From 5299606d0e6adf5f522cc6cbfb35ea39fc138bb4 Mon Sep 17 00:00:00 2001
From: Adam Smith <adamsmith@yzguy.io>
Date: Wed, 30 Sep 2026 05:18:14 +0000
Subject: wwan: T9326: always pre-negotiate the attach-time PDN type before
 connect

modem_connect() only ran the --3gpp-set-initial-eps-bearer-settings
pre-step (added by T9326) when the requested ip-type included IPv6,
gated on options.partition('ip-type=')[2].partition(',')[0] in ('ipv6',
'ipv4v6'). A bare 'ipv4' request skipped it entirely.

Confirmed live (same MC7455/Google Fi setup as T9326's original report)
that the underlying ip-version-mismatch rejection isn't IPv6-specific:
with the attach committed to ip-type=ipv6, a bare ip-type=ipv4
--simple-connect fails outright with the same QMI CallEndReason, not
just the ipv4v6 case's silent single-family drop. A WWAN interface
whose configured address family changes (e.g. dropping dhcpv6 down to
dhcp-only) can hit exactly this, and won't self-heal on retry since
nothing about a failed connect touches the attach-committed PDN type -
vyos-netlinkd's reconcile loop would back off and retry the identical
failing request forever.

Removed the gate entirely: the pre-step already fails silently and
falls through unchanged on a modem/network that doesn't need it, so
there's no reason to skip it for any particular family.
---
 python/vyos/utils/wwan.py | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

(limited to 'python')

diff --git a/python/vyos/utils/wwan.py b/python/vyos/utils/wwan.py
index 8ee6a5a9a..cf7d7b143 100644
--- a/python/vyos/utils/wwan.py
+++ b/python/vyos/utils/wwan.py
@@ -236,23 +236,16 @@ def modem_connect(ifname: str, options: str) -> bool:
     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
-    # CallEndReason ip-version-mismatch) once an IPv4 session already exists for
-    # that APN. ModemManager's --simple-connect with ip-type=ipv4v6 opens two
-    # separate WDS sessions (one per family) rather than negotiating both
-    # together, which is what a normal handset attach does and why this is
-    # invisible on most other devices.
-    #
-    # Pre-negotiating the attach-time PDN type upfront avoids the rejection; the
-    # resulting bearer only sets up what the *next* --simple-connect is allowed
-    # to request and can't be connected directly, so a failure here isn't fatal
-    # - unsupported modems simply proceed to --simple-connect exactly as before.
-    if options.partition('ip-type=')[2].partition(',')[0] in ('ipv6', 'ipv4v6'):
-        # best effort by definition, so do not report the rejection a modem
-        # without attach configuration support answers with on every dial
-        call(f'mmcli --modem {modem} --3gpp-set-initial-eps-bearer-settings="{options}"',
-             stdout=DEVNULL, stderr=DEVNULL)
+    # A network only commits to one PDN type per APN at attach time, and
+    # rejects any later --simple-connect for a family that doesn't match it
+    # (QMI ip-version-mismatch, T9326) - pre-negotiating it here avoids that.
+    # The resulting bearer can't be connected directly, so a failure here
+    # isn't fatal - unsupported modems just proceed to --simple-connect.
+    call(
+        f'mmcli --modem {modem} --3gpp-set-initial-eps-bearer-settings="{options}"',
+        stdout=DEVNULL,
+        stderr=DEVNULL,
+    )
 
     command = f'mmcli --modem {modem} --simple-connect="{options}"'
     return call(command, stdout=DEVNULL) == 0
-- 
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