feat(network): add *BSD support via an ifconfig fallback

Network.scan() read interface facts exclusively from Linux sysfs
(/sys/class/net), so it could not run on *BSD. Abstract the OS-specific
bits behind small helpers that use sysfs when present and fall back to
parsing `ifconfig -a` otherwise:

- Add netbox_agent/ifconfig.py: parse `ifconfig -a` for per-interface MAC
  and MTU (the facts scan() reads from /sys on Linux).
- scan() enumerates interfaces and reads MAC/MTU/bonding/virtual via
  _use_sysfs()-guarded helpers; the Linux path is behaviorally unchanged.
- ethtool is already skipped when the binary is absent, so *BSD NICs get
  ethtool=None (interface type falls back to Other), which downstream
  already handles.
- Guard the MTU update so a missing (None) MTU never clears a known one.
- Add a fixture + test parsing real FreeBSD `ifconfig` output.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: eric-eisenhart

netbox_agent/ifconfig.py

@@ -0,0 +1,44 @@
+import re
+import subprocess
+
+
+class Ifconfig:
+    """Parse ``ifconfig -a`` output.
+
+    Used on systems without Linux sysfs (``/sys/class/net``) -- e.g. *BSD -- to
+    provide the per-interface facts that :class:`~netbox_agent.network.Network`
+    otherwise reads from ``/sys``: the hardware (MAC) address and the MTU.
+
+    Pass ``output`` to parse a captured string (used by the tests); otherwise it
+    runs ``ifconfig -a`` itself.
+    """
+
+    def __init__(self, output=None):
+        if output is None:
+            output = subprocess.getoutput("ifconfig -a")
+        self.output = output
+        self.interfaces = self.parse()
+
+    def parse(self):
+        interfaces = {}
+        current = None
+        for line in self.output.splitlines():
+            # Interface header lines start in column 0, e.g.
+            #   vtnet0: flags=1008843<UP,BROADCAST,...> metric 0 mtu 1500
+            header = re.match(r"^(\S+?): flags=\S*<[^>]*>(.*)$", line)
+            if header:
+                current = header.group(1)
+                mtu = re.search(r"\bmtu (\d+)", header.group(2))
+                interfaces[current] = {
+                    "mac": None,
+                    "mtu": int(mtu.group(1)) if mtu else None,
+                }
+                continue
+            if current is None:
+                continue
+            # Indented link-layer line carries the MAC, e.g.
+            #   "\tether bc:24:11:6e:21:cd"
+            ether = re.match(r"\s+ether ([0-9a-fA-F:]{17})\b", line)
+            if ether:
+                interfaces[current]["mac"] = ether.group(1)
+        return interfaces

netbox_agent/network.py

@@ -11,6 +11,7 @@
 from netbox_agent.config import config
 from netbox_agent.config import netbox_instance as nb
 from netbox_agent.ethtool import Ethtool
+from netbox_agent.ifconfig import Ifconfig
 from netbox_agent.ipmi import IPMI
 from netbox_agent.lldp import LLDP
 
@@ -46,13 +47,69 @@ def __init__(self, server, *args, **kwargs):
     def get_network_type():
         return NotImplementedError
 
