interfaces: T3871: keep an accelerated-networking VF off its NIC's .link file

On Azure every Hyper-V NIC shares one ID_PATH and has no slot, so it is
keyed on its MAC. Its accelerated-networking VF carries the same MAC and
matched the NIC's .link file, so udev tried to give the VF the NIC's name.

The .link file of a Hyper-V NIC now also matches Driver=hv_netvsc, so the
VF cannot match it. This holds for a lone NIC keyed on the VMBus path too.
A NIC absent at a pass cannot say what it is, so its file keeps the pin
it already carries. NICs that are not Hyper-V ones get no Driver line, and
their files do not change. The 34-to-35 migration passes the hardware it
found, so the pin is written on the first boot of an upgrade too.

1 files changed, 40 insertions, 3 deletions

diff --git a/python/vyos/ifconfig/ifname_store.py b/python/vyos/ifconfig/ifname_store.py
index e0a6b4cbe..20731aed1 100644
--- a/python/vyos/ifconfig/ifname_store.py
+++ b/python/vyos/ifconfig/ifname_store.py
@@ -60,6 +60,8 @@ _PORT_LABEL = re.compile(r'^Ethernet(\d+)$')
 # compares tuples element-wise, so a None here would raise against an int
 _LABEL_UNKNOWN = 1 << 30
 _VMWARE_PCI_VENDOR = '0x15ad'
+# a Hyper-V NIC carries no slot, path or label of its own - only its MAC
+_HYPERV_DRIVER = 'hv_netvsc'
 _DMI_SYS_VENDOR = Path('/sys/class/dmi/id/sys_vendor')
 _MAC_RE = re.compile(r'([0-9a-fA-F]{2}(:[0-9a-fA-F]{2}){5})')
 
@@ -119,6 +121,11 @@ def canonical_sort_key(device: dict) -> tuple:
     return (rank, label, segments, path, device.get('mac') or '')
 
 
+def is_hyperv_nic(device: dict) -> bool:
+    properties = device.get('properties') or {}
+    return properties.get('ID_NET_DRIVER') == _HYPERV_DRIVER
+
+
 def _sysfs(path: Path) -> str:
     try:
         return path.read_text().strip()
@@ -529,40 +536,70 @@ def _link_type_for(name: str) -> str:
     return 'ether'
 
 
-def render_link(name: str, key: str) -> str:
+def render_link(name: str, key: str, driver: str = '') -> str:
     """Render a systemd .link file body, matching on the stored property.
 
     The device type has to match as well, and a radio is 'wlan' - a .link
     naming a type the device is not simply never applies, leaving the
     interface on its probe-order name. resolve() already names by type (see
     _prefix_for()), so the recorded name is what says which.
+
+    A MAC is not unique to one interface: an accelerated-networking VF
+    carries its NIC's MAC, and matched the NIC's file - udev then tried to
+    give the VF the NIC's name. The driver tells them apart.
     """
+    match_driver = f'Driver={driver}\n' if driver else ''
     return (
         '# Generated by VyOS - do not edit.\n'
         "# Interface names are managed via 'interface-mapping.json'.\n"
         '[Match]\n'
         f'Type={_link_type_for(name)}\n'
         f'Property={key}\n'
+        f'{match_driver}'
         '\n'
         '[Link]\n'
         f'Name={name}\n'
     )
 
 
-def sync_link_files(store: dict, link_dir: Path = None) -> list:
+def _pinned_driver(path: Path, key: str) -> str:
+    """The driver an existing file already pins for this key, if any"""
+    try:
+        body = path.read_text()
+    except OSError:
+        return ''
+    if f'Property={key}\n' not in body:
+        return ''
+    m = re.search(r'^Driver=(\S+)$', body, re.M)
+    return m.group(1) if m else ''
+
+
+def sync_link_files(store: dict, link_dir: Path = None, devices: list = None) -> list:
     """One .link file per recorded name, so udev applies it as the device is
     added - before anything can observe a probe-order name.
     """
     link_dir = link_dir or LINK_DIR
     link_dir.mkdir(parents=True, exist_ok=True)
 
+    # a Hyper-V NIC shares its MAC with its accelerated-networking VF, so
+    # its file names the driver too - also when the NIC is keyed on the VMBus
+    # path, as a lone one is. A NIC absent this boot cannot say which, and
+    # keeps the pin its file already carries.
+    drivers = {}
+    for device in devices or []:
+        key = device.get('key') or ''
+        if key and is_hyperv_nic(device):
+            drivers[key] = _HYPERV_DRIVER
+
     written = {}
     for name, key in store.get('interfaces', {}).items():
         # never for a radio: the key is the phy's address, which every
         # interface created on that phy shares, so the file would rename
         # whichever of them udev saw next
         if key and not name.startswith('wlan'):
-            written[link_dir / f'{LINK_PREFIX}{name}.link'] = render_link(name, key)
+            path = link_dir / f'{LINK_PREFIX}{name}.link'
+            driver = drivers.get(key) or _pinned_driver(path, key)
+            written[path] = render_link(name, key, driver)
 
     for path, body in written.items():
         if path.exists() and path.read_text() == body: