feat: report listening sockets

get_listening_sockets() in the shape of napalm-device-types'
ListeningSocketsMixin, whose ss/cgroup reading is Linux's, and with its
rule: read as root first, and without root when that brings nothing back,
which the reading reports as `attributed: False`.

- FreeBSD: `sockstat -46lq -P tcp,udp`, which sees every socket either way.
- OpenBSD: `fstat -n` as root (the sockets nothing is connected to; port 0
  is unbound), `netstat -an` without root, as fstat shows a user only
  their own processes; those sockets come without a process.
- Addresses as ss prints them: `*` becomes 0.0.0.0 or :: by family, IPv6
  without brackets, a zone (`fe80::1%lo0`) becomes the interface. One entry
  per socket, the first process holding it.

No get_kernel_facts on purpose: KernelFactsMixin reports a Linux kernel's
modules and CONFIG_ options, which a BSD kernel does not have.

Fixtures recorded on the FreeBSD 15.1 and OpenBSD 7.9 VMs with test
listeners on 127.0.0.1 and ::1 (NetOrk/netork#798).

napalm_bsd/base.py

@@ -42,6 +42,10 @@ class BsdDriver(OSDriver):
     #: Prints ``key=value`` lines; see :meth:`_platform`.
     PLATFORM_COMMAND = ""
     ROUTES_COMMAND = "netstat -rn"
+    #: Lists listening sockets with their processes; as root it names them all.
+    LISTENING_COMMAND = ""
+    #: Lists them without root, if the command above needs it to see them all.
+    LISTENING_FALLBACK_COMMAND = ""
     #: lstart is five words; :func:`parse.processes` reads it as one field.
     PS_COMMAND = "ps -axww -o user,pid,ppid,%cpu,%mem,vsz,rss,stat,lstart,command"
 
@@ -245,6 +249,34 @@ class BsdDriver(OSDriver):
         """Neither BSD ships an LLDP daemon in its base system."""
         return {}
 
+    # -- listening sockets -------------------------------------------------------
+
+    def _parse_listening(self, output: str, *, attributed: bool) -> list[dict[str, Any]]:
+        """Parse :attr:`LISTENING_COMMAND` (*attributed*) or its fallback."""
+        raise NotImplementedError
+
+    def get_listening_sockets(self) -> dict[str, Any]:
+        """Every listening TCP and bound UDP socket, with the process holding it.
+
+        Same shape as napalm-device-types' ``ListeningSocketsMixin`` -- whose
+        ``ss``/cgroup reading is Linux's -- and the same rule: read as root
+        first, and without root when that brings nothing back, which the
+        reading then says (``attributed: False``). BSD has no systemd units or
+        container IDs to name.
+        """
+        privileged = self.run_command(self.LISTENING_COMMAND, privileged=True)
+        if privileged.exit_code == 0 and privileged.stdout.strip():
+            return {
+                "attributed": True,
+                "sockets": self._parse_listening(privileged.stdout, attributed=True),
+            }
+        command = self.LISTENING_FALLBACK_COMMAND or self.LISTENING_COMMAND
+        plain = self.run_command(command, privileged=False)
+        return {
+            "attributed": False,
+            "sockets": self._parse_listening(plain.stdout, attributed=False),
+        }
+
     # -- accounts, processes, cron -----------------------------------------------
 
     def get_users(self) -> list[dict[str, Any]]: