Add support for DHCP server/relay

This patch introduces a new yang yang model for DHCP server and relay,
using dnsmasq to provide the functionality on a per-interface basis.

Available DHCP options will be queried by confd on startup and can
then be configured in a flexible manner.

The DHCP option 82 feature has been realized by patching dnsmasq
(see patches/dnsmasq/2.90/0000-relay-agent-info.patch).

Signed-off-by: Stefan Schlosser <sgs@grmmbl.org>

src/statd/python/cli_pretty/cli_pretty.py

@@ -57,6 +57,12 @@ class PadSoftware:
     state = 10
     version = 23
 
+class PadDhcpServer:
+    iface = 7
+    ip = 17
+    mac = 19
+    host = 21
+    exp = 7
 
 class PadUsbPort:
     title = 30
@@ -350,6 +356,34 @@ class STPPortID:
         )
         return f"{prio:1x}.{pid:03x}"
 
+class DhcpServer:
+    def __init__(self, data):
+        self.data = data
+        self.iface = get_json_data('', self.data, 'if-name')
+        self.leases = []
+        now = datetime.now(timezone.utc)
+        for lease in get_json_data([], self.data, 'server', 'lease', 'host'):
+            dt = datetime.strptime(lease["expires"], "%Y-%m-%dT%H:%M:%S%z")
+            exp =  (dt - now).total_seconds()
+            self.leases.append({
+               "ip": lease["ip-address"],
+               "mac": lease["hardware-address"],
+               "host": lease["hostname"],
+               "exp": int(exp)
+            })
+
+    def print(self):
+        for lease in self.leases:
+            ip = lease["ip"]
+            mac = lease["mac"]
+            exp = "%ds" % lease["exp"]
+            host = lease["host"][:20]
+            row = f"{self.iface:<{PadDhcpServer.iface}}"
+            row += f"{ip:<{PadDhcpServer.ip}}"
+            row += f"{mac:<{PadDhcpServer.mac}}"
+            row += f"{host:<{PadDhcpServer.host}}"
+            row += f"{exp:<{PadDhcpServer.exp}}"
+            print(row)
 
 class Iface:
     def __init__(self, data):
@@ -1038,6 +1072,23 @@ def show_ntp(json):
         row += f"{source['poll']:>{PadNtpSource.poll}}"
         print(row)
 
+def show_dhcp_server(json):
+    if not json.get("infix-dhcp-server:dhcp-server"):
+        print("DHCP server not enabled.")
+        return
+
+    hdr = (f"{'IFACE':<{PadDhcpServer.iface}}"
+           f"{'IP':<{PadDhcpServer.ip}}"
+           f"{'MAC':<{PadDhcpServer.mac}}"
+           f"{'HOSTNAME':<{PadDhcpServer.host}}"
+           f"{'EXPIRES':<{PadDhcpServer.exp}}")
+    print(Decore.invert(hdr))
+
+    servers = get_json_data({}, json, "infix-dhcp-server:dhcp-server", "server-if")
+    for s in servers:
+        server = DhcpServer(s)
+        server.print()
+
 def main():
     global UNIT_TEST
 
@@ -1074,6 +1125,8 @@ def main():
 
     parser_show_boot_order = subparsers.add_parser('show-boot-order', help='Show NTP sources')
 
+    parser_show_routing_table = subparsers.add_parser('show-dhcp-server', help='Show DHCP server')
+
     args = parser.parse_args()
     UNIT_TEST = args.test
 
@@ -1091,6 +1144,8 @@ def main():
         show_hardware(json_data)
     elif args.command == "show-ntp":
         show_ntp(json_data)
+    elif args.command == "show-dhcp-server":
+        show_dhcp_server(json_data)
     else:
         print(f"Error, unknown command '{args.command}'")
         sys.exit(1)

src/statd/python/dhcp_server_status/__init__.py

@@ -0,0 +1,4 @@
+from .dhcp_server_status import main
+
+if __name__ == "__main__":
+    main()

