
 	fclose(stream);
 	/* Note: fclose() already closes the underlying fd from fdopen() */
@@ -227,7 +228,7 @@ static int sr_generic_cb(sr_session_ctx_t *session, uint32_t, const char *model,
 
 	err = ly_add_yanger_data(ctx, parent, yanger_args);
 	if (err)
-		ERROR("Error adding yanger data");
+		ERROR("Error adding yanger data for xpath: %s", xpath);
 
 	sr_release_context(con);
 

test/case/statd/system/ietf-system.json

@@ -110,15 +110,13 @@
       }
     },
     "infix-system:dns-resolver": {
-      "options": {},
       "server": [
         {
           "address": "192.168.2.1",
           "origin": "dhcp",
           "interface": "e7"
         }
-      ],
-      "search": []
+      ]
     },
     "clock": {
       "boot-datetime": "2026-01-02T20:42:11+00:00",