feat: SystemIdentityMixin reads a host's SMBIOS identity (4.9.0)

What ties a server to its BMC: the BMC reports the server's serial
number and system UUID, the host reads the same values from its DMI
tables. Both drivers that read DMI (napalm-linux, napalm-proxmox) had a
copy of the shell for it, and neither read the board serial.

SystemIdentityMixin.get_system_identity() reads product_uuid,
product_serial and board_serial in one framed command and returns them
with vendor placeholders empty: a Supermicro board's product serial is
0123456789 on every one of them, others read "To be filled by O.E.M."
or "Default string", and many cheap boards share the UUID
03000200-0400-0500-0006-000700080009. is_placeholder_identity() is the
same filter for a BMC driver's side. A driver supplies only
_run_system_identity_command(command, privileged=); the files are
root's.

napalm_device_types/__init__.py

@@ -125,6 +125,12 @@ from napalm_device_types.systemd import (
     parse_systemd_services,
 )
 from napalm_device_types.updates import UpdateMixin
+from napalm_device_types.system_identity import (
+    SYSTEM_IDENTITY_COMMAND,
+    SystemIdentityMixin,
+    is_placeholder_identity,
+    parse_system_identity,
+)
 from napalm_device_types.virtual_ips import (
     VIRTUAL_IPS_COMMAND,
     VirtualIpsMixin,
@@ -205,6 +211,10 @@ __all__ = [
     "UpdateMixin",
     "VIRTUAL_IPS_COMMAND",
     "VirtualIpsMixin",
+    "SystemIdentityMixin",
+    "SYSTEM_IDENTITY_COMMAND",
+    "is_placeholder_identity",
+    "parse_system_identity",
     "OpenSshServerMixin",
     "SSH_ALGORITHM_CLASSES",
     "SshHardeningPlan",

napalm_device_types/models.py

@@ -1151,3 +1151,13 @@ class ManagementProtocolsDict(TypedDict):
     snmp: ProtocolStateDict
     kvm: ProtocolStateDict
     virtual_media: ProtocolStateDict
+
+
+class SystemIdentityDict(TypedDict):
+    """A host's SMBIOS identity, what ties it to its BMC (:mod:`napalm_device_types.system_identity`).
+
+    Each value is empty when unknown or a vendor placeholder."""
+
+    system_uuid: str              # lowercase
+    product_serial: str
+    board_serial: str

napalm_device_types/system_identity.py

@@ -0,0 +1,115 @@
+# -*- coding: utf-8 -*-
+"""The SMBIOS identity of a host: system UUID, product serial, board serial.
+
+What ties a server to its BMC. The BMC reports the server's serial number and
+system UUID; the host reads the same values from its firmware tables. Both sides
+read them the same way on every Linux host, so the command, its parse and the
+placeholder filter live here once, and a driver only carries the command across.
+
+**Placeholders are no identity.** Board vendors leave defaults in the DMI tables
+that are the same on thousands of machines: a Supermicro board's product serial
+is ``0123456789``, others read ``To be filled by O.E.M.`` or ``Default string``,
+and a common UUID on cheap boards is ``03000200-0400-0500-0006-000700080009``.
+Matching on those would join unrelated machines, so they read as empty.
+
+**Root.** ``product_uuid`` and ``product_serial`` are readable by root only; without
+it they come back empty, which is "not known", not a mismatch.
+"""
+
+from __future__ import annotations
+
+import re
+from typing import TYPE_CHECKING
+
+from napalm_device_types.models import SystemIdentityDict
+from napalm_device_types.terminal import strip_terminal_codes
+
+_BEGIN = "IDBEGIN"
+_END = "IDEND"
+_DMI = "/sys/class/dmi/id"
+
+#: Reads the three files in one round trip, framed so a banner or prompt around the
+#: output cannot shift a field.
+SYSTEM_IDENTITY_COMMAND = (
+    f"printf '{_BEGIN}\\n%s\\n%s\\n%s\\n{_END}\\n' "
+    f"\"$(cat {_DMI}/product_uuid 2>/dev/null)\" "
+    f"\"$(cat {_DMI}/product_serial 2>/dev/null)\" "
+    f"\"$(cat {_DMI}/board_serial 2>/dev/null)\""
+)
+
+#: Lowercased defaults board vendors leave in place.
+_PLACEHOLDERS = frozenset({
+    "", "none", "n/a", "na", "not specified", "not applicable", "not available",
+    "to be filled by o.e.m.", "to be filled by oem", "default string", "default",
+    "system serial number", "base board serial number", "chassis serial number",
+    "serial number", "0123456789", "1234567890", "123456789", "o.e.m.", "oem",
+    "03000200-0400-0500-0006-000700080009",
+})
+#: A value of one repeated character ("0", "00000000", "FFFF-...") or of zeros and Fs.
+_REPEATED = re.compile(r"^(.)\1*$")
+
+
+def is_placeholder_identity(value: str | None) -> bool:
+    """Whether *value* is a vendor default rather than this machine's identity."""
+    text = (value or "").strip().lower()
+    if text in _PLACEHOLDERS:
+        return True
+    compact = text.replace("-", "").replace(" ", "")
+    return bool(_REPEATED.match(compact))
+
+
+def _clean(value: str) -> str:
+    value = value.strip()
+    return "" if is_placeholder_identity(value) else value
+
+
+def parse_system_identity(output: str) -> SystemIdentityDict:
+    """The identity from :data:`SYSTEM_IDENTITY_COMMAND`'s output, placeholders empty.
+
+    :raises ValueError: when the output carries no intact frame.
+    """
+    lines = strip_terminal_codes(output).splitlines()
+    try:
+        start = lines.index(_BEGIN) + 1
+        end = lines.index(_END, start)
+    except ValueError:
+        raise ValueError("system identity: no intact IDBEGIN/IDEND frame") from None
+    fields = (lines[start:end] + ["", "", ""])[:3]
+    uuid, product_serial, board_serial = (_clean(f) for f in fields)
+    return {
+        "system_uuid": uuid.lower(),
+        "product_serial": product_serial,
+        "board_serial": board_serial,
+    }
+
+
+class SystemIdentityMixin:
+    """Adds :meth:`get_system_identity` to a driver that can run a command on a Linux host.
+
+    The template form (README, "Function classes"): command and parse are the same
+    everywhere and concrete here; a driver supplies only
+    :meth:`_run_system_identity_command` -- how a command reaches its host, and how it
+    gains root there. Mixed in by the drivers that can, so
+    ``hasattr(driver, "get_system_identity")`` stays a truthful answer.
+    """
+
+    if TYPE_CHECKING:  # pragma: no cover - declared for type checkers only
+
+        def _run_system_identity_command(self, command: str, *, privileged: bool) -> str:
+            """Run *command* on the host and return what it printed; as root when
+            *privileged* (``product_uuid`` and ``product_serial`` are root's)."""
+            ...
+
+    def get_system_identity(self) -> SystemIdentityDict:
+        """
+        Returns the host's SMBIOS identity, each value empty when unknown or a vendor
+        placeholder:
+
+        * system_uuid (str) - lowercase
+        * product_serial (str)
+        * board_serial (str)
+
+        :raises ValueError: if the output carried no intact reading.
+        """
+        output = self._run_system_identity_command(SYSTEM_IDENTITY_COMMAND, privileged=True)
+        return parse_system_identity(output)