-    def scan(self):
-        nics = []
-        for interface in os.listdir("/sys/class/net/"):
+    def _use_sysfs(self):
+        """Whether Linux sysfs (/sys/class/net) is available.
+
+        When it isn't (e.g. *BSD), interface facts come from ``ifconfig`` instead.
+        """
+        return os.path.isdir("/sys/class/net")
+
+    def _ifconfig_interfaces(self):
+        """Lazily parse ``ifconfig -a`` once, for the non-sysfs (BSD) code path."""
+        if not hasattr(self, "_ifconfig_cache"):
+            self._ifconfig_cache = Ifconfig().interfaces
+        return self._ifconfig_cache
+
+    def _interface_names(self):
+        if self._use_sysfs():
             # ignore if it's not a link (ie: bonding_masters etc)
-            if not os.path.islink("/sys/class/net/{}".format(interface)):
-                continue
+            return [
+                i
+                for i in os.listdir("/sys/class/net/")
+                if os.path.islink("/sys/class/net/{}".format(i))
+            ]
+        return list(self._ifconfig_interfaces().keys())
+
+    def _interface_mac(self, interface, ethtool):
+        if config.network.primary_mac == "permanent" and ethtool and ethtool.get("mac_address"):
+            mac = ethtool["mac_address"]
+        elif self._use_sysfs():
+            mac = open("/sys/class/net/{}/address".format(interface), "r").read().strip()
+            if mac == "00:00:00:00:00:00":
+                mac = None
+        else:
+            mac = self._ifconfig_interfaces().get(interface, {}).get("mac")
+            if mac == "00:00:00:00:00:00":
+                mac = None
+        if mac:
+            mac = mac.upper()
+        return mac
+
+    def _interface_mtu(self, interface):
+        if self._use_sysfs():
+            return int(open("/sys/class/net/{}/mtu".format(interface), "r").read().strip())
+        return self._ifconfig_interfaces().get(interface, {}).get("mtu")
+
+    def _interface_bonding(self, interface):
+        if self._use_sysfs() and os.path.isdir("/sys/class/net/{}/bonding".format(interface)):
+            slaves = open("/sys/class/net/{}/bonding/slaves".format(interface)).read().split()
+            return True, slaves
+        return False, []
+
+    def _interface_virtual(self, interface):
+        if self._use_sysfs():
+            return Path(f"/sys/class/net/{interface}").resolve().parent == VIRTUAL_NET_FOLDER
+        # No sysfs (e.g. *BSD): fall back to a name-based heuristic for the common
+        # virtual interface types.
+        return bool(
+            re.match(
+                r"^(lo|tun|tap|bridge|vlan|gif|gre|epair|pflog|pfsync|enc|ipfw)\d*$", interface
+            )
+        )
 
+    def scan(self):
+        nics = []
+        for interface in self._interface_names():
             if config.network.ignore_interfaces and re.match(
                 config.network.ignore_interfaces, interface
             ):
@@ -90,33 +147,15 @@ def scan(self):
                 ip_addr.append(addr)
 
             ethtool = Ethtool(interface).parse()
-            if (
-                config.network.primary_mac == "permanent"
-                and ethtool
-                and ethtool.get("mac_address")
-            ):
-                mac = ethtool["mac_address"]
-            else:
-                mac = open("/sys/class/net/{}/address".format(interface), "r").read().strip()
-                if mac == "00:00:00:00:00:00":
-                    mac = None
-            if mac:
-                mac = mac.upper()
+            mac = self._interface_mac(interface, ethtool)
+            mtu = self._interface_mtu(interface)
 
-            mtu = int(open("/sys/class/net/{}/mtu".format(interface), "r").read().strip())
             vlan = None
             if len(interface.split(".")) > 1:
                 vlan = int(interface.split(".")[1])
 
-            bonding = False
-            bonding_slaves = []
-            if os.path.isdir("/sys/class/net/{}/bonding".format(interface)):
-                bonding = True
-                bonding_slaves = (
-                    open("/sys/class/net/{}/bonding/slaves".format(interface)).read().split()
-                )
-
-            virtual = Path(f"/sys/class/net/{interface}").resolve().parent == VIRTUAL_NET_FOLDER
+            bonding, bonding_slaves = self._interface_bonding(interface)
+            virtual = self._interface_virtual(interface)
 
             nic = {
                 "name": interface,
@@ -555,7 +594,7 @@ def batched(it, n):
                 nic_update += 1
 
             if hasattr(interface, "mtu"):
-                if nic["mtu"] != interface.mtu:
+                if nic["mtu"] and nic["mtu"] != interface.mtu:
                     logging.info(
                         "Interface mtu is wrong, updating to: {mtu}".format(mtu=nic["mtu"])
                     )

