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pespin has posted comments on this change by canghaiwuhen. ( https://gerrit.osmocom.org/c/osmo-sgsn/+/41948?usp=email )

Change subject: Modified to dynamically adjust the returned QoS length to ensure compatibility with older modules. ......................................................................

Patch Set 3:

(3 comments)

File src/sgsn/gprs_sm.c:

https://gerrit.osmocom.org/c/osmo-sgsn/+/41948/comment/917e6626_43ca723f?usp... : PS3, Line 215: uint8_t qos_len = pdp->req_qos_len; Ideally we should store a struct with the decoded fields parsed, and then use an encode counterpart which would encode amount of fields based on the parsed request. See how that's done in open5gs.git/lib/gtp/v1/types.c ogs_gtp1_parse_pdp_context() and ogs_gtp1_build_pdp_context().

https://gerrit.osmocom.org/c/osmo-sgsn/+/41948/comment/9af3517a_5a42526d?usp... : PS3, Line 217: qos_len = 3; // Safety fallback for R97 This is backed on 3GPP TS 24.008 10.5.6.5: """ A QoS IE received without octets 6-22, without octets 14-22, without octets 15-22, without octets 17-22, without octets 19-22 or without octets 21-22 shall be accepted by the receiving entity.

NOTE: This behavior is required for interworking with entities supporting an earlier version of the protocol, or when the Maximum bit rate for downlink or for downlink and uplink is negotiated to a value lower than 8700 kbps.

"""

https://gerrit.osmocom.org/c/osmo-sgsn/+/41948/comment/3a970f63_4b97991c?usp... : PS3, Line 221: msgb_lv_put(msg, qos_len, (uint8_t *)&default_qos); let's better do:

uint8_t qos_len;

if (pdp->req_qos_len == 0 || pdp->req_qos_len > sizeof(default_qos)) qos_len = sizeof(default_qos); else qos_len = pdp->req_qos_len;