From f728e321d1fb781e26bbc103ac9923064ec86086 Mon Sep 17 00:00:00 2001
From: Christian Poessinger <christian@poessinger.com>
Date: Mon, 4 Apr 2022 20:24:38 +0200
Subject: wwan: T4338: changing interface description should not trigger
 reconnect

Changing the WWAN interface description will trigger an interface reconnect.
Reconnects should only be triggered in changes to the connection parameters
like bond interfaces.

(cherry picked from commit 76a049c7d30f3e64989b9697d65d15bfd3005316)
---
 src/conf_mode/interfaces-wwan.py | 75 ++++++++++++++++++++++++++++------------
 1 file changed, 52 insertions(+), 23 deletions(-)

diff --git a/src/conf_mode/interfaces-wwan.py b/src/conf_mode/interfaces-wwan.py
index 57acb866c..a1a9360d7 100755
--- a/src/conf_mode/interfaces-wwan.py
+++ b/src/conf_mode/interfaces-wwan.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2020-2021 VyOS maintainers and contributors
+# Copyright (C) 2020-2022 VyOS maintainers and contributors
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 or later as
@@ -21,6 +21,7 @@ from time import sleep
 
 from vyos.config import Config
 from vyos.configdict import get_interface_dict
+from vyos.configdict import leaf_node_changed
 from vyos.configverify import verify_authentication
 from vyos.configverify import verify_interface_exists
 from vyos.configverify import verify_vrf
@@ -50,6 +51,32 @@ def get_config(config=None):
     base = ['interfaces', 'wwan']
     wwan = get_interface_dict(conf, base)
 
+    # We should only terminate the WWAN session if critical parameters change.
+    # All parameters that can be changed on-the-fly (like interface description)
+    # should not lead to a reconnect!
+    tmp = leaf_node_changed(conf, ['address'])
+    if tmp: wwan.update({'shutdown_required': {}})
+
+    tmp = leaf_node_changed(conf, ['apn'])
+    if tmp: wwan.update({'shutdown_required': {}})
+
+    tmp = leaf_node_changed(conf, ['disable'])
+    if tmp: wwan.update({'shutdown_required': {}})
+
+    tmp = leaf_node_changed(conf, ['vrf'])
+    # leaf_node_changed() returns a list, as VRF is a non-multi node, there
+    # will be only one list element
+    if tmp: wwan.update({'vrf_old': tmp[0]})
+
+    tmp = leaf_node_changed(conf, ['authentication', 'user'])
+    if tmp: wwan.update({'shutdown_required': {}})
+
+    tmp = leaf_node_changed(conf, ['authentication', 'password'])
+    if tmp: wwan.update({'shutdown_required': {}})
+
+    tmp = leaf_node_changed(conf, ['ipv6', 'address', 'autoconf'])
+    if tmp: wwan.update({'shutdown_required': {}})
+
     # We need to know the amount of other WWAN interfaces as ModemManager needs
     # to be started or stopped.
     conf.set_level(base)
@@ -113,11 +140,12 @@ def apply(wwan):
                 break
             sleep(0.250)
 
-    # we only need the modem number. wwan0 -> 0, wwan1 -> 1
-    modem = wwan['ifname'].lstrip('wwan')
-    base_cmd = f'mmcli --modem {modem}'
-    # Number of bearers is limited - always disconnect first
-    cmd(f'{base_cmd} --simple-disconnect')
+    if 'shutdown_required' in wwan:
+        # we only need the modem number. wwan0 -> 0, wwan1 -> 1
+        modem = wwan['ifname'].lstrip('wwan')
+        base_cmd = f'mmcli --modem {modem}'
+        # Number of bearers is limited - always disconnect first
+        cmd(f'{base_cmd} --simple-disconnect')
 
     w = WWANIf(wwan['ifname'])
     if 'deleted' in wwan or 'disable' in wwan:
@@ -134,24 +162,25 @@ def apply(wwan):
 
         return None
 
-    ip_type = 'ipv4'
-    slaac = dict_search('ipv6.address.autoconf', wwan) != None
-    if 'address' in wwan:
-        if 'dhcp' in wwan['address'] and ('dhcpv6' in wwan['address'] or slaac):
-            ip_type = 'ipv4v6'
-        elif 'dhcpv6' in wwan['address'] or slaac:
-            ip_type = 'ipv6'
-        elif 'dhcp' in wwan['address']:
-            ip_type = 'ipv4'
-
-    options = f'ip-type={ip_type},apn=' + wwan['apn']
-    if 'authentication' in wwan:
-        options += ',user={user},password={password}'.format(**wwan['authentication'])
-
-    command = f'{base_cmd} --simple-connect="{options}"'
-    call(command, stdout=DEVNULL)
-    w.update(wwan)
+    if 'shutdown_required' in wwan:
+        ip_type = 'ipv4'
+        slaac = dict_search('ipv6.address.autoconf', wwan) != None
+        if 'address' in wwan:
+            if 'dhcp' in wwan['address'] and ('dhcpv6' in wwan['address'] or slaac):
+                ip_type = 'ipv4v6'
+            elif 'dhcpv6' in wwan['address'] or slaac:
+                ip_type = 'ipv6'
+            elif 'dhcp' in wwan['address']:
+                ip_type = 'ipv4'
+
+        options = f'ip-type={ip_type},apn=' + wwan['apn']
+        if 'authentication' in wwan:
+            options += ',user={user},password={password}'.format(**wwan['authentication'])
 
+        command = f'{base_cmd} --simple-connect="{options}"'
+        call(command, stdout=DEVNULL)
+
+    w.update(wwan)
     return None
 
 if __name__ == '__main__':
-- 
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