uqmi: add mtu config option possibility

There are mobile carrier who have different MTU size in their network.
With this change it is now possible to configure this with the qmi
proto handler.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

package/network/utils/uqmi/files/lib/netifd/proto/qmi.sh

@@ -23,17 +23,18 @@ proto_qmi_init_config() {
 	proto_config_add_boolean autoconnect
 	proto_config_add_int plmn
 	proto_config_add_int timeout
+	proto_config_add_int mtu
 	proto_config_add_defaults
 }
 
 proto_qmi_setup() {
 	local interface="$1"
 	local dataformat connstat
-	local device apn auth username password pincode delay modes pdptype profile dhcpv6 autoconnect plmn timeout $PROTO_DEFAULT_OPTIONS
+	local device apn auth username password pincode delay modes pdptype profile dhcpv6 autoconnect plmn timeout mtu $PROTO_DEFAULT_OPTIONS
 	local ip4table ip6table
 	local cid_4 pdh_4 cid_6 pdh_6
 	local ip_6 ip_prefix_length gateway_6 dns1_6 dns2_6
-	json_get_vars device apn auth username password pincode delay modes pdptype profile dhcpv6 autoconnect plmn ip4table ip6table timeout $PROTO_DEFAULT_OPTIONS
+	json_get_vars device apn auth username password pincode delay modes pdptype profile dhcpv6 autoconnect plmn ip4table ip6table timeout mtu $PROTO_DEFAULT_OPTIONS
 
 	[ "$timeout" = "" ] && timeout="10"
 
@@ -68,6 +69,11 @@ proto_qmi_setup() {
 		return 1
 	}
 
+	[ -n "$mtu" ] && {
+		echo "Setting MTU to $mtu"
+		/sbin/ip link set dev $ifname mtu $mtu
+	}
+
 	echo "Waiting for SIM initialization"
 	local uninitialized_timeout=0
 	while uqmi -s -d "$device" --get-pin-status | grep '"UIM uninitialized"' > /dev/null; do