modemmanager: rework initial EPS bearer modes

Commit 246506690f ("modemmanager: always reset the init_eps if not
configured") changed the behaviour for an unset 'init_epsbearer' from
leaving the modem untouched to clearing the initial EPS bearer on every
setup. This is a regression for users upgrading from 24.10:

- Modems without support for setting the LTE attach configuration (e.g.
  Sierra Wireless EM7430) fail the setup with
  MM_INIT_EPS_BEARER_SET_FAILED and never come up.
- Attach settings preloaded by the carrier firmware are wiped.

The same commit also removed the explicit 'none' case, so 'none' now
silently skips the initial EPS bearer setup, while it cleared it in
24.10. Neither matches the documentation.

Make all modes explicit, each naming where the initial EPS bearer
settings come from:

- modem:      leave the settings stored on the modem unchanged (default)
- network:    set an empty initial EPS bearer, the network assigns the
              APN; replaces the implicit clear, e.g. after a SIM swap
- connection: use the connection options (apn, iptype, ...)
- custom:     use the init_* options

'none' and 'default' are kept as deprecated aliases for 'modem' and
'connection'. 'none' maps to 'modem' as documented in the README and as
it behaves since 246506690f, although an explicit 'none' cleared the
initial EPS bearer in 24.10; use 'network' for that. Unknown values fall
back to 'modem'. The README now documents the modes and how to clear
stale settings manually.

Fixes: https://github.com/openwrt/packages/issues/30299
Signed-off-by: Michael Pfeifroth <micpf@westermo.com>

net/modemmanager/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=modemmanager
 PKG_VERSION:=1.24.0
-PKG_RELEASE:=15
+PKG_RELEASE:=16
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://gitlab.freedesktop.org/mobile-broadband/ModemManager.git

net/modemmanager/README.md

@@ -27,7 +27,7 @@ Once installed, you can configure the 2G/3G/4G modem connections directly in
         option signalrate  '30'
         option allow_roaming '1'
         option force_connection '1'
-        option init_epsbearer '<none|default|custom>'
+        option init_epsbearer '<modem|network|connection|custom>'
         option timeout     '120'
 
 Only 'device' and 'proto' are mandatory options, the remaining ones are all
@@ -56,16 +56,25 @@ The 'force_connection' option is designed to ensure that the modem automatically
 attempts to reconnect regardless of any errors encountered during the
 connection process.
 
-If there is no Circuit switch network available, then an initial EPS
-bearer must be set, so this could be used during the network registration
-process in 4G and 5G network. For this resaon a new configuration option
-'init_epsbearer' was added, which could have the following values.
-* none:    Do not set an initial EPS bearer (default)
-* default: Use the configuration option 'apn', 'iptype', 'allowedauth',
-           'username' and 'password' for setting the initial EPS bearer.
-           These are the same options as when establishing a connection.
-* custom:  This could be used to use diffrent options when establishing a
-           connection. The options are prefixed with an 'init'. So we have
-           the following options 'init_apn', 'init_iptype',
-           'init_allowedauth', 'init_username' and 'init_password' for
-           setting the initial EPS bearer.
+On 4G and 5G networks, the modem attaches to the network with an initial
+EPS bearer, before the data connection is established. The 'init_epsbearer'
+option selects where the settings for this initial EPS bearer come from:
+* modem:      Leave the initial EPS bearer settings stored on the modem
+              unchanged (default). These are usually provided by the carrier
+              firmware or set by a previous configuration.
+* network:    Set an empty initial EPS bearer, so the network assigns the APN.
+              Use this to override settings left on the modem, e.g. after
+              swapping the SIM card.
+* connection: Use the options 'apn', 'iptype', 'allowedauth', 'username' and
+              'password', the same options as for the data connection.
+* custom:     Use separate options, prefixed with 'init_': 'init_apn',
+              'init_iptype', 'init_allowedauth', 'init_username' and
+              'init_password'.
+
+The values 'none' and 'default' are deprecated aliases for 'modem' and
+'connection'.
+
+The initial EPS bearer settings stored on the modem can also be cleared once
+manually:
+
+    mmcli -m <modem> --3gpp-set-initial-eps-bearer-settings=""

net/modemmanager/files/lib/netifd/proto/modemmanager.sh

@@ -530,10 +530,10 @@ modemmanager_init_epsbearer() {
 	local apn="$4"
 	local timeout="$5"
 
