wwan: T7487: identify modem by port ownership, not interface number

modem_index() in python/vyos/utils/wwan.py derived the ModemManager modem index straight from the interface name (wwan0 -> 0). The kernel-assigned WWAN interface number and ModemManager's own modem index are two independently enumerated values and are not guaranteed to match - on a box with more than one modem, they can enumerate in different orders, so modem index 0 does not necessarily own wwan0. Every function in this module funnels through modem_index() (start_modem_manager, modem_disconnect, modem_connect, and both admin-disconnect marker helpers), and is_wwan_connected() in vyos.utils.network had its own separate copy of the same assumption - so a single reversed enumeration order silently commands the wrong physical modem for every one of them.

modem_index() now lists every modem ModemManager currently knows about and returns whichever one actually has ifname in its own port list, instead of assuming the correspondence. A modem that has not shown up on the bus yet looks the same as one that will never exist, so this waits up to the same modem_wait_timeout budget start_modem_manager() already gives a modem to become dialable, then returns None if nothing claimed the interface. is_wwan_connected() now calls the same resolver instead of keeping its own copy of the old assumption.

None is a real, expected return now, not just a theoretical one - the three callers that previously assumed modem_index() always produced *a* string (right or wrong) are updated: start_modem_manager() bails out early (matching the tolerance its own caller's w.exists() check already has for hardware that isn't detected yet), modem_disconnect() and modem_connect() treat it as nothing to disconnect / a failed dial, matching each function's own existing return contract. show_wwan.py's modem_info() raises a clear, specific error instead, which its own top-level exception handler already reports cleanly. set_admin_disconnected()/clear_admin_disconnected() only ever used modem_index() to validate the interface name looks like a WWAN interface in the first place, so they're unaffected.

2 files changed, 65 insertions, 5 deletions

diff --git a/python/vyos/utils/network.py b/python/vyos/utils/network.py
index cb5863e51..93ed05f6b 100644
--- a/python/vyos/utils/network.py
+++ b/python/vyos/utils/network.py
@@ -290,6 +290,7 @@ def is_wwan_connected(interface):
     carrier network or not """
     from vyos.utils.dict import dict_search
     from vyos.utils.process import is_systemd_service_active
+    from vyos.utils.wwan import modem_index
 
     if not interface.startswith('wwan'):
         raise ValueError(f'Specified interface "{interface}" is not a WWAN interface')
@@ -299,7 +300,9 @@ def is_wwan_connected(interface):
     if not is_systemd_service_active('ModemManager.service'):
         return False
 
-    modem = interface.lstrip('wwan')
+    modem = modem_index(interface)
+    if modem is None:
+        return False
 
     try:
         tmp = cmdl(['mmcli', '--modem', modem, '--output-json'])
diff --git a/python/vyos/utils/wwan.py b/python/vyos/utils/wwan.py
index d8da34bfa..6b07e90bb 100644
--- a/python/vyos/utils/wwan.py
+++ b/python/vyos/utils/wwan.py
@@ -25,9 +25,11 @@ would have done.
 
 import os
 
+from json import loads
 from time import sleep
 
 from vyos.utils.dict import dict_search
+from vyos.utils.misc import wait_for
 from vyos.utils.process import call
 from vyos.utils.process import cmdl
 from vyos.utils.process import DEVNULL
@@ -52,11 +54,54 @@ modem_wait_poll = 0.250
 # survive a reboot, and a commit re-asserts the configured state too.
 admin_disconnect_dir = '/run/vyos-wwan'
 
-def modem_index(ifname: str) -> str:
-    """ Return the ModemManager modem index backing an interface, wwan0 -> 0 """
+def _modem_owning_port(ifname: str):
+    """ Return the ModemManager modem index whose own port list includes
+    ifname, or None if no currently-known modem owns it. """
+    try:
+        modem_list = loads(cmdl(['mmcli', '--list-modems', '--output-json'])).get('modem-list', [])
+    except OSError:
+        return None
+
+    for modem_path in modem_list:
+        idx = modem_path.rsplit('/', 1)[-1]
+        try:
+            detail = loads(cmdl(['mmcli', '--modem', idx, '--output-json']))
+        except OSError:
+            continue
+        ports = dict_search('modem.generic.ports', detail) or []
+        if any(port.split(' ')[0] == ifname for port in ports):
+            return idx
+
+    return None
+
+def modem_index(ifname: str):
+    """ Return the ModemManager modem index backing an interface, or None if
+    no modem currently owns it.
+
+    The kernel-assigned WWAN interface number and ModemManager's own modem
+    index are independently enumerated and are not guaranteed to match - on
+    a box with more than one modem, wwan0 does not necessarily belong to
+    modem 0 (T7487). Resolved by real port ownership instead: every modem
+    ModemManager currently knows about is listed, and whichever one
+    actually has ifname among its own ports is returned.
+
+    A modem that has not shown up on the bus yet looks the same here as one
+    that will never exist, so this waits up to modem_wait_timeout for it to
+    appear before giving up - the same budget start_modem_manager already
+    gives a modem to become dialable, since a modem slow enough to need
+    that budget is also slow enough to not be listed yet when this is first
+    called. """
     if not ifname.startswith('wwan'):
         raise ValueError(f'Specified interface "{ifname}" is not a WWAN interface')
-    return ifname[len('wwan'):]
+
+    index = None
+    def _resolve():
+        nonlocal index
+        index = _modem_owning_port(ifname)
+        return index is not None
+    wait_for(_resolve, interval=modem_wait_poll, timeout=modem_wait_timeout)
+
+    return index
 
 def modem_state(index: str) -> str:
     """ ModemManager state of a modem, empty if it cannot be read yet """
@@ -84,6 +129,13 @@ def start_modem_manager(ifname: str) -> None:
         cmdl(['systemctl', 'start', service_name])
 
     index = modem_index(ifname)
+    if index is None:
+        # No modem currently owns ifname at all - nothing more this can do.
+        # Matches the pre-existing tolerance for hardware that isn't detected
+        # yet: interfaces_wwan.py's own w.exists() check right after this
+        # call already bails out the same way.
+        return None
+
     counter = int(modem_wait_timeout / modem_wait_poll)
     while counter > 0:
         counter -= 1
@@ -150,13 +202,18 @@ def modem_disconnect(ifname: str, quiet: bool = False) -> None:
     """ Disconnect every bearer of the modem backing ifname. The number of
     bearers a modem can hold is limited, so we always disconnect before we
     dial again. """
-    call(f'mmcli --modem {modem_index(ifname)} --simple-disconnect',
+    modem = modem_index(ifname)
+    if modem is None:
+        return None
+    call(f'mmcli --modem {modem} --simple-disconnect',
          stdout=DEVNULL if quiet else None,
          stderr=DEVNULL if quiet else None)
 
 def modem_connect(ifname: str, options: str) -> bool:
     """ Dial the modem backing ifname, returns True if the modem connected """
     modem = modem_index(ifname)
+    if modem is None:
+        return False
 
     # Some networks only ever admit a single combined IPv4+IPv6 PDN context per
     # APN and reject a standalone IPv6 "Start Network" request outright (QMI