Some phones, such as the Sony Ericsson Z520, reject or ignore the Activate PDP Context Accept if they dislike the max-sdu-size value in the QoS profile. Make this value configurable via the VTY so it can be adjusted to accommodate such devices.
The Activate PDP Context Accept was always sending sizeof(default_qos) (14 bytes) as the QoS profile length, regardless of what the UE requested. Older modules such as the Air20X may crash and restart during PDP attachment because of that.
In GTP, qos_req.l encodes 1 ARP byte followed by the QoS profile octets, so (qos_req.l - 1) is the actual profile length. Mirror back the same QoS profile length the UE sent in its request, capped at sizeof(default_qos) to avoid overrunning the default_qos buffer. This matters in particular for R97/R98 UEs that send a 3-byte QoS profile and should not receive a 14-byte response.