-	if [ "$eps" = "none" ]; then
-		echo "Deleting inital EPS bearer"
+	if [ "$eps" = "network" ]; then
+		echo "Setting network-assigned initial EPS bearer"
 	else
-		echo "Setting '$eps' inital EPS bearer apn to '$apn'"
+		echo "Setting '$eps' initial EPS bearer apn to '$apn'"
 	fi
 
 	mmcli --modem="${device}" \
@@ -629,44 +629,51 @@ proto_modemmanager_setup() {
 	}
 
 	# set initial eps bearer settings
-	if [ -z "${init_epsbearer}" ]; then
-		modemmanager_init_epsbearer "none" "$device" "" "$apn" "${timeout}"
-	else
-		case "$init_epsbearer" in
-			"default")
-				cliauth=""
-				for auth in $allowedauth; do
-					cliauth="${cliauth}${cliauth:+|}$auth"
-				done
-				connectargs=""
-				append_param "apn=${apn}"
-				append_param "${iptype:+ip-type=${iptype}}"
-				append_param "${cliauth:+allowed-auth=${cliauth}}"
-				append_param "${username:+user=${username}}"
-				append_param "${password:+password=${password}}"
-				modemmanager_init_epsbearer "default" \
-					"$device" "${connectargs}" "$apn" \
-					"${timeout}"
-				;;
-			"custom")
-				cliauth=""
-				for auth in $init_allowedauth; do
-					cliauth="${cliauth}${cliauth:+|}$auth"
-				done
-				connectargs=""
-				append_param "apn=${init_apn}"
-				append_param "${init_iptype:+ip-type=${init_iptype}}"
-				append_param "${cliauth:+allowed-auth=${cliauth}}"
-				append_param "${init_username:+user=${init_username}}"
-				append_param "${init_password:+password=${init_password}}"
-				modemmanager_init_epsbearer "custom" \
-					"$device" "${connectargs}" "$init_apn" \
-					"${timeout}"
-				;;
-		esac
-		# check error for init_epsbearer function call
-		[ "$?" -ne "0" ] && return 1
-	fi
+	case "${init_epsbearer:-modem}" in
+		"modem"|"none")
+			echo "Using initial EPS bearer stored on the modem"
+			;;
+		"network")
+			modemmanager_init_epsbearer "network" \
+				"$device" "" "" "${timeout}"
+			;;
+		"connection"|"default")
+			cliauth=""
+			for auth in $allowedauth; do
+				cliauth="${cliauth}${cliauth:+|}$auth"
+			done
+			connectargs=""
+			append_param "apn=${apn}"
+			append_param "${iptype:+ip-type=${iptype}}"
+			append_param "${cliauth:+allowed-auth=${cliauth}}"
+			append_param "${username:+user=${username}}"
+			append_param "${password:+password=${password}}"
+			modemmanager_init_epsbearer "connection" \
+				"$device" "${connectargs}" "$apn" \
+				"${timeout}"
+			;;
+		"custom")
+			cliauth=""
+			for auth in $init_allowedauth; do
+				cliauth="${cliauth}${cliauth:+|}$auth"
+			done
+			connectargs=""
+			append_param "apn=${init_apn}"
+			append_param "${init_iptype:+ip-type=${init_iptype}}"
+			append_param "${cliauth:+allowed-auth=${cliauth}}"
+			append_param "${init_username:+user=${init_username}}"
+			append_param "${init_password:+password=${init_password}}"
+			modemmanager_init_epsbearer "custom" \
+				"$device" "${connectargs}" "$init_apn" \
+				"${timeout}"
+			;;
+		*)
+			echo "Unknown init_epsbearer '${init_epsbearer}'," \
+				"using initial EPS bearer stored on the modem"
+			;;
+	esac
+	# check error for init_epsbearer function call
+	[ "$?" -ne "0" ] && return 1
 
 	if [ -z "${allowedmode}" ]; then
 		modemmanager_set_allowed_mode "$device" "$interface" "any"