tests/fixtures/ifconfig/freebsd_carp.txt

@@ -0,0 +1,39 @@
+vtnet0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
+        options=cc039a<TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,TSO6,VLAN_HWTSO,LINKSTATE,TXCSUM_IPV6,HWSTATS>
+        ether bc:24:11:6e:21:cd
+        inet 157.131.224.217 netmask 0xffffffc0 broadcast 157.131.224.255
+        media: Ethernet autoselect (10Gbase-T <full-duplex>)
+        status: active
+        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
+vtnet1: flags=1008943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
+        options=cc039a<TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,TSO6,VLAN_HWTSO,LINKSTATE,TXCSUM_IPV6,HWSTATS>
+        ether bc:24:11:90:23:4d
+        inet 10.0.6.2 netmask 0xffffff00 broadcast 10.0.6.255
+        inet 10.0.6.1 netmask 0xffffff00 broadcast 10.0.6.255 vhid 10
+        carp: MASTER vhid 10 advbase 1 advskew 100
+              peer 224.0.0.18 peer6 ff02::12
+        media: Ethernet autoselect (10Gbase-T <full-duplex>)
+        status: active
+        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
+lo0: flags=1008049<UP,LOOPBACK,RUNNING,MULTICAST,LOWER_UP> metric 0 mtu 16384
+        options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
+        inet 127.0.0.1 netmask 0xff000000
+        inet6 ::1 prefixlen 128
+        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
+        groups: lo
+        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
+pfsync0: flags=1000041<UP,RUNNING,LOWER_UP> metric 0 mtu 1500
+        options=0
+        syncdev: vtnet1 maxupd: 128 defer: off version: 1500
+        syncok: 1
+        groups: pfsync
+pflog0: flags=1000141<UP,RUNNING,PROMISC,LOWER_UP> metric 0 mtu 33152
+        options=0
+        groups: pflog
+tailscale0: flags=1008043<UP,BROADCAST,RUNNING,MULTICAST,LOWER_UP> metric 0 mtu 1280
+        options=4080000<LINKSTATE,MEXTPG>
+        inet 100.78.225.91 netmask 0xffffffff broadcast 100.78.225.91
+        inet6 fd7a:115c:a1e0::ac01:e185 prefixlen 48
+        groups: tun
+        nd6 options=101<PERFORMNUD,NO_DAD>
+        Opened by PID 26613

tests/network.py

@@ -1,3 +1,4 @@
+from netbox_agent.ifconfig import Ifconfig
 from netbox_agent.lldp import LLDP
 from tests.conftest import parametrize_with_fixtures
 
@@ -34,3 +35,23 @@ def test_lldp_parse_with_vlan(fixture):
     lldp = LLDP(fixture)
     assert lldp.get_switch_vlan("eth0") == {"300": {"pvid": True}}
     assert lldp.get_switch_vlan("eth1") == {"300": {}}
+
+
+@parametrize_with_fixtures(
+    "ifconfig/",
+    only_filenames=[
+        "freebsd_carp.txt",
+    ],
+)
+def test_ifconfig_parse_freebsd(fixture):
+    interfaces = Ifconfig(fixture).interfaces
+    # MAC + MTU are picked up from the ether/header lines
+    assert interfaces["vtnet0"]["mac"] == "bc:24:11:6e:21:cd"
+    assert interfaces["vtnet0"]["mtu"] == 1500
+    assert interfaces["vtnet1"]["mac"] == "bc:24:11:90:23:4d"
+    assert interfaces["vtnet1"]["mtu"] == 1500
+    # interfaces without an ether line have no MAC, but still an MTU
+    assert interfaces["lo0"]["mac"] is None
+    assert interfaces["lo0"]["mtu"] == 16384
+    assert interfaces["pflog0"]["mtu"] == 33152
+    assert interfaces["tailscale0"]["mtu"] == 1280