Add support for DNS resolver operational data

Example status output:

    "infix-system:dns-resolver": {
      "options": {
        "timeout": 3,
        "attempts": 5
      },
      "search": [
        "example.com",
        "foo.com"
      ],
      "server": [
        {
          "address": "1.2.3.4",
          "origin": "static"
        },
        {
          "address": "192.168.2.1",
          "origin": "dhcp",
          "interface": "e5"
        }
      ]
    }

Fixes #510

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

Author: troglobit

src/confd/yang/confd.inc

@@ -33,7 +33,7 @@ MODULES=(
 	"infix-dhcp-client@2025-01-20.yang"
 	"infix-dhcp-server@2025-01-13.yang"
 	"infix-meta@2024-10-18.yang"
-	"infix-system@2024-11-27.yang"
+	"infix-system@2025-01-25.yang"
 	"infix-services@2024-12-03.yang"
 	"ieee802-ethernet-interface@2019-06-21.yang"
 	"infix-ethernet-interface@2024-02-27.yang"

src/confd/yang/infix-system.yang

@@ -6,6 +6,12 @@ module infix-system {
   import ietf-system {
     prefix sys;
   }
+  import ietf-interfaces {
+    prefix if;
+  }
+  import ietf-yang-types {
+    prefix yang;
+  }
   import iana-timezones {
     prefix iana-tz;
   }
@@ -22,8 +28,12 @@ module infix-system {
   contact      "kernelkit@googlegroups.com";
   description  "Infix augments and deviations to ietf-system.";
 
+  revision 2025-01-25 {
+    description "Add DNS resolver status.";
+    reference "internal";
+  }
   revision 2024-11-27 {
-    description "Add NTP status";
+    description "Add NTP status.";
     reference "internal";
   }
   revision 2024-09-13 {
@@ -305,6 +315,8 @@ module infix-system {
   augment "/sys:system-state" {
     container ntp {
       description "NTP status";
+      config false;
+
       container sources {
         list source {
           key address;
@@ -328,11 +340,80 @@ module infix-system {
             type uint8;
             description "Interval between transmitted NTP messages, expressed as a power of two in seconds";
           }
+        }
+      }
+    }
 
+    container dns-resolver {
+      description "List of active DNS servers";
+      config false;
+
+      container options {
+        description "Resolver options.";
+
+        leaf timeout {
+          description "Number of seconds before resolves tries another server.";
+          type uint8;
+          units "seconds";
+        }
+        leaf attempts {
+          description "Number of times the resolver reties before giving up.";
+          type uint8;
+        }
+      }
+
+      leaf-list search {
+        type inet:domain-name;
+        description "Ordered list of domains to search when resolving a host name.";
+      }
+
+      list server {
+        key "address";
+
+        leaf address {
+          description "IP address of DNS server";
+          type inet:ip-address;
+        }
+
+        leaf origin {
+          description "How DNS server was acquired";
+          type enumeration {
+            enum static {
+              description "Statically configured";
+            }
+            enum dhcp {
+              description "Dynamically acquired via DHCP";
+            }
+          }
+        }
+
+        leaf interface {
+          type if:interface-ref;
+          description "Interface DNS server was learned from, if DHCP";
+        }
+      }
+
+      container statistics {
+        description "DNS resolver statistics";
+
+        leaf cache-size {
+          description "Current number of entries in DNS cache";
+          type yang:counter32;
+        }
+
+        leaf cache-hits {
+          description "Number of successful cache lookups";
+          type yang:counter64;
+        }
+
+        leaf cache-misses {
+          description "Number of failed cache lookups";
+          type yang:counter64;
         }
       }
     }
   }
+
   deviation "/sys:system/sys:hostname" {
     deviate replace {
       type infix-sys:hostname;

src/confd/yang/infix-system@2024-11-27.yang renamed to src/confd/yang/infix-system@2025-01-25.yang

@@ -1,4 +1,5 @@
 import subprocess
+import ipaddress
 
 from .common import insert
 from .host import HOST
@@ -61,6 +62,65 @@ def add_ntp(out):
 
     insert(out, "infix-system:ntp", "sources", "source", source)
 
+def add_dns(out):
+    options = {}
+    servers = []
+    search = []
+
+    content = HOST.read_multiline("/etc/resolv.conf.head", [])
+    for line in content:
+        line = line.strip()
+
+        if line.startswith('nameserver'):
+            ip = line.split()[1]
+            try:
+                ipaddress.ip_address(ip)
+                servers.append({
+                    "address": ip,
+                    "origin": "static"
+                })
+            except ValueError:
+                continue
+
+        elif line.startswith('search'):
+            search.extend(line.split()[1:])
+
+        elif line.startswith('options'):
+            opts = line.split()[1:]
+            for opt in opts:
+                if opt.startswith('timeout:'):
+                    options["timeout"] = int(opt.split(':')[1])
+                elif opt.startswith('attempts:'):
+                    options["attempts"] = int(opt.split(':')[1])
+
+    output = HOST.run_multiline(['/sbin/resolvconf', '-l'], [])
+    for line in output:
+        line = line.strip()
+        if line.startswith('nameserver'):
+            parts = line.split('#', 1)
+            ip = parts[0].split()[1]
+
+            iface = None
+            if len(parts) > 1:
+                iface = parts[1].strip()
+
+            try:
+                ipaddress.ip_address(ip)
+                servers.append({
+                    "address": ip,
+                    "origin": "dhcp",
+                    "interface": iface
+                })
+            except ValueError:
+                continue
+
+        elif line.startswith('search'):
+            search.extend(line.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)
+
 def add_software_slots(out, data):
     slots = []
     for slot in data["slots"]:
@@ -136,4 +196,6 @@ def operational():
 
     add_software(out_state)
     add_ntp(out_state)
+    add_dns(out_state)
+
     return out