src/statd/python/dhcp_server_status/dhcp_server_status.py

@@ -0,0 +1,83 @@
+#!/usr/bin/python3
+#
+# This script is used to query dnsmasq daemons via dbus and
+# fills/cleans the infix-dhcp-server packet statistics.
+#
+
+import argparse
+import json
+import dbus
+import re
+
+
+DBUS_NAME = "org.freedesktop.DBus"
+DBUS_OBJECT = "/org/freedesktop/DBus"
+DBUS_IFACE = "org.freedesktop.DBus"
+
+DNSMASQ_NAME = "uk.org.thekelleys.dnsmasq"
+DNSMASQ_IFACE = "uk.org.thekelleys.dnsmasq"
+DNSMASQ_OBJECT = "/uk/org/thekelleys/dnsmasq"
+
+
+def get_servers(bus):
+    try:
+        remote_object = bus.get_object(DBUS_NAME, DBUS_OBJECT)
+        iface = dbus.Interface(remote_object, DBUS_IFACE)
+    except dbus.DBusException:
+        return []
+
+    servers = []
+    for name in iface.ListNames():
+        r = re.search(r"%s.(\w+)$" % DNSMASQ_NAME, name)
+        if r:
+            server = {
+                "ifc": r.group(1),
+                "name": str(name)
+            }
+            servers.append(server)
+
+    return servers
+
+
+def get_iface(bus, name):
+    try:
+        remote_object = bus.get_object(name, DNSMASQ_OBJECT)
+        iface = dbus.Interface(remote_object, DNSMASQ_IFACE)
+    except dbus.DBusException:
+        return None
+    finally:
+        return iface
+
+
+def main():
+    bus = dbus.SystemBus()
+    servers = get_servers(bus)
+
+    parser = argparse.ArgumentParser(prog='dhcp-server-status')
+    parser.add_argument("-c", "--clean", help="DHCP server interface")
+    args = parser.parse_args()
+
+    if args.clean:
+        for server in servers:
+            if server["ifc"] != args.clean:
+                continue
+            iface = get_iface(bus, server["name"])
+            if not iface:
+                continue
+            print("Cleaning metrics for DHCP server on %s" % server["ifc"])
+            iface.ClearMetrics()
+    else:
+        data = []
+        for server in servers:
+            iface = get_iface(bus, server["name"])
+            if not iface:
+                continue
+            data.append({
+                "if-name": server["ifc"],
+                "metrics": iface.GetMetrics()
+            })
+        print(json.dumps(data))
+
+
+if __name__ == "__main__":
+    main()

src/statd/python/pyproject.toml

@@ -6,7 +6,8 @@ license = "MIT"
 packages = [
     { include = "yanger" },
     { include = "cli_pretty" },
-    { include = "ospf_status" }
+    { include = "ospf_status" },
+    { include = "dhcp_server_status" }
 ]
 authors = [
   "KernelKit developers"
@@ -21,3 +22,4 @@ build-backend = "poetry.core.masonry.api"
 yanger = "yanger.__main__:main"
 cli-pretty = "cli_pretty:main"
 ospf-status = "ospf_status:main"
+dhcp-server-status = "dhcp_server_status:main"

src/statd/python/yanger/__main__.py

@@ -70,6 +70,9 @@ def main():
     elif args.model == 'infix-containers':
         from . import infix_containers
         yang_data = infix_containers.operational()
+    elif args.model == 'infix-dhcp-server':
+        from . import infix_dhcp_server
+        yang_data = infix_dhcp_server.operational()
     elif args.model == 'ietf-system':
         from . import ietf_system
         yang_data = ietf_system.operational()

src/statd/python/yanger/infix_dhcp_server.py

@@ -0,0 +1,79 @@
+from datetime import datetime
+from .host import HOST
+
+
+def lease_info(ifname):
+    """Populate DHCP leases table"""
+    leases = f"/var/run/dnsmasq-{ifname}.leases"
+    hosts = []
+    try:
+        with open(leases, 'r', encoding='utf-8') as fd:
+            for line in fd:
+                tokens = line.strip().split(" ")
+                if len(tokens) != 5:
+                    continue
+
+                host = {
+                    "ip-address": tokens[2],
+                    "hardware-address": tokens[1],
+                }
+                dt = datetime.utcfromtimestamp(int(tokens[0]))
+                host["expires"] = dt.isoformat() + "+00:00"
+
+                if tokens[3] != '*':
+                    host["hostname"] = tokens[3]
+                if tokens[4] != '*':
+                    host["client-identifier"] = tokens[4]
+
+                hosts.append(host)
+    except (IOError, OSError, ValueError):
+        pass
+
+    return {
+        "host-count": len(hosts),
+        "host": hosts
+    }
+
+
+def status(servers):
+    """Populate DHCP server status"""
+
+    data = HOST.run_json(['/usr/libexec/statd/dhcp-server-status'], default=[])
+    if data == []:
+        return
+
+    for entry in data:
+        metrics = entry["metrics"]
+
+        servers.append({
+            "if-name": entry["if-name"],
+            "packet-statistics": {
+                "sent": {
+                    "offer-count": metrics["dhcp_offer"],
+                    "ack-count": metrics["dhcp_ack"],
+                    "nak-count": metrics["dhcp_nak"]
+                },
+                "received": {
+                    "decline-count": metrics["dhcp_decline"],
+                    "discover-count": metrics["dhcp_discover"],
+                    "request-count": metrics["dhcp_request"],
+                    "release-count": metrics["dhcp_release"],
+                    "inform-count": metrics["dhcp_inform"]
+                }
+            },
+            "server": {
+                "lease": lease_info(entry["if-name"])
+            }
+        })
+
+
+def operational():
+    """Return operational status for DHCP server"""
+    out = {
+        "infix-dhcp-server:dhcp-server": {
+            "server-if": []
+        }
+    }
+    status(out['infix-dhcp-server:dhcp-server']['server-if'])
+
+    return out